Audel™ HVAC Fundamentals Volume 3 Air

Audel™ HVAC Fundamentals Volume 3 Air
Audel
™
HVAC Fundamentals
Volume 3
Air-Conditioning, Heat
Pumps, and Distribution
Systems
All New 4th Edition
James E. Brumbaugh
Vice President and Executive Group Publisher: Richard Swadley
Vice President and Executive Publisher: Robert Ipsen
Vice President and Publisher: Joseph B. Wikert
Executive Editor: Carol A. Long
Acquisitions Editor: Katie Feltman, Katie Mohr
Editorial Manager: Kathryn A. Malm
Development Editor: Kenyon Brown
Production Editor: Vincent Kunkemueller
Text Design & Composition: TechBooks
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Library of Congress Control Number:
eISBN: 0-7645-7626-7
Printed in the United States of America
10 9 8 7 6 5 4 3 2 1
For Laura, my friend, my daughter.
Contents
Introduction
xvii
About the Author
xix
Chapter 1
Radiant Heating
Types of Radiant Panel Heating Systems
Floor Panel Systems
Ceiling Panel Systems
Wall Panel Systems
Hydronic Radiant Floor Heating
System Components
Designing a Hydronic Radiant Floor
Heating System
Coils and Coil Patterns
Installing a Hydronic Radiant Floor
Heating System
(PEX Tubing)
Servicing and Maintaining Hydronic
Radiant Floor Heating Systems
Troubleshooting Hydronic Floor Radiant
Heating Systems
Hydronic Radiant Heating Snow- and
Ice-Melting Systems
Electric Radiant Floor Heating
Installing Electric Heating Mats or Rolls
Installing Electric Cable
Servicing and Maintaining an Electric
Radiant Floor Heating System
Troubleshooting Electric Radiant Floor
Heating Systems
Cooling for Hydronic Radiant Floor
Systems
1
2
2
2
5
6
6
28
41
44
49
49
51
52
58
65
67
67
68
v
vi Contents
Chapter 2
Radiators, Convectors,
and Unit Heaters
Radiators
Radiator Efficiency
Radiator Heat Output
Sizing Radiators
Installing Radiators
Radiator Valves
Radiator Piping Connections
Vents and Venting
Steam Traps
Troubleshooting Radiators
Convectors
Convector Piping Connections
Hydronic Fan Convectors
Troubleshooting Hydronic Fan
Convectors
Steam and Hot-Water Baseboard
Heaters
Construction Details
Integral Fin-and-Tube Baseboard Heaters
Installing Baseboard Units
Baseboard Heater Maintenance
Electric Baseboard Heaters
Installing Electric Baseboard Heaters
Kickspace Heaters
Floor and Window Recessed Heaters
Unit Heaters
Chapter 3
71
72
74
77
78
79
86
92
93
99
99
100
101
106
106
107
108
112
113
119
119
124
127
129
130
Unit Heater Piping Connections
Unit Heater Controls
Gas-Fired Unit Heaters
Oil-Fired Unit Heaters
135
138
140
141
Fireplaces, Stoves, and Chimneys
Fireplaces
145
145
Fireplace Location
Fireplace Dimensions
145
146
Contents vii
Fireplace Construction Details
Firebox, Lintel, and Mantel
Fireplace Hearth
Ash Dump, Ashpit, and
Cleanout Door
Smoke Chamber
Fireplace Dampers
Chapter 4
149
150
151
152
152
153
Modified Fireplaces
Freestanding Fireplaces
Rumford Fireplace
Chimney Draft
Chimney Construction Details
Chimney Flues and Chimney Liners
Smoke Pipe
Cleanout Trap
Chimney Downdraft
Prefabricated Metal Chimneys
Troubleshooting Fireplaces and
Chimneys
Stoves, Ranges, and Heaters
Installation Instructions
Operating Instructions
156
157
158
162
164
165
167
168
168
169
169
169
177
178
Water Heaters
Types of Water Heaters
179
179
Direct-Fired Water Heaters
Automatic Storage Water Heaters
Multicoil Water Heaters
Multiflue Water Heaters
Instantaneous Water Heaters
Indirect Water Heaters
Quick-Recovery Heaters
Slow-Recovery Heaters
Heat Pump Water Heaters
Combination Water Heaters
180
180
182
183
184
185
189
189
190
191
Water Heater Construction Details
192
Water Storage Tanks
193
viii Contents
Tank Fittings
Dip Tubes
Anodes
Valves
Safety Relief Valves
Vacuum Relief Valve
194
194
197
197
197
206
Gas-Fired Water Heaters
Storage Capacity
209
209
Gas Burners
Automatic Controls on Gas-Fired
Water Heaters
Combination Gas Valve
Installation and Operation of
Gas-Fired Water Heaters
Hot-Water Circulating Methods
Building and Safety Code
Requirements
Lighting and Operating Instructions
Installation and Maintenance
Checklist
Troubleshooting Gas-Fired Water
Heaters
Oil-Fired Water Heaters
Electric Water Heaters
Troubleshooting Electric Water Heaters
Manual Water Heaters
Assembly and Installation of Manual
Water Heaters
Chapter 5
210
210
221
225
230
230
231
232
233
238
240
242
245
246
Solar Water Heaters
246
Heating Swimming Pools
Classifying Pool Heaters
Gas-Fired Pool Heaters
Oil-Fired Pool Heaters
Electric Pool Heaters
Heat-Exchanger Pool Heaters
Solar Pool Heaters
249
251
255
259
260
263
264
Contents ix
Heat Pump Pool Heaters
Sizing Pool Heaters
The Surface-Area Method
The Time-Rise Method
Sizing Indoor Pool Heaters
Installing Pool Heaters
Pool Heater Repair and Maintenance
Troubleshooting Pool Heaters and
Equipment
Chapter 6
Ventilation Principles
The Motive Force
Inductive Action of the Wind
Induced Draft
Combined Force of Wind Effect
and Thermal Effect
Mechanical Ventilation
Air Ventilation Requirements
Roof Ventilators
Types of Roof Ventilators
Stationary-Head Ventilators
Revolving Ventilators
Turbine Ventilators
Ridge Ventilators
Siphonage Ventilators
Fan Ventilators
Components of a Roof Ventilator
Motive Force to Cause Air Circulation
Capacity of Ventilators
Design and Placement of Inlet Air
Openings
Fresh Air Requirements
Ventilator Bases
Angle Rings
Stiffener Angles
Prefabricated Roof Curbs
Ventilator Dampers
267
267
270
271
271
271
273
274
281
282
282
285
285
287
287
289
289
290
290
291
293
294
294
295
296
296
298
299
299
302
303
303
304
x Contents
Louver Dampers
Sliding Sleeve Dampers
Sliding Cone Dampers
Butterfly Dampers
Chapter 7
305
306
306
306
Method of Calculating Number and
Size of Ventilators Required
Ventilator Calculation Examples
Air Leakage
Garage Ventilation
Ventilation of Kitchens
General Ventilation Rules
307
308
309
310
311
312
Ventilation and Exhaust Fans
Codes and Standards
Definitions
Types of Fans
Furnace Blowers
Basic Fan Laws
Series and Parallel Fan Operation
Fan Performance Curves
General Ventilation
315
315
315
317
319
319
321
322
322
Determining CFM by the Air-Change
Method
Determining CFM by the Heat Removal
Method
Determining Air Intake
Screen Efficiency
Static Pressure
Local Ventilation
Exhaust-Hood Design
Recommendations
Fan Motors
Troubleshooting Fans
Fan Selection
Fan Installation
Fan Installation Checklist
Air Volume Control
323
325
326
326
327
328
332
333
337
341
344
344
347
Contents xi
Noise Control
Fan Applications
Attic Ventilating Fans
Exhaust Fans
Kitchen Exhaust Fans
Bathroom Exhaust Fans
Chapter 8
347
347
348
355
355
356
Whole-House Ventilation
356
Air-Conditioning
Properties of Air
361
362
Humidity
Temperature
Pressure
362
365
368
Compression and Cooling
Measuring the Physical Properties
of Air
Cleaning and Filtering the Air
Standards of Comfort
The Comfort Chart
Cooling Load Estimate Form
Indoor-Outdoor Design Conditions
Ventilation Requirements
Cooling a Structure
External Sources of Heat
Internal Sources of Heat
Calculating Infiltration and Ventilation
Heat Gain
Rule-of-Thumb Methods for Sizing
Air Conditioners
HVAC Contractor’s Cooling Load
Estimate
Using the ACCA Design Manuals
for Sizing Air-Conditioning Systems
Central Air-Conditioning
Cooling Methods
Central Air-Conditioning Applications
Room Air Conditioners
370
372
374
376
377
379
383
384
386
386
392
394
394
395
396
397
397
410
421
xii Contents
Chapter 9
Air-Conditioning Equipment
Mechanical Refrigeration Equipment
Compressors
Troubleshooting Compressors
Compressor Replacement
Electric Motors
Troubleshooting Electrical Motors
Gas Engines
Electrical Components
Troubleshooting Electrical Components
Condenser
Condenser Service and Maintenance
Troubleshooting Condensers
Receiver
Evaporator
Evaporator Service and Maintenance
Troubleshooting Evaporators
423
423
424
430
435
435
436
437
437
438
439
442
443
443
447
447
447
Refrigerants
Liquid Refrigerant Control Devices
Automatic Expansion Valves
Thermostatic Expansion Valves
Float Valves
Capillary Tubes
Refrigerant Piping
448
449
449
450
453
454
454
Refrigerant Piping Service and
Maintenance
Troubleshooting Refrigerant Piping
455
456
Filters and Dryers
Pressure-Limiting Controls
Water-Regulating Valves
Automatic Controls
System Troubleshooting
General Servicing and Maintenance
Regular Maintenance
Pumping Down
Purging
Evacuating the System
457
457
458
459
459
460
463
464
464
464
Contents xiii
Charging
Silver-Brazing Repairs
Chapter 10
Heat Pumps
Heat Pump Operating Principles
Heating Cycle
Cooling Cycle
Defrost Cycle
Types of Heat Pumps
465
467
471
471
471
473
473
476
Air-Source Heat Pumps
Ground-Source Heat Pumps
Water-Source Heat Pumps
476
481
483
Other Types of Heat Pumps
485
Gas-Fired Heat Pumps
Dual-Fuel Heat Pump System
Dual-Source Heat Pumps
Ductless Heat Pumps
Heat Pump Performance and Efficiency
Ratings
Seasonal Energy Efficiency Ratio (SEER)
Heating Season Performance Factor
(HSPF)
Coefficiency of Performance (COP)
Energy Efficiency Rating (EER)
Energy Star Rating
485
486
486
487
487
488
488
488
488
488
Heat Pump System Components
488
Compressor
Indoor Coil and Blower
Outdoor Coil and Fan
Refrigerant Lines
Reversing Valve and Solenoid
Thermostatic Expansion Valve
Desuperheater
Control Box
Fan/Blower Motors
Heat Pump Defrost System
High-Pressure Switch
Low-Pressure Switch
490
491
491
491
491
493
494
494
499
499
500
501
xiv Contents
Other Electric/Electronic Heat Pump
Controls and Connections
Accumulator
Room Thermostat
Service Valves and Gauge Ports
Gauge Manifold
Filter Dryer
Crankcase Heater
Muffler
Sizing Heat Pumps
Heat Pump Installation
Recommendations
Heat Pump Operating Instructions
Heating
Cooling
Heat Pump Service and Maintenance
Service and Maintenance Checklist
Adjusting Heat Pump Refrigerant Charge
Chapter 11
501
501
501
502
503
503
503
505
505
507
510
510
511
511
512
513
Troubleshooting Heat Pumps
Troubleshooting Heat Pump
Compressors
517
Humidifiers and Dehumidifiers
Humidifiers
519
521
Spray Humidifiers
Pan Humidifiers
Stationary-Pad Humidifiers
Steam Humidifiers
Bypass Humidifiers
Power Humidifiers
522
523
524
524
525
526
Automatic Controls
Installation Instructions
Service and Maintenance Suggestions
Troubleshooting Humidifiers
Dehumidifiers
Absorption Dehumidifiers
Spray Dehumidifiers
514
526
529
534
535
537
538
541
Contents xv
Refrigeration Dehumidifiers
Automatic Controls
Installation Suggestions
Operating and Maintenance Suggestions
Chapter 12
541
542
542
542
Troubleshooting Dehumidifiers
543
Air Cleaners and Filters
Electronic Air Cleaners
547
547
Charged-Media Air Cleaners
Two-Stage Air Cleaners
Automatic Controls
Clogged-Filter Indicator
Performance Lights
Sail Switch
In-Place Water-Wash Controls
Cabinet-Model Control Panels
Installation Instructions
Electrical Wiring
Maintenance Instructions
Replacing Tungsten Ionizing Wires
Troubleshooting Electronic Air Cleaners
Air Washers
Air Filters
Dry Air Filters
Viscous Air Filters
Filter Installation and Maintenance
549
553
554
556
557
559
561
563
564
564
565
568
569
571
572
574
574
575
Appendix A Professional and Trade Associations
577
Appendix B Manufacturers
589
Appendix C HVAC/R Education, Training,
Certification, and Licensing
601
Appendix D Data Tables
605
Appendix E Psychrometric Charts
643
Index
647
Introduction
The purpose of this series is to provide the layman with an introduction to the fundamentals of installing, servicing, troubleshooting,
and repairing the various types of equipment used in residential and
light-commercial heating, ventilating, and air conditioning (HVAC)
systems. Consequently, it was written not only for the HVAC technician and others with the required experience and skills to do this
type of work but also for the homeowner interested in maintaining
an efficient and trouble-free HVAC system. A special effort was
made to remain consistent with the terminology, definitions, and
practices of the various professional and trade associations involved
in the heating, ventilating, and air conditioning fields.
Volume 1 begins with a description of the principles of thermal
dynamics and ventilation, and proceeds from there to a general
description of the various heating systems used in residences and
light-commercial structures. Volume 2 contains descriptions of the
working principles of various types of equipment and other components used in these systems. Following a similar format, Volume 3
includes detailed instructions for installing, servicing, and repairing
these different types of equipment and components.
The author wishes to acknowledge the cooperation of the many
organizations and manufacturers for their assistance in supplying
valuable data in the preparation of this series. Every effort was
made to give appropriate credit and courtesy lines for materials and
illustrations used in each volume.
Special thanks is due to Greg Gyorda and Paul Blanchard (Watts
Industries, Inc.), Christi Drum (Lennox Industries, Inc.), Dave
Cheswald and Keith Nelson (Yukon/Eagle), Bob Rathke (ITT Bell &
Gossett), John Spuller (ITT Hoffman Specialty), Matt Kleszezynski
(Hydrotherm), and Stephanie DePugh (Thermo Pride).
Last, but certainly not least, I would like to thank Katie Feltman,
Kathryn Malm, Carol Long, Ken Brown, and Vincent Kunkemueller,
my editors at John Wiley & Sons, whose constant support and
encouragement made this project possible.
James E. Brumbaugh
About the Author
James E. Brumbaugh is a technical writer with many years of experience working in the HVAC and building construction industries.
He is the author of the Welders Guide, The Complete Roofing
Guide, and The Complete Siding Guide.
Chapter 1
Radiant Heating
Heat is lost from the human body through radiation, convection,
and evaporation. Radiation heat loss represents the transfer of
energy by means of electromagnetic waves. The convection loss is
the heat carried away by the passage of air over the skin and clothing. The evaporation loss is the heat used up in converting moisture
on the surface of the skin into vapor.
Heat transfer, whether by convection or radiation, follows the
same physical laws in the radiant heating system as in any other;
that is, heat flows from the warmer to the cooler exposure at a rate
directly proportional to the existing temperature difference.
The natural tendency of warmed air to rise makes it apparent
that this induced air current movement is greater at the cooler floor
and exterior walls of the average heated enclosure than at its ceiling. It is through absorption by these air currents that the radiant
panel releases the convection component of its heat transfer into
the room air.
The average body heat loss is approximately 400 Btu per hour;
total radiation and convection account for approximately 300 to
320 Btu of it. Because this is obviously the major portion, the problem of providing comfort is principally concerned with establishing
the proper balance between radiation and convection losses.
It is important to understand that bodily comfort is obtained in
radiant heating by maintaining a proper balance between radiation
and convection. Thus, if the air becomes cooler and accordingly the
amount of heat given off from the body by convection increases,
then the body can still adjust itself to a sense of comfort if the heat
given off from the body by radiation is decreased. The amount
given off from the body by radiation can be decreased by raising the
temperature of the surrounding surfaces, such as the walls, floor,
and ceiling. For comfort, the body demands that if the amount of
heat given off by convection increases, the heat given off by radiation must decrease, and vice versa.
The principles involved in radiant heating exist in such commonplace sources of heat as the open fireplace, outdoor campfires, electric spot heaters, and similar devices. In each of these examples, no
attempt is made to heat the air or enclosing surfaces surrounding
the individual. In fact, the temperature of the air and surrounding
1
2 Chapter 1
surfaces may be very low, but the radiant heat from the fireplace or
campfire will still produce a sensation of comfort (or even discomfort from excess heat) to those persons within range. This situation
can occur even though a conventional thermometer may indicate a
temperature well below freezing. Radiant heat rays do not perceptibly heat the atmosphere through which they pass. They move from
warm to colder surfaces where a portion of their heat is absorbed.
This chapter is primarily concerned with a description of radiant
panel heating, which can be defined as a form of radiant heating in
which large surfaces are used to radiate heat at relatively low temperatures. The principal emphasis will be on hydronic and electric
radiant floor heating.
Types of Radiant Panel Heating Systems
Radiant panel heating systems use water-filled tubing or electric heating mats or rolls installed in the floors, walls, and ceilings to distribute the heat. Radiant floor heating is by far the most popular
installation method in residential and light-commercial construction.
Note
The word panel is used to indicate a complete system of tubing
loops in a single room or space in a structure. It may also be used
to indicate a premanufactured radiant floor heating panel.
Floor Panel Systems
Floor panels are usually easier to install than either ceiling or wall
panels. Using floor panels is the most effective method of eliminating
cold floors in slab construction. Another advantage of heating with
floor panels is that much of the radiated heat is delivered to the lower
portions of the walls. The principal disadvantage of using floor panels
is that furniture and other objects block portions of the heat emission.
Floor panels are recommended for living or working areas constructed directly on the ground, particularly one-story structures.
Partial ceiling or wall treatment may be used as a supplement wherever large glass or door exposures are encountered. A typical floor
installation is shown in Figure 1-1.
Ceiling Panel Systems
The advantage of a ceiling panel is that its heat emissions are not
affected by drapes or furniture. As a result, the entire ceiling area
can be used as a heating panel. Ceiling panels are recommended for
rooms or space with 7-foot ceilings or higher. A ceiling panel
should never be installed in a room with a low ceiling (under 7 feet)
because it may produce an undesirable heating effect on the head.
Radiant Heating 3
TUBE SIZE:
1 ⁄ " – 3 ⁄ " = 9" SPACING
4
2
3 ⁄ " – 1" = 12" SPACING
4
11 ⁄2" X TUBE
SPACING
9" – 12"
FLOOR COVERING:
TILE, TERRAZZO
ASPHALT TILE, LINOLEUM
2" – 4" BURY
3' – 0" MIN
W P INSUL
1 ⁄ " MIN
2
Concrete thickness to suit
architectural requirements.
COARSE DRAINED GRAVEL
6" MIN THICKNESS
SOIL FILL
Supply line feeds outer
panel edge first.
11⁄2" X TUBE SPACING
Area of panel extends beyond
last tube by 1 ⁄2" tube spacing.
Balancing and shutoff
valves in floor box.
SUPPLY
Figure 1-1
RETURN
Diagram of a typical radiant floor heating installation.
In multiple-story construction, the use of ceiling panels appears
to be more desirable from both the standpoint of physical comfort
and overall economy. The designed utilization of the upward heat
transmission from ceiling panels to the floor of the area immediately above will generally produce moderately tempered floors.
Supplementing this with automatically controlled ceiling panels
4 Chapter 1
will result in a very efficient radiant heating system. Except directly
below roofs or other unheated areas, this design eliminates the need
for the intermediate floor insulation sometimes used to restrict the
heat transfer from a ceiling panel exclusively to the area immediately below. It must be remembered, however, that when intermediate floor insulations are omitted, the space above a heated ceiling
will not be entirely independent with respect to temperature control
but will necessarily be influenced by the conditions in the space
below. A typical ceiling installation is shown in Figure 1-2.
UNHEATED SPACE
HEATED ROOM ABOVE
Heat to room above equals
about 25% of output down.
METAL LATH OR
GYPSUM BOARD
PLASTER
1⁄ " COVER
4
INSULATION-6" ROCKWOOL
OR MORE
STANDARD 3 ⁄4"
PLASTER
3 ⁄ " NOMINAL
8
TUBE (1 ⁄2" O.D.)
4 1 ⁄2 "
TO 9"
Supply line feeds
outer panel edge first.
11⁄2 X TUBE SPACING
NOTE:
At least 67% of
ceiling is covered
and unheated
section is on the
inside.
Area of panel extends
beyond last tube by
1⁄ tube spacing.
2
In upfeed system raise
return to cross. Continue
up after crossing.
SHUTOFF
3⁄
4"
SUPPLY
Figure 1-2
BALANCING
VALVES
3⁄
4"
RETURN
Diagram of a typical radiant ceiling heating panel.
Radiant Heating 5
Apartment buildings and many office and commercial structures
should find the ceiling panel method of radiant heating most desirable. In offices and stores, the highly variable and changeable furnishings, fixtures, and equipment favor the construction of ceiling
panels, to say nothing of the advantage of being able to make as
many partition alterations as desired without affecting the efficiency of the heating system.
Wall Panel Systems
Walls are not often used for radiant heating because large sections
of the wall area are often interrupted by windows and doors.
Furthermore, the heat radiation from heating coils placed in the
lower sections of a wall will probably be blocked by furniture. As a
result, a radiant wall installation is generally used to supplement
ceiling or floor systems, not as a sole source of heat.
Wall heating coils are commonly used as supplementary heating
in bathrooms and in rooms in which there are a number of large
picture windows. In the latter case, the heating coils are installed in
the walls opposite the windows. Wall heating coils will probably
not be necessary if the room has good southern exposure. A typical
wall installation is shown in Figure 1-3.
BALANCING AND SHUTOFF
VALVES IN WALL BOX
DIRECTION OF FLOW
SAME AS MAINS
Typical wall installation. Panel is
installed on wall as high as possible.
Figure 1-3
6 Chapter 1
Hydronic Radiant Floor Heating
Hydronic radiant floor systems heat water in a boiler, heat pump,
or water heater and force it through tubing arranged in a pattern of
loops located beneath the floor surface. These systems can be classified as being either wet installations or dry installations depending on how the tubing is installed.
In wet installations, the tubing is commonly embedded in a concrete foundation slab or attached to a subfloor and covered with a
lightweight concrete slab. Dry installations are so called because the
tubing is not embedded in concrete.
System Components
The principal components of a typical hydronic radiant floor heating system can be divided into the following categories:
1.
2.
3.
4.
5.
6.
7.
8.
Boilers, water heaters, and heat pumps
Tubing and fittings
Valves and related controls
Circulator
Expansion tank
Air separator
Heat exchanger
Thermostat
Boilers, Water Heaters, and Heat Pumps
The boilers used in hot-water radiant heating systems are the
same types of heating appliances as those used in hydronic heating systems. Information about the installation, maintenance, service, and repair of hydronic boilers is contained in Chapter 15 of
Volume 1.
Gas-fired boilers are the most widely used heat source in hydronic
radiant heating systems. Oil-fired boilers are second in popularity and
are used most commonly in the northern United States and Canada.
Coal-fired boilers are still found in some hydronic radiant heating
systems, but their use has steadily declined over the years.
Note
Hydronic radiant floor heating systems operate in an 85–140ºF
(29–60ºC) temperature range. This is much lower than the 130–
160ºF (54–71ºC) temperature operating range required in other
hydronic systems. As a result, the boilers used in floor systems
Radiant Heating 7
operate at lower boiler temperatures, which results in a much
longer service life for the appliance.
The electric boilers used in hydronic radiant floor systems are
competitive with other fuels in those areas where electricity costs
are low. Their principal advantage is that they are compact appliances that can be installed where space is limited.
Radiant floor systems can also be heated with a geothermal heat
pump. In climates where the heating and cooling loads are equal or
almost equal in size, a geothermal heat pump will be very cost effective.
Most standard water heaters produce a maximum of 40,000 to
50,000 Btu/h. This is sufficient Btu input to heat a small house or to
separately heat a room addition, but it cannot provide the heat
required for medium to large houses. As a result, some HVAC manufacturers have developed high-Btu-output dedicated water heaters for
radiant heating systems. These water heaters are designed specifically
as single heat sources for both the domestic hot water and the spaceheating requirements. As is the case with boilers used in hydronic
radiant heating systems, they operate in conjunction with a circulating pump and an expansion tank. See Chapter 4 (“Water Heaters”)
for additional information about combination water heaters.
Tubing and Fittings
The tubing in a radiant heating system is divided into the supply
and return lines. The supply line extends from the discharge opening of a boiler to the manifold. It carries the heated fluid to the
loops (circuits) in the floors, walls, or ceilings. A return line extends
from the return side of a manifold to the boiler. It carries the water
from the heating panels back to the boiler where it is reheated.
Hydronic radiant floor heating systems use copper, plastic (PEX
or polybutylene tubing), or synthetic-rubber tubing to form the
loops. Because of space limitations, only the two most commonly
used types are described in this chapter: copper tubing and PEX
(plastic) tubing. Information about the other types of tubing used in
hydronic heating systems can be found in Chapter 8 (“Pipes, Pipe
Fittings, and Piping Details”) of Volume 2.
Loops or Circuits
The words loop and circuit are synonyms for the length of tubing within
a zone. Sometimes both are used in the same technical publication. At
other times, one or the other is used exclusively. Many loops or circuits
of the same length will form a zone. Circuits also refer to the electrical
circuit required to operate the heating system.
8 Chapter 1
Copper Tubing
In most modern radiant floor heating systems, the water is circulated through copper or cross-linked polyethylene (PEX) tubing
(see Figure 1-4). The metal coils used in hydronic radiant heating
systems commonly are made of copper tubing (both the hard and
soft varieties). Steel and wrought-iron pipe also have been used in
hydronic floor heating systems, but it is rare to find them in modern
residential radiant floor heating systems.
3⁄
4-INCH
ID
1⁄
2-INCH
ID
3⁄
8-INCH
ID
Inside diameters (ID) of commonly
used copper tubing in hydronic
radiant floor heating systems.
Figure 1-4
Copper tubing.
The soft tempered Type L copper tubing is recommended for
hydronic radiant heating panels. Because of the relative ease with
which soft copper tubes can be bent and shaped, they are especially
well adapted for making connections around furnaces, boilers, oilburning equipment, and other obstructions. This high workability
characteristic of copper tubing also results in reduced installation
Radiant Heating 9
time and lower installation costs. Copper tubing is produced in
diameters ranging from 1⁄8 inch to 10 inches and in a variety of different wall thicknesses. Both copper and brass fittings are available.
Hydronic heating systems use small tube sizes joined by soldering.
The size of the pipes or tubing used in these systems depends on
the flow rate of the water and the friction loss in the tubing. The
flow rate of the water is measured in gallons per minute (gpm), and
constant friction loss is expressed in thousandths of an inch for
each foot of pipe length. For a description of the various types of
tubing used in hydronic heating systems, see the appropriate sections of Chapter 8 (“Pipes, Pipe Fittings, and Piping Details”) in
Volume 2.
Most of the fittings used in hydronic radiant heating systems are
typical plumbing fittings. They include couplings (standard, slip,
and reducing couplings), elbows (both 45° and 90° elbows), male
and female adapters, unions, and tees (full size and reducing tees)
(see Figure 1-5).
Three special fittings used in hydronic radiant heating systems are
the brass adapters, the brass couplings, and the repair couplings. A
brass adapter is a fitting used to join the end of a length of 3⁄4-inch
diameter copper tubing to the end of a length of plastic polyethylene
tubing. A brass coupling, on the other hand, is a fitting used to join
two pieces of plastic heat exchanger tubing. A repair coupling is a
brass fitting enclosed in clear vinyl protective sheath to prevent concrete from corroding the metal fitting. The fitting is strengthened by
double-clamping it with stainless steel hose clamps.
A decoiler bending device or jig should be used to bend metal
tubing into the desired coil pattern. Only soft copper tubing can be
easily bent by hand. It is recommended that a tube bender of this
type be made for each of the different center-to-center spacing
needed for the various panel coils in the installation.
Soft copper tubing is commonly available in coil lengths of 40
feet, 60 feet, and 100 feet. When the tubing is uncoiled, it should be
straightened in the trough of a straightener jig. For convenience of
handling, the straightener should not be more than 10 feet long.
Note
Most copper tubing leaks will occur at bends or U-turns in the floor
loops.These leaks are caused by water or fluids under high pressure
flowing through the weakened sections of tubing. The weakened
metal is commonly caused by improper bending techniques.
Whenever possible, continuous lengths of tubing should be used
with as few fitting connections as possible. Coils of 60 feet or 100 feet
10 Chapter 1
UNION
T-FITTING
90° ELBOW
FEMALE ADAPTER
MALE ADAPTER
REDUCER
3⁄ "
4
1⁄ "
2
RIGID PIPE
FEMALE ADAPTER
RIGID PIPE
END CAP
MALE ADAPTER
BRANCH FITTING
90° ELBOW
Figure 1-5
COPPER
T-FITTING
45° ELBOW
Some examples of copper tubing fittings.
are best for this purpose and are generally preferred for floor panels. The spacing between the tubing should be uniform and
restricted to 12 inches or less. Use soldered joints to make connections between sections of tubing or pipe.
Radiant Heating 11
Cross-Linked Polyethylene (PEX) Tubing
Cross-linked polyethylene (PEX) tubing is commonly used indoors in
hydronic radiant heating panels or outdoors embedded beneath the
surface of driveways, sidewalks, and patios to melt snow and ice. It
is made of a high-density polyethylene plastic that has been subjected
to a cross-linking process (see Figures 1-6, 1-7, and 1-8). It is flexible, durable, and easy to install. There are two types of PEX tubing:
• Oxygen barrier tubing
• Nonbarrier tubing
EVOH OXYGEN BARRIER
CROSS-LINKED
POLYETHYLENE
ADHESIVE LAYER
Radiant
Figure 1-6
PEX
PEX tubing. (Courtesy Watts Radiant, Inc.)
Oxygen barrier tubing (BPEX) is treated with an oxygen barrier
coating to prevent oxygen from passing through the tubing wall
and contaminating the water in the system. It is designed specifically to prevent corrosion to any ferrous fittings or valves in the
piping system. BPEX tubing is recommended for use in a hydronic
radiant heating system.
Nonbarrier tubing should be used in a hydronic radiant heating
system only if it can be isolated from the ferrous components by a
corrosion-resistant heat exchanger, or if only corrosion-resistant
system components (boiler, valves, and fittings) are used.
PEX tubing is easy to install. Its flexibility allows the installer to
bend it around obstructions and into narrow spaces. A rigid plastic
cutter tool, or a copper tubing cutter equipped with a plastic cutting wheel, should be used to cut and install PEX tubing. Both tools
produce a square cut without burrs.
PEX tubing can be returned to its original shape after accidental
crimping or kinking by heating it to about 250–275°F. This attribute
of PEX tubing makes it possible to perform field repairs without
removing the damaged tubing section. This is not the case with polybutylene tubing, which is not cross-linked. Synthetic rubber tubing
12
MANUFACTURER
TRADE NAME
TUBING TYPE
TUBE SIZE
PRESSURE RATINGS
THIRD-PARTY
CERTIFICATION
VANGUARD VANEX® PEX PORTABLE TUBING 1 ⁄2" (CTS-OD) 100 PSI @ 180F / 160 PSI @ 73F [ NSF-pw CL-R/CL-TD
ASTM F876 / F877 / F2023 ]
CAN B 137.5
L23707 ICBO ES ER-5287 HUD MR 1276 SDR9 .070 DATE CODE
ASTM
SPECIFICATION
Figure 1-7
PEX tubing markings. (Courtesy Vanguard Piping Systems, Inc.)
MANUFACTURER'S
STANDARD
DATE CODE
DIMENSION RATIO
Radiant Heating 13
1
2
3
Crimping Fittings
1. Expand the end of the PEX tubing with
the expansion tool provided by the
PEX tube manufacturer.
2. Insert the brass fitting into the end of
the expanded PEX tube.
3. Use the expansion tool to pull the brass
sleeve back over the PEX tube and
fitting for a tight connection.
FITTING
SLEEVE
1
2
3
Compression Fitting
1. Slide the locking nut and split compression ring up the tubing.
2. Insert the tubing onto the compression
fitting.
3. Tighten the nut onto the compression
fitting snugly.
4. Re-tighten the fittings after the heat has
been turned on and the hot water has
circulated through the tubing.
FITTING
RING
NUT
Figure 1-8
PEX tubing fittings.
(Courtesy Watts Radiant, Inc.)
14 Chapter 1
is also not cross-linked, but its material composition and its flexibility
make it very resistant to crimping or kinking damage.
Manifolds
A manifold is a device used to connect multiple tubing lines to a single supply or return line in a hydronic radiant floor heating system
(see Figures 1-9 and 1-10). Each heating system has at least two
ELECTRIC
ACTUATOR WITHOUT
END SWITCH
MANUAL VALVE
OPERATOR (INCL. W/
VALVED MANIFOLDS)
ELECTRIC
ACTUATOR
WITH END
SWITCH
Flow indicators (when used)
require flow indicator
manifold, item 3.
RETURN MANIFOLD
WITH FLOW
INDICATOR VALVES
MANIFOLD WITH
INTEGRAL
VALVES
BALL VALVES AND PIPING
BY OTHERS
RETURN
FLOW
THREADED 1" BSP
FLOW
FLOW
FLOW
MANIFOLD WITHOUT
VALVES (USE AS
RETURN OR SUPPLY)
FLOW
THREADED 1" BSP
TUBING CONNECTIONS
3 ⁄ " EURO CONICAL
4
BALL VALVES AND PIPING
BY OTHERS
SUPPLY
FLOW
THREADED 1" BSP
FLOW
FLOW
FLOW
OPTIONAL TAKEOFF CAPS TO
CAP OFF UNUSED TAKEOFFS
FLOW
THREADED 1" BSP
TUBING CONNECTIONS
3 ⁄ " EURO CONICAL
4
Manifolds with integral valves should be used as return manifolds unless flow indicators are desired. If both flow
indication and electric valve actuators are needed, use manifold with flow indicator valves on their turn and
manifold with integral valves on the supply. Apply any desired combination of 2-wire and 4-wire electric actuators.
Figure 1-9
Weil-McLain hydronic radiant heating manifold.
(Courtesy Weil-McLain)
1
2
3
4
RETURN
3
RETURN
3
RETURN
2
RETURN
1
SUPPLY
2
SUPPLY
1
SUPPLY
1
SUPPLY
1
RETURN: FLOW INDICATORS
SUPPLY: ELECTRIC VALVES
RETURN: FLOW INDICATORS
SUPPLY: NO VALVES
RETURN: ELECTRIC VALVES
SUPPLY: NO VALVES
RETURN: NO VALVES
SUPPLY: NO VALVES
This combination allows
independent zone control
and easy balancing.
This combination provides
easy balancing, but does
not provide independent
zone control.
This combination provides
independent zone control.
Balancing will be more difficult
than combination 1 or 2.
This combination provides
no balancing means. Use
ball valves in tubing circuits
if balancing is needed.
Figure 1-10
Manifold combinations. (Courtesy Weil-McLain)
15
16 Chapter 1
types of manifolds: a supply manifold and a return manifold. A supply manifold receives water from the heating appliance (that is, the
boiler, water heater, or heat pump) through a single supply pipe and
then distributes it through a number of different tubing lines to the
room or space being heated (see Figure 1-11). A return manifold
provides the opposite function. It receives the return water from the
room or space through as many tubing lines and sends it back to the
boiler by a single return pipe. A supply manifold and a return manifold are sometimes referred to jointly as a manifold station.
Figure 1-11
Typical manifold location.
Preassembled manifolds are available from manufacturers for
installation in most types of heating systems. Customized manifolds
can also be ordered, but they are more expensive than the standard,
preassembled types.
A supply manifold, when operating in conjunction with zone
valves, can be used to control the hot water flow to the distribution
lines in the radiant heating system. The zone valves, which are usually ball valves, can be manually adjusted or automatically opened
Radiant Heating 17
and closed with a zone valve actuator. Some zone valves are designed
as fully open or fully closed valves. Others are operated by a modulating actuator that can adjust the opening to the heat required by the
zoned space.
A supply manifold with zoning capabilities is sometimes called a
zone manifold or distribution manifold. In addition to zone valves,
these manifolds also can be ordered to include supply and return
water sensors, the circulator, and a control panel with indoor and
outdoor sensors.
Depending on the heating system requirements, a manifold may
also include inline thermometers or a temperature gauge to measure
the temperature of the water flowing through the tubing; check
valves or isolation valves to isolate the manifold so that it can be serviced or repaired; drain valves to remove water from the manifold;
an air vent to purge air from the system; and pump flanges (for the
circulator) plus all the required plumbing connections and hardware.
Manifold balancing valves regulate each zone (loop) to ensure
efficient heat distribution and eliminate those annoying cold and
hot spots on the floor. These valves can be adjusted to deliver the
design flow rate of water in gallons per minute (gpm). Some manifolds are designed to electronically read the flow and temperature
of the water in individual tubing loops. This function results in
rapid and accurate data feedback for balancing. It also makes troubleshooting problems easier.
Manifolds are available for mounting on walls or installation in
concrete slabs. The latter type, sometimes called a slab manifold, is
made of copper and is available with up to six supply and six return
loop connections. Slab manifolds also should be equipped with a
pressure-testing feature so that they can be tested for leaks before
the slab is poured.
Slab manifolds are installed with a box or form that shields the
device from the concrete when it is poured. All connections remain
below the level of the floor except for the tops of the supply and
return tubing.
Valves and Related Control Devices
Valves and similar control devices are used for a variety of different
purposes in a hydronic radiant floor heating system. Some are used
as high-limit controls to prevent excessively hot water from flowing
through the floor loops. Some are used to isolate system components, such as the circulating pump, so that it can be serviced or
removed without having to shut down the entire system. Others are
used to regulate the pressure or temperature of the water, to reduce
18 Chapter 1
the pressure of the water before it enters the boiler, or to regulate
the flow of water.
Many of the different types of valves and control devices used in
hydraulic radiant floor heating systems are listed in the sidebar. A brief
description of the more commonly used ones is provided in this section. For a fuller, more detailed description of their operation, maintenance, service, and repair, read the appropriate sections of Chapter 9
(“Valves and Valve Installation”) of Volume 2. Not all the valves listed
in the sidebar or the ones described in this chapter will necessarily be
used in the same heating system. The valves chosen will fit the requirements of a specific application (see Figures 1-12, 1-13, and 1-14).
Hydraulic Heating System Valves and Related Control Devices
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Air vent
Aquastat
Backflow preventers
Ball valves
Boiler drain valve
Check valves
Feed water pressure regulator
Flow control valve
Gate valve
Globe valve
Isolation valve
Mixing valve
Motorized zone valve
Pressure-reducing valve
Pressure relief valve
Purge and balancing valves
Solenoid valve
Air Vent
An air vent is a device used to manually or automatically expel air
from a closed hydronic heating system. An automatic air vent valve
provides automatic and continuous venting of air from the system.
The function of both types is to prevent air from collecting in the
piping loops.
Radiant Heating 19
7
9
16
17
18
7
19
14
20
22
1
13
15
6
2
4
10
12
11
11
15
8
4a
15
5
21
3
1. Air scoop.
2. Backflow preventer.
3. Boiler drain valve.
4. Boiler fill valve.
4a. Combination backflow preventer
and boiler fill valve.
5. Bronze check valve.
6. Expansion tank.
7. Flow check valves.
8. Flow control valve.
9. Gate or globe valve.
10. Mixing valve.
15
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
Purge valve.
Pressure relief valve.
Hot water safety relief valve.
Test plug.
Ball valve.
Automatic float vent valve.
Float vent.
Water pressure reducing valve.
Service check valve.
Combination temperature
and pressure gauge.
21. Boiler energy saver.
Typical locations of valves and related control
devices in a hydronic heating system. (Courtesy Watts Regulator Co.)
Figure 1-12
Aquastat
An aquastat is a control device consisting of a sensing bulb, a
diaphragm, and a switch (see Figure 1-14). As the temperature surrounding the sensing bulb increases, the gas inside the bulb
expands and flows into the diaphragm. This action causes the
diaphragm to expand and activate the switch controlling the connected device. When temperatures exceed the high-limit setting on
20
TO
BASEBOARD
FLOW CONTROL
VALVE
THERMOMETER
3-WAY
VALVE
27" MIN
THERMOSTAT
M
H
C
THERMOMETER
COMPRESSION
TANK
FLOW CONTROL
VALVE
RADIANT
ZONE
M
27" MIN
H
C
RADIANT
ZONE
3-WAY MIXING
THERMOSTAT
VALVE
FILL
VALVE
RELIEF
VALVE
BOILER
Piping diagram of a zoned radiant heating system supplying hot water to both
floor panels and baseboards.
Figure 1-13
Radiant Heating 21
COMPRESSION
TANK
SHUT OFF
VALVE
THERMOMETER
FILL
VALVE
SHUT OFF
VALVE
HOT
RELIEF
VALVE
SHUT OFF VALVE
27" MIN
M
H
BOILER
TEMPERED
SUPPLY TO PANEL
C
MIXING VALVE
RETURN
AQUASTAT
SHUT OFF VALVE
DRAIN
SHUT OFF
VALVE
CIRCULATING
PUMP
FROM
PANEL
Note: Circulating pumps, illustrated in the above applications, circulate tempered water through the
system. The aquastat shuts the circulating pump off if the tempered water exceeds the temperature
set point, which is normally ± 5°F (± 2°C) of the tempering valve discharge.
Piping diagram of a radiant heating system with
circulator controlled by aquastat.
Figure 1-14
the aquastat, it shuts off the circulator or circulators until the
problem can be corrected.
The switching contacts of some aquastats can be manually adjusted
for temperature settings. In other systems, the switching contacts of an
aquastat may be preset at a predetermined temperature setting.
Backflow Preventer
A backflow preventer is a valve used to prevent the mixing of boiler
hot water with domestic (potable) water (see Figure 1-15). Most
systems use an inline backflow preventer. It must be installed with
the arrow on the side of the valve facing the direction of water flow.
Sometimes a backflow preventer and boiler fill valve are combined
in the same unit.
Ball Valve, Gate, and Globe Valves
A ball valve can be used to isolate components or lines, or to regulate flow. A gate valve is often used to isolate components for service, repair, or replacement. They are not designed to regulate the
flow of water. A globe valve is used to regulate the flow of water in
a radiant heating system.
Note
Use a fully closing ball or gate valve on the supply and return line
so that the manifold can be isolated and serviced without interrupting the pressure in the rest of the system.
22 Chapter 1
FAST FILL LEVER AND
CAP ASSEMBLY
SEAT AND DISC ASSEMBLY
DIAPHRAGM
RELIEF VALVE
BACKFLOW
PREVENTER
TO RADIATION
HOT WATER
BOILER
COLD WATER
TO
EXPANSION TANK
DRAIN
SHUT OFF
VALVE
Feed water pressure
regulator installed in
the cold water return
line. Note: horizontal
installation required.
RETURN
Figure 1-15
Feed water pressure regulator. (Courtesy Watts Regulator Co.)
Boiler Drain Valve
A boiler drain valve is a quarter-turn ball valve used to drain water
from a boiler. As shown in Figure 1-12, it is located near the bottom of the boiler close to a floor drain.
Check Valves
A check valve (also called a shutoff valve) is used to ensure that
water is flowing in the correct direction by providing positive shutoff to the flow. Typical locations of check (shutoff) valves are
shown in Figures 1-12, 1-13, and 1-14.
A swing check valve is designed to prevent the backflow of water.
A flow-control valve is a check valve used to prevent circulation of
the hot water through the heating system when the thermostat has
not called for circulation. The flow-control check valve must be used
when the radiant panels are located below the boiler.
Note
Flow-control valves should not be used when the radiant floor
panel is below the level of the boiler.
Another type of check valve used in a radiant floor heating system is the isolation valve (also sometimes called a service valve).
Radiant Heating 23
The isolation valve is used to isolate a hydronic system component
for servicing and/or removal so that it can be repaired or replaced.
Isolating the component eliminates the need to drain and refill the
system with water.
Caution
Reduce the system pressure to a safe level before attempting to
remove system components.
Caution
An isolation valve is not designed to isolate a pressure (safety)
relief valve or other safety or flow-sensitive components.
Feed Water Pressure Regulators
A feed water pressure regulator is used to fill both the boiler and
system piping (including the floor panel loops) with water. A typical location of a feed water pressure regulator in the cold-water
return line is illustrated in Figure 1-15. These valves also maintain
the water pressure at the required level in the system at all times. If
a leak should occur in the system, the feed water pressure regulator
is designed to provide the required amount of makeup water. Using
the feed water pressure regulator speeds filling and purging of air
from the piping during the initial fill procedure.
Disconnect Switch
Two principal types of on-off switches are used to open or close an
electrical circuit: the disconnect switch and the thermostat (see
Thermostat in this section).
The disconnect switch is a manually operated on-off switch used
to shut down the entire heating system when a problem is beginning to develop. When the switch is in the off position, the circuit
opens and the electricity operating the boiler, heat pump, or water
heater is shut off. When it is in the on position, the circuit closes
(that is, completes itself) and electricity bypasses the boiler, heat
pump, or space-heating water heater.
Inline Thermometer
An inline thermometer is a device that is used to monitor the water
temperature as it circulates through the system. Two inline thermometers are installed in the heating system. One monitors the temperature
of the water as it enters the supply line. The other monitors the temperature of the water as it leaves. The difference between these two
measurements provides clues to the operating efficiency of the system.
Mixing Valve
A thermostatic mixing valve is used in a radiant heating system to
recirculate a variable portion of the return water and at the same
24 Chapter 1
time add a sufficient quantity of hot boiler water to maintain the
required water temperature in the loops. These valves are also
called thermostatic mixing valves, water blending valves, water
blenders, water tempering valves, or tempering valves. Typical
locations of mixing valves are shown in Figures 1-12, 1-13,
and 1-14.
Both manual and automatic modulating mixing valves are used
in hydronic heating systems. The manual mixing valve is often used
to control the water temperature in a high-mass concrete slab. It is
not as accurate as an automatic valve (for example, a thermostatic
valve), but the high-mass concrete slab stores it and releases it
slowly over a long period of time, making exact temperature control unnecessary.
The three-way and four-way thermostatic mixing valves provide
automatic control of the mixed water temperatures. The valve
varies the flow of hot water between its hot port and its cold port
so that it can deliver through its mixed port a steady flow of water
at a constant temperature.
Mixing valves are often used with high-temperature boilers designed
to provide water at temperatures of more than 160F.
Motorized Zone Valve
A motorized zone valve is used to control the flow of water
through a single zone (see Figure 1-16). It consists of a valve body
combined with an electric actuator. A radiant panel heating system will often use a number of motorized zoning valves to maintain a uniform temperature throughout the rooms and spaces in
the structure. As shown in Figure 1-17, a motorized zone valve is
used to control each zone. Motorized zone valves are controlled
by an aquastat, individual thermostats at each loop, or a room
thermostat.
Honeywell V4043
motorized zone valve.
Figure 1-16
(Courtesy Honeywell, Inc.)
Radiant Heating 25
ZONE THERMOSTATS
ZONE 1
ZONE 2
ZONE 3
ZONE 4
PANEL
PANEL
PANEL
PANEL
MOTORIZED
VALVE
MOTORIZED
VALVE
REMOTE
BULB
OUTDOOR
BULB
MOTORIZED
VALVE
3-WAY
VALVE
MOTORIZED
VALVE
FOR
ADDITIONAL
ZONES
SAFETY
CONTROL
TEMPERATURE
CONTROL
CONTROL
PANEL
OUTDOOR
CONTROLLER
BOILER
CIRCULATOR
POWER
BURNER
A typical control system for a multiple-zone radiant
heating system. (Courtesy Honeywell Tradeline)
Figure 1-17
Note
A zone valve simplifies the piping required for a hydronic heating system because it eliminates the need for a flow check valve and relays.
Pressure-Reducing Valve
A pressure-reducing valve is designed to reduce the pressure of the
water entering the system and to maintain the pressure at a specific
minimum setting (usually about 12 lbs). A typical location of a pressure relief valve is shown in Figure 1-12.
Pressure Relief Valve
A pressure relief valve (also sometimes called a safety relief valve) is
used to prevent excessive and dangerous pressure from entering the
system. It is located on top of the boiler or very close to it (see
Figures 1-12, 1-13, and 1-14).
Purge and Balancing Valves
Purge and balancing valves are used on either the supply or return
side of the manifold in systems where multiple manifolds are served
by only one circulator. Among its varied functions is (1) to allow
adjustments of proper water flow for each loop; (2) to function as a
shutoff valve and a drain valve for each zone or loop; (3) to control
(balance) water flow through the circulation loop; and (4) to provide a means of expelling air from heating zones during initial loop
fill (valve is located on the boiler return piping). If the heating system contains individual loops of unequal length, each should be
equipped with a balancing valve.
26 Chapter 1
Circulator
The circulator (circulating pump) provides the motive force to circulate the water through the radiant heating system. Sometimes a
variable-speed pump is used to maintain a supply water temperature between 90°F and 150°F.
In some zoned systems, a circulator operates in conjunction with a
zone thermostat instead of a zoning valve to maintain a uniform
floor temperature in each room or space of the structure. The zone
thermostat controls the temperature in the zone by turning the circulator on and off. The size of the circulating pump selected for a radiant panel heating system will depend on the pressure drop in the
system and the rate at which water must circulate. The circulation
rate of the water is determined by the heating load and the design
temperature drop of the system and is expressed in gallons per
minute (gpm). This can be calculated by using the following formula:
gpm Total Heating Load
T 60 8
The total heating load is calculated for the structure and is
expressed in Btu per hour. A value of 20°F is generally used for the
design temperature drop (T) in most hot-water radiant panel heating systems. The other two values in the formula are the minutes
per hour (60) and the weight (in pounds) of a gallon of water (8).
By way of example, the rate of water circulation for a structure
with a total heating load of 30,000 Btu per hour may be calculated
as follows:
30,000 Btu/hr
20 60 8
30,000
3.13
9600
gpm Expansion Tank
An expansion tank (also called a compression tank) is required for
use in all closed hydronic radiant heating systems (see Figure 1-18).
Water and other fluids expand when they are heated. The expansion tank provides space to store the increased volume to prevent
stress on the system.
Air Separator
An air separator (also called an air scoop or an air eliminator) is a
device used in a closed radiant heating system to capture and remove
air trapped in the water (see Figure 1-18). Some of these devices are
Radiant Heating 27
Air separator
and expansion tank.
Figure 1-18
FLOAT VENT
SERVICE CHECK VALVE
AIR SCOOP
SERVICE CHECK VALVE
EXPANSION TANK
equipped with tappings for the installation of an expansion tank
and air vent.
Heat Exchanger
A heat exchanger is a device used in some radiant heating systems
to separate dissimilar fluids such as water mixed with antifreeze (in
snow- and ice-melting applications) and water (for radiant floor
heating tubing and domestic hot water). Its function is to allow the
transfer of heat between the fluids without allowing them to mix
and thereby contaminate one another.
Automatic Controls
While any thermostatic method of control will function with a radiant floor heating system, the most desirable method is one based on
continuously circulating hot water. The temperature of the water
should be automatically adjusted to meet outdoor conditions, but
the circulation itself is controlled by interior limiting thermostats
instead of the simple off-on method of circulating hot water at a
fixed temperature (see Figure 1-19).
Some radiant floor heating systems are designed with a thermostat for each zone (see Figure 1-17). A more common method is to
group several rooms or spaces together and control them by a single thermostat. In this approach, the kitchen and dining room may
be included in one thermostat-controlled loop, the bedrooms in
another, the bathrooms in still another, and so on.
28 Chapter 1
Honeywell T87F thermostat for zone control in
hydronic and radiant heating systems.
COVER RING
60
MOLDED
LEVELING
POST
70
50
80
WALLPLATE
SHOWN
HONEYWELL
80
50
60
70
NO. 4 X 1 INCH
SHEET METAL SCREWS (2)
1
L1 (HOT) COMBINATION
FAN AND LIMIT
CONTROL
R Y
W
FAN
MOTOR
L2
BURNER
MOTOR
R W
T
T
R8184G
2
F
137421A
WALLPLATE
LIMIT FAN
1
L1
(HOT)
L2
3
GAS VALVE
WHITE
ORANGE
F
CAD
CELL
COMBINATION
FAN AND LIMIT
CONTROL
OIL VALVE
IGNITION
THERMOSTAT
Y
THERMOSTAT CABLE
ENTRANCE HOLES
ADD T87F AS
SHOWN ON OUTLET
BOX MOUNTING
BLACK
1
TH
TR
TH
TR
TRANSFORMER
FAN
MOTOR
Power supply, provide disconnect means and
overload protection as required.
T87F used for 2-wire, spst control of heating only in a
typical gas system. (Courtesy Honeywell, Inc.)
1 Power supply, provide disconnect means and
overload protection as required.
2 R8184 protectorelay oil primary contains
internal transformer.
3 Connect oil valve, if applicable.
T87F used for 2-wire, spst control of heating only in a
typical oil system. Low voltage power for the control
circuit is supplied by a transformer in the oil primary
control. (Courtesy Honeywell, Inc.)
Examples of thermostat controls used in hydronic radiant
heating systems.
Figure 1-19
Many HVAC control manufacturers are now producing control
consoles such as the one shown in Figure 1-20.
Designing a Hydronic Radiant Floor Heating System
Design of a hydronic radiant floor heating system should be
attempted only by those with the qualifications, training, and experience to do it right. It is very important that the design of a radiant
panel heating system be correct at the outset. The fact that the coils
or cables are permanently embedded in concrete, or located beneath
Radiant Heating 29
ROOM
THERMOSTAT
REMOTE
BULB
PANEL
CONTROL
PANEL
POWER
SAFETY
CONTROL
TEMPERATURE
CONTROL
AUXILIARY
SWITCH
3-WAY
VALVE
VALVE
MOTOR
BOILER
CIRCULATOR
BURNER
ROOM THERMOSTAT
(OPTIONAL)
OUTDOOR
BULB
REMOTE
BULB
PANEL
CONTROL
PANEL
OUTDOOR
CONTROLLER
POWER
SAFETY
CONTROL
BOILER
CIRCULATOR
BURNER
Figure 1-19
(Continued)
other materials, makes corrections or adjustments very difficult and
expensive.
Many manufacturers of radiant panel heating system equipment
have devised simplified and dependable methods for designing this
type of heating system. In most cases, the manufacturer will provide
any available materials to assist in calculating the requirements of a
particular radiant floor heating system. Various design manuals, manufacturer-specific installation guides, and software tools are available
for use in designing and sizing radiant floor heating systems.
30 Chapter 1
MIX DEMAND
BOILER DEMAND
DHW DEMAND
SETPOINT DEMAND
WWSD
MINIMUM
MAXIMUM
VIEW
°F
12
DHW
%
1
SETBACK
RESET RATIO
NONE
CHARACTERIZED
HEATING CURVE
TEST
OFF NOT TESTING
RED TESTING
RED TESTING PAUSED
For maximum heat,
press and hold test
button for 3 seconds.
MENU
ITEM
Made in Canada by
tekmar Control Systems Ltd.
UNIVERSAL RESET CONTROL 363
MIXING, BOILER & DHW
1
2
3
4
5
MIX COMBOILSETP/
DEMANDDEMDEMDHW
6
7
8
9 10 11
POWER BOIL DHW MIX
N L P1 PMP / VIV P2
C
US
LR 58223
POWER
120 V ±10% 50/60 HZ 2000 VA
RELAYS
240 V (AC) 7.5 A 1/3 HP, PILOT DUTY 240 VA
VAR. PUMP 240 V (AC) 2.4 A 1/6 HP, FUSE T2.5 A 250 V
DEMANDS 20 TO 260 V (AC) 2 VA
SIGNAL WIRING MUST BE RATED AT LEAST 300 V.
12 13 14 15 16
BOILER PWR OPN CLS/
MIX
VAR
DO NOT APPLY POWER
17 18 19 20 21 22 23 24 25 26
COM 10K TN1/ COM 10K UNOCOM MIXBOILOUT
2 TN2
1 SW
INPUT
OUTDOOR
SENSOR INCLUDED
INPUT
MIX DEMAND
SIGNAL
INPUT
BOILER
DEMAND
SIGNAL
INPUT
UNIVERSAL
SENSOR INCLUDED
INPUT
SETPOINT OR
DHW
DEMAND
SIGNAL
INPUT
UNIVERSAL
SENSOR INCLUDED
INPUT
Tekmar
TIMER
INPUT
120 V (AC)
POWER
SUPPLY
OR
OUTPUT
BOILER SYSTEM
PUMP
INPUT (MIX)
Tekmar INDOOR
SENSOR
M
M
OUTPUT
DHW PUMP OR
DHW VALVE
OR
OR
OUTPUT
MIXED SYSTEM
PUMP
OUTPUT
BOILER
OUTPUT
OUTPUT
MIXING VALVE &
VAR. SPEED
DRIVEN PUMP ACTUATING MOTOR
INPUT (MIX)
Tekmar SLAB
SENSOR
INPUT
UNIVERSAL
SENSOR
(OPTIONAL)
INPUT (MIX)
INPUT
ROOM
REMOTE
TEMPERATURE
DISPLAY
UNIT (RTU)
MODULE (RDM)
OR
INPUT
(BOIL
OR MIX)
Tekmar ZONE
CONTROL
Tekmar Universal reset Control 363. (Courtesy Tekmar Control Systems, Inc.)
The control panel operates in conjunction with both indoor and outdoor sensors to control space and
heating temperatures (multiple zones or single-zone), domestic hot water supply, slab heat, and snow–
melting applications. The control panel uses an outdoor reset to adjust the boiler and mixed loop water
temperatures delivered to the heating system. A variable speed driven wet-rotor circulator or a floating
action driven mixing valve is used as a mixing device.
Figure 1-19
(Continued)
A radiant floor heating system in which there is a constant (uninterrupted) circulation of water is the preferred design. The benefits
of constant water circulation through the circuits are as follows:
• It maintains an even floor temperature.
• It prevents hot spots from forming when there is no call for
heat.
• It prevents air from entering the system.
• It reduces the risk of the water freezing in systems where
antifreeze cannot be used (that is, systems in which the water
Radiant Heating 31
RESET
PROCESSOR ACTIVE
DOMESTIC HOT WATER
ZONE 1 CONTROL
ZONE 2 CONTROL
TEMPERATURE
SETPOINT ACTUAL
500
100
50
WATTS
REGULATOR
BOILER ENERGY SAVER
BES BOARD
TERMINAL BLOCK
T
T
Z2
T
T
Z1
BES BOARD
TERMINAL BLOCK
NC
RY
LIMIT
CONTROLS
ZONE 2
ZONE 1
THERMOSTAT THERMOSTAT
Figure 1-20
Watts Boiler Energy Saver and wiring diagrams.
(Courtesy Watts Regulator Company)
heater heats both the water for space heating and the water
for cooking and bathing purposes).
The flow of water in some radiant heating systems is controlled
by the circulator (pump). When the room thermostat calls for heat,
the pump starts and rapidly circulates heated water through the
radiant panels until the heat requirement is satisfied. The pump is
then shut off by the thermostat. In some systems, a flow-control
valve is forced open by the flow of water through the pipes as long
as the pump is running, permitting free circulation of heated water
through the system. When the pump stops, the control valve closes,
preventing circulation by gravity, which might cause overheating.
The principal disadvantage of a system with this off-on control is that
it results in temperature lag and causes the panels to intermittently
heat and cool.
The continuous circulation of water through radiant heating
panels is made possible by means of an outdoor-indoor control.
32 Chapter 1
In this arrangement, hot water from the boiler is admitted to the system in modulated quantities when the temperature of the circulating
water drops below the heat requirement of the panels. This modulated bleeding of water into the panel is accomplished through a
bypass valve. When no additional heat is required, the valve is closed.
When more heat is required, the valve is gradually opened by the
combined action of the outdoor temperature bulb and a temperature
bulb in the supply main. This system gives control by the method of
varying the temperature of the water.
Air Venting Requirements
A common defect encountered in hot-water system design is improper
venting. The flow of water should be automatically kept free of air
binding throughout the system. Air in the pipes or pipe coils almost
always results in a reduction of heat.
A practical method of venting is shown in Figure 1-21. The key to
this method is the use of automatic air vents. Each air vent should be
located in an area readily accessible for repair. The air trap test cock
should be placed where it can be easily operated. Both the air trap and
the air trap test cock must be located where they are not subject to
freeze-up, as both are noncirculating except during venting operation
(automatic or manual).
Sizing Calculations
The successful operation of any hot-water heating system requires
the incorporation of design provisions that ensure an even and balanced flow of water through the pipes or coils of the installation.
The procedure for designing a hydronic radiant floor heating
system may be outlined as follows:
1. Determine the total rate of heat loss per room in the structure.
2. Determine the available area for panels (loops) in each room.
3. Determine the output required by each panel to replace the
heat loss.
4. Determine the required surface temperature for each panel.
5. Determine the required heat input to the panel (should equal
heat output).
6. Determine the most efficient and economical means of sup-
plying heat to the panel.
7. Install adequate insulation on the reverse side and edges of the
panel to prevent undesirable heat loss.
8. Install the panels opposite room areas where the greater heat
loss occurs.
Radiant Heating 33
A
B
M
M
H
P
P
R
K
H
P
C
H
Y
G
M
K
F
G
D
F
E
G
N
G
Symbols:
Indicates downward grade of tubing. A automatic air trap at top of main flow riser;
B automatic air trap at top of main return riser; C automatic air trap at top of special loop K required by
possible obstruction and when small size vent by-pass is also not permissible at Y ; D heater; E pump;
F check valve; G drain valve; H heating panel coil; K loop in main flow (See C ); M trap shut-off valve
(for repair); N expansion tank; P manual test cock (air trap); R open and automatic vent tube
(1⁄2 in. copper).
Note—By reversing direction of grade at H air trap B can be eliminated. Same riser vent layout should
be used for up-feed systems. Test cocks P should be located accessible for occasional use. Open ends
of vent tubes R (normally dry) can discharge visibly into nearest drain or sink.
Figure 1-21
An automatic vent radiant heating system.
Note
Always keep floor temperatures at or slightly below recommended
high limits.
Radiant Floor Construction Details
Radiant floor construction can be divided into two broad categories based on the installation method used: (1) wet installation
and (2) dry installation. The wet installation method involves
completely embedding the tubing in a concrete slab or covering it with
a thin layer of concrete (commonly a gypsum-based lightweight pour).
34 Chapter 1
The dry installation method is so-called because the tubing is installed
without embedding it in concrete.
The examples of radiant floor construction described in this section represent the most commonly used forms. They are offered
here only as examples, not as planning guides for contractors. The
actual construction plans will depend on the design of the hydronic
radiant floor heating system, the impact of local building codes and
regulations, and other variables.
Slab-on-grade construction
In slab-on-grade construction, the tubing is attached to a wire mesh
or special holding fixtures to keep it in place until the concrete is
poured around it. The tubing loops are embedded in the middle of
the concrete slab and are located approximately 2 inches below the
slab surface (see Figure 1-22). A brief summary of the steps involved
in slab-on-grade construction is as follows:
1. Compact the soil base to prevent uneven settling of the slab.
2. Cover the compacted soil with a lapped 6-mil vapor barrier.
3. Cover the vapor barrier with 2-inch-thick extruded polystyrene
4.
5.
6.
7.
8.
insulation.
Install rigid polystyrene insulation vertically on the inside surface of the exterior foundation walls to prevent edgewise
(horizontal) heat loss.
Lay concrete reinforcing mesh over the insulation.
Position the tubing on top of the reinforcement mesh according
to the tubing layout plan.
Tie the tubing to the reinforcement mesh with tie straps or wire.
Cover the tubing with a minimum of 9 inches of concrete.
Thin-Slab Construction
In this type of wet installation, a layer of lightweight concrete or
lightweight gypsum is poured over the tubing to form a thin slab
(see Figure 1-23). Thin-slab construction is used over a wood subfloor supported by wood framing.
A summary of the steps involved in forming a thin-slab floor
system using poured concrete to form the slab may be outlined as
follows:
1. Apply a lapped 6-mil polyethylene vapor barrier to the wood
subfloor.
2. Position the tubing on the subfloor according to the tubing
layout plan.
Radiant Heating 35
CONCRETE SLAB
EXTRUDED
POLYSTYRENE
INSULATION
TUBING
LOOP
VAPOR
BARRIER
TOP OF TUBE
LOCATED ABOUT 2"
BELOW TOP OF
SLAB SURFACE
COMPACTED SOIL
TUBE TIED TO WIRE
MESH BY PLASTIC OR
METAL WIRE
CONCRETE SLAB
6-MIL VAPOR BARRIER
LAPPED 12" ALONG ALL
EDGES
2" THICK EXTRUDED POLYSTYRENE INSULATION
Figure 1-22
Slab-on-grade construction.
3. Fasten the tubing to the wood subfloor with plastic clips or
metal staples.
4. Pour concrete over the tubing and subfloor.
5. Install batt insulation in the joist cavities beneath the subfloor.
If lightweight gypsum cement instead of concrete is used to
form the slab, pour the gypsum in two stages. The first pour
should be no higher than the tops of the tubes. When this first
layer dries, it will shrink slightly and pull back from the tubing. Apply a second layer of gypsum to completely cover the
first layer and the tops of the tubing.
Sandwich Floor Construction
Sandwich floor construction is available in a number of different
configurations (see Figure 1-24). This construction method involves
36 Chapter 1
STAPLE FASTENING
TUBING TO WOOD DECK
CONCRETE SLAB
WOOD DECK
BATT INSULATION
FOIL FACING
FLOOR
JOIST
Figure 1-23
AIR GAP BETWEEN
INSULATION AND
WOOD DECK
Thin-slab construction details.
locating the tubing between the subfloor and additional flooring layers. In some cases, aluminum plates are added for heat dispersion.
The two layers of a sandwich floor have wood sleepers installed
between them for adding the tubing and subsequent flooring layers.
These systems all contain less thermal mass than slab systems, and
some allow for more rapid temperature responsiveness.
Staple-Up Method
In the staple-up method, the tubing is located below the subfloor.
This method of installing tubing is very common in both new
construction and remodeling work. Its use is recommended when
retrofitting because it avoids the problem and expense of having
to remove the existing floor covering.
Note
The staple-up construction method will require drilling holes for
the tubing in some of the supporting joists.
The staple-up construction method illustrated in Figure 1-25 is
used without heat transfer plates. The tubing is fastened to the bottom of the subfloor in the joist cavities. Install either 31⁄2-inch batts
or 2-inch polystyrene rigid insulation in the joist cavities below the
tubing with a 11⁄2- to 4-inch air gap between the subfloor and the
insulation.
Radiant Heating 37
1"
31/2"
6"
3/ "
4
17/16"
3/ "
4
4"
Sandwich construction
over concrete slab with
tubing spaced 6 inches
on centers.
TUBING
CONCRETE SLAB
TUBING LOOP
SPACE
1'
6"
11/2"
3/ -INCH
4
THICK FACED
RIGID POLYSTYRENE
INSULATION BOARD.
3/ -INCH
4
PLYWOOD
Sandwich construction
over framing with tubing
spaced 6 inches on centers.
3/ "
4
11/ "
16
3/ "
4
AIR GAP
2 3/4"
7 5/8"
3 1/2"
3 1/2-Inch faced batt
insulation installed
between floor joists
with 2 3/4-inch air gap.
Figure 1-24
Examples of sandwich floor construction.
(Courtesy Watts Radiant, Inc.)
38 Chapter 1
31/2-INCH MINIMUM
BATT INSULATION
WITH FOIL FACING
SUBFLOOR
Figure 1-25
FOIL FACING
TOWARD BOTTOM
OF SUBFLOOR
TUBING
STAPLED TO
BOTTOM OF
SUBFLOOR
11/2-INCH
AIR GAP
3/ -INCH
4
SUBFLOOR
FOIL FACING
TOWARD
BOTTOM OF
SUBFLOOR
2-INCH POLYSTYRENE
RIGID BOARD INSULATION
WITH FOIL FACING
Staple-up method.
The heating efficiency of the staple-up construction method can
be greatly improved by adding preformed, grooved aluminum heat
transfer plates beneath the subfloor (see Figure 1-26). The plates
are stapled to the bottom of the subfloor in the joist cavities, and
the tubing is inserted in the preformed plate grooves. Insulation is
installed beneath the tubing with a 2- to 4-inch air space between
the top of the insulation and the bottom of the subfloor. The heat
from the tubing spreads horizontally across the plate surface and
then flows upward into the room or space above the floor. Without
these plates, a percentage of the heat from the tubing is lost because
it flows down into the spaces below the room being heated. To
compensate for the heat loss, the heating system must operate at
higher temperatures. This results in higher heating costs.
A variation of the staple-up construction method is to hang the
tubing several inches below the subfloor in the joist cavities.
Aluminum heat-transfer plates are fastened to the bottoms of the
floor joists leaving an air gap between the plates and the bottom of
the subfloor.
Radiant Heating 39
Tubing stapled to
bottom of subfloor.
Aluminum heat
transfer plate
stapled to joists.
Figure 1-26
SUBFLOOR
AIR GAP
Tubing supported in
grooves of preformed
aluminum heat
transfer plate stapled
to bottom of subfloor.
FLOOR
JOIST
Staple-up method with heat transfer plates.
Tubing Installed Above the Subfloor
Figure 1-27 illustrates a common dry installation method of
installing the tubing above the subfloor. It consists of wood sleepers
nailed to the top surface of the wood subfloor with the tubing
located in the spaces between the sleepers. Plywood is nailed to the
tops of the sleepers to support the floor covering material.
TUBING STAPLED
TO SUBFLOOR
SUBFLOOR
Figure 1-27
SLEEPER
MORTAR FILLER
(OPTIONAL)
FLOOR JOIST
Tubing installed above the subfloor between sleepers.
40 Chapter 1
Note
A loose, noninsulating masonry filler poured around the tubing
will increase the thermal mass of the floor. Do not use loose fill
insulation, such as perlite or vermiculite. These are insulating
materials that will interfere with the heat radiation from the tubing.
Masonry filler is not an insulating material.
An alternative method is to install heat-transfer plates between
the sleepers and use the plates to support (cradle) the tubing. In
both cases, a suitable insulation must be installed between the floor
joists (see Figure 1-28).
Still another method is to install factory-made, grooved wood
panels beneath the finished floor. The dimensions of the panels may
vary, depending on the manufacturer. The tubing is inserted in the
panel grooves and set flush with the panel surface.
Floor Coverings
Floor covering materials reduce the amount of heat radiation rising
into the room or space above the floor. The insulating properties of
floor coverings must be considered when designing a hydronic or
electric radiant floor heating system. Plush carpets and polyurethane
carpet pads should not be installed over a radiant floor heating
system. The same holds true for thick wood floors or multiple layers
of plywood subfloors. Both have a high thermal resistance.
SLEEPER
NAILED TO
SUBFLOOR
FLOOR COVERING
SUBFLOOR
FOIL FACED BATT
INSULATION
HEAT TRANSFER PLATES
STAPLED TO SLEEPERS
TUBING SUPPORTED BY
HEAT TRANSFER PLATE
Tubing installed above the subfloor between
sleepers with heat-transfer plates. (Courtesy Weil-McLain)
Figure 1-28
Radiant Heating 41
Carpets are commonly installed over a carpet pad. The combined carpet and cushion R-value (that is, its insulating value)
should not exceed a maximum of R-4.0. Use either a foam rubber
or waffle rubber pad. To reduce the resistance even further, consider eliminating the carpet pad.
Sheet final and tile floor coverings radiate the heat much faster
than carpet, thereby reducing the lag time between when the hot
water flows through the circuit and the heat is actually delivered to
the room or space above.
Coils and Coil Patterns
Hydronic radiant floor heating panels are available as prefabricated
units, or they can be constructed at the site. The principal coil patterns used in radiant floor heating systems are the following:
1. Coil pattern for uniform heat distribution.
2. Coil pattern for perimeter heat distribution along two walls.
3. Coil pattern for perimeter heat distribution along one wall.
Counterflow Spiral Tube Layout Pattern
The tube layout illustrated in Figure 1-29 provides the most even
and uniform heat distribution for a room in a radiant floor heating
system. It accomplishes this by running the supply and return lines
parallel to one another. As a result, an average temperature is created between the tubes.
Double Serpentine Layout Pattern
In some rooms, there will be a significant amount of heat loss
through two adjacent exterior walls. As shown in Figure 1-30,
the supply tubing runs along the perimeter of the walls where the
hot water can provide maximum heat transfer. It then turns
inward in a series of serpentine-like loops to the center of the
room (the area of lowest heat loss) before returning to the manifold.
Single Serpentine Layout Pattern
If a major heat loss occurs along a single exterior wall, the supply
tubing runs along the perimeter of that wall before returning in a
series of serpentine loops to the return manifold (see Figure 1-31).
In a well-designed hydronic radiant floor heating system, the linear travel from the heating unit and pump should be the same for
each of the panels (see Figure 1-32). This will result in the flow
through each panel being in natural balance.
42 Chapter 1
Figure 1-29
Counterflow spiral tube layout pattern.
Figure 1-30
Double serpentine layout pattern.
Radiant Heating 43
Figure 1-31
Single serpentine layout pattern.
P-1
P-3
P-2
P = PANEL COILS
MAIN FLOW
(FROM HEATER AND PUMP)
MAIN RETURN
(TO PUMP AND HEATER)
CORRECT METHOD
P-1
P-2
P-3
INCORRECT METHOD
Correct and incorrect method of laying out a forced hotwater distribution system.The travel from pump and heater should be
the same through P1, P2, and P3 as shown in the correct method.
Figure 1-32
44 Chapter 1
Installing a Hydronic Radiant Floor Heating System
(PEX Tubing)
These installation recommendations are provided for general information only. The architect or HVAC contractor is responsible for
all design details and installation procedures for the specific radiant
floor heating system. The architect or contractor is also responsible
for maintaining the work in compliance with all applicable building
codes, local and national.
Note
Install all the components of a hydronic radiant floor heating system in accordance with the equipment manufacturer’s instructions
and all applicable codes. Failure to do so could result in severe
personal injury, death, or substantial property damage.
Installation Recommendations
The following installation recommendations are provided as a general reference. Each manufacturer will provide instructions specific
to its product.
System Inspection
After the PEX tubing has been embedded or concealed, it
becomes a relatively permanent part of the structure. Because of
the difficulty of servicing embedded or concealed loops, it is
essential that a final inspection be performed to make sure the
tubing or piping has not been damaged during construction and
that all tubing or piping loops have been installed in compliance
with local codes and ordinances. Check the following:
• Check to make sure the tubing or piping loops have been installed
according to the layout (coil patterns) in the building plan.
• Inspect the tubing or piping for kinks, scrapes, slits, or crush
damage.
• Inspect the tubing or piping for correct spacing.
• Make sure all manifolds are correctly located and provide
easy access.
• Check to make sure the tubing or piping connections to the
manifold are tight.
• Make sure the tubing or piping is properly fastened and there
is a correct spacing maintained between the fasteners.
Tubing Length and Diameter
It is important to know the length and inside diameter (ID) of the tubing when creating a circuit (loop). Excessive circuit lengths will result
in a significant temperature drop in the circuit. The temperature drop
Radiant Heating 45
is the difference between the supply (hotter) water entering the circuit
and the return (cooler) water leaving the circuit. In residential heating
systems, the temperature drop is normally 15–20°F. If the temperature
drop is greater than 15–20°F, it will result in insufficient heat and/or
uneven heat being delivered to the room or space.
Long loops also result in increased friction in the tubing, which
slows the flow rate of the water. This pressure drop must be overcome by the circulator (pump) in order to maintain a uniform flow
rate for the water in the tubing.
A typical residential hydronic radiant heating system uses 1⁄2inch-ID tubing. The maximum recommended length for this
diameter is 300 feet. Most circuits (loops) in residential heating
systems are shorter (about 100 to 250 feet long). Tubing with an
ID of 5⁄8–inch or 3⁄4–inch, on the other hand, can be used in circuits up to a maximum of 450 feet in length.
In addition to the tubing ID, the length of the tubing required
per square foot of floor will also be affected by such variables as the
type of slab used, the heat load for the structure, the type of appliance (boiler, water heater, or heat pump), the type of controls used,
and even the climate.
Tubing Spacing
Another important factor to consider when designing and installing
a hydronic radiant floor heating system is the spacing of the tubing
in the loops. Most residential heating systems are based on the use
of 1 to 11⁄2 linear feet of 1⁄2-inch-ID tubing per square foot of floor
area with the tubing spaced 9 to 12 inches apart. That is only a general rule, however, because there are situations where the tubing
must be spaced closer to increase the heat output (for example,
under windows, along cold exterior walls, and so on). A 3-inch to
6-inch spacing of the tubing will require 2 to 4 linear feet of tubing
per square foot of heated floor area.
Loop Continuity
The tubing loop extending from the manifold supply port to the manifold return port must be one continuous length. Never splice together
two lengths of tubing to form a loop. Doing so will weaken the loop.
Insulation
Install insulation beneath the tubing to prevent the downward loss of
a portion of the heat. In uninsulated slab-on-grade construction, for
example, a portion of the heat will be lost to the ground. The ground
becomes a heat sink if there is no insulation installed. Use 1- to 2-inchthick rigid polystyrene to insulate a slab-on-grade radiant heating system. Batt and blanket insulation are also in other types of radiant
46 Chapter 1
heating systems. See “Radiant System Construction Details” for
examples of the use of the different types of insulation.
Vapor Barrier
A vapor barrier of 6-mil polyethylene sheeting should be installed
between a thin slab and the wood sheathing to limit the transfer of
moisture from the slab to the wood. Check the local building code
for the use of a vapor barrier. Not all codes require it.
Panel Testing Procedures
Radiant heating coils should be tested for leaks after they have been
secured in position but before they are covered with concrete or some
other covering material. Both a compressed-air test and a hydraulic
pressure test are used for this purpose.
The compressed-air test requires a compressor, a pressure gauge,
and a shutoff valve. The idea is to inject air under pressure into the
radiant heating system and watch for a pressure drop on the gauge.
A continually dropping pressure is an indication of a leak somewhere in the system.
The pressure gauge is attached to one of the radiant heating
coils, and the shutoff valve is placed on the inlet side of the gauge in
a valve-open position. The air compressor is then connected, and
compressed air is introduced into the system under approximately
100 psi. After the introduction of the air, the shutoff valve is closed
and the compressor is disconnected. The system is now a closed
one. If there are no leaks, the air pressure reading on the gauge will
remain at approximately 100 psi. A steady drop in the air pressure
reading means a leak exists somewhere in the system. A leak can be
located by listening for the sound of escaping air. Another method
is to use a solution of soap and water and watch for air bubbles.
The hydraulic pressure test requires that the coils be filled with
water and the pressure in the coils be increased to approximately
275 to 300 psi. Care must be taken that all air is removed from the
coils before the system is closed. The system is then closed, and the
gauge is watched for any change in pressure. A leak in the system
will be indicated by a steady drop in pressure on the gauge. The
source of the leak can be located by watching for the escaping
water. If a leak is discovered, the coil should be repaired or replaced
and a new test run on the system.
Installation Guidelines
Guidelines
• Run the tubing parallel to the wall or walls with the greatest heat
loss.
(continues)
Radiant Heating 47
Guidelines (continued)
• Maintain a 12-inch gap between the outermost tubing and an
exterior wall.
• Space tubing 6 inches o.c. between the first two loops along the
wall or walls with the greatest heat loss.
• Tie tubing every 3 feet or less with plastic tie wraps. Note:
Never tie tubing anywhere within the end of a loop.
• Always use a vapor barrier under the slab. Note: Place the vapor
barrier between the ground and insulation, if the latter is used
under the slab.
• Place a vapor barrier between the soil and any insulation installed
under the slab.
• Insulate under the slab if groundwater comes within 3 feet.
• Always install edge insulation along the foundation walls to
prevent edgewise (horizontal) heat loss.
Whenever possible, follow the radiant heating system manufacturer’s installation guidelines. The procedure described here for
installing a hydronic radiant floor heating system (using PEX tubing) is offered as a general guideline. It may be outlined as follows:
1. Attach the manifold wall brackets to the wall.
2. Assemble the manifold (if it is not a factory-assembled unit)
and clamp it into position on the wall brackets.
3. Mount a pipe bend support directly below the manifold to
hold the supply pipe.
4. Connect the supply pipe to the manifold and lay out the pipe
5.
6.
7.
8.
9.
10.
loop by following the layout plan.
Mount a pipe bend support below the manifold to hold the
return pipe.
Create coil pattern.
Cut the return pipe and connect it to the manifold.
Mark or number the first loop for identification.
Check the length of the first loop against the layout plan by
using the length markings on the outside of the pipe. A significant deviation in overall length between the layout plan and
the installed pipe loop will require an adjustment of the loop
balance settings.
Repeat steps 1 through 8 for the remaining loops in the system.
48 Chapter 1
11. Close the supply, return, and shutoff valves on the first manifold.
12. Connect hoses to the end caps on the manifold.
13. Connect the end of one of the hoses to the main and the end
of the other hose to a drain.
14. Open the end cap valves for filling and draining the system.
15. Open the supply and return valves on the manifold for the
first loop.
16. Turn on the water and allow it to flow through the loop until
all the air has been expelled. Purging the air from the system
is a very important step. Air trapped in the loops will cause
the system to operate inefficiently.
Note
If the water will not flow through the loop, the pipe may be buckled
or crimped or there may be a blockage at the manifold connection.
Check and repair before proceeding to the next step.
17. Repeat steps 10 through 15 until each loop in the heating
18.
19.
20.
21.
system has been filled with water and any air trapped in the
piping has been removed.
Open all the system valves and perform a pressure test (at 3 to
4 bar pressure). The pressure will drop during the first few
hours and then remain stable if there are no leaks and the
ambient temperature remains constant.
Install the floor covering (cement, carpet, tiles, and so on).
Close all the loop valves and open the shutoff valves.
Fill the boiler and the supply pipes with water, and purge the air.
Open every valve and fixture (faucets and so on) in the system
and continue purging until all the air trapped in the pipes has
been pushed out of the lines and the water flows freely from the
fixtures. Purge the air from the end caps at each end of the
manifolds. In a structure with several floors, purge the air from
the manifold located at the lowest level first.
Note
There must be shutoff valves on the manifolds to properly purge
air from the loops.
22. Open all the loops in the heating system and check to make
sure the air has been removed. If there is still air in the tubing,
repeat steps 20 and 21 until all air has been removed.
23. Place the system under pressure by starting the boiler and circulator.
Radiant Heating 49
Servicing and Maintaining Hydronic Radiant Floor
Heating Systems
Hydronic radiant floor heating systems require very little service
and maintenance, but this does not mean they should be ignored.
The following recommendations apply to all floor heating systems:
• Check the system pressure on a regular basis. An incorrect
pressure reading may indicate air trapped in the system. An
air pocket or bubble will block the flow of water and cause
pressure readings outside the norm.
• Check the system for leakage. If the tubing is attached under
the floor to the stud bottoms, access to the tubing or tubing
connections to make repairs is relatively easy. If the tubing is
embedded in cement above the subfloor, however, locating a
leak is more difficult and expensive.
• Check to make sure there is enough water in the system. If
not, it may need refilling.
If purging air, repairing leaks, and/or refilling the system with
water does not result in maintaining the required pressure in the
system, ask for a service call from a certified HVAC technician with
experience in hydronic floor radiant heating systems.
Troubleshooting Hydronic Floor Radiant Heating Systems
Problems with hydronic floor radiant heating systems (see Table 1-1)
will occur in the following areas:
1.
2.
3.
4.
Heating appliance (boiler, heat pump, or water heater)
Circulator (circulating pump)
Automatic controls
Tubing
Most of the troubleshooting and repair procedures for the various components of a hydronic floor radiant heating system have
been described in considerable detail in other chapters. Use the volume index to locate those sources of information.
The first step when troubleshooting a radiant floor system is to
check the controls. Turn the room thermostat on or off and wait for
a few minutes for the system to respond. If the system responds by
turning on or off within 2 or 3 minutes, the controls are not the
problem.
50 Chapter 1
Table 1-1
Troubleshooting Hydronic Floor Radiant
Heating Systems
Symptom and Possible Cause
Suggested Remedy
Insufficient heat.
(a) Slow initial response time.
(b) Insufficient heat generally
occurring on design
temperature day.
(c) Boiler or other heat source
problem.
(d) Defective floor sensor.
(a) Normal for hydronic floor
heating system.
(b) Improper system design;
add auxiliary heat.
(c) Check heat source for
problem and correct.
(d) Replace.
No heat.
(a) Defective room thermostat
and/or floor sensor.
(b) Boiler or other heat source
problem.
(c) Defective circulator.
(a) Replace thermostat and/or
floor sensor.
(b) Check heat source for
problem and correct.
(c) Test; repair or replace.
Floor temperature too hot or too cold.
(a) Defective mixing valve.
(b) Incorrect mixing valve
setting.
(c) Defective outdoor air
sensor.
(a) Replace defective valve.
(b) Adjust valve setting;
change valve setting
number according to
specifications in
manufacturer’s installation
manual.
(c) Test and replace.
Floor temperature too cold.
(a) Boiler or other heat source
problem.
(b) Circulator working against
large system temperature
drop; not moving enough
water.
(a) Check heat source for
problem and correct.
(b) Check temperature drop
when system is warm;
circulator is undersized if
drop is found to be too
large; correct as necessary.
Radiant Heating 51
Table 1-1 (continued)
Symptom and Possible Cause
Suggested Remedy
(c) Circulator working against
small system temperature
drop; water and floor
temperatures almost equal,
resulting in little heat
transfer.
(c) Check temperature drop
when system is warm;
circulator is oversized if
temperatures almost equal;
increase floor temperature
if less than 85ºF to be too
large.
Hot spot in floor.
(a) Excessive high and
concentrated temperatures
in floor caused by tubing
or tubing connection break.
(a) Locate break and repair.
Check the boiler, heat pump, or water heater for a problem.
These appliances and their troubleshooting methods are described
in Chapter 15 (“Steam and Hydronic Boilers”) in Volume 1,
Chapter 10 (“Heat Pumps”) in Volume 2, and Chapter 4 (“Water
Heaters”) in Volume 2, respectively.
Note
Some heating systems have a thermometer installed in the circulation loop. The thermometer displays the temperature of the
circulating water. A low fluid temperature displayed while the
circulator is operating will indicate a problem with the boiler, heat
pump, or water pump.
The troubleshooting and repair of circulators (water-circulating
pumps) is covered in Chapter 10 (“Steam and Hydronic Line
Controls”) in Volume 2.
Problems requiring repairs or replacements of the manifolds or
loops, especially embedded loops in wet installations, require the
expertise of HVAC technicians experienced in the installation and
maintenance of floor radiant heating systems.
Hydronic Radiant Heating Snow- and Ice-Melting Systems
Radiant systems used to melt snow and ice on driveways, sidewalks, and other outdoor surfaces are inexpensive to operate
because they are used only when required. They begin to operate at
a reduced output mode when the outdoor temperatures drop below
a certain preset point and then switch to full operation when rain or
snow reaches the surface.
52 Chapter 1
The simplest form of control for snow-melting and ice-melting
installations is a remote, manually operated on-off switch. The switch
is commonly located inside the garage and operated only when
required. Some snow- and ice-melting installations are operated by an
automatic control system connected to a thermostat and a heating
boiler, heat pump, or water heater.
Because the tubes carrying the heated water are located outdoors
beneath the driveway surface, an antifreeze solution such as propylene glycol should be added to protect the system from freezing.
Electric Radiant Floor Heating
A number of manufacturers produce electric radiant floor heating systems for use in residential and light commercial construction. They
are safe, relatively easy to install, and extremely energy efficient.
Note
Electric radiant heating produces electromagnetic fields, and
these EMFs may cause health problems. The potential health
risk from EMFs can be minimized or even eliminated by (1)
following the wiring and grounding methods recommended
by the National Electrical Code; (2) purchasing and installing a
radiant heating system that produces very low EMFs (some
manufacturers claim zero EMFs for their systems); and (3)
avoiding systems that produce EMFs higher than 2 mG at 2
feet.
Most of these electric radiant floor heating systems consist of a
thin electric mat or roll applied to the subfloor where it is embedded in a thinset or self-leveling cement. Watts Radiant manufactures heating mats (HeatWeave UnderFloor mats) for installation
between the floor joists under the subfloor.
System Components
An electric floor heating system in which electric heating mats or
rolls are used will include some or all of the following components,
depending on the system design:
1.
2.
3.
4.
5.
6.
7.
Heating mats or rolls
Thermostat
Floor sensor
Ground fault circuit interrupter
Relay contactor
Timer
Dimmer switch
Radiant Heating 53
Heating Mats or Rolls
The electric mats or rolls used in electric floor radiant heating systems are made of coils of heat resistance wire joined to a supporting
material. They are only 1⁄8 inch thick, which means they can be
installed over the subfloor and under the floor covering without
significantly raising the floor level (see Figure 1-33). The heating
element of a constant-wattage electric heating cable or wire operates on 120 volts or 240 volts.
Electric heating mats or rolls are produced in a wide variety of
sizes to fit different floor dimensions. Custom sizes can also be
ordered from manufacturers to fit areas with curves, angles, and
other nonstandard shapes.
An entire electric radiant floor heating system can be ordered
from any one of the manufacturers listed in the sidebar. When
ordering the materials for one of these heating systems, send them
an installation layout plan listing the exact dimensions of the rooms
or spaces to be heated. The plan may be for an entire house, an
addition to a house, or a single room or space.
Note
The manufacturer will cut the mats or rolls to the sizes listed in
the installation plan. Once the mats or rolls are cut, they cannot
be returned if a mistake is discovered unless it can be shown
that the manufacturer was at fault.
The recommended heating capacity for electric resistance heating is
specified by the building codes on a watt-per-square-foot-of-livingarea basis. The electric heating mats or rolls are designed to draw 8 to
15 watts per square foot. Their operation is very similar to that of an
electric blanket.
Manufacturers of Electric Radiant Heating Mats or Rolls
Flextherm, Inc.
2400, de la Province Street
Longueuil, Quebec J4G 1G1
Canada
450-442-9990
800-353-9843
www.flextherm.com
Heatway, Inc. (Watts Heatway, Inc.)
3131 W. Chestnut Express Way
Springfield, MO 65802
800-255-1996
www.heatway.com
(continues)
54 Chapter 1
Manufacturers of Electric Radiant Heating Mats or Rolls (continued)
NuHeat Industries Ltd.
1689 Cliveden Ave.
Delta, BC V3M 6V5
Canada
800-778-9276
604-529-4400
www.nuheat.com
SunTouch Electric Floor Warming
A Division of Watts Radiant, Inc.
3131 W. Chestnut Expressway
Springfield, MO 65802
417-522-6128
www.suntouch.net
WarmlyYours, Inc.
1400 E. Lake Cook Road, Suite 140
Buffalo Grove, Illinois 60089
800-875-5285
www.WarmlyYours.com
Warmzone, Inc.
Salt Lake City, Utah
888-488-9276
801-994-8450
www.warmzone.com
Watts Radiant, Inc.
A Division of Watts Water Technologies, Inc.
31341 West Chestnut Expressway
Springfield, Missouri 65802
800-276-2419
978-688-1811
www.wattsradiant.com
Automatic Controls
The automatic controls of a typical electric radiant floor heating
system consist of a thermostat, a GFCI safety breaker, and an
optional timer. If a floor-heating thermostat is used instead of a
room thermostat, the former is wired to a floor sensor that detects
the actual floor temperature. A GFCI and a timer are integral components of a floor-warming thermostat.
Radiant Heating 55
MAT POWER LEAD
MAT SUPPORTING MATERIAL
HEATING WIRE
GROUND SHIELD
DUPONT T ETZOL
INNER COVER
POLYVINYLIDONE
FLUORIDE HYLAR COVER
DUPONT KEVLAR CORE
HEATING ELEMENTS
Construction details of a typical electric heating mat or
roll. (Courtesy Watts Radiant, Inc.)
Figure 1-33
Thermostat
The thermostat is the controlling device for an electric radiant
floor heating system. Most modern systems use a programmable
thermostat, which contains an integral ground fault circuit interrupter (GFCI) and a manual high-low temperature setback switch
56 Chapter 1
(see Figure 1-34). A programmable thermostat is connected to an
embedded floor sensor that monitors the floor temperature and transmits it to a digital display on the thermostat. A programmable thermostat can be programmed for four setting changes each day of the week.
ON
FLOOR
TEMPERATURE
ON/STAND-BY
SWITCH
STAND BY
MO
GFCI WARNING
LIGHT AND
TEST BUTTON
CURRENT
MODE AND
SETPOINT
TEST
CURRENT
PROGRAM NO.
DAY
HOUR
DAY AND CLOCK
SETTINGS
MIN
PGM
PROGRAMMING
MODE PGM
PRE-DEFINED
SETPOINTS
CLEAR
MODE/RET
MODE SELECTION/
EXIT PROG.
2
INCREASE/
DECREASE
TEMPERATURE
Programmable thermostat with digital display for an
electric radiant floor heating system. (Courtesy Watts Radiant, Inc.)
Figure 1-34
Nonprogrammable thermostats are used commonly for small
spot-warming areas. They are also equipped with a GFCI device.
Note
Never exceed the maximum capacity of the thermostat to heat
the floor. If additional power is required, zone with additional programmable thermostats or use a relay contactor.
Floor Sensor
A floor sensor is a temperature-monitoring device embedded in the
floor and connected to a programmable thermostat. It should be
installed in such a way as to give the truest floor temperature. Its
installation will also be governed by the type of floor covering.
Radiant Heating 57
Many manufacturers will recommend the location of the floor sensor for the different types of floor coverings used with their floor
sensor (see Figure 1-35).
FLOOR SURFACE
JOIST
SUBFLOOR
MINIMUM 1"
INSULATION
ANGLED HOLE DRILLED
FOR FLOOR SENSOR
SENSOR
8"
INSULATION
CONSTRUCTION
ADHESIVE
Floor sensor installed in angled hole drilled in the
bottom of the subfloor. (Courtesy Watts Radiant, Inc.)
Figure 1-35
Ground Fault Circuit Interrupter
A ground fault circuit interrupter (GFCI) is used to monitor the flow
of electricity through the heat resistance wire in the mat or roll for
any loss of current. If a loss of current is detected, the GFCI immediately cuts off the electricity to the heating system. This is done to
prevent damage to the heat resistance wire in the heating mat or roll.
The GFCI is an integral part of a programmable thermostat.
An indicating-type GFCI circuit breaker may be installed to
serve as a local disconnect. It should be installed near the end of the
line close to the thermostat.
Relay Contactor
A relay contactor is a device used in conjunction with a single controller to operate the heating in large rooms or spaces. Both singleand double-relay contactors are used in heating systems.
Timer
A timer is an optional device used to control when the heating system is turned on and off. It can be used to program 14 events, or
two on-off cycles per day for a 2-day or 5-day period. It also can be
used in conjunction with a dimmer switch to regulate floor temperature. It cannot moderate the floor temperature.
Dimmer Switch
A dimmer switch is a device with an on-off button and a sliding
manual control used in some systems to increase or decrease the
floor temperature. It can be used in conjunction with a 7-day programmable timer to program a weekly period repetitively.
58 Chapter 1
Installing Electric Heating Mats or Rolls
Electric heating mats or rolls must be installed in accordance
with the manufacturer’s instructions and any local codes or ordinances.
Before installing the heating mats or rolls, check the shipment to
make sure the manufacturer has included everything. If the order is
complete, remove the mats or rolls from their boxes and test the
ohm resistance of each to make sure it has not been damaged during shipment.
Note
This will be the first of three resistance tests. The second resistance test is performed after the mats have been secured to the
subfloor, and the third after the floor covering has been applied
over the mats.
To perform a resistance test, set a digital multimeter to the 200ohms setting and connect the mat lead wires to the multimeter
probes. Make sure the resistance reading is within the range of plus
10 percent to minus 5 percent of the resistance rating listed on the
mat tag.
An insulation test should be performed to make sure there is no
short or ground in the mat or roll. To conduct an insulation test, set
the digital multimeter to the megohms setting and connect the silver
braid (ground) and black lead to the multimeter probes. The multimeter should read “open” or “OL.” Check the instructions with
the multimeter to confirm which code represents the “open line.”
Repeat this test between the silver braid (ground) and the white
lead wire.
Caution
The installation of electrical heating systems involves some risk of
fire and/or electrical shock that can result in injury or even death.
With that in mind, only a qualified, certified electrician or someone with similar training and experience should connect the electric heating mats or rolls to the thermostat and the electrical
circuit. Connections should be made in accordance with local
codes and ordinances and the provisions in the latest edition of
the National Electrical Code. The heating mats or rolls must be
installed by a qualified contractor or homeowner before the connections to the electrical circuits and control device are made.
Installing Electric Mats or Rolls over Subfloors
Keep a permanent record of the location of the mats or rolls and the
floor sensor, if one is installed.
Radiant Heating 59
Note
Do not install solid-based furniture, built-in cabinets, bookcases,
room dividers, or plumbing fixtures over heating mats or rolls.
The procedure for installing electric heating mats or rolls over a
subfloor may be outlined as follows:
1. Use the installation plan provided by the manufacturer to lay
the mats or rolls out in the room. This dry run is done to
make sure the mats or rolls cover the floor properly (see
Figure 1-36).
2. Cut the supporting material (but not the heat resistance wire)
and turn the mat or roll to fit the dimensions of the room (see
Figure 1-37).
Step 1: Laying the mats on the floor.
Lay the mats out on the floor and "dry" fit them to the dimensions of the room
according to the installation plan and the floor markings.
• Do not walk on the heating elements (wires)
• Do not drop tools on the heating element (wire) or strike it with a
hammer or tool.
• Place cardboard or carpet sections over the mat and the heating
element to protect the latter from damage.
Figure 1-36
Laying the mats or rolls out on the floor.
(Courtesy WarmlyYours.com, Inc.)
6
7
8
9
10
11
12
60 Chapter 1
Step 2: Fitting the mats on the floor.
Fit the heating mats (rolls) one panel at a time. Cut and turn the mats according to the
installation plan and the floor markings, and then modify the roll into successive and
interconnected panels shaped to cover the planned area.
Figure 1-36
(Continued)
3. Glue the mat to the subfloor to prevent it from moving out of
4.
5.
6.
7.
8.
position.
Test the ohm resistance of each heating roll after it has been
secured to the subfloor to make sure it wasn’t damaged during installation. This is the second resistance test.
Cover the roll with a layer of thinset cement. Allow the thinset cement sufficient time to cure. Do not turn on the radiant
heating system until the thinset cement has cured according to
the recommended time on the packaging.
Consult the installation plan and mark the approximate
location of the heating elements on the cement surface with
chalk.
Cover the layer of thinset cement with the floor covering (tile,
carpet, and so on). Note: Do not nail, screw, or staple near the
heating elements and cold lead wires when installing the floor
covering. Use the chalk lines as a guide.
Test the ohm resistance of the heating rolls to verify that they
were not damaged when the floor covering was applied. This
is the third resistance test.
Radiant Heating 61
180 degree turn:
Cutting and turning the mat. Caution: DO
NOT CUT the heating element (wire).
90 degree (flip over) turn:
Make a straight cut and flip the
section over so that the heating
element (wire) is now above the
mesh and continues in a
perpendicular direction.
Make a straight cut and then slide
the balance of the panel around and
head back in the opposite direction.
Filling free form spaces:
Fill free form spaces with loose
lengths of the heating element
(wire) after removing about 6
inches of mat.
Turning the mat or roll to fit the dimensions of the
room. (Courtesy WarmlyYours.com, Inc.)
Figure 1-37
9. Hardwire the electric mat or roll to the thermostat. This step
should be done only by an electrician or an individual with
the required experience of working with electrical systems.
Installing Electric Heating Mats or Rolls in Joist Cavities under Subfloors
Electric heating mats or rolls are also available for use in joist cavities beneath wood subfloors in residential and light commercial
construction. The joists are spaced 16 inches on centers.
62 Chapter 1
These mats or rolls may be jointed to fill larger spaces, but they
must be wired in parallel (not in series) when joined together. The
mats are rated either 120 VAC or 240 VAC. They are wide enough
to fit into joist cavities with joists separated 16 inches on center.
The following installation steps are offered only as a guideline.
Specific instructions can be obtained from the manufacturer and
should be carefully followed.
The procedure for applying electric radiant heating mats or rolls
in joist cavities under subfloors may be outlined as follows:
1. Install the floor sensor.
2. Push a length of mat into the joist cavity so that it touches the
bottom of the subfloor. The heating wires must be between
the supporting mesh and the bottom of the subfloor.
3. Staple one edge of the supporting mesh to the side of the joist.
Place the staples a minimum of 1⁄2 inch from the heating wire
and 3⁄4 inch down from the subfloor on the joist.
4. Push the other edge of the mat against the subfloor and nail
the mesh to the joist surface. Use the same staple locations.
Pull the mat snug against the subfloor as you staple the opposite edge to the joist. There will be a slight droop when you
are finished. A gap of not more than 1 inch between the mat
and the subfloor is acceptable (see Figure 1-38).
5. Cut the supporting mesh of the mat when it reaches the end
of the joist cavity or some other blockage. Do not cut the
heating wire. Pull the heating wire (without the mesh) down
and across a notch cut into the bottom of the floor joist (see
Figure 1-39). The notch must not exceed 1⁄4 inch in depth
and must be covered by a steel nailing plate. Avoid nicking
or damaging the heating wire when nailing the plate to the
bottom of the joist.
Note
Check the local building codes to see if notching the bottom of
the joist for routing the heating wire is permitted. Some codes
prohibit notching the joist. Notching the joist is allowed by the
BOCA National Building Code (Section 2308.8.2 of the 2000 edition) in each of the one-third ends of a joist span (never in the
middle one-third of the span).
6. If notching the joist is not permitted, drill a 2-inch diameter
hole through the side of the joist and pull the heating wire
with its supporting mesh through the hole. Cut away the
mesh next to the hole after it has been pulled through.
Radiant Heating 63
Installation details
HEATING WIRE
WOVEN MAT
INSULATION
(MINIMUM R-13)
JOISTS
Stapling mat to side
of floor joist
Figure 1-38
Installing the mat or roll between the joists.
(Courtesy Watts Radiant, Inc.)
64 Chapter 1
SUBFLOOR
NYLON
WIRE CLIP
BLUE
HEATING
WIRE
PROTACTIVE
ROLL PLATE
Extending a heating wire down and
around a floor joist. (Courtesy Watts Radiant, Inc.)
Figure 1-39
7. If a second mat is required to finish out a room area, start the
second mat flush with the end of the first mat and wire them
in parallel (not series). Do not overlap the mats.
8. Connect the mat leads to the junction box in accordance with
the provisions of the local building code or the latest edition
of the National Electrical Code, if there is no applicable local
code. Use additional electrical boxes where required. Connect
the floor sensor and power supply.
Caution
Use an experienced and qualified electrician to make these electrical connections. There is always the possibility of severe shock
injury, death, and/or property damage if the electrical work is
done by inexperienced and unqualified workers.
9. After all the controls have been installed, energize the heating
system briefly to see if it is operational.
Radiant Heating 65
10. If the system is operating properly, turn off the power and push
foil-faced blanket or batt insulation (minimum R-13 rating) into
the joist cavities. Leave a clearance of 1⁄2 inch to 1 inch between
the mat or roll and the insulation (see Figure 1-40).
11. Seal the ends of the joist cavities by installing the last of the
insulation vertically. Push the insulation up tight against the
subfloor and staple it there so that no heat can escape through
the band joists, rim joists, or the open end of a joist cavity.
Installing Electric Cable
Not all electric radiant floor heating systems use mats or rolls to
produce the heat. Before mats or rolls became popular, floor systems consisted of coiled electric heating cables. The procedure for
installing electric heating cables may be outlined as follows:
1. Make sure the power supply is shut off before beginning any
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
work.
Begin the electrical rough-in work by installing the electrical
box for the thermostat on the wall.
Pull the power supply cable into the thermostat electrical box.
Punch out the conduit holes on the box. The heating cable
and thermostat sensor leads will be pulled through these electrical box holes later.
Lay the cable out on the floor according to the specified coil
pattern.
Staple the electric cable to the floor through plastic strapping
to prevent the coils from moving out of position.
Pull the cable and thermostat sensor leads through the
punched out conduit holes in the electrical box.
Cover the cable with a thin coat of mortar.
Allow the mortar a day to dry and then apply the floor covering (for example, carpet, wood flooring).
Install the thermostat in the thermostat electrical box.
Connect to the power supply.
Note
Only a qualified HVAC technician or someone with an equivalent
amount of work experience should be allowed to install an electrical radiant floor heating system. Electricity in inexperienced
hands can cause serious injury and even death.
66
SUBFLOOR
HEATWEAVE MAT 1"
BELOW SUBFLOOR
2" AIR SPACE BETWEEN
HEATWEAVE AND INSULATION
R-13 INSULATION SEALING
END OF HEATED JOIST CAVITY
R-13 MINIMUM UNDERFLOOR INSULATION
RIM/BAND
JOIST
RIM/BAND JOIST INSULATION (MINIMUM R-13, OR
GREATER AS REQUIRED BY LOCAL CODE)
FOIL-FACED INSULATION
(MINIMUM R-13)
BEST
(RECOMMENDED)
Figure 1-40
BUBBLE-WRAP WITH
KRAFT-FACED INSULATION
(MINIMUM R-13)
KRAFT-FACED INSULATION
(MINIMUM R-13)
BETTER
GOOD
Installing insulation. (Courtesy Watts Radiant, Inc.)
Radiant Heating 67
Servicing and Maintaining an Electric Radiant Floor
Heating System
There are no valves, fittings, or moving parts to service or repair in
an electric radiant floor heating system. Consequently, there is no
need for a maintenance schedule.
Note
Manufacturers provide repair kits with accompanying instructions
for repairing mats or rolls damaged at the job site. They do not,
however, warranty the repair or ensure proper function of the
product following the repair because they have no means of controlling the repair work. Only a qualified electrician should make
repairs to mats or rolls.
Caution
Before troubleshooting or repairing an electric heating system,
make sure the power is turned off and the mat or roll is disconnected from the power source. Do not cut the heating wire with
the mat or roll still connected to the power source.
Note
On rare occasions, a cable in a heating mat may break. When this
occurs, it can be easily detected by using an instrument that functions as an underground fault detector. Repairing the break is simply
a matter of locating it, removing the small section of floor above it,
splicing the cable, and then replacing the flooring. As was already
mentioned, the ground fault circuit interrupter is used to monitor
electricity flow to determine if there has been any loss of current. If
there has been a loss, the thermostat will cut off power to the heating system until the problem is located and corrected.The GFCI on
a programmable thermostat should be tested immediately after
installing the thermostat, and once a month after the initial test to
make sure the GFCI is continuing to operate properly. Testing
instructions are provided by the manufacturer of the programmable
thermostat.
Troubleshooting Electric Radiant Floor Heating Systems
Caution
Never attempt to service or repair the electric controls inside
an electric furnace cabinet unless you have the qualifications
and experience to work with electricity. Potentially deadly highvoltage conditions exist inside these furnace cabinets. Refer to
Table 1-2.
68 Chapter 1
Table 1-2
Troubleshooting Electric Radiant Floor
Heating Systems
Symptom and Possible Cause
Suggested Remedy
No heat.
(a) Power may be off. Check
fuse or circuit breaker panel
for blown fuses or tripped
breakers.
(b) Check thermostat
(programmable type) for
dead batteries.
(a) Replace fuses or reset
breakers. If the problem
repeats itself, call an
electrician or an HVAC
technician.
(b) Replace batteries and reset
thermostat.
Not enough heat.
(a) Thermostat set too low.
(b) Cables require time to heat.
(a) Adjust setting. Note:
Thermostats in electric
heating systems must be set
several degrees higher than
the desired room
temperature.
(b) Allow the cables enough
time to warm up before
changing thermostat setting
to a higher one.
Cooling for Hydronic Radiant Floor Systems
Hydronic radiant floor heating systems are capable of providing
both heating and cooling independently of air movement. For the
heating cycle, hot water is circulated through the pipe coils. For the
cooling cycle, cold water (above the dew point) is circulated, and
the heating cycle is reversed. By keeping the water temperature
above 65°F, harmful moisture condensation is avoided.
Radiant panel cooling results only in the removal of sensible
heat, and there is sometimes an uncomfortable feeling of dampness.
As a result, a separate means of dehumidification is often necessary.
Often this can be quite expensive because it may require the installation of a separate dehumidification unit and round flexible air
ducts to the various rooms and spaces in the structure.
A common and effective method of cooling a structure equipped
with a hydronic radiant floor heating system is to add forced-air cooling. There are several very efficient add-on cooling systems available
Radiant Heating 69
ESP BLOWER
COIL UNIT
CONDENSATE
LINE
TRAP
CONDENSING
UNIT
Figure 1-41
R
LIN EFR
ES IGE
RA
NT
Space-Pak air distribution system.
(Courtesy Dunham-Bush, Inc.)
for use with radiant heating. One of the more commonly used ones is
the Unico air-conditioning system (see Figure 1-41). It consists of one
or more chillers to move the chilled water throughout the house. Air
handlers transfer the cold air to the interior rooms and spaces. The
cool air travels from the air handler to the rooms and spaces inside
the structure through small, round, flexible ducts.
Chapter 2
Radiators, Convectors,
and Unit Heaters
The two basic methods by which heat-emitting units transfer heat
to their surroundings are (1) radiation and (2) convection.
Radiation is the transmission of thermal energy by means of electromagnetic rays. In other words, an object is warmed by heat
waves radiating from a hot surface. Convection is the transfer of
heat by natural or forced movement (circulation) of the air across a
hot surface. In actual practice, heat-emitting units will transfer heat
partially by radiation (up to 30 percent) and partially by convection
(70 to 90 percent).
The output of heat-emitting units is expressed in terms of Btu
per hour (Btu/h), in square feet of equivalent direct radiation
(EDR), or in 1000 Btu per hour (MB/h). The required radiation of
an installation is determined on the basis of the Btu-per-hour capacity of each heat-emitting unit. See Determining Required Radiation
in this chapter.
The selection of a heat-emitting unit will depend on the type of
heating system, the cost, the required capacity, and the application.
For example, electric unit heaters should be used only where the
cost of electricity is especially low. These heaters are generally associated with high operating costs. On the other hand, they are relatively inexpensive, and their installation cost is low because no
separate piping or boiler is required. Each type of heat-emitting
unit will have similar advantages and disadvantages that you must
carefully consider before choosing the type most suited for the
installation.
The principal types of heat-emitting units used in heating systems
are:
1.
2.
3.
4.
5.
6.
Radiators
Convectors
Baseboard heaters
Kickspace heaters
Floor and window recessed heaters
Unit heaters
71
72 Chapter 2
Radiators
A cast-iron radiator is a heat-emitting unit that transmits a portion
of its heat by radiation and the remainder by convection. An
exposed radiator (or freestanding radiator) transmits approximately half of its heat by radiation, the exact amount depending on
the size and number of the sections. The balance of the emission is
by conduction to the air in contact with the heating surface, and the
resulting circulation of the air warms by convection.
Cast-iron radiators have been manufactured in both column and
tubular types (see Figures 2-1 and 2-2). Column and large-tube
radiators (with 21⁄2-inch spacing per section) have been discontinued. The small-tube radiator with spacings of 13⁄4 inches per section
is now the prevailing type. Ratings for various cast-iron radiators
are given in Tables 2-1, 2-2, and 2-3, courtesy of the American
Society of Heating, Refrigerating, and Air-Conditioning Engineers.
WALL
2 COLUMN 3 COLUMN 4 COLUMN
Figure 2-1
WINDOW
HOSPITAL
Various types of column cast-iron radiators.
As shown in Figure 2-1, each radiator section has 11⁄4-inchdiameter openings located at the top and bottom on each side.
These openings (called waterways in hot-water radiators) are the
passages through which the steam or hot water flows between the
radiator sections. Round metal fittings are installed in these openings to join the sections together when forming a larger radiator
module.
The radiators used in modern steam and hot-water heating systems are designed with nipples located in both the upper and
lower portions of each radiator section, but this was not always
the case with steam radiators. The earliest cast-iron steam radiators used in the old one-pipe steam heating systems were produced
Radiators, Convectors, and Unit Heaters 73
3 TUBE
4 TUBE
5 TUBE
HOSPITAL
WINDOW
Figure 2-2
Various types of tubular cast-iron radiators.
with nipples located only in the bottom portion of each section.
This was done because steam is light and rises quickly in the radiator, pushing air ahead of it. The air is expelled through an air
vent located near the top of the radiator; the steam returns to the
bottom of the same radiator section and then moves through the
nipple to the adjoining section. Hot-water cast-iron radiators, on
the other hand, require nipples at both the top and bottom of each
section to improve water circulation. Hot water is heavier than
steam and will not move as quickly without the assistance of two
sets of nipples.
Wall and window radiators are cast-iron units designed for
specific applications. Wall radiators are hung on the wall and are
especially useful in installations where the floor must remain clear
for cleaning or other purposes. They may consist of one or more
74 Chapter 2
Table 2-1 Column-Type Cast-Iron Radiators
Generally Accepted Rating per Section*
One-Column
Height (in)
15
18
20
22
23
26
32
38
45
ft2
Btu/h
11⁄2
360
12⁄3
2
21⁄2
3
400
480
600
720
Four-Column
Height (in)
13
16
18
20
22
26
32
38
45
ft2
Btu/h
3
720
4
5
61⁄2
8
10
960
1200
1560
1920
2400
Two-Column
ft2
Btu/h
11⁄2
360
2
21⁄4
21⁄3
22⁄3
31⁄3
4
5
480
540
560
640
800
960
1200
Five-Column
ft2
Btu/h
42⁄3
1120
7
1680
10
2400
Three-Column
ft2
Btu/h
21⁄4
540
3
720
33⁄4
41⁄2
5
6
900
1080
1200
1440
Six-Column
ft2
Btu/h
3
33⁄4
41⁄2
5
720
900
1080
1200
*These ratings are based on steam at 215°F and air at 70°F. They apply only to installed radiators exposed in
a normal manner, not to radiators installed behind enclosures, behind grilles, or under shelves.
(Courtesy 1960 ASHRAE Guide)
flat wall radiator sections. Window radiators are located
beneath a window on an exterior wall. The heat radiating from
the surface of the unit provides a very effective barrier against
drafts.
Radiator Efficiency
Radiator efficiency is an important operating characteristic of the
heating system. The following recommendations are offered as a
guide for obtaining higher radiator operating efficiency:
Radiators, Convectors, and Unit Heaters 75
Table 2-2 Large-Tube Cast-Iron Radiators (sectional,
cast-iron, tubular-type radiators of the large-tube pattern,
that is, having tubes approximately 13⁄8 inches in diameter,
21⁄2 inches on centers)
Number of
Tubes per
Section
Catalog Rating
per Section*
Height
Width
Section
Center Leg Height‡
Spacing† to Tapping
ft2
Btu/h
in
in
in
in
3
13⁄4
2
21⁄3
3
31⁄2
420
480
560
720
840
20
23
26
32
38
45⁄8
21⁄2
21⁄2
21⁄2
21⁄2
21⁄2
41⁄2
41⁄2
41⁄2
41⁄2
41⁄2
4
21⁄4
21⁄2
23⁄4
31⁄2
41⁄4
540
600
660
840
1020
20
23
26
32
38
21⁄2
21⁄2
21⁄2
21⁄2
41⁄2
41⁄2
41⁄2
41⁄2
22⁄3
3
31⁄2
41⁄3
5
640
720
840
1040
1200
20
23
26
32
38
9–89⁄18
21⁄2§
21⁄2§
21⁄2§
21⁄2§
21⁄2§
41⁄2
41⁄2
41⁄2
41⁄2
41⁄2
3
31⁄2
4
5
6
720
840
960
1200
1440
20
23
26
32
38
9–103⁄8
21⁄2
21⁄2
21⁄2
21⁄2
21⁄2
41⁄2
41⁄2
41⁄2
41⁄2
41⁄2
21⁄2
3
32⁄3
600
720
880
14
17 113⁄8–1213⁄16
20
21⁄2
21⁄2
21⁄2
3
3
3 or 41⁄2
5
6
7
1
13
6 ⁄4–6 ⁄15
*These ratings are based on steam at 215F and air at 70F. They apply only to installed radiators exposed in
a normal manner, not to radiators installed behind enclosures, behind grilles, or under shelves.
†
Maximum assembly 60 sections. Length equals number of sections times 21⁄2 in.
‡
Where greater than standard leg heights are required, this dimension shall be 6 in, except for 7-tube sections,
in heights from 13 to 20 in, inclusive, for which this dimension shall be 41⁄2 in. Radiators may be furnished
without legs.
§
For five-tube hospital-type radiation, this dimension is 3 in.
(Courtesy 1960 ASHRAE Guide)
76 Chapter 2
Table 2-3 Small-Tube Cast-Iron Radiators
Number
of Tubes
per
Section
3§
4§
5§
6§
Section Dimensions
Catalog Rating
A
B Width
per Section*
Height ‡ Min
Max
ft2
Btu/h
in
in
in
1.6
1.6
1.8
2.0
2.1
2.4
2.3
3.0
3.7
384
384
432
480
504
576
552
720
888
25
19
22
25
22
25
19
25
32
31⁄4
47⁄16
47⁄16
47⁄16
55⁄8
55⁄8
613⁄16
613⁄16
613⁄16
31⁄2
413⁄16
413⁄16
413⁄16
65⁄16
65⁄16
8
8
8
C
Spacing †
in
13⁄4
13⁄4
13⁄4
13⁄4
13⁄4
13⁄4
13⁄4
13⁄4
13⁄4
D Leg
Height ‡
in
21⁄2
21⁄2
21⁄2
21⁄2
21⁄2
21⁄2
21⁄2
21⁄2
21⁄2
*These ratings are based on steam at 215F and air at 70F. They apply only to installed radiators exposed in
a normal manner, not to radiators installed behind enclosures, behind grilles, or under shelves.
†
Length equals number of sections times 13⁄4 in.
‡
Overall height and leg height, as produced by some manufacturers, are 1 inch greater than shown in columns
A and D. Radiators may be furnished without legs.Where greater than standard leg heights are required, this
dimension shall be 41⁄2 in.
§
Or equal.
(Courtesy 1960 ASHRAE Guide)
1. A radiator must be level for efficient operation. Check it with
2.
3.
4.
5.
a carpenter’s level. Use wedges or shims to restore it to a level
position.
Make sure the radiators have adequate air openings in the
enclosure or cover. The openings must cover at least 40 percent of the total surface of the unit.
Unpainted radiators give off more heat than painted ones. If
the radiator is painted, strip the paint from the front, top, and
sides. The radiator will produce 10 to 15 percent more heat at
a lower cost.
Check the radiator air valve. If it is clogged, the amount of
heat given off by the radiator will be reduced. Instructions for
cleaning air valves are given in Troubleshooting Radiators in
this chapter.
Radiators must be properly vented. This is particularly true of
radiators located at the end of long supply mains. Instructions
Radiators, Convectors, and Unit Heaters 77
for venting radiators are given in Vents and Venting in this
chapter.
6. Never block a radiator with furniture or drapes. Nothing should
block or impede the flow of heat from the radiator.
7. Placing sheet metal or aluminum foil against the wall behind
the radiator will reflect heat into the room.
Radiator Heat Output
The heat output of a cast-iron radiator is determined by the following
factors:
• Ambient temperature (that is, the temperature of the air surrounding the radiator). The ambient temperature is assumed
to be 70ºF for purposes of sizing estimates.
• Temperature of the radiator surface. The surface temperature
will depend on the temperature of the steam or hot water circulating through the radiator sections. Steam is always hotter
than hot water.
• Surface area of the radiator. Repeated tests have shown that
the amount of heat given off by ordinary cast-iron radiators
per degree difference in temperature between the steam (or
water) in the radiator and the surrounding air is about 1.6 Btu
per square foot of heating surface per hour.
A relative radiating surface of a radiator is measured in terms of
the square feet of equivalent direct radiation (EDR). A cast-iron
radiator will give off heat at the rate of 240 Btu per hour when supplied with steam at 21⁄2 lbs of pressure (220°F) with a surrounding
air temperature of 70°F. It is determined as follows:
(220 70) 1.6 240 Btu
One square foot of steam radiation equals 1.6 square feet of
hot-water radiation or 1.4 square inches of warm-air pipe area.
Tables 2-1, 2-2, and 2-3 list the heating surfaces for various column
and tubular cast-iron radiators.
The cast-iron radiators in hot-water heating systems deliver water
at a temperature of no more than 180ºF. As a rule, a square-foot
EDR for a hot-water cast-iron radiator will emit 170 Btu per hour.
There is no IBR code covering recessed radiation. As a result, manufacturers of recessed heat-emitting units must rate and certify their
own product. The Weil-McLain Company is typical of these manufacturers. Its certified ratings are determined from a series of tests
conducted in accordance with the IBR Testing and Rating Code for
78 Chapter 2
Baseboard Type Radiation whenever the provisions of the code should
be applied. The Weil-McLain ratings include a 15 percent addition for
heating effect and barometric pressure correction factor allowed by
the IBR code. Other manufacturers use similar rating methods.
Sizing Radiators
To size a column-type or tube-type cast-iron radiator, first measure
its height in inches and then count the number of sections and the
number of tubes or columns in each section (see Figure 2-3). The
22"
RADIATOR CONSISTING OF SIX
FOUR-COLUMN SECTIONS
18"
3 Tubes
4 Tubes
5 Tubes
6 Tubes
7 Tubes
1 Column
2 Cols.
3 Cols.
4 Cols.
5 Cols.
2.60
3.00
22"
1.72
2.25
2.67
3.00
4.20
1.50
2.00
3.50
3.75
20"
2.25
3.00
4.50
FOUR-COLUMN
SECTION
23"
26"
30"
2.00
2.50
3.00
3.50
2.33
2.75
3.50
4.00
4.75
2.00
2.67
3.75
5.00
7.00
3.00
1.67
2.33
3.00
4.00
5.00
6.30
4.33
32"
3.50
4.33
5.00
2.50
3.33
4.50
6.50
8.50
36"
38"
3.50
4.25
5.00
3.50
45"
6.00
3.00
4.00
5.00
8.00
10.0
5.00
6.00
10.0
1. Find the Sq. Ft. EDR per section above (4.00).
2. Multiply by the number of sections altogether in that radiator to get Sq. Ft. EDR for the
entire radiator (4.00 6 24 Sq. Ft. EDR).
3. Multiply by 240 BTUs per hour to get the steam design output or Multiple by 170 BTUs
per hour to get the hot water design output.
Figure 2-3
Sizing cast-iron radiators. (Courtesy John D. Howell [hydronics.com])
Radiators, Convectors, and Unit Heaters 79
sections are the divisions or separations of a cast-iron radiator as
seen when standing directly in front of it. When you look at the
radiator from its narrow end, you can see that each section consists
of one or more vertical columns or pipes.
Note
These vertical columns or pipes (they are called columns in the
traditional cast-iron radiators) are 21⁄2 inches wide. In newer radiators, they are called tubes and are only 11⁄2 inches wide.
Find the square-foot EDR (equivalent direct radiation) of one
section of the radiator. Multiply that figure by the number of sections in the radiator module to arrive at the square-foot EDR rating
of that radiator. Multiply the square-foot EDR rating by 240 Btu
per hour to obtain the heating capacity of that radiator in a steam
heating system or by 170 Btu per hour for its heating capacity in a
hot-water heating system.
Installing Radiators
A cast-iron radiator is constructed by joining together a number of
individual sections (see Figure 2-4). The number of sections used
depends on the heating requirements for the room or space. For
purposes of on-site handling, these radiators are supplied up to a
A cast iron radiator is made up of
individual sections joined together
to form a larger radiator module.
For ease of site handling these radiators are
supplied up to a maximum of ten section
modules.
Figure 2-4
Joining together radiator sections.
(Courtesy John D. Howell [hydronics.com])
80 Chapter 2
maximum of 10 section modules. Additional sections can be joined
together on site to form longer radiators (see Figure 2-5). The procedure used to join the sections will depend on whether the nipples
are threaded or smooth and beveled.
Figure 2-5 Forming longer
radiators on-site.
(Courtesy John D. Howell [hydronics.com])
Joining Threaded Radiator Sections
In older cast-iron radiators, each section has a pair of 11⁄4-inchdiameter threaded openings. One pair of openings has left-handed
threads, and the opposite pair on the facing section has righthanded threads (see Figure 2-6).
SYMBOL
PLAIN
Side with left
handed threads.
Figure 2-6
Side with right
handed threads.
Left-handed and right-handed threaded waterways.
(Courtesy John D. Howell [hydronics.com]).
To join the radiator sections together, connect the openings
threads with left- and right-handed threaded nipples and joining
gaskets. Proceed as follows:
1. Clean the gasket seating areas of the four waterway openings
with abrasive cloth (not a file) to ensure that they are free of
paint, dirt, and any other contaminants that would interfere
with the joining of the two radiator section surfaces (see
Figure 2-7).
Radiators, Convectors, and Unit Heaters 81
Cleaning gasket seating area around waterway opening
on radiator section. (Courtesy John D. Howell [hydronics.com])
Figure 2-7
2. Align the sections accurately. Make sure that the end sections
being joined together have opposite threads—in other words,
left-handed threads on one section facing right-handed
threads on the other.
Note
Sections with an O symbol positioned on the top left-hand side
are left-handed threads. Sections with no symbol have righthanded threads.This holds true for all models except 6/58, which
is the reverse. The side with a symbol on it has right-handed
threads, and the plain side has left-handed threads.
3. Make sure the top and bottom seams on the cast-iron radiator
sections match. The top seams are commonly smoother than
the bottom ones.
4. Screw the nipples into the first pair of threads by turning only
one turn each (see Figure 2-8).
5. Place a jointing gasket over each nipple.
Warning
Do not use jointing compound or PFT tape when jointing gaskets
and nipples. Doing so will invalidate the radiator manufacturer’s
guarantee.
6. Using the largest radiator section as a base unit, add smaller
sections to it by carefully aligning and mating the opposing
waterways and protruding nipples (see Figure 2-9).
82 Chapter 2
Installing
nipples and gaskets.
Figure 2-8
NIPPLE
GASKET
(Courtesy John D. Howell [hydronics.com])
Adding smaller
sections to a larger base
unit.
Figure 2-9
(Courtesy John D. Howell [hydronics.com])
7. Determine the insertion depth of the joining key by measuring
it along the top of the radiator from the position of the new
joint to the point where it will project from the base unit waterway. Mark this point on the joining key shaft (see Figure 2-10).
8. Insert the joining key through one of the waterways of the
second section (see Figure 2-11). Applying slight pressure,
pull the two sections together with one hand and begin to
turn the joining key with the other hand until they begin to
join together. Stop when both are engaged.
Radiators, Convectors, and Unit Heaters 83
JOINING KEY
Figure 2-10
Measuring the insertion depth with the joining key.
(Courtesy John D. Howell [hydronics.com])
Note
Use a wood block under the joining key to keep it in line. Doing so
will ensure that the waterway threads are not damaged by the key
shaft.
9. Repeat step 8 by inserting the joining key through the second
waterway (each radiator section has a waterway at the top
and bottom). Alternate between both waterways a few turns
at a time until the end sections meet and the nipples are handtight. Do not fully tighten yet.
10. Make a final check to ensure that both radiator sections are
uniformly aligned, and then fully tighten them to a recommended torque of 140–150 lbs/ft (see Figure 2-12). Do not
over-tighten or you may strip the threads.
11. Add additional radiator sections by following the same procedures previously described. When the required number of sections
84 Chapter 2
Turn joining key clockwise.
Figure 2-11
Inserting the joining key. (Courtesy John D. Howell [hydronics.com])
have been added, lift and carry the completed radiator in the
upright position to the installation point. Do not carry it on its
side because doing so will place stress on the joints.
Note
Site assembly following the aforementioned procedures should
produce a radiator capable of reaching a test pressure of 140 psi.
Remove radiator sections by reversing the aforementioned installation steps. Before attempting to unscrew the nipples with the joining
key, look through the waterways for the rough or smooth side of the
Radiators, Convectors, and Unit Heaters 85
Figure 2-12
Tightening the sections to the required torque.
(Courtesy John D. Howell [hydronics.com])
nipples. If the rough side is visible, turn the joining key counterclockwise. If the smooth side is visible, turn it clockwise (see Figure 2-13).
Joining Radiator Sections with Smooth Beveled Nipples
Modern radiators have threadless push nipples instead of threaded
ones. A push nipple is a short, smooth, beveled pipe. The bevel creates a bulge in the middle of the nipple. When the nipple is pushed
into the opening in the radiator section, the bulge creates a tight
Turn joining key counterclockwise.
Turn joining key clockwise.
Turning the joining key counterclockwise or
clockwise as required. (Courtesy John D. Howell [hydronics.com])
Figure 2-13
86 Chapter 2
seal. Push nipples have replaced threaded nipples in radiators
because the latter are almost impossible to remove after years of
use. Corrosion on the threads causes a weld-like seal to form, making
it very difficult to disassemble the radiator.
Radiator Valves
Various valves are required for the efficient operation of radiators.
These valves (or vents) are used to bleed air from the radiator when
the heating system first starts. The choice of valve will depend on
the requirements of the particular system.
The four principal functions provided by valves operating in
conjunction with radiators are as follows:
1. Admission and throttling of the steam or hot-water supply.
2. Expulsion of the air liberated on condensation.
3. Expulsion of air from spaces being filled by steam or hot
water.
4. Expulsion of the condensation.
Radiator valves (packed or packless), manual or automatic air
valves, and thermostatic expulsion valves (traps) are used to perform the aforementioned functions.
The packed-type radiator valve is an ordinary low-pressure
steam valve that has a stuffing box and a fibrous packing to prevent
leakage around the stem (see Figure 2-14). The objection to this
type of valve is the frequent need for adjustment and renewal of the
packing to keep the joint tight. These valves also require many
turns of the stem to fully open.
The packless radiator valve is one that has no packing of any
kind. Sealing is obtained by means of a diaphragm (see Figure
2-15) or a bellows (see Figure 2-16). On each valve, there is no connection between the actuating element (stem and screw) and the valve
being sealed hermetically; hence, there can be no leakage. With the
diaphragm arrangement, a spring is used to open the valve. With
bellows construction, there is no spring; a shoulder on the end of the
stem works in a bearing on the valve inside the bellows.
Some so-called packless radiator valves actually employ spring
discs to secure a tight joint. Although called packless, the spring
discs form a metallic equivalent of packing.
Both manual and automatic air valves are used to remove air
from radiators. The manual valves are not well adapted for this
function because they usually receive only irregular attention. Air is
Radiators, Convectors, and Unit Heaters 87
HANDWHEEL
PACKING
NUT
VALVE
SPINDLE
GLAND
STUFFING
BOX
SCREW
THREAD
BONNET
VALVE
INLET
OUTLET
SEAT
PARTITION
Figure 2-14
SPHERICAL OR "GLOBE" SHAPED CASTING
Typical packed radiator valve.
constantly forming in the radiator and should be removed as it forms.
After the air valve remains closed for some time, the radiator gradually fills with air (or becomes air bound), as shown in Figure 2-17,
with the air at the bottom and the steam at the top. On opening the
valve (see Figure 2-18), the air is pushed out by the incoming steam.
The radiator is gradually filled with steam until it begins to come
out of the air valve (see Figure 2-19). At this point, the air valve
should be closed.
An automatic air valve is one form of the thermostatic valve (see
Figure 2-20). Automatic operation is made possible by a bimetallic
element contained in the valve. The principles generally employed
to secure automatic action are as follows:
1.
2.
3.
4.
Expansion and contraction of metals.
Expansion and contraction of liquids.
Buoyancy of flotation.
Air expansion.
88 Chapter 2
VALVE STEM
PRESSURE BUTTON
DIAPHRAGM
MOTION
COMPLIFIER
OPENING
SPRING
VALVE & SEAT
Figure 2-15
Diaphragm-type packless radiator valve. (Courtesy Trane Co.)
When the relatively cold air passes
through the valve, the metal strips lie in
contracted position (with legs close
together and the valve open), allowing
air to escape (see Figure 2-21). The steam
then enters the valve, and its higher temperature causes the metal strips in the
bimetallic element to expand. The brass
strip expands more than the iron strip,
which causes the end containing the valve Figure 2-16 Bellowsspindle to rise and close (see Figure 2-22). type packless radiator
When the strips are fully expanded, the valve. (Courtesy Sarco Co.)
Radiators, Convectors, and Unit Heaters 89
Figure 2-17
Air-bound radiator.
AIR VALVE
CLOSED
OPEN
AIR
Figure 2-18
AIR
Air is pushed out by incoming steam.
valve is closed, shutting off the escape of steam (see Figure 2-23). In
case the radiator becomes flooded with water, the additional water
entering will cause the float to push up the valve and prevent the
escape of water (see Figure 2-24).
Because an automatic air valve is used only for expelling air
from a radiator, it should be distinguished from a thermostatic
expulsion valve. A thermostatic expulsion valve opens to air and
condensation and closes to steam. The low temperature of the air
and condensation causes the bimetallic element to contract and
90 Chapter 2
Steam escaping
from air valve.
Figure 2-19
STEAM
ADJUSTABLE
VALVE SEAT
NEEDLE VALVE
FLOAT
RADIATOR
CONNECTION
BEARING
BRASS STRIP
IRON STRIP
Figure 2-20
Working components of an automatic air valve.
open the valve, whereas the relatively high temperature of the
steam causes the element to expand and close the valve.
Although a thermostatic expulsion valve is sometimes referred to
as a trap, this term is more correctly used to indicate a larger unit
not connected to a radiator and having the capacity to drain condensation from large mains. As distinguished from the thermostatic
valve, a trap handles only condensation and not air.
A bellows charged with a liquid is used on some of the thermostatic valves as an actuating element instead of the bimetallic device.
Radiators, Convectors, and Unit Heaters 91
AIR
INITIAL POSITION
OF FLOAT
INITIAL POSITION
OF BIMETAL ELEMENT
COOL
AIR
METAL STRIPS
CONTRACTED
Figure 2-21
Bimetal strips contracted and valve open.
AIR
VALVE RISING
TO CLOSE
ORIGINAL LEVEL
OF FLOAT
HOT
STEAM
INITIAL
POSITION
Figure 2-22
METAL STRIPS
EXPANDING
Bimetal strips expanding.
92 Chapter 2
HOT STEAM
(ALL AIR EXPELLED)
VALVE
CLOSED
INITIAL
POSITION
Figure 2-23
STRIPS
EXPANDED
Bimetal strips fully expanded and valve closed.
VALVE CLOSED BY
BUOYANCY OF
FLOAT
WATER
Figure 2-24
Valve closed by buoyancy of float.
The operating principle of a Trane bellows-type thermostatic valve
is illustrated in Figures 2-25, 2-26, 2-27, and 2-28.
Additional information about valves and valve operating principles is contained in Chapter 9 of Volume 2 (“Valves and Valve
Installation”).
Radiator Piping Connections
Some typical radiator piping connections are shown in Figures
2-29, 2-30, 2-31, 2-32, and 2-33. The important thing to remember
when connecting a radiator is to allow for movement of the risers
Radiators, Convectors, and Unit Heaters 93
Condensate being
discharged from heating unit.
Figure 2-25
Steam enters trap.
Pressure within the bellows
increases and causes it to
expand.
Figure 2-26
and runouts. This movement is caused by the expansion and contraction resulting from temperature changes in the piping.
Vents and Venting
Each volume of water contains a small percentage of air at atmospheric pressure mechanically mixed with it. This air is liberated
94 Chapter 2
All condensate is
drained from unit.
Figure 2-27
Steam completely
surrounds the bellows.
Figure 2-28
during vaporization and causes some problems for the circulation
of steam in the system. As steam starts to fill a heating system, it
can enter the radiators, convectors, or baseboard units only as fast
as the air escapes. For this reason, some means must be provided to
vent this air from the system.
Radiators, Convectors, and Unit Heaters 95
ECC.
BUSHING
RADIATOR
RECESSED AND GRILLED
UNION ELL
FIRST FLOOR
BASEMENT
CEILING
WEBSTER
RETURN TRAP
WEBSTER
SUPPLY VALVE
SUPPLY
RETURN
Figure 2-29
Radiator supply and return connections for first-floor
installation.
SUPPLY VALVE
WITH ORIFICE
ECC. BUSHING
WEBSTER
RETURN TRAP
FLOOR
RETURN
Figure 2-30
installation.
RADIATOR
SUPPLY
CEILING BELOW
Radiator supply and return connections for upper-floor
96 Chapter 2
RISER
RUNOUT
ABOVE
FLOOR
WALL LINE
RADIATOR
SWING
JOINT
RUNOUT
BELOW FLOOR
PLAN
RISER
AIR
VALVE
RADIATOR
ANGLE
VALVE
RUNOUT
ABOVE FLOOR
FLOOR
HOT
COLD
RUNOUT BELOW
FLOOR RADIATOR
ELEVATION
Figure 2-31
One-pipe radiator connections. (Courtesy 1960 ASHRAE Guide)
Air Vent Locations
The location of a radiator vent will depend on the type of heating
system.
• Hot-water (hydronic) system radiators. The air vent is
located at the top of the radiator on the side opposite the inlet
(supply) pipe.
• Steam system radiators. No air valve is required for a radiator in a two-pipe steam heating system. In a one-pipe steam system, the radiator should have an air valve (vent) installed halfway
down on the side opposite the inlet pipe.
Radiators, Convectors, and Unit Heaters 97
SUPPLY
MAIN
TRAP
DRY
RETURN
VALVE
AT LEAST
18"
ECCENTRIC
BUSHING
DIRT
POCKET
BOILER WATER LINE
WET
RETURN
Figure 2-32
DIRT
POCKET
CHECK
VALVE
Two-pipe connections to radiator installed on wall.
RISERS
VALVE
WATER-TYPE
RADIATOR
ECCENTRIC
BUSHING
COOLING LEG
AT LEAST
5' LONG
TRAP
GATE VALVE
F&T
TRAP
DIRT
POCKET
DRY
RETURN
Two-pipe top and bottom opposite-end radiator
connections. (Courtesy 1960 ASHRAE Guide)
Figure 2-33
98 Chapter 2
Adjustable air valves are often found in systems fired by automatic oil or gas burners. This type of air valve permits the adjustment of radiators varying in size and/or distance from the furnace
or boiler so that radiators heat at an equal rate.
Nonadjustable air valves are not recommended because the
larger radiators will still contain air after the smaller ones have
been completely vented. The same problem occurs with the last
radiator on a long main. Often the air valve on this radiator does
not have enough time to rid the system of air before the on period is
completed and the thermostat shuts off the burner. One method of
handling this problem is by installing a large-size quick vent at the
end of the long main (see Figure 2-34).
BOTH RADIATORS HOT
FULL OF STEAM
FULL OF STEAM
LARGEST SIZE
QUICK VENT
LONG MAIN
3⁄
4
INCH CONNECTION
BOILER
Figure 2-34
Large-size quick vent installed at end of long main.
Double- or triple-venting is an extreme method of solving the
problem of a persistently cold radiator (see Figure 2-35). There is
usually only one opening for an air valve on a radiator. A second
opening can be added by using a 1⁄8-inch pipe tap and a drill of the
proper size.
If a multiple-valve arrangement for a radiator fails to produce
the desired results, the only other possibility is to lengthen the
burner on period. This can be accomplished on oil burners by altering the differential.
Air must also be vented from hot-water heating systems. Trapped
air will cause these systems to operate unsatisfactorily, and a means
Radiators, Convectors, and Unit Heaters 99
LARGE
QUICK VENT
ALL OUT AID
ESPECIALLY FOR BATHROOMS
MAIN
Figure 2-35
Triple-venting a radiator.
should be provided to eliminate it. Manually operated air valves
located at the highest levels in the heating system and automatic air
valves placed at critical points will usually vent most of the trapped
air.
Steam Traps
Steam enters the top of the radiator in a two-pipe steam heating
system. As the steam moves through the radiator, a portion of it
condenses and the water drips down to the bottom of the unit
where it exits through a condensate pipe. In the two-pipe system, a
steam trap is installed where the condensate pipe is connected to
the radiator. The function of the steam trap is to remove the water
(condensate) and prevent any steam from escaping the radiator and
entering the condensate return lines. Additional information about
steam traps can be found in Chapter 10 (“Steam and Hydronic Line
Controls”) of Volume 2.
Not all radiators in two-pipe steam heating systems use steam
traps to prevent the steam from entering the condensate return
lines. Some are equipped with a small check valve, an internal
opening, or a seal.
Troubleshooting Radiators
If a radiator in a hot-water or steam heating system is not producing enough heat (or not producing heat at all), it may not be the
fault of the radiator. Check the room thermostat and the automatic
100 Chapter 2
fuel-burning equipment (gas burner, oil burner, or coal stoker) to
determine if they are malfunctioning. Methods for doing this are
detailed in the appropriate chapters of Volumes 1 and 2. If you are
satisfied that they are operating properly, the problem is probably
with the radiator.
Hot water or steam enters a radiator at an inlet in the bottom
and must rise against the pressure of the air contained in the radiator. A radiator is equipped with an automatic or manual air valve at
the top to allow the air to escape and consequently permit the water
or steam to rise.
In radiators equipped with automatic air valves, rising water or
steam usually has enough force to push the air in the radiator out
through the valve. The valve is automatically closed by a thermostatic
control when it comes in contact with the hot water or steam. If a
radiator equipped with an automatic air valve is not producing
enough heat, the valve may be clogged. This can be checked by closing the shutoff valve at the bottom of the radiator and unscrewing the
air valve. If air begins to rush out, open the radiator shutoff valve to
see if it will heat up. An increase of heat is an indication that the air
valve is clogged. Close the radiator shutoff valve again, remove the
air valve, and clean it by boiling it in a solution of water and baking
soda for 20 or 30 minutes. The radiator should now operate properly.
A radiator equipped with a manual air valve should be bled of
air at the beginning of each heating season. It should also be bled if
it fails to heat up properly. This is a very simple operation. Open
the manual air valve until water or steam begins to run out. The
water or steam running out indicates that all the air has been eliminated from the radiator.
Sometimes radiators are painted to improve their appearance.
When a metallic paint (such as aluminum or silver) is used, the
heating efficiency is reduced by 15 to 20 percent. If you must paint
a radiator, use a nonmetallic paint for all surfaces facing the room.
Dirty surfaces will also reduce the heating efficiency of a radiator. A
good cleaning will eliminate the problem.
Convectors
A convector is a heat-emitting unit that heats primarily by convection. In other words, most of the heat is produced by the movement
of air around and across a heated metal surface. The air movement
across this surface can be gravity-induced or forced. As a result,
convectors are classified as either gravity air convectors or forcedair convectors. They are used in hydronic (forced hot-water) and
two-pipe steam heating systems.
Radiators, Convectors, and Unit Heaters 101
Small, upright gravity and forced-air convectors are commonly
found in older heating installations. The design of this type of unit
was probably influenced by cast-iron radiators. A much more efficient convector is the fin-and-tube baseboard unit (see Fin-andTube Baseboard Units in this chapter).
Typical radiation
convector. (Courtesy Trane, An American
Figure 2-36
Standard Company)
An example of a modern convector is illustrated in Figure 2-36.
The convector cabinets are available in a variety of different bakedon enamel color finishes. Some convectors have a small door on the
front of the cabinet to provide entry for cleaning the heating element
(see Figure 2-37). On other convectors, the entire front panel will
swing upward for access. The heating element consists of aluminum
fins attached to three copper tubes (see Figure 2-38). The tubes are
supported by brass headers and hangers on each end of the assembly.
The rating of convectors used in hot-water heating systems is
determined by water temperature, temperature drop, and inlet air
temperature. The rating of those used in steam heating systems is
determined by steam pressure and the entering air temperature. The
convector manufacturer provides specifications for its convectors,
including sizing data tables.
Convector Piping Connections
The piping connections for a typical gravity convector are shown in
Figure 2-39. Supply connections to the convector heating element
are made at the top, bottom, or end of the inlet header. Return connections are made at the bottom or end of the header at the opposite end of the unit. Figure 2-40 illustrates two recommended piping
connections for convectors used in a hot-water heating system.
Typical convector piping connections for units used in steam heating
systems are shown in Figures 2-41 and 2-42.
102 Chapter 2
ACCESS
DOOR
HEATING ELEMENT
Figure 2-37
Location of access door and heating element assembly.
(Courtesy Trane, An American Standard Company)
3-POSITION HANGER
VENT PLUG
Heating element consisting of die
formed aluminum fins mechanically
bonded to copper tubes.
BRASS HEADER
Figure 2-38
Heating element assembly.
(Courtesy Trane, An American Standard Company)
Radiators, Convectors, and Unit Heaters 103
AIR OUTLET
GRILLE
CONVECTOR
ENCLOSURE
CONVECTOR
ELEMENT
VERTICAL
TRAP
AIR INLET OPENING
INLET
VALVE
STEAM
SUPPLY
Figure 2-39
CONDENSATE
RETURN
Typical convector connections. (Courtesy 1960 ASHRAE Guide)
AIR
CHAMBER
AIR
VALVE
PIPE
PLUG
HEADER
STREET
ELBOW
STREET
ELBOW
REGULATING
ELBOW
Convector piping connections in a hot-water heating
system. (Courtesy Dunham-Bush, Inc.)
Figure 2-40
104 Chapter 2
RADIATOR
VALVE
SUPPLY
STUB
FLOOR
PLATE
SUPPLY
RUNOUT
SUPPLY
RISER
Figure 2-41
Typical convector connections in a steam heating system.
(Courtesy Dunham-Bush, Inc.)
Gravity convector piping connections are very similar to those
used with radiators, except that the lines must be sized for a greater
condensation rate. The usual method for determining convector
capacities is to convert them to the equivalent square feet of direction radiation (EDR):
EDR Convector Rating (Btuh)
240 Btu
Radiators, Convectors, and Unit Heaters 105
STEAM
VALVE
HEADER
HEADER
ELBOW
HEADER
VERTICAL
TRAP
HEADER
COMBINATION
VALVE AND
REGULATING
FITTING
HEADER
ANGLE
PATTERN
TRAP
ANGLE
PATTERN
TRAP
ELBOW
3 ⁄ " X 1⁄ "
4
2
ELBOW
HEADER
ADJUSTABLE
REGULATING
FITTING
ELBOW
HEADER
VERTICAL
REGULATING
FITTING
HEADER
HEADER
3⁄ "
4
UNION
FINISH
FLOOR LINE
X 1⁄2"
ELBOW
ANGLE
PATTERN
TRAP
Figure 2-42 Convector piping connections in a steam heating system.
The 240 Btu figure represents the amount of heat in Btu given
off by ordinary cast-iron radiators per square foot of heating surface per hour under average conditions.
The connections used for a forced hydronic convector are similar
to those used with unit heaters (see Unit Heater Piping Connections
in this chapter).
106 Chapter 2
Hydronic Fan Convectors
Hydronic system fan convectors are equipped with small fans controlled by a fan switch. The fan blows air across the heating element assembly and into the room or space. If there is no heat, a
low-limit aquastat will shut off the fan when the temperature drops
below a predetermined setting.
Troubleshooting Hydronic Fan Convectors
Check the room thermostat first and then the boiler to determine if
either is malfunctioning (see Table 2-4). Procedures for troubleshooting boilers, water heaters, and thermostats are detailed in
the appropriate chapters of Volumes 1 and 2.
Table 2-4
Troubleshooting Fan Convectors
Symptom and Possible Cause
Possible Remedy
Fan does not operate.
(a) Low water temperature.
(b) Low water flow rate.
(c) Tripped circuit breaker or
blown fuse.
(d) Faulty aquastat.
(e) Air-bound coil.
(a) Check for problem with boiler,
water heater, or piping and
repair.
(b) Check piping and correct.
(c) Reset circuit breaker or replace
fuse. If problem continues,
request a service call from an
electrician or HVAC technician.
(d) Replace aquastat.
(e) Check bleeder vent and repair.
Poor heat output.
(a) Low water temperature.
(b) Low water flow rate.
(c) Incorrect clearances around
convector.
(a) Check boiler or water heater
and repair.
(b) Check piping and correct as
necessary.
(c) Check specified clearance in
local code and manufacturer’s
specifications and correct.
Fan operates at only one speed or runs intermittently.
(a) Broken or loose wiring
connection.
(b) Poorly balanced system.
(c) Air-bound unit.
(a) Replace wire if connection
broken; tighten connection.
(b) Check piping and correct as
necessary.
(c) Check air vent and correct as
necessary.
Radiators, Convectors, and Unit Heaters 107
Note
The boiler or dedicated water heater should be set at a minimum
temperature of 140ºF for the fan convector to operate efficiently.
Check the manufacturer’s installation instructions to make certain the convector is properly piped (correct sizing, layout, and so
on). If the flow rate for the convector is less than 1 gpm, then there
is a piping problem.
Check the wiring to make sure the convector is wired properly,
and then examine the wires for loose connections or damaged
wiring. If the wiring, piping, and boiler (or water heater) check out
all right, the problem is in the convector itself.
Steam and Hot-Water Baseboard Heaters
Baseboard heaters are designed to be installed along the bottom of
walls where they replace sections of the conventional baseboard (see
Figure 2-43). Locating them beneath windows or along exterior
walls is a particularly effective method of eliminating cold drafts.
Figure 2-43
Typical baseboard heating installation. (Courtesy Vulcan Radiator Co.)
108 Chapter 2
Baseboard heaters are frequently used in steam and hot-water
heating systems (see Figures 2-44 and 2-45). In a series-loop system, supply and branch piping can be eliminated by using the baseboard heater to replace sections of the piping. In other words, there
is no need for supply and return branches between the baseboard
heater and the mains.
Baseboard heaters are also available with electric heating elements controlled by a centrally located wall-mounted thermostat or
a built-in thermostat. Each unit is actually a separate heater (see
Electric Baseboard Heaters in this chapter), but they can be joined
and wired together to form a baseboard heating system.
The Institute of Boiler and Radiator Manufacturers (IBRM) has
established testing and rating methods of baseboard heat-emitting
units. The output for baseboard units is rated in Btu per hour per
linear foot.
Construction Details
Two types of baseboard heaters are used in steam and hot-water
(hydronic) heating systems: those with separate fins attached to the
tubing and those with the fins cast as an integral part of the unit.
The integral-fin units are made of cast iron. Those with separate fins
are made of nonferrous metals such as copper, aluminum, or alloys.
Separate Fin-and-Tube Baseboard Units
An example of a baseboard heater with the fins attached to the tubing is shown in Figure 2-45. The size and length of the tube, as well
as the number, size, and spacing of the metal fins, will vary from
one manufacturer to the next. Fin shapes, sizes, and spacing can be
ordered to specification from the manufacturer. Basically the fins
are either square or rectangular (see Figure 2-46). Some will have
special design features, such as flared ends (see Figure 2-47).
The assembly of the heating element is covered by a sheet-metal
enclosure. Openings are cut into the face of the cove to increase
air circulation. When steam or hot water is passed through the
tube, the heat is transmitted to the fins by conduction through the
metals. The heat transmitted to the fins is transferred to the air by
convection.
The heating-element tube is available in a variety of sizes, including 3⁄4, 1, 11⁄4, and 11⁄2 inches (see Figure 2-48). On short pipe runs,
the 3⁄4-inch tube is recommended in order to ensure water velocities
in the turbulent flow range. On long runs and with loop systems, it
may be desirable to use 1- or 11⁄4-inch tube sizes.
Use of the small tube sizes results in lower cost for connecting
piping in a run and for valves, expansion joints, balancing cocks,
Radiators, Convectors, and Unit Heaters 109
DAMPER
ASSEMBLY
DAMPER
PIVOT
RETURN
TUBE
RETURN TUBE
HANGER
SUPPLY TUBE
HANGER
HEATING
ELEMENT
FRONT PANEL
ELEMENT GUIDE
Design features of a hot-water heating baseboard
unit. (Courtesy Weil-McLain Co.)
Figure 2-44
110 Chapter 2
Figure 2-45
Return tube installation for hot-water heating system.
(Courtesy Weil-McLain Co.)
Figure 2-46
Typical fin shapes. (Courtesy Vulcan Radiator Co.)
Figure 2-47
Heating-element fins with flared ends. (Courtesy Weil-McLain Co.)
Radiators, Convectors, and Unit Heaters 111
3 ⁄ " COPPER TUBE
4
(ALUMINUM FINS)
111⁄14⁄4COPPER
" COPPERTUBE
TUBE
(ALUMINUM
(ALUMINUMFINS)
FINS)
Figure 2-48
1" COPPER TUBE
(ALUMINUM FINS)
11⁄4" STEEL TUBE
(STEEL FINS)
1" STEEL TUBE
(STEEL FINS)
2" STEEL TUBE
(STEEL FINS)
Heating-element tube sizes. (Courtesy Vulcan Radiator Co.)
and fittings. There is also a lower heating-element cost involved
with the small tube sizes.
The fins and tubing can be made of the same or different metals
(see Figures 2-49 and 2-50). The following combinations are
among those possible:
1.
2.
3.
4.
5.
6.
Copper fins on copper tubing.
Aluminum fins on copper tubing.
Aluminum fins on aluminum tubing.
Aluminum fins on steel tubing.
Stainless-steel fins on stainless-steel tubing.
Cupronickel fins on cupronickel tubing.
These different metals exhibit different heating characteristics,
and all are not suitable for the same application. For example, steel
heating elements are recommended for high-temperature water systems. Copper-aluminum elements, on the other hand, work well
with water temperatures up to 300°F. Copper-aluminum heating
elements also produce a high heat output, but the copper tube has a
very high rate of expansion (higher than steel). All these factors
112 Chapter 2
Figure 2-49
Copper-aluminum heating elements.
(Courtesy Vulcan Radiator Co.)
Figure 2-50
Steel heating elements. (Courtesy Vulcan Radiator Co.)
have to be taken into consideration when selecting a suitable heating element for the installation.
Integral Fin-and-Tube Baseboard Heaters
A cast-iron baseboard heater with the fins cast as an integral part of
the unit is shown in Figures 2-51 and 2-52. These baseboard
heaters can be used in series-loop, one-pipe, and two-pipe (reversereturn) forced hot-water heating systems and in two-pipe steam or
vapor heating systems. They are not recommended for use in onepipe steam heating systems.
There are several advantages to using cast-iron baseboard heaters.
Because the fins are a part of the casting, they will not bend, dent, or
come apart. Cast iron is corrosion resistant and will not expand or
Radiators, Convectors, and Unit Heaters 113
Cast-iron baseboard heater with fins cast as an integral
part of the unit. (Courtesy Burnham Corp.)
Figure 2-51
Figure 2-52
Integral fin-and-tube construction details.
(Courtesy Burnham Corp.)
contract with temperature changes. This last feature eliminates the
expansion and contraction noises that frequently occur with nonferrous, separate fin-and-tube units, which allows them to fit closer
to the wall.
Installing Baseboard Units
A steel fin-and-tube baseboard heating element will expand as
much as 1⁄8 inch per 10 feet with a 70°F to 200°F temperature rise.
114 Chapter 2
A copper element will expand as much as 1⁄16 inch per 10 feet under
the same conditions. This potential expansion of the heating element must be provided for when installing the system or problems
will arise. The following provisions are recommended:
1. Allow a clearance of at least 1⁄4 inch around all piping that
passes through floors or wall partitions.
2. Wrap pipe passing through a floor or wall partition with a felt
or foam sleeve to act as a cushion (see Figure 2-53).
WALL PARTITION
FELT SLEEVE
Figure 2-53
Clearance provided for expansion through wall partition.
(Courtesy Vulcan Radiator Co.)
3. Try to limit straight runs of pipe to a maximum of 30 feet.
Wherever longer runs are necessary, install a bellows-type
expansion joint near the center and anchor the ends.
4. Where a baseboard system extends around a corner, provide
extra clearance at the ends (expansion will generally occur
away from the corner) (see Figure 2-54).
5. When a baseboard system is installed around three adjacent
walls (forming a U), always use an expansion joint in the center leg of the U (see Figure 2-55).
6. When making piping connections, be sure to keep all radiator
elements in proper vertical position so that fin edges will not
touch other metal parts.
Radiators, Convectors, and Unit Heaters 115
Extra clearance with felt
or foam sleeve wrapped
around the pipe.
Extra clearance should be provided for an extension
around a corner. (Courtesy Vulcan Radiator Co.)
Figure 2-54
FINNED-TUBE
UNITS
Figure 2-55
EXPANSION
JOINT
Location of expansion joint.
7. Be sure to support all mains and other piping runs adequately
so that their weight will not cause bowing of the heating
elements.
8. Install a felt sleeve around the pipe where it rests against a
rigid hanging strap (see Figure 2-56).
Before installing the baseboard heater, check the walls carefully
for straightness. The baseboard heaters must be absolutely straight
or their operating efficiency will be reduced. Therefore, it would be
a mistake to use a wall to align the units if the wall were not straight.
116 Chapter 2
FELT
Figure 2-56
Felt support for heating element. (Courtesy Vulcan Radiator Co.)
Shims may have to be used on wavy walls to keep the baseboard system straight.
Many baseboard heaters can be recessed the depth of the plaster.
The back of each unit is nailed to the studs before plastering, and
the top of the baseboard heater hood serves as a plaster stop. The
top accessories must be installed before plastering.
The procedure for installing a steam or hot-water baseboard
heating system may be summarized as follows:
1. Place the backing of the unit against the wall surface or studs
(in a recessed installation) and mark the location of the studs
(see Figure 2-57).
2. Punch holes in the backing and screw it to the studs.
Unit back installed flush against wall surface
or studs. (Courtesy Vulcan Radiator Co.)
Figure 2-57
Radiators, Convectors, and Unit Heaters 117
3. Install cover support brackets approximately 3 feet apart (see
Figure 2-58).
4. Place cradle hangers on rivet head and set the heating element
on the cradles, making sure the fins are vertical and that all
hangers are free to swing (see Figure 2-59).
Figure 2-58
Installing support brackets.
(Courtesy Vulcan Radiator Co.)
Figure 2-59
Setting heating elements in place.
(Courtesy Vulcan Radiator Co.)
5. Complete piping and test for leaks before snapping on the
fronts.
6. Snap the front cover onto the support brackets by hooking
the top lip over the upper arms and snapping the bottom lip
over the bottom arms (see Figure 2-60).
7. Add joining pieces and end enclosures where appropriate (see
Figures 2-61 and 2-62).
118 Chapter 2
Figure 2-60
Snapping on the front cover.
(Courtesy Vulcan Radiator Co.)
Figure 2-61
Installing joint pieces. (Courtesy Vulcan Radiator Co.)
Figure 2-62
Installing corner and end enclosures.
(Courtesy Vulcan Radiator Co.)
Radiators, Convectors, and Unit Heaters 119
Hot-water heating systems can be divided by temperature into
the following three types:
1. High-temperature water systems, 350°F to 450°F.
2. Medium-temperature water systems, 250°F to 350°F.
3. Low-temperature water systems, below 250°F.
Although low-temperature hot-water heating systems are the predominant type used in the United States, there is a growing tendency
to apply high-temperature water not only to underground distribution piping (as in district heating) but also to direct radiation.
When fin-tube baseboard units are used in a high-temperature
hot-water heating system, care must be taken to keep the enclosure
surface temperature to a minimum. This can be accomplished as
follows:
1.
2.
3.
4.
5.
Use the highest enclosure height practical.
Use heating elements only one row high.
Use a maximum fin spacing of 33 per foot.
Spread the heating element out along the entire wall length.
Limit the water temperature to that necessary to offset building heat loss.
Because of the higher heat level, the expansion of heating elements becomes more of a factor with high-temperature hot-water
heating systems. As a result, more expansion joints should be used
along the length of the heating elements than is the case with lowtemperature water.
Baseboard Heater Maintenance
The baseboard heaters used in steam or hot-water heating systems
must be routinely cleaned and vacuumed to ensure that the convective fins are clean. If the fins are covered with a layer of dust or dirt,
it will impede the radiation of heat into the room or space. Remove
the baseboard cover at least once every two months to check the
cleanliness of the fins.
Electric Baseboard Heaters
Electric baseboard heaters are designed for use in residential, commercial, industrial, and institutional heating systems. This chapter
will be primarily concerned with a description of residential heaters.
The electric heaters designed for use in commercial, industrial, or
120 Chapter 2
institutional installations differ from the residential type by being
larger in capacity; otherwise, they are essentially identical in design
(see Figure 2-63).
An electric baseboard heater contains one or more heating elements placed horizontally. Each electric heating element is a unit
assembly consisting of a resistor, insulated supports, and terminals
for connecting the resistor to the electric power supply.
By definition, a resistor is a material used to produce heat by
passing an electrical current through it. Solids, liquids, and gases
may be used as resistors, but solid resistors are the type most frequently used. Resistors may be made up of wire or metal ribbon,
supported by refractory insulation, or embedded in refractory insulating material surrounded by a protective sheath of metal. A typical heating element used in Vulcan electric baseboard heaters is
Figure 2-63
Duraline electric heater. (Courtesy Vulcan Radiator Co.)
Radiators, Convectors, and Unit Heaters 121
shown in Figure 2-64. It consists of nichrome heater coils embedded in a ceramic core.
Figure 2-64
Heater core. (Courtesy Vulcan Radiator Co.)
Each resistor is generally rated from 80 to 250 watts (270 to 850
Btu per hour) per linear foot of baseboard unit. The manufacturer
will give the ratings for each unit (rather than per linear foot) but
will also include its overall length in the data.
Either wall-mounted or built-in thermostats can be used to control the heating elements in electric baseboard heaters. These thermostats (either low-voltage or line voltage types) are designed for
single- or multiple-unit control with single- or two-stage heating
elements. Normally, multiple-unit control is not feasible with twostage units or with a built-in thermostat. It is recommended that
single-stage heating units be used when it is necessary or desirable
to control more than one unit from one thermostat.
Close control of temperatures can be obtained by installing a
time-delay relay in the electric baseboard unit. This type of relay is
particularly useful when a time delay is needed on switch make or
break. Additional information about time-delay relays is included
in Chapter 6 of Volume 2 (“Other Automatic Controls”).
A temperature-limit switch (thermal cutout) should be installed
in each unit to prevent excessive temperature buildup. The maximum surface temperature for each baseboard enclosure should be
limited to 190°F. Exceeding this limit may result in damage to the
heater.
A typical temperature-limit switch used in an electric baseboard
installation is the linear capillary type that ensures constant protection over the entire length of the heater. An automatic resetting
feature allows the heater to resume operation once conditions
return to normal. The temperature-limit switch is usually located
between the heater and the thermostat or disconnect switch in the
wiring (see Figures 2-65 and 2-66). The only exception occurs
when a built-in simultaneous switching thermostat is used (see
Figure 2-67).
122 Chapter 2
SINGLE-STAGE EXTERNAL
TEMPERATURE REGULATOR
TEMPERATURE
LIMIT SWITCH
OPTIONAL
HOT
SINGLE-STAGE
HEATER
COMMON
OPTIONAL
HOT
COMMON
SINGLE-STAGE EXTERNAL
TEMPERATURE REGULATOR
TEMPERATURE
LIMIT SWITCH
OPTIONAL
HOT
COMMON
SINGLE-STAGE
HEATER
HOT
COMMON
Figure 2-65
Single-stage wiring diagrams. (Courtesy Vulcan Radiator Co.)
Radiators, Convectors, and Unit Heaters 123
TWO-STAGE EXTERNAL
TEMPERATURE REGULATOR
TEMPERATURE LIMIT
SWITCH
OPTIONAL
HOT
COMMON
B
R
BUILT-IN
DISCONNECT SWITCH
W
TWO-STAGE
HEATER
Figure 2-66
Two-stage wiring diagram. (Courtesy Vulcan Radiator Co.)
TEMPERATURE LIMIT
SWITCH
OPTIONAL
B
R
HOT
W
TWO-STAGE
HEATER
COMMON
BUILT-IN
DISCONNECT SWITCH
BUILT-IN SIMULTANEOUS
SWITCHING THERMOSTAT
Two-stage wiring diagram with built-in simultaneous
switching thermostat. (Courtesy Vulcan Radiator Co.)
Figure 2-67
124 Chapter 2
In a baseboard heating system, each temperature-limit switch
must be wired to break the electrical circuit only to the heating element or elements of the unit on which it is installed.
Installing Electric Baseboard Heaters
Read the manufacturer’s instructions carefully before attempting to
install an electric baseboard heater. Particular attention should be
paid to wiring instructions and required clearances. Check the local
codes and ordinances before beginning any work. All installation
must comply with local and national electrical codes, with the former
taking precedence.
Caution
To prevent electrical shock and possible equipment damage,
always disconnect the power supply before connecting or disconnecting wiring.
Warning
Special care must be taken when installing a line voltage (240 VAC)
thermostat.A 240-VAC electric shock may cause serious injury or
death.
A minimum clearance is generally required from the bottom of
an electric heater to any obstructing surface, such as a floor, floor
covering, ledge, or sill. The amount of clearance will depend on the
particular unit and manufacturer.
Check the heater operating voltage on the model before
installing it. The watt output of an electric heating unit depends on
the supply (line) voltage. When the supply voltage equals the rated
voltage of the unit, the output will equal the rated watts. Never
connect a heater to a supply voltage greater than 5 percent above
the marked operating voltage on the model label. A heater connected to a supply voltage that is less than the marked voltage on
the model label will result in a watt output that is less than the
model label rating. This will cause a reduced heating effect, which
should be taken into consideration when determining heating
requirements.
Note
Connecting a 120-volt baseboard heater to a 240-volt circuit will
cause the heating element to overheat and destroy the heater.
Connecting a 240-volt heater to a 120-volt circuit, on the other
hand, will result in the heater delivering only about 25 to 30 percent
of its designed output.
Radiators, Convectors, and Unit Heaters 125
A change in watt output with respect to a variation in supply
voltage may be conveniently calculated with the following formula:
2 (supply voltage rated voltage) amps at related voltage
change in watt output.
For example, the change in watt output for a 120-volt/500watt/4.2-amp heating unit connected to a 115-volt line can be calculated as follows:
2 (115 volt 120 volt) 4.2 amp
2 (5 volt) 4.2 amp
10 volt 4.2 amp
42 watt change in output.
Thus, the output of this unit at 115 volts will be 458 watts (500
watts 42 watts). The use of these calculations should be restricted
to a 10-volt difference in the supply voltage at 120 volts and a
20-volt difference, or 208 volts, 240 volts, and 277 volts.
Some manufacturers of electric baseboard heating equipment
produce heaters designed for installation as individual units or as
components of a larger baseboard heating system. The procedure
for installing individual units is as follows:
1. Locate the unit on the wall so that the minimum clearance is
maintained between the bottom edge of the heater and the
finished flooring (see Figure 2-68).
Figure 2-68
Locating and marking the heater. (Courtesy Vulcan Radiator Co.)
126 Chapter 2
2. Position the unit so that the knockouts in the junction box are
aligned with the electrical rough-in location.
3. Locate the wall studs or mullions, and mark the location on
the backing of the unit.
4. Drill or punch mounting holes in the backing a suitable dis-
tance below the hood and above the bottom edge.
5. Connect armored or nonmetallic sheathed cable through the
knockout in the backing or bottom of the junction box (see
Figure 2-69). When entering through the backing, make up
electrical connector, slide excess cable back into the wall
space, and nail or screw the heater backing to the wall.
Figure 2-69
Making the electrical connections.
(Courtesy Vulcan Radiator Co.)
6. Make electrical connection of branch circuit wiring to the
heater. Maintain continuity of grounding (see next paragraph).
7. Snap the heater cover over the brackets and at the same time
align the thermostat operating shaft (built-in thermostats with
the hole in the cover) (see Figure 2-70).
8. Slide the end enclosures over each end of the unit (see Figure
2-71), and tighten the cover screws (see Figure 2-72).
For each electric heater unit, continuity of grounding must be
maintained through circuit wiring devices. All branch circuit wiring
Radiators, Convectors, and Unit Heaters 127
Figure 2-70
Snapping cover over brackets. (Courtesy Vulcan Radiator Co.)
and connections at the heater must be
installed in accordance with local codes and
regulations and the appropriate sections of
the most recent edition of the National
Electrical Code.
Individual electric heaters can be mounted
and wired to form a continuous baseboard
heating system. The units used in a baseboard system should be ordered with a
right-end mounted junction box to facilitate
the wiring of the adjacent unit. The instructions for installing individual electric heaters
should be followed for each unit in the baseboard system (see steps 1–7 of aforemen- Figure 2-71 Typical
end enclosure.
tioned installation procedure).
As shown in Figure 2-73, straight-line (Courtesy Vulcan Radiator Co.)
installation along a wall is simply a matter
of butting the two units and connecting them with a joining piece
(see Figure 2-74). Inside- and outside-corner installation methods
are shown in Figures 2-75 and 2-76.
Kickspace Heaters
A typical kickspace heater is shown in Figure 2-77. It consists of a
copper tube with an attached aluminum finned heating element, a
115-volt electric motor, and a blower/fan. Hot water from the
boiler is circulated through the copper tube inside the unit. The
128 Chapter 2
Figure 2-72
Tightening cover screws. (Courtesy Vulcan Radiator Co.)
Figure 2-73
Straight-line installation. (Courtesy Vulcan Radiator Co.)
blower, which is driven by the small electric motor, forces air across
the heating element, picks up the heat, and sends it into the room.
The blower is turned on or off automatically in response to the
thermostat setting. The blower speed is set manually. The blower
motor operates in conjunction with a 120ºF (49ºC) reverse-acting
aquastat.
Kickspace heaters are designed for use in one-pipe or two-pipe
hydronic heating systems or in a series loop where pressure and
temperature drop can be tolerated. They are used beneath kitchen
Radiators, Convectors, and Unit Heaters 129
sinks, along short entrances and hallways,
and inside bathrooms where space restrictions do not permit the installation of the
longer baseboard heaters. Kickspace
heaters are not designed for use in steam
heating systems. They are also not recommended for use in a gravity-flow hotwater system unless a separately installed
pump is provided to circulate the water.
Kickspace heaters are offered in three
models: horizontal heaters, vertical heaters,
and surface-mounted wall heaters. The
horizontal models are installed beneath Figure 2-74 Joining
kitchen cabinets, bathroom sink enclo- piece.
sures, and similar areas where vertical (Courtesy Vulcan Radiator Co.)
height is limited. The vertical models are
installed fully recessed between wall studs. The air is discharged
upward through a louvered front panel. The surface-mounted wall
model is mounted on the interior surface of a wall. The air is discharged evenly through a louvered front panel in an upward
direction.
Floor and Window Recessed Heaters
Recessed radiation is designed for installation below large glass
areas that extend to the floor and do not permit the use of baseboard radiation. The heat-emitting unit illustrated in Figure 2-78
is an example of recessed radiation used in a hydronic heating
installation.
A typical hot-water recessed radiation heater consists of an
enclosure, a finned element, two element glides, two rubber grommets, and a floor grille with or without dampers (see Figure 2-79).
The operating principle of this unit is relatively simple. The air
entering the unit at the cool-air inlet is separated from the rising
heated air by a baffle (see Figure 2-80). The baffle is designed to
separate the cool inlet air from the rising heated air and to accelerate the flow of air through the unit for maximum heat output. The
baffle is held in position by a guide on each end of the enclosure
and a bracket in the center.
Figures 2-81 and 2-82 show openings used to accommodate
recessed floor units in a wood floor and in masonry construction.
In a wood floor installation where the unit is to be installed parallel
to the joists, an opening with the same dimensions as shown should
be prepared by installing headers between joists.
130 Chapter 2
Figure 2-75
Inside-corner installation. (Courtesy Vulcan Radiator Co.)
Unit Heaters
A unit heater is an independent, self-contained appliance designed
to supply heat to a given space. It is frequently referred to as a space
heater.
The typical unit heater consists of a heating element, a fan or
propeller and motor, and a metal casing or enclosure. Unit heaters
supply heat by forced convection using steam, hot water, gas, oil, or
Radiators, Convectors, and Unit Heaters 131
Outside-corner installation. (Courtesy Vulcan Radiator Co.)
Figure 2-76
ELECTRIC
CONNECTION
BOX
ADUASTAT
RETURN WATER
SWITCH
SUPPLY HOT WATER
HE
DIS ATED
CHA
R
AIR GE
RET
UR
AIR N
Figure 2-77
Kickspace heater. (Courtesy Beacon/Morris)
electricity as the heat source. The air is drawn into the unit heater
and forced over the heating surfaces by a propeller or a centrifugal
fan before it is expelled on a horizontal or vertical air current (see
Figure 2-83).
Horizontal heaters have a specially designed broad-blade fan and
are used for horizontal discharge space and spot heating assignments.
When equipped with louver fin diffusers, the air stream can be
directed in an unlimited number of diffusion patterns. A typical
horizontal pipe suspended unit heater is shown in Figure 2-84.
132 Chapter 2
Figure 2-78
Typical floor recessed unit. (Courtesy Weil-McLain Co.)
GRILLE
BAFFLE
WELDED END
ENCLOSURE
RUBBER
GROMMET
3⁄ "
4
ELEMENT
GLIDE
Figure 2-79
BOX TYPE
ALUMINUM
FINS
COPPER
TUBE
Typical components of a recessed radiation unit.
(Courtesy Weil-McLain Co.)
Radiators, Convectors, and Unit Heaters 133
Operating
principle. (Courtesy Weil-McLain Co.)
Figure 2-80
63 ⁄8"
62 3
8⁄ "
AS REQUIRED
Figure 2-81
Wood floor opening. (Courtesy Weil-McLain Co.)
134 Chapter 2
"
63 ⁄ 8
62 3
⁄8 "
Top of box when
nailed to stakes.
To be flush with
finished floor.
1⁄ "
2
Figure 2-82
MAX
Stake arrangement for masonry floor opening.
(Courtesy Weil-McLain Co.)
Figure 2-83
Typical air discharge paths. (Courtesy Vulcan Radiator Co.)
Radiators, Convectors, and Unit Heaters 135
TUBES
SUPPLY AND
RETURN TAPPINGS
FAN
GUARD
RUBBER
GROMMETS
LOUVER
STOP DEVICE
LOUVERS
FAN AND
MOTOR
Figure 2-84
Direct pipe suspended horizontal unit heater.
Forced-air unit heaters are small blower units that exhibit several times the capacity of a gravity circulation unit of the same size.
Unit Heater Piping Connections
The following general notes on piping propeller unit heaters are
presented based on competent engineering installation practice:
1. Suspend unit heaters securely with provisions for easy removal.
2. Make certain that units hang level vertically and horizontally.
3. Provide for expansion in supply lines. Note swing joints in
suggested piping arrangements.
4. Provide unions adjacent to unit heaters in both supply and
return laterals. Also provide shutoff valves in all supply laterals.
5. Use 45°-angle runoffs from all supply and return mains.
6. Make certain that you have provided minimum clearances on
all sides. Clearances will be specified in the heater manufacturer’s installation literature.
136 Chapter 2
7. When required, dirt pockets should be formed with pipe of
the same size as the return tapping of the unit heater.
8. Pipe in the branching line should be the same size as the tap-
ping in the trap.
Figures 2-85 through 2-90 illustrate typical piping details for
propeller-type horizontal unit heaters used in steam and hot-water
heating systems.
The vapor steam system shown in Figure 2-85 uses an overhead
steam main and a gravity dry return. Strainer and float-type steam
traps are used between the unit heater and the return main. A floattype air vent is installed below the float trap.
SUPP
LY M
AIN
VALVE
UNION
FLOAT
VENT
UNION
DIRT
POCKET
FLOAT TRAP
TO RETURN MAIN
Figure 2-85
Piping connections for a vapor steam heating system.
Radiators, Convectors, and Unit Heaters 137
VALVE
FLOAT VENT
45° ELL
PLY
SUP
N
MAI
FLOAT TRAP
UNION
UNION
STRAINER
DIRT POCKET
DIRT POCKET
FLOAT TRAP
Piping connections for a low-pressure or
vacuum steam heating system.
Figure 2-86
As shown in Figure 2-86, the overhead steam main of a lowpressure or vacuum system can be vented and dripped independently.
The steam supply to the unit heater is taken off the top of the main.
The float vent is eliminated on systems using a vacuum pump.
Overhead supply and return mains are used (with bottom connections to the mains) in forced hot-water heating systems. The
supply main is connected to the bottom of the unit heater. Either an
automatic air vent or manual vent (pet cock) can be used at the high
point on the return main (see Figure 2-87).
In the two-pipe steam system shown in Figure 2-88, the steam
supply of the unit heater is taken from the top of the main. The
return from the unit heater is vented before dropping to the wet
return. The distance to the water line of the boiler must be sufficient to allow for the pressure drop in the piping.
138 Chapter 2
PET COCK
AUTOMATIC
AIR VENT OPTIONAL
SQUARE HEAD
COCK
RETUR
N
LL
45° E
UNION
LY
SUPP
45° ELL
UNION
DRAIN VALVE
VALVE
Piping connections for a forced hot-water
heating system.
Figure 2-87
Both an overhead supply main and an overhead return are used
in the high-pressure steam system shown in Figure 2-89. The top of
the bucket trap must be located below the return outlet of the coil
for complete drainage of the condensation.
Unit heater piping connections for a Trane high-pressure steam
system are illustrated in Figure 2-90. In this system, an overhead
supply main is used with a lower return main. Where steam pressure fluctuates over a wide range, a swing-check valve should be
placed in the return lateral between the strainer and the bucket trap
to prevent reverse flow of the condensation or steam flashing when
the pressure drops suddenly. The top of the bucket trap must be
located below the return outlet of the coil for complete drainage of
the condensation.
Unit Heater Controls
Two control systems are used with unit heaters. The simpler type
provides on-off operation of the fan. The other system provides
Radiators, Convectors, and Unit Heaters 139
VALVE
45° ELL
FLOAT
VENT
UNION
AIN
LY M
SUPP
UNION
DIRT
POCKET
WATER LINE
OF BOILER
12" MIN.
SWING
CHECK
TO
R
R
ETU
NM
AIN
Piping connections for a two-pipe steam
heating system.
Figure 2-88
modulating control of the heat source and continuous operation of
the fan. It is considered the more effective control system.
Modulating control is obtained with either pneumatic or electric
equipment. It allows a constant discharge of warm air and eliminates
intermittent blasts of hot air. The continuous circulation prevents
air stratification, which occurs when the fan is off. A proportional
room thermostat governs a valve that controls the heat source or a
bypass around the heating limit. Fan operation is governed by an
auxiliary switch or a limit thermostat. Either device is designed to
stop the fan when the heat is shut off.
In an on-off control system, the fan motor is controlled by a
room thermostat. A backup safety device in the form of a limit
140 Chapter 2
45° ELL
VALVE
VALVE
45° ELL
UNION
AIN
LY M
P
SUP
RN
U
RET
IN
MA
UNION
BUCKET TRAP
SWING CHECK
DIRT POCKET
Piping connections for a standard high-pressure
steam heating system.
Figure 2-89
thermostat will stop the fan when heat is no longer being supplied
to the unit heater.
Gas-Fired Unit Heaters
A gas-fired unit heater is designed to operate on either natural or
propane gas (see Figure 2-91). These units should be installed in a
location where there will be sufficient ventilation for combustion
and proper venting under normal conditions of use.
Local codes and regulations should be followed closely when
installing a gas-fired unit heater.
The automatic controls used to operate a gas-fired unit heater
closely resemble those found on other types of gas heating equipment, such as furnaces, boilers, and water heaters. For example, the
unit heater illustrated in Figure 2-92 is equipped with a 24-volt gas
valve with a built-in pilot relay, pilot gas adjustment, shutoff device
for use with a thermocouple-type pilot for complete gas shutoff
operation, and a gas-pressure regulator.
Radiators, Convectors, and Unit Heaters 141
VALVE
45° ELL
UNION
PLY
SUP
N
MAI
BUCKET TRAP
DIRT POCKET
STRAINER
AIN
NM
UR
RET
Piping connections for a Trane high-pressure steam
heating system. (Courtesy The Trane Co.)
Figure 2-90
A separate gas-pressure regulator and pilot valve are generally
supplied with control systems when the gas valve does not have a
built-in gas-pressure regulator. The usual fan and limit controls are
used on most gas-fired unit heaters. A wiring diagram for a typical
control system is shown in Figure 2-93.
Oil-Fired Unit Heaters
Direct oil-fired, suspended unit heaters operate on the same principle as the larger oil-fired heating equipment (furnaces, boilers,
water heaters, and so on). An oil burner located on the outside of
142 Chapter 2
ALUMINIZED STEEL
DRAFT DIVERTER
VENT TO
STACK
DIVERTER
OPENING
ADJUSTABLE
DEFLECTOR BLADES
FAN
FAN
GUARD
STAINLESS STEEL
HEAT EXCHANGER
STAINLESS
STEEL
BURNER
SECONDARY
AIR INLET
DIE-FORMED
STAINLESS STEEL
TUBES
CASING BOTTOM HINGED
TO DROP FOR EASY
SERVICING OF BURNER
PILOT
SAFETY
VALVE
BURNER
MANIFOLD
BURNER
PORT
INSPIRATOR
TUBE
BURNER
TUBES
MAIN
MANUAL
SHUT-OFF
Modine gas-fired unit heater showing principal
components. (Courtesy Janitrol)
Figure 2-91
Gas-fired unit
heater. (Courtesy National Oil Fuel Institute)
Figure 2-92
Radiators, Convectors, and Unit Heaters 143
GRND.
HOT
SUMMER SW.
(IF USED)
MOTOR
1
2
FAN SW.
115 VOLT
LIMIT SW.
TRANS.
24 VOLT
STAT
VALVE
DUMMY
ON VALVE
(IF USED)
MOTOR
SUMMER SW.
(IF USED)
1
FAN SW.
2
GRND.
115 VOLT
HOT
LIMIT SW.
JCT. BOX
TRANS.
STAT
VALVE
DUMMY
(IF USED)
LOW VOLTAGE STAT. WITH POWER DIRECTLY TO UNIT
FIELD WIRING
Figure 2-93
FACTORY WIRING
Wiring diagram for a gas-fired unit heater. (Courtesy Janitrol)
144 Chapter 2
Figure 2-94
Oil-fired unit heater. (Courtesy National Oil Fuel Institute)
the unit supplies heat to the combustion chamber, and a fan blows
the heat into the room or space to be heated (see Figure 2-94).
An oil-fired unit heater should be located where it will heat efficiently and where it will receive sufficient air for combustion.
Proper venting is also important. The waste products of the combustion process must be carried to the outdoors.
Chapter 3
Fireplaces, Stoves, and Chimneys
Until recently, fireplaces, stoves, ranges, wood heaters, and similar
heating apparatus were the only sources of heat for cooking,
domestic hot water, and personal comfort. These apparatus generally burned solid fuels, such as wood, coke, or the different types of
coal, but many later models could also be modified to burn fuel oil,
gas (both natural and manufactured), and kerosene.
Central heating and the availability of clean, inexpensive, nonsolid fuels (natural gas, oil, and electricity) have relegated these
heating apparatus to a minor, decorative role except in remote rural
areas of the country. At least this has been the situation until the
late 1960s. The growing interest among people in leaving the cities
and returning to the land, and the rising cost and potential scarcity
of the more popular heating fuels, has brought renewed interest in
the solid-fuel-burning fireplace, stove, range, and heater.
Fireplaces
A fireplace is essentially a three-sided enclosure in which a fire is
maintained. The heat from the fire enters the room from the open
side of the enclosure. The traditional masonry fireplace is a recessed
opening in the wall directly connected to a chimney. Modern prefabricated, freestanding fireplaces resemble stoves, but their operating principle is still that of the traditional fireplace; that is to say,
heat is radiated from the opening out into the room.
Although a fireplace is not as complicated an apparatus as the
furnace or boiler of a modern central heating system, its location,
dimensions, and construction details still require careful planning if
maximum heating efficiency and trouble-free operation are desired.
These aspects of fireplace design and construction are examined in
the sections that follow.
Fireplace Location
The location of the fireplace is determined by the location of the chimney. Unfortunately, chimney location—particularly in newer homes—
is too often dictated by how the chimney will look, rather than how it
will work. As a result, the chimney is often made too low or located
where it may be obstructed by a section of the house or building. The
top of the chimney should be at least 2 feet higher than the roof.
145
146 Chapter 3
Fireplace Dimensions
The principal components of a masonry fireplace are described in
the next section (Fireplace Construction Details). The following
components are important to the operation of a fireplace:
1.
2.
3.
4.
5.
The opening
The throat
The smoke chamber (and shelf)
The damper
The flue
These components are interdependent and must be properly dimensioned with respect to one another or the fireplace will not operate
properly. Table 3-1 lists typical dimensions for finished masonry fireplaces, and these dimensions are identified in Figures 3-1, 3-2, and 3-3.
8"
SOOT POCKET
T
T
MANTEL
E
E
F
F
h
JAMB
w
TRIMMER
Figure 3-1
Fireplace elevation.
Table 3-1
Recommended Dimensions for a Finished Masonry Fireplace (Letters at heads of
columns refer to Figures 3-1, 3-2, and 3-3.)
Opening
Width, w
Height, h
Depth, d
Minimum
Back
(Horizontal), c
(in)
(in)
(in)
(in)
147
24
28
24
30
36
42
36
42
48
42
48
54
60
42
48
54
60
66
72
24
24
28
28
28
28
32
32
32
36
36
36
36
40
40
40
40
40
40
16–18
16–18
16–18
16–18
16–18
16–18
18–20
18–20
18–20
18–20
18–20
18–20
18–20
20–22
20–22
20–22
20–22
20–22
22–28
14
14
14
16
22
28
20
26
32
26
32
38
44
24
30
36
42
48
51
Vertical
Back
Wall, a
Inclined
Back
Wall, b
Outside Dimensions of
Standard Rectangular
Flue Lining
Inside Diameter of
Standard Round
Flue Lining
(in)
(in)
(in)
(in)
16
16
20
20
20
20
24
24
24
28
28
28
28
29
29
29
29
29
29
1
14
14
14
14
14
14
14
14
14
14
14
14
14
17
17
17
17
17
17
1
8 ⁄2 by 8 ⁄2
81⁄2 by 81⁄2
81⁄2 by 81⁄2
81⁄2 by 13
81⁄2 by 13
81⁄2 by 18
81⁄2 by 18
13 by 13
13 by 13
13 by 13
13 by 18
13 by 18
13 by 18
13 by 13
13 by 18
13 by 18
18 by 18
18 by 18
18 by 18
10
10
10
10
12
12
12
12
15
15
15
15
15
15
15
15
18
18
18
148 Chapter 3
FLUE
MANTEL
DAMPER
SMOKE
SHELF
6" TO 8"
b
j
FIRE BRICK
ASH DUMP
d
a
h
ANGLE
ASHPIT
HEADER
TRIMMER ARCH
WOOD CENTER
Fireplace sectional view illustrating two
types of hearth construction.
Figure 3-2
The dotted lines and letters (FF, EE, and TT) in Figure 3-1 are
used to indicate the dimensions of the throat, smoke chamber, and
flue. The throat (or damper opening) is identified by the line FF in
Figure 3-1. The throat should be approximately 6 to 8 inches (or
more) above the bottom of the lintel. The area of the throat should
be not less than that of the flue, and its length should be equal to
the width of the fireplace opening.
Starting approximately 5 inches above the throat (that is, at line
EE), the inner wall surfaces should gradually slope inward approximately 30° to the beginning of the chimney flue (line TT in Figure 3-1).
Fireplaces, Stoves, and Chimneys 149
METAL
LATH
d
FURNACE
FLUE
PLASTER
c
ASH DUMP
w
HEARTH
Figure 3-3
Fireplace plan.
The smoke chamber is the area between the throat and the beginning of the flue (that is, between lines EE and TT in Figure 3-1).
The smoke shelf is the area extending from the throat to the line of
the flue wall (see Figure 3-2). This dimension will vary depending
on the depth of the firebox. The damper opening (throat) should
never be less than the flue area.
Fireplace Construction Details
Construction details of a typical masonry fireplace are shown in
Figure 3-4. Because this type of fireplace is recessed in a wall, it is
easier and less expensive to build it while the structure is under construction.
The principal components of a masonry fireplace are as follows:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Firebox
Lintel
Mantel
Hearth
Ashpit
Ash dump
Cleanout door
Smoke chamber
Smoke shelf
Throat
150 Chapter 3
FLUE LINING
CHIMNEY BLOCK
PORTLAND
CEMENT
STUCCO
FURRING
PLASTER
METAL
LATH
SMOKE CHAMBER
PRECAST
CONCRETE
MANTEL
SMOKE SHELF
HEADER
BLOCK
THROAT AND DAMPER
TO BE FULL WIDTH OF
OPENING
CONCRETE
BRICK
FIREBRICK LINES
JAMBS AND BACK
ASH
DUMP
CONCRETE TITLE
HEARTH
GRADE
CLEAN-OUT DOOR
BASEMENT FLOOR
10"
ASHPIT
FOUNDATION SLAB
Figure 3-4
Construction details of a masonry fireplace.
11. Damper
12. Flue and flue lining
Firebox, Lintel, and Mantel
That portion of the fireplace in which the fire is maintained is sometimes called the firebox. This is essentially a three-sided enclosure
Fireplaces, Stoves, and Chimneys 151
FLUE
8"
SOOT POCKET
MANTEL
DAMPER
6" TO 8"
SMOKE
SHELF
ANGLE IRON
LINTEL
JAMB
FIREBOX
FIREBOX
ASH DUMP
TRIMMER
ELEVATION
Figure 3-5
HEADER
FIREBRICK
ASHPIT
SECTION
Firebox, lintel, and mantel.
with the open side facing the room. The area (in square inches) of
the fireplace opening is directly related to the area of the chimney
flue. The rule-of-thumb is to make the fireplace opening approximately 12 times the area of the flue.
As shown in Figure 3-5, the lintel spans the top of the fireplace
opening. This is a length of stone or metal used to support the
weight of the fireplace superstructure. The mantel is a horizontal
member extending across the top of the fireplace where it generally serves a decorative function. Sometimes the terms mantel
and lintel are used synonymously. When this is the case, the mantel is used in the form of a wood beam, stone, or arch and functions as a lintel to support the masonry above the fireplace
opening.
Fireplace Hearth
The hearth is the surface or pavement in the fireplace on which the
fire is built. The hearth is sometimes made flush with the floor and
will extend out in front of the fireplace opening where it provides
protection to the floor or floor covering against flying embers or
ashes (see Figure 3-3). The recommended length of the hearth is the
width of the fireplace opening plus 16 inches.
152 Chapter 3
Ash Dump, Ashpit, and
Cleanout Door
An ashpit is a chamber located beneath the
fireplace where the ashes from the fire are
collected. An ash dump should be installed
in the hearth toward the back of the fire- Figure 3-6 Centrally
place. This is a metal plate that is pivoted pivoted ash dump.
so that the ashes can be easily dropped (Courtesy Portland Stove Foundry Co.)
into the ashpit (see Figure 3-6). Ashes are
removed from the ashpit through a cleanout door (see Figure 3-7).
DUMP ASH
FURNACE THIMBEL
ASHPIT
SOOT POCKET
CLEAN-OUT DOORS
CLEAN-OUT DOOR
BASEMENT FLOOR
Figure 3-7
Location of ash dump, ashpit, and cleanout door.
Smoke Chamber
The smoke chamber of the fireplace is a passage leading from the
throat to the chimney flue (see Figure 3-4). It should be constructed so that it slopes at a 45° angle from the smoke shaft to the
flue opening. The smoke chamber should also be constructed so
that a smoke shelf extends straight back from the throat to the
back of the flue line. The purpose of the smoke shelf is to prevent
downdrafts from flowing into the fireplace. The damper should be
mounted on the smoke shelf so that it covers the throat when it is
closed. When open, the damper functions as a baffle against downdrafts.
Fireplaces, Stoves, and Chimneys 153
Fireplace Dampers
One of the most frequent complaints about fireplaces is smoke
backing up into the room. This condition, particularly if it persists,
can usually be traced to a problem with the damper.
On very rare occasions, a fireplace and chimney will be built
without a damper. When this is the case, the construction should be
modified to incorporate a suitable damper; otherwise, it will be
impossible to build and maintain a fire in the fireplace.
The damper should be installed at the front of the fireplace and
should be wide enough to extend all the way across the opening.
The two most common locations for a fireplace damper are shown
in Figures 3-8 and 3-9. If the damper is placed higher up in the
chimney, it is controlled with a long operating handle extending to
just under the edge of the fireplace opening.
CHIMNEY FLUE
FLUE LINING
Figure 3-8 Damper mounted
on edge of smoke shelf.
(Courtesy Portland Stove Foundry Co.)
SMOKE CHAMBER
SMOKE SHELF
A rotary-control damper designed for use in the throat of a
fireplace is shown in Figure 3-10. This particular damper has a
tilting lid that rotates on its lower edge rather than on centrally
located pivots like other rotary dampers (see Figure 3-11). The lid
is operated by a brass handle attached to a rod that extends
through the face brick or tiling over the fireplace opening.
Dampers equipped with ratchet-control levers are shown in
Figure 3-12.
154 Chapter 3
Figure 3-9 Damper installed just above the
fireplace opening. (Courtesy Portland Stove Foundry Co.)
Figure 3-10
Rotary damper with lid that rotates on its lower edge.
(Courtesy Portland Stove Foundry Co.)
Fireplaces, Stoves, and Chimneys 155
Figure 3-11 Rotary damper with lid that tilts on centrally
located pivots. (Courtesy Portland Stove Foundry Co.)
COVER
COTTER PIN
GUIDE STOP
OPERATING ARM
LID LIFTS OUT
Figure 3-12
NO BOLTS
Damper equipped with ratchet-control levers.
(Courtesy Portland Stove Foundry Co.)
156 Chapter 3
Modified Fireplaces
A modified fireplace consists of a heavy metal manufactured unit
designed to be set in place and concealed by brickwork or other
masonry construction (see Figures 3-13, 3-14, and 3-15).
CONNECTION TO CHIMNEY FLUE
SMOKE DOME
DAMPER
THROAT OPENING
DOWNDRAFT SHAFT
WARM AIR OUTLET
FIREBOX
DAMPER CONTROL
HEATING CHAMBER
HEATING
SURFACES
INTAKE BAFFLE
AIR INTAKE
Prefabricated firebox used in the construction of a
modified fireplace.
Figure 3-13
Modified fireplaces are usually more efficient than the allmasonry type because provisions are made for circulating the
heated air. As shown in Figure 3-16, cool air enters the inlets at the
bottom and is heated when it comes into contact with the hot surface of the metal shell. The heated air then rises by natural circulation and is discharged through the outlets at the top. These
warm-air outlets may be located in the wall of the room containing
the fireplace, in the wall of an adjacent room, or in a room on the
second floor. Sometimes a fan is installed in the duct system to
improve the circulation.
Fireplaces, Stoves, and Chimneys 157
CHIMNEY FLUE
DAMPER
CONTROL
DAMPER
CONTROL
AIR INTAKE
Figure 3-14
FIREBOX OUTLINE
FIREPLACE BRICKWORK
Construction details of a modified fireplace.
Freestanding Fireplaces
A freestanding fireplace is a prefabricated metal unit sold at many
hardware stores, building supply outlets, and lumberyards.
Some typical examples of freestanding fireplaces are shown in
Figures 3-17 and 3-18. These fireplaces are exposed on all sides,
and their operation is essentially identical to stoves. They are available in a wide variety of styles and colors, and they are easy to
install and operate. Because they are lightweight, no special supportive foundation is necessary, although it is a good idea to install
a base under the unit to prevent stray sparks and embers from
falling onto the floor or floor covering. Most local codes and regulations require that a protective base be used, and the manufacturer’s installation literature probably also recommends its use.
The protective base serves the same purpose as a hearth extension on a masonry or modified fireplace. The base should be made
from some sort of noncombustible material and should be large
158 Chapter 3
FLUE
MANTLE
B
HEAT OUTLET
ASH DUMP
AIR INLET
HEARTH
Figure 3-15
Typical modified fireplace.
enough in area to extend at least 12 inches beyond the unit in all
directions (see Figure 3-19).
Rumford Fireplace
Most of the heat produced by a fireplace is radiant heat. Radiant
heat moves in a straight line from its source to the nearest solid
object, which may be a wall, floor, ceiling, or a piece of furniture,
leaving the air through which it passes unaffected. These solid
objects absorb the radiant heat and transfer it to the air by conduction and convection. The fireplace design that produces the maximum amount of radiant heat is the Rumford fireplace.
Fireplaces, Stoves, and Chimneys 159
WARM-AIR
DUCT
METAL SHELL
COOL-AIR DUCT
Figure 3-16
Operating principles of a modified fireplace.
160 Chapter 3
Count Rumford and His Fireplace
The Rumford fireplace is not a modern design. It was invented in
the eighteenth century by Benjamin Thompson, an American and a
contemporary of Benjamin Franklin. Both Thompson and Franklin
were concerned with the problem of improving the efficiency of
the fireplace, which was the primary heat source for structures in
the eighteenth century. The fireplaces of that time were smoky,
sources of drafts, passageways for heat to escape from the rooms,
and inefficient producers of heat. Benjamin Franklin’s successful
approach to the problem was to replace the masonry fireplace
built into the wall of the structure with a freestanding, metal,
wood-burning stove. Franklin stoves were used for both spaceheating and cooking. Benjamin Thompson’s approach was to
redesign the dimensions of the fireplace to make it more efficient.
The design proved very successful, and many Rumford fireplaces
were built and used as primary space-heating sources for houses
until they were replaced by central heating systems in the late
nineteenth and early twentieth centuries. Thompson left America
in 1796 and settled in Europe, where he lived for the remainder of
his life. It was during that period that he was awarded the title
Count Rumford. The name Rumford later became associated with
his fireplace design.
A Rumford fireplace differs from a traditional one principally
in its shallower firebox, its steeply angled sidewalls (built at a
sharp 45º angle), and its lower fireback (back wall) (see Figure
3-20). This type of firebox radiates heat down to the floor at different angles instead of straight into the room on a horizontal path, as
30"
8"
30"
Figure 3-17
28"
Wall-model freestanding fireplace. (Courtesy Malm Fireplace, Inc.)
Fireplaces, Stoves, and Chimneys 161
30"
8"
28"
30"
REQUIRED CLEARANCES FROM
COMBUSTIBLE WALL ... 9 INCHES
15"
25
"
47
"
10"
15"
331/2"
7 1/ 2 "
41"
16"
39
"
12"
21
28"
12"
7"
"
1 /4
7"
Figure 3-18
Corner-model freestanding fireplace. (Courtesy Malm Fireplace, Inc.)
7"
12"
12"
20
"
12"
PROTECTIVE BASE
20"
30"
Dimensions of a typical protective base showing
clearances of fireplace. (Courtesy Malm Fireplace, Inc.)
Figure 3-19
162 Chapter 3
STEEPLY ANGLES
SIDEWALLS
LOWER FIREBACK
(BACK WALL)
SHALLOW FIREBOX
Figure 3-20
Distinguishing features of a Rumford fireplace.
does a traditional fireplace. The floor absorbs the radiant heat and
transfers it to the room air by conduction and convection.
The throat of a Rumford fireplace is located in such a way that a
plumb line can be dropped from the center of the throat to the center of the firebox (see Figure 3-21). This straight vertical path from
the firebox to the chimney flue minimizes turbulence which, when
present, restricts the flow of smoke and gases. Turbulence in a
Rumford fireplace can be further reduced by modifying the horizontal smoke shelf so that it slopes upward from the throat to the
vertical wall of the flue.
A damper is normally installed at the throat of a Rumford fireplace, as in traditional types, but some Rumford fireplaces also
have dampers at both the throat and the top of the chimney. In theory, the use of two dampers traps warm air in the chimney, thereby
preventing cold downdrafts. The best performance for a Rumford
fireplace is obtained by using an exterior air supply.
Chimney Draft
A properly designed and constructed chimney is essential to a fireplace because it provides the draft necessary to remove the smoke
and flue gases. The motive power that produces this natural draft is
the slight difference in weight between the column of rising hot flue
gases inside the chimney and the column of colder and heavier air
outside the chimney.
Fireplaces, Stoves, and Chimneys 163
The centerline
of the throat
aligns with the
centerline of
the fireplace box.
Straight vertical path from center of Rumford
fireplace to chimney flue.
Figure 3-21
164 Chapter 3
Table 3-2
Correction Factors for Altitudes Above Sea Level
Altitude (in feet)
Correction Factor
1000
2000
3000
5000
10,000
0.966
0.932
0.900
0.840
0.694
The intensity of the draft will depend on the height of the chimney
and the difference in temperature between the columns of air on the
inside and the outside. It is measured in inches of a water column.
The theoretical draft of a chimney in inches of water at sea level
can be determined with the following formula:
D 7.00 H ¢
1
1
≤
461 T 461 T1
where D theoretical draft
H distance from top of chimney to grates
T temperature of air outside the chimney
T1 temperature of gases inside the chimney
For altitudes higher than sea level, the calculations obtained in
the formula should be corrected by the factors listed in Table 3-2.
Thus, if the structure is located at an altitude of approximately 1000
feet, the results obtained in the formula should be multiplied by the
correction factor 0.966 to obtain the correct draft for that altitude.
Chimney Construction Details
Because of its height and weight, a masonry chimney should be supported by a suitable foundation. This foundation should extend at
least 10 inches below the bottom of the chimney and a similar distance beyond its outer edge on all sides (see Figure 3-4). The foundation can be made more stable by making the base larger in area
than the top. This can be accomplished by stepping down the footing at an angle.
Chimney Cap
The chimney cap (or capping) is both a decorative and functional
method of finishing off the top of the chimney (see Figure 3-22).
Built of brick, concrete, or concrete slab, the chimney capping tends
to counteract eddy currents coming from a high roof. The slab-type
Fireplaces, Stoves, and Chimneys 165
TILE
CONCRETE OR STONE CAPS
ADD TO A CHIMNEY
Extended tile improves an
ordinary chimney, staggered
heights are pleasing.
Figure 3-22
Typical chimney caps.
Slab-type
chimney capping.
Figure 3-23
capping shown in Figure 3-23 is an effective means of preventing
downdrafts. Chimney cappings are usually designed to harmonize
with the architecture of the structure.
Chimney Flues and Chimney Liners
The chimney flue is the passage through which the smoke, gases,
and other products of the combustion process travel to the outdoors. A chimney liner (sometimes called a flue liner or flue lining)
is a metal tube inserted into the chimney to protect its walls against
the potentially damaging gases of the combustion process. It is also
used to size the diameter of the chimney flue opening for different
appliances. The chimney liner must be code-approved for use in
chimneys. Aluminum chimney liners are recommended for use with
gas appliances.
166 Chapter 3
Although most flues are lined with a fireproof material, chimneys with walls 8 inches or more in thickness do not need a flue lining. Fired-clay linings are used for flues in chimneys having walls
less than 8 inches thick. Chimneys without a flue lining should be
carefully pargeted and troweled so that the surface is as smooth as
possible.
NOTE SLOPED
FACE TO DEFLECT WIND
FLUE
LINING
CUT FLUE
LINING TO
FIT AT ANGLE
DAMPER
DAMPER
CONTROL
1ST FLOOR
FIREPLACE
FIREBRICK
A
A
ASH
PIT
FURNACE
FLUE
FIREPLACE
FLUE NOT OVER
30° SLOPE
FROM
VERTICAL
WARM AIR
OUTLET GRILLE
BASEMENT
FIREPLACE
COLD AIR
INTAKE
GRILLE
BASEMENT
FIREPLACE
FLUE
FURNACE
FLUE
SECTION - AA
Figure 3-24
Chimney with more than one flue.
Fireplaces, Stoves, and Chimneys 167
Flue construction is very important. If the flue is too small, it will
restrict the passage and slow the rise of the flue gases. A flue that is
too large will cause the fireplace to smoke when the fire is first
started. Because the flue is too large, the fire takes longer to heat the
air, and consequently the flue gases are initially slow to overcome
the heavy cold air found in the chimney.
If the same chimney is used to serve fireplaces on two or more
floors, each fireplace should have a separate flue (see Figure 3-24).
This also holds true when a furnace (or boiler) and one or more
fireplaces use the same chimney. Each heat source should be connected to a separate flue in the chimney.
Do not allow two (or more) flues to end on the same level at the
top of the chimney. Doing so can result in smoke or gases from one
flue being drawn down into the other one. One of the flues should
be at least 6 inches higher than the other.
Smoke Pipe
The smoke pipe is used to connect the heating equipment to the
chimney flue. Never allow the smoke pipe to extend beyond the
flue lining in the chimney or it will obstruct the flow of smoke and
other gases (see Figures 3-25 and 3-26).
LINED WITH
FIRE CLAY
RESTRICTED
DRAFT
Smoke pipe extending
too far into chimney.
Figure 3-25
168 Chapter 3
SMOKE PIPE ENDS
FLUSH WITH
FLUE LINING
Proper connection of smoke
pipe to chimney flue.
Figure 3-26
Cleanout Trap
Chimneys used with coal-fired and oil-fired heating equipment
should be equipped with cleanout traps. Access is provided in the
ashpit (see Figure 3-4).
Chimney Downdraft
Sometimes the air will not rise properly in a chimney and will fall
back into the fireplace or stove. This downdraft (or backdraft)
condition results in poor combustion, smoke, and odors. It is
generally caused by either deflected air currents or chilled flue
gases.
Air currents can be deflected down into a chimney by higher
nearby objects, such as a portion of the structure, another building,
a tree, or a hill. It is therefore important to build the chimney higher
than any other part of the structure or any nearby objects. Because
the deflected air entering the chimney has not passed through a hot
fire, it will cool the air in the flue and weaken the draft. When the
air becomes cooler, it also becomes heavier and falls back down
into the chimney.
Fireplaces, Stoves, and Chimneys 169
Chimneys built on the outside of a structure,
particularly those exposed on three sides, must
have walls at least 8 inches thick in order to
prevent chilling of the flue gases. Remember
that flue gases must not be allowed to cool. The
cooler the gas, the heavier it becomes.
Prefabricated Metal Chimneys
Prefabricated (factory-built) metal chimneys
are commonly made of 24-gauge galvanized
steel or 16-ounce copper (see Figures 3-27 and
3-28). These chimneys normally can be used
with any type of gas-, oil-, wood-, or coal-burning appliance; however, check the Underwriters
Laboratories (UL) certification for the intended
fuel use because some are restricted to gas fuels.
Freestanding fireplaces, such as those illustrated in Figures 3-17, 3-18, and 3-19, are
equipped with lengths of pipe designed to extend
upward from the top of the unit for approximately 8 feet (see Figure 3-29). These lengths of
pipe are available with porcelain enamel surfaces
that match the color of the fireplace.
Prefabricated metal chimneys are designed
for ceiling support installation, through-the-wall
installation, and cathedral ceiling or open-beam
installation (see Figures 3-30 and 3-31). Check
the local codes and regulations before installing a
metal chimney. Closely follow the chimney manufacturer’s installation instructions.
Note
Both double-wall and single-wall metal chimney pipes are available. A single-wall pipe is
considered an extreme fire hazard.
Figure 3-27
Prefabricated
metal chimney
used with oil-, gas-,
coal-, and woodburning fireplaces.
(Courtesy Metalbestos)
Troubleshooting Fireplaces and Chimneys
Table 3-3 lists the most common problems associated with the
operation of a fireplace.
Stoves, Ranges, and Heaters
A stove is a device used for heating or for both heating and cooking
purposes (see Figures 3-32 and 3-33). Heating is generally regarded
170 Chapter 3
Table 3-3
Troubleshooting Fireplaces and Chimneys
Symptom and Possible Cause
Possible Remedy
Persistent smokiness.
(a) No damper.
(b) Damper set too low.
(c) Damper too narrow.
(d) Damper set at back
of fireplace opening.
(e) No smoke shelf.
(f) No smoke chamber
or poorly designed one.
(g) Fireplace opening too
large for flue size.
(h) Insufficient combustion air.
(i) Downdrafts occur.
(j) Chimney clogged with
debris.
(a) Install a suitable damper.
(b) Correct.
(c) Extend damper all the way
across opening.
(d) Relocate damper to the front.
(e) Install smoke shelf.
(f) Install a suitable smoke
chamber or make necessary
modifications in old one.
(g) Reduce the size of opening.
(h) Open window a crack or
provide other means of
supplyingcombustion air.
(i) Extend chimney higher;
protect chimney opening with
cap designed to deflect
downdraft.
(j) Clean chimney.
Fire dies out.
(a) Insufficient combustion air.
(b) Clogged or dirty flue.
(c) Closed damper.
(d) Fuel logs too green.
(e) Fuel logs improperly
arranged.
(a) Open window a crack or
provide other means of
supplying combustion air.
(b) Check flue; correct and/
or clean.
(c) Open damper.
(d) Replace with suitable logs.
(e) Rearrange and rebuild fire.
as the primary function of a stove. The heat is delivered to the room
by both radiation and convection.
Brick, tile, and masonry stoves first appeared in Europe as early
as the fifteenth century. The first cast-iron stove was produced in
Massachusetts in 1642, but it was a rather crude device by modern
Fireplaces, Stoves, and Chimneys 171
Vent pipe design for wall
heaters with inputs up to 65,000 Btu.
Figure 3-28
(Courtesy Metalbestos)
standards because it had no grates. Benjamin Franklin revolutionized the design of the stove with the introduction in 1742 of the
model that bears his name (see Figure 3-34).
Sometimes the terms stove and range are used synonymously.
This confusion, or blurring of the differences between the two,
probably results from the incorporation of such features as an
oven, cooking surface, and hot-water tank in the design of the stove
(see Figures 3-35 through 3-38).
A range is a cooking surface and an oven combined in a single unit.
It differs from a stove by being specifically designed for cooking,
although it can supply a certain amount of warmth to the kitchen.
Ranges can be divided into a number of different categories depending on the type of fuel used. There are four basic categories of ranges:
1. Gas ranges
2. Electric ranges
172 Chapter 3
SHANTY CAP
Figure 3-29
Shanty cap
and pipe.
(Courtesy Portland Stove Foundry Co.)
CHIMNEY PIPE
ROOF JACK
3. Kerosene ranges
4. Solid-fuel ranges
Gas ranges use both natural and manufactured gases. Kerosene
ranges have been further developed to use either gasoline or fuel oil.
The solid fuels used in ranges include wood, charcoal, coal (lignite,
bituminous, anthracite), and coke.
The range shown in Figure 3-39 uses wood, coal, or oil. The fuel
grates and ashes (from the ashpit) are removed through the front of
the range. These ranges also contain a large removable copper tank,
which is used to supply hot water for cooking and other purposes.
Fireplaces, Stoves, and Chimneys 173
ROUND TOP
STORM COLLAR
ADJUSTABLE
FLASHING
ATTIC INSULATION SHIELD
FINISH SUPPORT PACKAGE
SMOKE PIPE ADAPTER
Prefabricated metal chimney and vent
details (ceiling support installations).
Figure 3-30
ROUND
TOP
ROUND TOP
STORM
COLLAR
ROOF SUPPORT
PACKAGE
FINISHING
COLLAR
SMOKE PIPE
ADAPTER
CATHEDRAL CEILING INSTALLATION
9" INSULATED
PIPE LENGTH
WALL BAND
SMOKE PIPE
ADAPTER
FIRE STOP/
WALL SPACER
FINISHING
COLLAR
FIRE STOP/TRIM
COLLAR
INSULATED
TEE/PLUG
WALL
SUPPORT KIT
THROUGH THE WALL INSTALLATION
Prefabricated metal chimney and vent details (throughthe-wall and cathedral ceiling installations).
Figure 3-31
174 Chapter 3
Wood-burning parlor
stove. (Courtesy Portland Stove Foundry Co.)
Figure 3-32
Figure 3-33
Atlantic box stove. (Courtesy Portland Stove Foundry Co.)
Fireplaces, Stoves, and Chimneys 175
Figure 3-34
The Franklin stove with folding doors.
(Courtesy Portland Stove Foundry Co.)
Reproduction of the eighteenth-century
cast-iron stove. (Courtesy Portland Stove Foundry Co.)
Figure 3-35
176 Chapter 3
Figure 3-36
Reproduction of the 1812 Franklin stove.
(Courtesy Portland Stove Foundry Co.)
Figure 3-37
Wood- and coal-burning range.
(Courtesy Portland Stove Foundry Co.)
Fireplaces, Stoves, and Chimneys 177
Franklin cast-iron stove based
on the 1742 design. (Courtesy Portland Stove Foundry Co.)
Figure 3-38
A wood heater is a device used specifically to provide heat to a
room or a similarly limited space. These are wood-burning units
that can also be equipped to burn coal, oil, or gas. These heaters are
similar to stoves in their operating principle. They should not be
confused with unit (space) heaters, which are suspended from ceilings or walls and operate on a completely different principle (see
Chapter 2, “Radiators, Convectors, and Unit Heaters”).
Some wood-burning stoves are equipped with a thermostat. The
thermostat consists of a bimetallic helix coil that opens and closes a
damper in response to temperature changes. The damper opens just
enough to admit precisely the amount of combustion air necessary
to maintain the heat at a comfortable level.
A mat or floor protector made of some sort of fireproof material
should be placed under a stove, range, or heater to protect the floor
or floor covering against live sparks or hot ashes. These units
should also be placed as far from a wall or partition as is necessary
to prevent heat damage.
Installation Instructions
Before installing a new stove, make certain the chimney is large
enough to accept the necessary smoke pipe. If another stove or
178 Chapter 3
Cast-iron range used with coal, wood,
or oil. (Courtesy Portland Stove Foundry Co.)
Figure 3-39
furnace is using the same chimney flue, connect the stove above or
below the other one (never at the same level). The area of a chimney flue should be about 25 percent larger than the area of the
smoke pipe that enters the chimney.
The same design and construction features required for a chimney serving a fireplace also apply to one used with a stove. If there
is no chimney, then one must be built.
Operating Instructions
Stoves are similar to fireplaces in that they possess no power in themselves to force smoke up a chimney. The pipe and chimney provide the
draft, and if they are defective, the stove will not work satisfactorily.
The installation must be capable of providing sufficient air for
the combustion process. At the same time, it must be able to expel
smoke and other gases to the outdoors.
Chapter 4
Water Heaters
A water heater is an appliance designed to heat water for such purposes as cooking, washing, and bathing. This water is generally
referred to as domestic hot water or potable water.
The most commonly used water heater is the vertical tank-type
stand-alone unit used in residences and small commercial buildings.
It is independent of the space heating system and is a separately
fired water heater. Other water heaters depend on an external heat
source such as a boiler. The domestic hot water is heated when it
circulates through a heat exchanger inserted in the hot-water or
steam heating boiler. These heat exchangers are used only with
boilers. In a warm-air heating system, domestic hot water is provided by an independent and separately fired water heater.
Types of Water Heaters
Water heaters can be divided into several groups or classes. The
most common classifications are based on the following criteria:
1.
2.
3.
4.
5.
6.
Size and intended usage.
Heating method.
Heat-control method.
Fuel type.
Flue location and design.
Recovery rate.
Water heaters are classified as either domestic or commercial
water heaters on the basis of their size and intended usage.
Domestic water heaters are those with input rates up to 75,000 Btu
per hour. Water heaters regarded as commercial types have input
rates in excess of 75,000 Btu per hour. Temperature is another of
the criteria used to distinguish between domestic and commercial
water heaters. For commercial usage, hot-water temperatures of
180°F or more are generally required. The hot water used in residences does not normally exceed 180°F. For domestic usage, 140°F
is generally considered adequate.
Another method of classifying water heaters is by how the heat
is applied. Direct-fired water heaters are those in which the water is
179
180 Chapter 4
heated by the direct combustion of the fuel. In indirect water heaters,
the service water obtains its heat from steam or hot water and not
directly from the combustion process. The advantages and disadvantages of both direct-fired and indirect water heaters are described
elsewhere in this chapter.
The heat-control method in a water heater may be either automatic or manual (nonautomatic). All water heaters used in residences are now of the automatic type.
Natural gas or propane, oil, coal, electricity, steam, or hot water
can be used to heat the water in a water heater. Either steam or hot
water can be used as the heat-conveying medium in indirect water
heaters. Neither, of course, is a fuel. The fuels used to heat the
domestic water supply are gas, oil, and coal. Gas is by far the most
popular fuel. Oil is gaining some popularity, but it still falls far
short of gas. The use of coal as a fuel for heating water is now
found only in rare cases. Although electricity is not a fuel, in the
strict sense of the word, it is generally used along with the three fossil fuels as an additional category for classification.
Quite often, water heaters are classified on the basis of flue location and design. This is a particularly useful criterion for classifying
the various automatic storage-type water heaters.
Water heaters can also be classified on the basis of their recovery
rate. Quick-recovery water heaters are capable of producing hot
water at a more rapid recovery rate than the slow-recovery types.
Quick-recovery heaters are often used in commercial structures
where there is a constant demand for hot water.
Direct-Fired Water Heaters
A direct-fired water heater is one in which the water is heated by
the direct combustion of a fuel such as gas, oil, or coal. The combustion flame directly impinges on a metal surface, which divides
the flame from the hot water. This metal surface is quite often (but
not always) the external wall of the hot-water storage tank. It
serves as a convenient heat transfer surface.
A direct-fired water heater is easily distinguished from an indirect water heater (see Indirect Water Heaters later in this chapter),
which uses an intermediate heat-conveying medium such as steam
or hot water, and an electric water heater, which depends on an
immersed electric heating element for its heat.
Automatic Storage Water Heaters
The underfired automatic storage heater in which a single tank is
used for both heating and storing the water is the most common
Water Heaters 181
water heater used in houses, apartments and small commercial buildings. These heaters generally have a 30-, 40-, or 50-gallon storage
capacity, although it is possible to purchase automatic storage heaters
with capacities ranging from 70 gallons to several hundred gallons.
Automatic storage heaters are classified according to the placement of the flue. Using flue placement as a basis for classification,
gas-fired automatic storage water heaters can be divided into the
following three basic types:
1. Internal or center flue.
2. External channel flue tank.
3. External flue and floating tank.
The internal or center flue gas-fired water heater (see Figure 4-1)
is very economical to manufacture, but proper flue baffling is
required for good efficiency.
The external channel flue gas-fired water heater provides a
much larger heating surface than the center flue. As shown in
Figure 4-2, the entire bottom surface of the tank serves as the heating surface. Heating is from the bottom of the tank, which acts to
increase efficiency.
VENT
HOT-WATER OUTLET
INLET WATER
DIP TUBE
INSULATION
INTERNAL FLUE
TANK
BAFFLE
INTERNAL FLUE
BAFFLE
JACKET
BURNER
TANK
THERMOSTAT
Figure 4-1
Internal flue tank construction (gas-fired water heater).
(Courtesy Robertshaw Controls Co.)
182 Chapter 4
VENT
CHANNEL FLUE
CHANNEL FLUE
External channel flue tank construction
(gas-fired water heater). (Courtesy Robertshaw Controls Co.)
Figure 4-2
An even larger heat transfer surface is provided by the external
flue and floating tank water heater illustrated in Figure 4-3. Both
the full bottom and sides of the tank serve as heat transfer surfaces.
The heat (and gases) passes around the storage tank and exits
through the vent.
The tank and flue construction of oil-fired automatic storage
water heaters is very similar to gas-fired types. The major difference
between the two lies in the combustion chamber. In gas-fired water
heaters, the burners are located inside the combustion chamber (see
Figures 4-1, 4-2, and 4-3). In oil-fired water heaters, the oil burner
is mounted externally, and the flames are shot into the combustion
chamber (see Figure 4-4).
Additional information about automatic storage water heaters
can be found in this chapter in the section Gas-Fired Water Heaters.
Multicoil Water Heaters
Sometimes the size of a structure or its use will result in a greater
demand for hot water than a conventional water heater can supply.
When this is the situation, it is recommended that a multicoil, or
large-volume, water heater be installed. These water heaters resemble instantaneous heaters externally but differ by containing more
than one heating coil. The separate heating coils are connected to
manifolds operated by a thermostat inserted in the storage tank.
Water Heaters 183
VENT
EXTERNAL
FLUE
TANK
Floating-tank external flue construction
(gas-fired water heater). (Courtesy Robertshaw Controls Co.)
Figure 4-3
Because multicoil water heaters have
large storage tanks, they are suitable for
use in restaurants, clubs, and structures
of similar size and use.
Multiflue Water Heaters
The multiflue water heater was developed for commercial uses to satisfy the
need for greater heat transfer surface
and to efficiently remove the higher
volume of noncombustible gases resulting from the higher gas inputs. The diagram of a gas-fired multiflue water
heater is shown in Figure 4-5. Compare
this with the diagram of the oil-fired
multiflue water heater illustrated in
Figure 4-4. Each is essentially a vertical
fire-tube boiler enclosed in an insulated
jacket.
Multiflue water heaters are characterized by a relatively high hot-water
recovery rate. These heaters are used in
conjunction with auxiliary storage and
Oil-fired
multiflue design used in
some high-capacity
commercial water heaters.
Figure 4-4
(Courtesy National Oil Fuel Institute)
184 Chapter 4
VENT
FLUE COLLECTOR
MULTIPLE FLUES
WATER
THERMOSTAT
OR THERMOSTATS
Figure 4-5
Multiple-flue, multiple-burner commercial water heater.
(Courtesy Robertshaw Controls Co.)
are frequently employed as booster heaters. It is common usage to
refer to a multiflue water heater as a booster heater.
Instantaneous Water Heaters
Automatic instantaneous water heaters (also sometimes called
point-of-use water heaters) are self-contained units available in
capacities ranging up to 445 gallons per hour (or up to 7.43 gallons
per minute at 100° temperature rise) (see Figure 4-6).
Basically, an instantaneous heater consists of a large copper coil
suspended over a series of burners. The copper coil, burners, valves,
and thermostats are all enclosed in a protective steel casing. An
instantaneous water heater does not have a hot-water storage tank;
this feature distinguishes them from other types of commercial
water heaters, such as the multicoil and multiflue.
The water to be heated circulates through the copper coil. The
operating principle of these heaters is very simple and ideal for situations requiring intermittent use. Any pressure drop in the system
(such as that caused by opening a faucet) provides the necessary
power to force open the gas valve and allow gas to flow to the
burners. The gas is ignited by the pilot, and the water in the coil is
Water Heaters 185
VENT
HOT-WATER OUTLET
THERMOSTAT
HEAT TRANSFER COILS
COLD-WATER INLET
BURNER
Figure 4-6
Instantaneous water heater. (Courtesy Robertshaw Controls Co.)
heated to the desired temperature. These heaters are ideally suited
for those public buildings or sites that require periods of high
demand (for example, public washrooms, sports arenas, ballparks,
stadiums, or recreational centers).
Indirect Water Heaters
An indirect water heater uses either steam or hot water to heat the
water used in the domestic hot-water supply system.
In small, residential-type boilers, a water heater element consisting
of straight copper tubes with U-bends or a coiled tube is located in
the hottest portion of the boiler water (see Figures 4-7 and 4-8). It is
positioned at the side of the boiler to create rapid natural circulation.
Because there is no separate water storage tank, this type of unit is
commonly called a tankless water heater.
In steam boilers, the copper tubes are generally placed below the
water line in the boiler. The system is designed so that the water is
heated after a single passage through the copper tubes.
Another type of indirect water heater utilizes a separate water
heater outside the boiler (see Figure 4-9). Hot water from the boiler
flows into the heater and around copper coils containing the
domestic hot-water supply before returning to the boiler. The water
inside the coils is heated and returned to a hot-water storage tank,
which is usually located at a level slightly higher than the heating
boiler.
186 Chapter 4
FLUE PIPING
OIL BURNER
CONTROL
OIL BURNER
TANKLESS DOMESTIC
HOT-WATER HEATER
CAST-IRON
BOILER
SECTION
COMBUSTION
TARGET WALL
Figure 4-7 Oil-fired hydronic boiler with a straight-tube tankless
water heater. (Courtesy Burnham Corp.)
The water to be heated can also be circulated around tubes
through which steam is circulated. The steam tubes are submerged
in a steel tank as shown in Figure 4-10. As in all methods of indirect
heating, the domestic water supply is kept sealed off from the hot
water or steam being used to heat it.
Indirect water heaters of the type illustrated in Figure 4-11 are
essentially space-heating boilers with built-in coil bundles through
which the hot water circulates. They differ from hot-water spaceheating boilers in the following two ways:
1. The coils are sized to absorb the total output of the boiler.
2. Water temperatures do not exceed 210°F.
Water Heaters 187
Oil-fired hydronic boiler with a coiled-tube tankless
water heater. (Courtesy H.B. Smith Co., Inc.)
Figure 4-8
3⁄
BOILER WATER
TEMPERATURE CONTROL
WATER LINE
4"
HOT WATER TO FIXTURES
HORIZONTAL
STORAGE TANK
1"
2" HEADER
COLD-WATER
INLET
1'0"
1"
WATER HEATER
STEAM BOILER
AUTOMATIC
FIRING DEVICE
2"
1"
DRAINS
Figure 4-9
FLOOR
Separate indirect water heater mounted outside the boiler.
(Courtesy 1965 ASHRAE Guide)
188 Chapter 4
HOT-WATER OUTLET
RELIEF VALVE
THERMOMETER
STEAM INLET
DRIP
BLOW-OFF
AIR VALVE
TAPPING
COLD-WATER INLET
Indirect water heater in which the water is circulated
around steam-filled tubes. (Courtesy 1965 ASHRAE Guide)
Figure 4-10
These indirect water heaters may be used as instantaneous
heaters. Because they can be used with any size storage tank, there
is no real upper limit on their storage capacity. The same is true of
their recovery rate.
The principal advantages of an indirect water heater are the
following:
1. Longer operating life (the metal surfaces of the heater are not
directly exposed to a flame).
HOT
WATER
Indirect water
heater with built-in coils
designed to absorb the total
heat output of the boiler.
Figure 4-11
(Courtesy Hydrotherm, Inc.)
AQUASTAT
Water Heaters 189
2. Scale formation and corrosion in the secondary heat
exchanger coils are minimized because of the relatively low
operating temperatures.
3. No hot-water storage tank (with the accompanying circulator,
controls, and piping) is required if the heater has been properly sized.
Quick-Recovery Heaters
This class of heater, as the name implies, has the ability to produce hot
water at a more rapid rate than the slow-recovery type. It is frequently
employed where repeated heavy requirement for hot water makes it
essential to have a sufficient amount of water available on demand.
Thermostats used are of the throttling or snap-action type.
Primarily the throttling thermostat is the one in which the
amount of gas valve opening is directly proportional to the temperature changes of water in the tank. In the snap-action thermostat, the change from a completely open to a completely closed
position of the valve, or vice versa, is accomplished by a snap action
produced by a clicker diaphragm motivated by the temperature in
the tank.
The essential difference between the slow- and quick-recovery
heater lies in the amount of gas consumed by each unit. Thus, for
example, a quick-recovery heater with a 25,000-Btu input will
deliver 25 gallons of hot water per hour indefinitely, whereas a
slow-recovery heater can never burn more than a certain relatively
low and known amount of gas with an accompanying reduction in
hot-water delivery.
Slow-Recovery Heaters
The gas-fired slow-recovery water heater is designed to keep a supply of hot water in the storage tank and, by means of a constantly
burning gas flame, deliver hot water continuously to this tank.
Thermostats employed can be of the graduating or snap-action
type. With the graduating thermostat, the burner operates between a
low and high flame—the low position of the flame serving as a pilot
to keep the heater lighted and serving as a source of standby heat.
The slow-recovery automatic water heater is very economical
since it can never burn more than a certain amount of gas, depending on the regulation offered by the thermostat. Also, the small
amount of heating surface keeps the standby loss at a minimum,
making this type of heater very advantageous where economy is the
primary consideration.
190 Chapter 4
Heat Pump Water Heaters
A heat pump water heater consists of a small electrically operated
compressor, the heat pump and domestic water supply controls,
and a water storage tank (see Figure 4-12). It uses the heat of the air
in the room and the energy used to operate its compressor to heat
the water in its storage tank. Unlike conventional gas-fired or electric resistance water heaters, the heat pump water heater does not
create heat. It transfers heat from one point to another. It is essentially a small heat pump that uses the room air as the heat source
and the water in the storage tank as the heat sink. Because it is a
heat pump, it can also cool the air and dehumidify it.
In some heat pump water heater installations, the heat pump and
water storage tank are separate. A water pump and piping flow
loop are used to circulate the water between the heat pump water
heater and the water storage tank. The water is heated in the heat
pump water heater and stored in the tank.
The principal advantage of using a heat pump water heater with
a separate water tank is that either can be replaced independently
of the other when they malfunction. Another important advantage
is their location flexibility.
The heat pump water heater may also be an integral part of the
water storage tank. In these installations, there is no need for a
water pump or flow loop. This arrangement also eliminates energy
loss from the flow loop piping or the need for freeze protection.
WARM AIR
COOL AIR
HEAT PUMP AND
COMPRESSOR UNIT
WARM WATER
HOT WATER
STORAGE
COLD WATER
Figure 4-12
Heat pump water heater.
Water Heaters 191
Heat pump water heaters are more expensive to purchase and
install than conventional electric resistance water heaters. On the
other hand, they use 50 percent less energy than conventional electric
resistance heaters.
Combination Water Heaters
Many of the earlier combination water/space heaters used in
hydronic systems did not keep the domestic hot water separated
from the hot water used for space heating. This feature resulted in
scale buildup in the water tank and oxygen-induced damage to the
tubing in the radiant heating panel. A combination water heater in
which the domestic hot water is separated from the space heating
water in the same appliance is shown in Figure 4-13. Two separate
corrugated stainless steel tanks are used in this design. The outer
tank contains the primary fluid (water) and is connected to the
space-heating circuit. The inner tank contains the domestic hot
water and is connected directly to the utility water supply and a
separate domestic hot-water circuit. The primary water in the outer
tank is heated by a gas or oil burner and does not exceed a temperature of 180ºF, which significantly reduces scale buildup in the
domestic (that is, inner) hot-water tank. The domestic hot-water
supply in the inner tank absorbs heat from the hot water in the
outer tank. There is no direct heating of the inner tank.
The two water circulation circuits supplied by this type of combination water heater are completely independent of one another.
PRIMARY HEATING SUPPLY CONNECTION
HOT WATER OUTLET
COLD WATER INLET
SAFETY LIMIT THERMOSTAT
(205°F) (MANUAL RESET)
PRIMARY CIRCUIT THERMOSTAT
(UP TO 180°F) SENSING BULB
SECONDARY CIRCUIT (DOMESTIC
WATER) THERMOSTAT SENSING BULB
FLUEWAY FITTED WITH
STAINLESS STEEL TURBULATORS
BAKED ENAMEL STEEL JACKET
BAFFLES (TURBULATORS)
STEEL BODY CONTAINING
PRIMARY WATER
11 ⁄2" OF RIGID (CFC-FREE)
POLYURETHANE INSULATION
CORRUGATED STAINLESS STEEL
HEAT EXCHANGER
PRIMARY WATER
PRIMARY HEATING RETURN
CONNECTION
BURNER
WATER COOLED IMMERSED
COMBUSTION CHAMBER
PRIMARY CIRCUIT DRAIN
CONNECTION
Figure 4-13
Combination water heater.
192 Chapter 4
This arrangement eliminates the problem of oxygen from hot
domestic water mingling with the space-heating water, thereby
reducing the possibility of oxygen production, which can damage
tubing or cause scale buildup in the tank.
Note
The primary water in the outer tank is never changed. Changing
the water can lead to the introduction of oxygen into the system.
The space-heating water in the outer tank is circulated in a closed
loop through baseboards, tubing or panels, and heat exchangers.
The only point of contact between the inner and outer tanks is
where the cold-water inlet pipe and the hot-water flow pipe extend
through the top of the combination water heater. The heater is
equipped with two separate built-in control systems, one for the
outer tank and one for the inner tank.
Some combination water heater installations consist of an indirect water heater connected to a high efficiency furnace or a boiler.
Liquid heat (from the hot water) is transferred to the air and then
distributed through a duct system by a blower.
Note
Combination water heaters are practical mostly in new construction or where a boiler or furnace must be replaced.
Water Heater Construction Details
The automatic controls, fuel-burning equipment (gas burners, oil
burner, and so on), and venting system found on a water heater will
depend on the type of fuel used and certain other variables. These
components are described in detail in appropriate sections of this
chapter and elsewhere in the book.
The direct-fired automatic storage water heater is the most commonly used heater in residences. Certain construction details of
these heaters remain essentially the same regardless of the type of
controls or fuel-burning equipment.
Principal among these are the following:
1.
2.
3.
4.
5.
Water storage tanks
Tank fittings
Dip tubes
Anodes
Valves
Water Heaters 193
Water Storage Tanks
The tank of a water heater provides storage space for the hot
water and also serves as a heat transfer surface. The design and
construction of the tank must be strong enough to withstand at
least 300 pounds per square inch without leakage or structural
deformation.
Corrosion is a major problem in water heater storage tanks. One
successful method of reducing corrosion has been to provide steel
tanks with glass linings. Older water heater tanks will be found
with copper or stone (Portland cement) linings, but these are
becoming increasingly rare.
Glass-lined tanks are also equipped with a sacrificial magnesium
anode rod, as shown in Figure 4-14. The corrosion process attacks
the metal anode rod first, rather than the metal of the tank walls.
The anode rod should be removed and replaced before decomposition occurs.
The operating life of a storage tank is directly related to the
temperature of the stored water when it is over 140°F. The ruleof-thumb is that each 20° rise above 140°F will reduce tank life by
40 percent.
PLASTIC-LINED
NIPPLES
SACRIFICIAL
ANODE ROD
GLASS-LINED
TANK
PLASTIC
DIP TUBE
PLASTIC-COVERED
COPPER TUBE
THERMOSTAT
Sacrificial anode installation in a residential water
heater tank. (Courtesy Robertshaw Controls Co.)
Figure 4-14
194 Chapter 4
Tank Fittings
Figures 4-15 and 4-16 illustrate the various fittings required on
both domestic and commercial water heaters.
Each tank should have fittings for hot-water outlet and coldwater inlet connections. These water connections generally consist
of threaded spuds welded into openings in the tank.
A fitting is also provided in the top of most tanks for the insertion of the sacrificial anode. Other fittings provide for the use of
immersion thermostats, immersion automatic gas shutoff devices,
drain cocks, pressure and temperature relief valves, and dip tubes.
Dip Tubes
Some water heaters are designed so that the cold-water inlet is at
the top of the tank. Because this is also the location of the hot-water
supply outlet, there will be an excessive mixing of the cold water
with the hot water unless provisions are made to keep the two separated. A dip tube is used for this purpose.
As shown in Figure 4-17, a dip tube is an extension of the coldwater supply pipe and is used to direct the cold water to the bottom
SACRIFICIAL ANODE
HOT-WATER OUTLET
FITTING FOR P&T VALVE
COLD-WATER INLET
OPTIONAL MOUNTING
MEANS AUTOMATIC GAS
SHUTOFF DEVICE
DIP TUBE
SACRIFICIAL ANODE
THERMOSTAT
THREADED SPUD
DRAW COCK
THREADED SPUD
Hot- and cold-water connections
are required to be adequately
marked to avoid improper
connections to the water supply.
In some cases the sacrificial
anode fitting is combined with
the hot-water outlet.
Figure 4-15
Typical water heater fittings. (Courtesy Robertshaw Controls Co.)
Water Heaters 195
IMMERSION
AUTOMATIC SHUTOFF
FITTING
IMMERSION
THERMOSTAT
FITTING
HOT-WATER
OUTLET
COLD-WATER
INLET
DRAIN COCK
FITTING
Commercial water heater fittings with low-level
cold-water inlets. (Courtesy Robertshaw Controls Co.)
Figure 4-16
of the tank. On older water heaters, dip tubes were made of metal.
Now they are generally made from a high-density, temperatureresistant plastic. In all water heaters, the water at the top of the
tank during cycling and intermittent standby conditions is always
warmer than the water at the bottom of the tank. If the dip tube is
too short, the cold water will mix with the water at the top of the
tank and reduce the temperature of the hot-water supply to an unacceptable level. On the other hand, a dip tube that is too long will create an excessive water variation between the top of the tank and the
lower thermostat control level. The dip tube must be of sufficient
length to avoid both these conditions.
Each dip tube is provided with a small hole near the top of the
tank, which functions as an antisiphon device. Sometimes it is
possible for a malfunction to close off the cold-water supply while
the hot water continues to be removed from the tank. Were it not
for the antisiphon hole, the water would be drawn to the bottom
196 Chapter 4
COLD-WATER INLET
HOT-WATER OUTLET
HOT-WATER
OUTLET LEVEL
ANTISIPHON HOLE
DIP TUBE
COLD-WATER
INJECTION LEVEL
AIR
OPEN HOTWATER LINE
ANTISIPHON HOLE
LOWEST WATER LEVEL
TO WHICH TANK WILL
SIPHON OFF WITH
ANTISIPHON HOLE
LEVEL TO WHICH TANK
COULD SIPHON OFF
WITHOUT ANTISIPHON
HOLE
BROKEN COLDWATER INLET
SIPHON ACTION
FLOW
Figure 4-17
Dip tube and antisiphon hole. (Courtesy Robertshaw Controls Co.)
of the dip tube, a dangerously low water level for the tank. The
siphon action is broken when the water reaches the level of the
antisiphon hole, and the hot water will not be drawn below this
level.
Water Heaters 197
Anodes
The inside surface of a domestic hot-water tank is covered with a
coating to protect the steel from corrosion. Sometimes, because of
a production error, a very small part of the surface may remain
uncoated and subject to corrosion. If another metal with less
resistance to corrosion than steel is inserted into the tank, the corrosion will attack it instead of the exposed steel surface on the
tank wall.
Metal rods called anodes are used to protect the walls of the
water storage tank from corrosion. They are made from either
magnesium or aluminum formed around a steel wire core. Because
both of these metals have less resistance to corrosion than steel,
corrosion will attack them instead of the exposed steel. In other
words, they sacrifice themselves to the electrolytic process. For this
reason, anodes are sometimes called sacrificial anodes.
An anode rod is installed by screwing it into the top of the water
storage tank. It can be unscrewed, removed, inspected, and replaced
by a new rod. A residential water tank will have one or two anode
rods depending on the life of the warranty. Two rods are used in
tanks with 12-year warranties. One rod is used if the warranty is half
as long. Water storage tanks used in commercial systems will have
anywhere from one to six anode rods.
Note
All the anode rods used in a tank must be made of the same
metal. Otherwise, some will corrode faster than others.
Valves
Three types of valves are used with domestic hot-water heaters:
temperature and pressure relief valves, vacuum relief valves, and
water-tempering valves. These valves are used to prevent damage to
the water heater from excessively high pressures, temperatures, or
vacuum conditions. They also protect the user from personal injury.
Safety Relief Valves
A relief valve for a domestic hot-water supply heater is an emergency
safety device. If properly installed, it allows water to escape and spill
out when excessive pressure, dangerously high temperature, or both
conditions are present in the water storage tank.
It is important to understand the relationship between excessive
pressure and high temperature for the safe operation of a hot-water
heater. Ignorance of this relationship may result in an explosion
severe enough to cause tragic loss of life and extensive property
damage. The two principal causes of hot-water storage tank explosions are (1) water in the tank at an excessively high temperature,
198 Chapter 4
and (2) a physical weakness of the tank caused by a defect, age, corrosion, or general deterioration.
Water under pressure (greater than atmospheric pressure) can be
heated above 212°F and still not boil (see Figure 4-18). As shown in
Figure 4-18, the pressure in the tank will rise as it is heated because
of thermal expansion. Such pressure cannot be relieved by backing
into the main if the cold water is blocked by a check valve or other
devices. If there is a failure in the heating-control device, the water
in the tank will continue to heat beyond 212°F, and the superheated
water will immediately flash into steam when a rupture occurs in
the storage tank. Such action instantaneously converts 1 cubic inch
of water into 1 cubic foot of steam with explosive force. This
tremendous steam-flash explosive force can shoot water heaters,
much like a jet-propelled rocket, through floors and roofs, burst
foundations, destroy property, and cause serious or fatal injuries
(see Figure 4-19).
Tests have shown that even though water pressure is raised
above the normal safe tank limit, the worst that can happen is for
the tank to rupture and cause water damage. When heat is applied,
however, the tank becomes a potential hazard because of the steamflash explosive possibilities. Protection against this danger can be
obtained by the proper installation of suitable pressure and temperature relief valves. No water heater can operate safely without these
safety relief valves.
A pressure relief valve is designed to prevent excessive pressure from
developing in the hot-water heater storage tank (see Figure 4-20).
This is exclusively a safety device and is not intended for use as a
regulating valve to control or regulate the flow pressure. This type
of valve starts to open at the set pressure and requires a certain
HEATED WATER EXPANDING BACK INTO MAIN WATER
SUPPLY LINE MAY BE BLOCKED FOR RELIEF BY
TO DRAIN
TO HOT
COLD WATER
FIXTURES
INLET
1. CHECK VALVES
2. PUMP TO SUPPLY WELL WATER
3. PRESSURE REDUCING VALVE
4. WATER METER DAMAGED BY HOT WATER
5. WATER SOFTENER
AUTOMATIC HOT WATER
STORAGE TANK
PRESSURE BOILING PT
45 LBS
292°F
297°F
50 LBS
75 LBS
320°F
100 LBS
337°F
125 LBS
353°F
Figure 4-18
Boiling points of water at various pressures.
(Courtesy A.W. Cash Valve Manufacturing Co.)
Water Heaters 199
Figure 4-19
Explosive power of superheated water.
(Courtesy A.W. Cash Valve Manufacturing Co.)
percentage of overpressure to open fully. As the pressure drops, it
starts to close and shuts at approximately the set pressure.
A temperature relief valve is used to prevent excessively high
water temperature from developing in the hot-water heater storage
tank. A temperature relief valve may be a separate unit or combined
in the same housing with a pressure relief valve to form a combination temperature and pressure relief valve (see Figure 4-21).
Water heater pressure and temperature relief valves must be
installed in accordance with AGA, UL, or FHA standard safety
requirements. Furthermore, the pressure and temperature relief
valve should be constructed and located in conformance with current American National Standard (Z21.22) listing requirements.
The manufacturer’s recommendations for locating the valve on the
storage tank should also be followed. Never reuse a relief valve if
the water heater is being replaced. Always be sure to use the capacity
relief valve recommended by the manufacturer for the installation.
A pressure and temperature relief valve is basically a pressure
relief valve with an added temperature-sensing element thermostat
located at the inlet of the valve to prevent overheating or explosive
dangers. The temperature-sensing element must be immersed in the
water within the top 6 inches of the tank (see Figures 4-22, 4-23,
and 4-24). This location is required for the immersion element
because the hottest water will occupy this portion of the tank.
The basic components of both a pressure relief valve and a combination pressure and temperature relief valve are shown in Figures 4-25
and 4-26. Note the position of the temperature-sensing element
200 Chapter 4
Pressure relief (only) valve used
to protect hot-water supply systems from excessive pressure.
Figure 4-20
(Courtesy A.W. Cash Valve Manufacturing Co.)
thermostat. When the water in the top of the tank approaches the
danger zone (210°F), the thermostat expands and lifts the valve disc
from the seat, allowing hot water to escape and cooler water to
replace it in the tank. A decrease of less than 10° in the water temperature causes the thermostat to contract and allows the loading
spring to reseat the valve, thus maintaining a supply of hot water at
all times.
Water Heaters 201
Combination pressure and temperature
relief valve. (Courtesy A.W. Cash Valve Manufacturing Co.)
Figure 4-21
Direct side
tapping. (Courtesy Watts Regulator Co.)
Figure 4-22
MAX. 6"
DRAIN
If a combination pressure and temperature relief valve is used, it
should be installed in a separate tapping in the top of the hot-water
storage tank (see Figure 4-24). If a separate tapping is not available,
then the valve should be installed in the hot-water discharge line to
202 Chapter 4
DRAIN
Figure 4-23
Direct top tapping.
(Courtesy Watts Regulator Co.)
the fixture outlets at a point as close to the tank as possible (see
Figure 4-24).
The relief valve should be installed in the upper end of a tee, the
lower end of which is connected to the tapping in the top of the
hot-water storage tank by means of a closed nipple. The hot-water
supply line to the fixture outlets is then connected to the branch of
the tee as shown in Figure 4-24. If the relief valve is located in the
hot-water supply line to the fixtures at a distance greater than 4
inches from the storage tank, excessive temperatures generated
within the tank may result in serious damage before the excessive
temperature is communicated through the water and piping to the
relief valve. The possibility of this situation arising can be avoided
by selecting a valve with a temperature-sensing element that is long
enough to extend into the top 6 inches of the tank.
VACUUM
RELIEF VALVE
PRESSURE- AND
TEMPERATURERELIEF VALVE
COLD
HOT
DRAIN
Figure 4-24 Relief valve installed in hot-water discharge line.
(Courtesy Watts Regulator Co.)
Water Heaters 203
PRESET
ADJUSTMENT
SPRING
MANUAL
RELIEF LEVER
SEAL
DIAPHRAGM
OUTLET
TO DRAIN
POPPET VALVE
PRESSURE CONNECTION
TO SYSTEM
INLET
Figure 4-25
Principal components of a pressure relief valve.
(Courtesy Robertshaw Controls Co.)
A temperature relief valve must be installed so that the temperaturesensing element is in contact with hot water in the top 6 inches of
the tank. This is a necessary safety precaution because of a condition called temperature lag, that is, the condition of temperature
variation between the hottest water in the top of the tank and water
temperature at varying distances away from the actual tank tapping
(see Figure 4-27). When the average temperature in the top 6 to 8
inches is 210°F, there will be a considerable temperature lag (under
no-flow conditions) at varying distances away from the tank. For
example, a temperature of 191°F can be found at a point even with
the top of the tank. At 4 inches above the top of the tank, the temperature has dropped off to 170°F. Taking these conditions into
account, then, it becomes clear why relief valves with extensiontype temperature-sensing elements are recommended. The temperature-sensing element must reach down to the point at which the
highest water temperature occurs.
Where separate pressure and temperature relief valves are used,
the temperature relief valve should be installed in the top of the
204 Chapter 4
MANUAL
RELIEF LEVER
TO
DRAIN
PISTON
SEAL
SENSOR PROBE
WAX FILL
Principal components of a pressure and temperature
relief valve. (Courtesy Robertshaw Controls Co.)
Figure 4-26
hot-water storage tank or as close as possible to the tank in the hotwater supply line to the fixtures as previously described, and the
pressure relief valve should be installed in the cold-water supply
line at a point as close to the hot-water storage tank as possible.
The rated capacity of temperature relief valves (in Btu/h) should
equal or exceed the input capacity of the hot-water heater (also
expressed in Btu/h). Both the pressure and temperature steam ratings should be listed on the side of the valve (see Figure 4-28).
Typical piping connections for an automatic storage water
heater are shown in Figure 4-29. A two-temperature capability is
provided by feeding the hot water directly to the appliances. A balancing valve is installed in the cold-water line to the tempering
valve to compensate for pressure drop through the heater. Because
the tempering valve cannot compensate for rapid pressure fluctuations, a pressure equalizing valve should be installed where the system
is subjected to water-pressure fluctuations.
Water Heaters 205
3⁄
4" PIPE
130°F
146°F 157°F 172°F
4"
4"
146°F
4"
4"
LOCATED
EVEN WITH
TOP OF TANK
170°F
4"
191°F
191°F
COLD WATER INLET
8
7
6
5
AV 210°F
4
TEMPERATURE DISTRIBUTION
UNDER NO-FLOW CONDITIONS
3
2
1
Temperature distribution under no-flow conditions
(temperature lag). (Courtesy A.W. Cash Valve Manufacturing Co)
Figure 4-27
AGA TEMPERATURE STEAM RATING
ASME PRESSURE STEAM RATING
Rating of a typical pressure and temperature
relief valve. (Courtesy Watts Regulator Co.)
Figure 4-28
206 Chapter 4
VACUUM
RELIEF VALVE
COLD
PRESSURE- AND
TEMPERATURERELIEF VALVE
DRAIN
HOT TO
APPLIANCES
TEMPERED
8” TO 12”
WATER HEATER
WATERTEMPERING
VALVE
BALANCING
VALVE
Figure 4-29
Automatic storage water heater piping connections.
(Courtesy Watts Regulator Co.)
Figure 4-30 illustrates the piping connections for large-size
instantaneous heat exchanger or converter heater applications. If
either leg of the circulator is valved off from the heater, an ASME
pressure relief valve must be installed.
Tankless heater piping connections are shown in Figure 4-31. As
in other installations, a balancing valve has been installed in the coldwater line to the tempering valve to compensate for pressure drop.
Vacuum Relief Valve
A vacuum relief valve is used to protect a hot-water supply system
by preventing vacuum conditions that could drain the system by
siphonage, burn out the water heater, or cause the storage tank to
collapse (see Figure 4-32).
The vacuum relief valve is installed in the cold-water supply line.
It closes tightly under system pressure and opens quickly in case of
emergency at less than 1⁄2-inch vacuum. When the valve opens, atmosphere is admitted and breaks the vacuum, preventing siphonage of
the system and the possible collapse of the storage tank.
Water-Tempering Valves
A water-tempering valve (see Figure 4-33) is used in a hot-water
supply system to provide domestic hot water at temperatures
Water Heaters 207
TEMPERED
140°F
COLD
AGA/ASME
T&P VALVE
NO. N170
TEMPERING
VALVE
ASME PRESSURERELIEF VALVE
HOT
COLD
CHECK
VALVE
STORAGE TANK
WATER
HEATER
OR
HOT-WATER
BOILER
Typical piping connections for large instantaneous heat
exchanger or converter-type heater applications. (Courtesy Watts Regulator Co.)
Figure 4-30
PRESSURERELIEF VALVE
WATERTEMPERING
VALVE
HOT-WATER BOILER
HOT TO
APPLIANCES
TEMPERED
TANKLESS
HEATER
HOT
8" TO 12"
PRESSURERELIEF VALVE
BALANCING
VALVE
COLD
CHECK
VALVE
Figure 4-31
Tankless heater piping connections. (Courtesy Watts Regulator Co.)
208 Chapter 4
Vacuum relief valve used to protect hot-water supply
systems from internal vacuum conditions. (Courtesy A.W. Cash Valve Manufacturing Co.)
Figure 4-32
Typical water-tempering
valve. (Courtesy Watts Regulator Co.)
Figure 4-33
considerably lower than those of the water in the supply mains.
These valves are especially recommended for larger hot-water supply systems requiring dependable control of the water temperature
at the fixture outlets.
A water-tempering valve is not designed to compensate for system-pressure fluctuations and should never be used where more
sophisticated pressure-equalized temperature controls are required
to provide antiscald performance. Water-tempering valves are
described in greater detail in Chapter 10 of Volume 2 (“Steam and
Hydronic Line Controls”).
Water Heaters 209
Gas-Fired Water Heaters
Gas-fired automatic storage water heaters are those in which the
hot-water storage tank, the gas burner assembly, the combustion
chamber and necessary insulation, and the automatic controls are
combined in a single self-contained, prefabricated unit or package.
Size limitations, resulting from the necessity of such heaters being
readily portable, generally restrict the storage tank capacity to
approximately 75 gallons.
In this type of water heater, the heat of the gas flame is transmitted to the water by direct conduction through the tank bottom
and flue surfaces. Some heaters have multiple central flues, while
in other designs the hot exhaust gases pass between the outer surfaces of the tank and the insulating jacket. In either case, these
areas become radiating surfaces serving to dissipate the heat of the
stored hot water to the flue or chimney when the burner is off.
This is particularly true if the flue or chimney has a good natural
draft.
The most commonly used gas-fired water heater is the underfeed
type. If properly maintained, gas underfeed water heaters will have
a long service life. They are generally inexpensive to purchase and
install. The older gas underfeed models were not especially efficient, but design improvements, such as greater tank insulation and
improved heat transfer surfaces, have improved their efficiency.
Locating the gas burner and flue outside the storage tank has
resulted in still another type of gas-fired water heater. These units
(sometimes called sidearm heaters) provide indirect heating of the
water, which allows the use of plastic-lined storage tanks and
reduces standby losses.
Storage Capacity
The average ratio of hourly gas input to the storage capacity in gallons of water (for gas-fired automatic storage water heaters of the
so-called rapid-recovery type) is such that the recovery (heating)
capacity in gallons of water raised 100°F in one hour, in most
instances, approximately equals the storage capacity of the tank in
gallons.
Where the water must be raised 120°F, the recovery (heating)
capacity in gallons per hour will be approximately 83 percent of the
storage capacity in gallons.
Where the water must be raised 140°F, the recovery (heating)
capacity in gallons per hour will be approximately 71 percent of the
storage capacity in gallons.
210 Chapter 4
Gas Burners
The burners used in gas-fired water heaters must be provided with
inlet gas orifices and some means of air intake. These conditions are
necessary to provide the required air-gas mixture for the flame.
Beyond these two basic requirements, gas burners will vary widely
in both design and construction. These variations in design and
construction are generally concerned with providing good flame
pattern and ignition. Flame characteristics are affected not only by
the design of the ports (raised, drilled, ribbon, slotted, or flush) but
also by their number, distribution, depth, and spacing. The gas
input rating is an important factor in determining the number, distribution, and size of the ports. Proper spacing is generally determined by observation. Some common types of gas burners used on
water heaters are shown in Figure 4-34.
The purpose of the gas orifice is to provide the proper input for
the type of gas (for example, natural, LP) and the normal range of
gas pressures. The gas passes into the mixing tube of the burner
where it mixes with the air. Air is generally admitted through
adjustable air shutters located around the gas orifice. The design
and arrangement of the burner ports control the burning characteristics and distribution of the flame.
The size of the ports and their distribution affects the flame characteristics. If the ports are too large (both individually and in their
distribution), the flame may flash back to the burner orifice. On the
other hand, blowing flames can result from porting that is too
small. As can be readily understood, good flame patterns are in part
determined by proper porting. The number and size of ports necessary to give proper flame characteristics must be calculated.
Automatic Controls on Gas-Fired Water Heaters
The principal automatic controls used to govern the operation of a
gas-fired water heater are as follows:
1. Thermostatic valve
2. Automatic pilot valve
3. Manual gas valves
4. Main gas–pressure regulator
5. Pilot gas–pressure regulator
6. Temperature and pressure relief valves
7. Automatic gas shutoff device
8. Pilot burner
Water Heaters 211
MILLED SLOT PORT CAST BURNER
MILLED SLOT
ORIFICE
AIR SHUTTER
MIXING TUBE
VERTICAL
DRILLED PORTS
ORIFICE
AIR SHUTTER
VERTICAL DRILLED
PORT CAST BURNER
HORIZONTAL
SLOT PORTS
HORIZONTAL SLOT
PORT CAST BURNER
STAMPED MONO-PORT
BURNER
ORIFICE
AIR-GAS MIXING AREA
STAMPED HORIZONTAL
PORT BURNER
MULTIPLE STAMPED
RIBBON PORTS
DOUBLE DELTA BURNER
Figure 4-34
Common types of gas burners used in water heaters.
(Courtesy Robertshaw Controls Co.)
212 Chapter 4
A thermostatic valve (see Figures 4-35 and 4-36) is used to control the gas input to the burners in relation to the water temperature in the storage tank. Thermostatic water temperature controls
are usually direct, snap-action bimetallic devices that react to a
drop in the temperature of the water in the storage tank. This drop
in temperature causes a thermal element immersed in the stored hot
water to contract and, through mechanical linkage, to open the
main gas valve on the unit. When the water in the tank reaches a
selected, predetermined setting, the thermal element expands and
closes the main gas valve. These thermostatic valves normally operate at a temperature differential of approximately 12°F. In other
words, if set to shut off the gas to the main burner when the tank
water temperature reaches 140°F, they will react to open the valve
when the temperature drops to 128°F.
THERMOSTAT
VALVE
"CLICKER" SNAP
MECHANISM
SHANK
COPPER TUBE
INVAR ROD
ADJUSTMENT
ROD
LEVER
WATER TANK
THERMOSTAT
TEMPERATURE DIAL
Figure 4-35
Principal thermostatic valve components.
(Courtesy Robertshaw Controls Co.)
Another important control on a gas-fired water heater is the
automatic pilot valve, which operates on the thermocouple principle (see Figures 4-37 and 4-38). This control automatically shuts
off the gas when pilot outage or improper ignition conditions occur.
When the electromagnet is deenergized, the magnet allows the
return spring to close the automatic pilot valve and shut off the gas
supply to both the main burner and the pilot. The 100 percent
automatic pilot shutoff condition is shown in Figure 4-39. As
Water Heaters 213
"CLICKER" SNAPPED
OVER CENTER
GAS FLOW
VALVE OPEN
COOLER WATER
(COPPER CONTRACTS)
INVAR MOVEMENT
TO CONTROL
OUTLET AND MAIN
BURNER
Figure 4-36
Thermostatic valve operating principles.
(Courtesy Robertshaw Controls Co.)
RESET
BUTTON
HOT
JUNCTION
MAIN GAS
PILOT GAS
COLD
JUNCTION
AUTOMATIC
PILOT VALVE
& SEAT
INLET
RETURN
SPRING
KEEPER
ELECTROMAGNET
THERMOCOUPLE
Figure 4-37
Principal components of an automatic pilot system.
(Courtesy Robertshaw Controls Co.)
214 Chapter 4
"HOT" JUNCTION
WELD
COPEL
(CONSTANTAN)
TERMINALS FOR
CONNECTION OF
MAGNET OPERATOR
STAINLESS
STEEL
INSULATOR
WASHER
+
COLD
JUNCTIONS
COPPER
TUBE
INSULATED
COPPER WIRE
Figure 4-38
Typical thermocouple construction. (Courtesy Robertshaw Controls Co.)
shown in Figure 4-40, the reset button must be depressed while the
pilot is being relit. If the flame is established, the pilot will continue
to burn after the reset button is released (see Figure 4-41).
Manual gas valves (gas cocks) function as a backup safety system
to the automatic pilot valve by providing manual control of the
main burner and pilot burner gas supply (see Figure 4-42). The
manual gas valve is also used with the automatic pilot valve to provide safe pilot lighting by ensuring that only pilot gas is flowing
during the pilot lighting operation.
Both pilot gas– and main gas–pressure regulators are used on
gas-fired water heaters. The pilot gas–pressure regulator is used to
regulate the pressure of the gas flowing to the pilot. The main
gas–pressure regulator performs the same function for gas flowing
to the main burners. These gas-pressure controls have been mandatory on gas-fired water heaters since 1972.
Schematics of several types of pressure regulators used on water
heaters are shown in Figures 4-42, 4-43, and 4-44. These devices
Water Heaters 215
PILOT OUTAGE
NO MAIN GAS
NO PILOT
GAS
INLET
RETURN SPRING
CLOSE VALVE
KEEPER
ELECTROMAGNET
DEENERGIZED
Figure 4-39
Automatic (100 percent) pilot shutoff condition.
(Courtesy Robertshaw Controls Co.)
operate on the balanced-pressure principle; that is to say, a main
pressure diaphragm and a balancing diaphragm act to balance out
or cancel the differences in inlet and outlet pressures caused by
pressure variations.
Domestic gas water heater combination controls provide for
main gas–pressure regulation by incorporating a pressure regulator
in the control. Independent pilot gas–pressure regulation is optional
(see Combination Gas Controls in this chapter).
The schematic of a Robertshaw pilot gas–pressure regulator is
shown in Figure 4-45. This particular pressure regulator has the
approximate diameter of a penny and is inserted downstream from
the pilot filter.
The following three types of safety controls (individually or in
combination) are also found on water heaters:
1. Automatic gas shutoff device
2. Pressure relief valve
3. Temperature relief valve
216 Chapter 4
PUSHED
DOWN
RESET
BUTTON
HOT
JUNCTION
(PILOT LIT)
INTERRUPTER
VALVE
COLD
JUNCTION
INLET GAS
RETURN
SPRING
KEEPER
ELECTROMAGNET
PILOT GAS
THERMOCOUPLE
Automatic pilot valve reset button depressed while
pilot is being lit. (Courtesy Robertshaw Controls Co.)
Figure 4-40
An automatic gas shutoff device is designed to shut off all gas to
the water heater when excessively high water temperature conditions occur. In most automatic gas shutoff systems, this device
operates in conjunction with the automatic pilot valve in the pilot
safety shutoff circuit. The automatic shutoff device is generally set
to shut off the automatic pilot valve when the water temperature in
the storage tank approaches 210°F.
A typical automatic shutoff device, such as the one shown in
Figure 4-46, is mounted on the tank surface so as to sense the water
temperature through the tank wall. These devices are normally
closed electrical switches connected in series in the automatic pilot
millivolt circuit. When the switch reaches its preset temperature
limit, it snaps open and deenergizes the electromagnet of the automatic pilot valve. This allows the closure spring of the automatic
pilot valve to close the valve. As a result, all gas is shut off to all
burners (including the pilot burner).
When the water temperature becomes too high, the volume of
water in the tank tends to expand. A temperature relief valve is
Water Heaters 217
BUTTON
RELEASED
PILOT LIT
MAIN GAS TO
MAIN BURNER
PILOT GAS
INLET
KEEPER
Pilot continues to burn after reset button
is released. (Courtesy Robertshaw Controls Co.)
Figure 4-41
"ON" POSITION
(SIDE VIEW)
MAIN GAS FLOW
PILOT GAS FLOW
MAIN GAS (OFF)
PILOT GAS FROM
AUTOMATIC PILOT VALVE
MAIN GAS (OFF)
"PILOT" POSITION
(TOP VIEW)
PILOT GAS TO PILOT GAS
FILTER, PILOT ADJUSTMENT
AND TO PILOT BURNER
"OFF" POSITION
(TOP VIEW)
PILOT GAS (OFF)
Figure 4-42
Diagram of a gas-cock parting. (Courtesy Robertshaw Controls Co.)
218 Chapter 4
VENT
SPRING
COVER
INTEGRAL VALVE
AND DIAPHRAGM
REGULATOR
VALVE BODY
OUTLET
OUTLET
INLET
Principal components of a pilot gas–pressure
regulator. (Courtesy Robertshaw Controls Co.)
Figure 4-43
SPRING
ADJUSTMENT
VENT ORIFICE
DIAPHRAGM
AND PAN
ASSEMBLY
SPRING
REGULATOR
VALVE
BALANCING
DIAPHRAGM
OUTLET
INLET
Figure 4-44
Operating principles of a balanced-pressure regulator.
(Courtesy Robertshaw Controls Co.)
Water Heaters 219
VENT ORIFICE
SPRING ADJUSTMENT
MAIN DIAPHRAGM
AND PAN ASSEMBLY
BALANCING
DIAPHRAGM
FROM INLET
VALVE STEM
THERMOSTATIC
VALVE ASSEMBLY
OUTLET
Diagram of a Robertshaw Unitrol R11OR series water
heater control incorporating a balanced-pressure regulator.
Figure 4-45
(Courtesy Robertshaw Controls Co.)
designed to release a portion of the water and at the same time
introduce cold water to reduce the temperature of the remaining
water. The temperature relief function must occur at or below
210°F on residential and commercial water heaters.
220 Chapter 4
AUTOMATIC PILOT VALVE
LEAD WIRES
THERMOCOUPLE
CLAMP ON TANK
HT-3
PILOT
LEAD WIRES
AUTOMATIC
PILOT VALVE RESET
JUNCTION BOX
Figure 4-46
Automatic gas shutoff device installation.
(Courtesy Robertshaw Controls Co.)
The purpose of a pressure relief valve is to release a portion of
the water from the heater or hot-water heating system when excessive pressure conditions occur. Pressure and temperature relief
valves are used on all types of tank water heaters regardless of the
fuel used to heat the water. See Relief Valves in this chapter.
The pilot burner gas supply is taken off ahead of the gas valve
in the thermostatic control. Pilots are usually of the safety type,
functioning to shut off the gas supply if the pilot burner flame is
extinguished.
Most of the control functions described in the preceding paragraphs can be combined in a single unit or combination gas control
(see next section).
Water Heaters 221
Combination Gas Valve
A combination gas valve (or combination gas control) combines in
a single unit all the automatic and manual control functions necessary to govern the operation of a gas-fired water heater.
A typical combination gas valve is shown in Figures 4-47 and 4-48.
This particular unit contains a water heater thermostat (thermostatic
valve), automatic pilot valve, automatic gas shutoff device, main
gas–pressure regulator, pilot gas–pressure regulator, and manual valve
(gas cock).
The installation instructions included with most combination
gas valves are usually very complete and should cover the following
points:
1.
2.
3.
4.
5.
6.
7.
8.
Disassembly and assembly instructions
Automatic shutoff valve and magnet replacement
Gas-cock lubrication
Thermostatic valve cleaning instructions
Pressure-regulator adjustment
Thermostat calibration
Lighting procedure
Test procedure
Figure 4-47
Robertshaw Unitrol R11ORTP combination gas valve.
(Courtesy Robertshaw Controls Co.)
222
REGULATOR ADJUSTMENT CAP
COMBINATION GAS COCK
& PRESSURE REGULATOR
NAT. GAS OR L.P. GAS
SCREW (1)
RETAINING SCREWS (2)
GAS COCK SPRING
VALVE ASSEMBLY
SET BUTTON RETAINER ASSEMBLY
PILOT FILTER
SHANK ASSEMBLY
BODY GASKET
COVER
SCREWS (4)
SCREW (4)
E.C.O. SWITCH TERMINAL
LEVER
BODY
DIAL
PRESSURE PLUG
*50650 AUTOMATIC PILOT VALVE
AND MAGNET ASSEMBLY
STOP ADJUSTMENT NUT
STOP
TEMP. ADJ. SCREW
*50655 TERMINAL RETAINER
PILOT REGULATOR RETAINING SPRING
PILOT REGULATOR ASSEMBLY
NAT. GAS OR L.P. GAS
Figure 4-48
PILOT REGULATOR GASKET
Exploded view of a Robertshaw Unitrol R11ORTP combination gas valve.
(Courtesy Robertshaw Controls Co.)
Water Heaters 223
Most control manufacturers provide test kits to test the operation of the thermocouple, thermomagnet, and automatic safety
shutoff device. The test kit consists of a millivolt meter and an
adapter for testing the thermomagnet (see Figure 4-49).
As shown in Figure 4-50, the manual valve (gas cock) is used
when lighting the pilot. The gas-cock dial (1) is turned to the off
position and at least 5 minutes is allowed to pass. This should be
sufficient time for any gas that has accumulated in the burner compartment to escape. The gas-cock dial is then turned to the start
position, and the set button (2) is depressed while the burner is
being lit (see Figure 4-51). The standby flame is allowed to burn for
approximately 1⁄2 minute before the reset button is released (see
Figure 4-52). Unless there is a problem, the burner should stay lit
after the reset button has been released. After releasing the reset
button, turn the gas-cock dial to the on position and turn the temperature dial (3) to the desired setting.
The combination valve shown in Figure 4-53 does not use a reset
button in the lighting procedure. The upper dial is turned counterclockwise to the pilot position and held against the spring-loaded stop
until the pilot burner lights. After the pilot burner burns for about 30
to 60 seconds, the upper dial is turned clockwise to on for automatic
control. The lower dial is then set for the desired water temperature.
TEST KIT
(MILLIVOLT METER)
MAGNET BASE
SWITCH TERMINAL
TERMINAL
RETAINER
ADAPTOR
(THERMOCOUPLE SETTING)
THERMOCOUPLE
Typical testing procedure with millivolt meter and
adapter. (Courtesy Robertshaw Controls Co.)
Figure 4-49
224 Chapter 4
2
1
3
Figure 4-50
Pilot lighting procedure. (Courtesy Robertshaw Controls Co.)
FLAME FROM EXTERNAL PORTING ON
THERMOCOUPLE HOT JUNCTION
FLAME SPREADER
LIGHT HERE
Figure 4-51
Standby flame pattern. (Courtesy Robertshaw Controls Co.)
Water Heaters 225
FLAME DIRECTED FROM INNER PORT
ON THERMOCOUPLE HOT JUNCTION
Figure 4-52
Full-input flame pattern. (Courtesy Robertshaw Controls Co.)
Installation and Operation of Gas-Fired
Water Heaters
The installation and operation of a gas-fired automatic storage
water heater involves little possibility of error if the instructions of
the manufacturer are strictly followed and due consideration is given
to the following factors:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
Location
Venting regulations
Water heater venting system
Size of flue pipe
Runs of flue pipe
Gas meter
Gas supply line
Hot-water circulation methods
Safety relief valves
Building and safety code provisions
Lighting and operating instructions
226 Chapter 4
LIGHTING/CONTROL DIAL
TEMPERATURE
SELECTION DIAL
PRESSURE-REG. ADJ.
PILOT GAS ADJUSTMENT
GAS COCK (DISC TYPE)
SELF-LUBRICATING
NO SERVICE REQUIRED
GASKET
RESET DIAL
TEMPERATURE DIAL
Figure 4-53
THERMOSTATIC VALVE
THERMOMAGNET ASSEMBLY
ITT General Controls water heater control.
(Courtesy ITT General Controls)
Location
The heater should be located at a point convenient to the flue or
chimney and, if possible, at a point approximately equidistant from
all hot-water outlets.
Venting Regulations
Many building codes prohibit connecting appliances to a common
flue or chimney with coal- or oil-fired equipment. Where regulations do not require venting of gas-fired equipment to a separate
flue and it is vented to a common flue with coal- or oil-fired units,
the flue pipe of the gas-fired water heater or other appliance should
be connected to the chimney at a point above the flue pipe from the
coal- or oil-fired equipment.
Water Heaters 227
When possible, a separate hole in the chimney should be used for
the water heater flue. If this is not possible, join the flue from the
water heater and the flue from the heating boiler (or furnace) with
a Y connection (never a T connection) and install a separate draft
regulator for each unit.
When the chimney cannot handle the combined input of both
the water heater and the heating plant, wire the two so that they do
not operate simultaneously.
Water Heater Venting Systems
The venting system of a fuel-fired water heater is designed to
transfer the products of combustion to the outdoors. By transferring these potentially harmful gases outside the structure, the living
spaces are maintained free of any possible air contamination.
Electric water heaters do not require venting systems.
A typical venting system for a fuel-fired water heater consists of
the following basic components:
1. Heater flues or heat exchangers
2. Draft diverter
3. Vent pipe connections
The design and arrangement of a venting system should take
advantage of the natural tendency of hot gases to rise. These flue gases
are a waste by-product of the combustion process. Because they are
hot gases, they are lighter than the surrounding ambient air, and they
tend to rise in a vertical path. The venting system should provide
essentially a vertical path to take advantage of this natural vertical
flow of the gases. The vent pipes should be of sufficient diameter to
carry the volume of gas without restricting its natural flow rate.
Excessive cooling of the flue gases can be avoided by providing a
controlled mixture of dilutant air from the draft diverter. If the flue
gases cool, condensation will occur, the gases will grow heavier, and
it will be impossible to maintain draft. The same condition (that is,
excessive cooling) will occur if the vents are unusually long or high.
This can be minimized by insulating the vent pipes.
Fans are used on some high-input water heaters to supplement
natural venting. The use of a fan is sometimes referred to as power
venting, and the water heaters are referred to as power-vent water
heaters. In most cases where a fan is used, proper venting can generally be obtained from a smaller-diameter vent pipe. However,
some provision should be made to automatically shut off the water
heater in case of a fan failure. Fan-assisted venting allows the use of
much longer horizontal or vertical flue pipes than would ordinarily
228 Chapter 4
be the case. As a result, the water heater can be located anywhere in
the structure. On the downside, the fan and water heater are electrically operated, and a power failure will shut down the unit.
Vent pipe connections are often made directly to the outdoors or
through a chimney wall. When direct venting is the case, the vent
pipe connects to a vent outlet hood.
Draft hoods are used on all water heaters that rely on natural vent
action to eliminate contaminating flue gases. The draft hood should
contain an inlet and outlet opening for the flue gases, and an air dilutant intake and relief opening to relieve downdraft conditions.
Examples of common types of draft hoods used on gas-fired
water heaters are shown in Figure 4-54. The vertical draft hood is
usually the most efficient for venting.
BAFFLE
FLUE GAS
DILUTANT AIR
VERTICAL DRAFT HOOD
HORIZONTAL DRAFT HOOD
Figure 4-54
FLUE GAS
DILUTANT AIR
VERTICAL TO HORIZONTAL
HORIZONTAL TO VERTICAL
Draft hoods commonly used on water heaters.
(Courtesy Robertshaw Controls Co.)
Water Heaters 229
A well-designed draft hood should be able to prevent excessive
updraft in the burner compartment and momentary excessive
downdraft conditions. Sometimes the flow rate of flue gases suddenly increases and results in an excessive updraft condition in the
burner compartment. The amount of air flowing into the flue
through the air dilutant intake is clearly insufficient to control the
condition. The diverter should be designed to allow an increase in
air intake during excessive updraft conditions so that the weight of
the flue gases is increased and the flow rate slowed.
When downdraft conditions occur, the baffles and relief opening
in the draft hood allow the downdraft to be relieved outside the flue
so that the burner flame is unaffected. This expulsion of the combustion by-products through the air intake is only a momentary
condition.
Size of Flue Pipe
The size of the flue pipe should not be less than that specified by the
manufacturer or that shown in available tables for the rated gas input.
Flue Pipe Run
Horizontal runs of the flue pipe should pitch upward toward the
chimney connection and should run as directly as possible, avoiding unnecessary bends or elbows. The backdraft diverter supplied
by the manufacturer or other approved draft hood of adequate size
should be employed.
Gas Meter
The gas meter must be of adequate size or capacity to supply not
only the requirements of the water heater but also the requirements
of all other gas-fired equipment.
Gas Supply Line
The gas supply line to the water heater should be adequate in size to
supply the full rated gas input of the heater at the available pressure, taking into consideration the pressure drop through the supply line. A separate gas supply line from the meter to the water
heater should be employed if the existing line from the meter is too
small to supply the combined requirements of the water heater and
other equipment or appliances that may be connected to it.
Safety Relief Valves
Both a pressure relief valve and a temperature relief valve are used
to ensure the safe operation of a water heater. The operating characteristics of these two safety relief valves have already been
described (see Safety Relief Valves in this chapter).
230 Chapter 4
Hot-Water Circulating Methods
If a building circulation loop is employed to maintain circulation of
the hot-water supply throughout the building for the purpose of
making the hot water more readily available at each fixture, the
return line from the circulating loop should be connected to the coldwater supply line of the heater. A swing-check valve must be installed
in a horizontal section of the return line at a point as close to its connection to the cold-water supply line as possible to prevent the possibility of backflow of cold water to the hot-water outlets of fixtures
that may be connected to the circulation loop at a location that may
be closer to the cold-water supply line than to the water heater.
If a check valve were not employed, and the pressure drop in the
line between the cold-water supply line and the hot-water outlet
were less than the pressure drop in the line between the heater and
the hot-water outlet, cold water could flow to the hot-water outlet.
Where a circulating pump is employed to accelerate the circulation in a building hot-water supply loop, it should be installed in
the return water line at a point as close to its connection to the
cold-water supply line as possible. To eliminate the unnecessary
wear and expense incidental to operating a circulating pump continuously, it should be controlled by a direct aquastat installed in
the return circulating line at a point conveniently close to the pump.
It is suggested that this aquastat be adjusted to close the pump
circuit when the water in the return line drops to (or below) 100° to
110°F and break the pump circuit when the water temperature at
that point rises to approximately 120° to 130°F if the desired hotwater temperature at the fixture is approximately 130° to 140°F.
Building and Safety Code Requirements
The building and safety codes of certain states require the use of dip
tubes in the hot-water storage tanks of automatic storage water
heaters or recovery water heating systems, while other codes prohibit their use.
The apparent purpose of code provisions prohibiting the use of
cold-water supply dip tubes in the tanks of underfired storage
water heaters is to prevent the possibility of developing dangerously excessive temperatures and pressures in the tank of the gas
supply to a manually controlled heater (if not turned off) or the
safety control of an automatic water heater that fails to function.
Under such circumstances, the water in the tank would drain to
the levels of the holes drilled in the dip tubes close to the top of the
dip tube before the siphon action would be broken.
Water Heaters 231
The water remaining in the tank, being practically at zero pressure, would vaporize rapidly if automatic temperature and safety
controls failed to function or the gas supply were not shut off. The
steam thus generated in the remaining space in the upper portion of
the tank would create a personal scalding hazard if communicated
to the hot-water supply piping and outlets, or could attain sufficient pressure to rupture the tank or piping.
An equally hazardous condition would be created if the tank of
a storage heater not equipped with a cold-water supply dip tube
were completely drained.
Under this condition, if the gas supply to a manually controlled
heater were not shut off, or the thermostatic and safety controls of
an automatic heater failed to function with the gas valve in the thermostat in the open position, explosive pressures would be almost
instantaneously developed if cold water were introduced into the
empty heater tank.
To avoid such hazards, the gas supply to either a manually controlled or automatic storage water heater should always be shut off
before draining the tank of the heater or the entire hot-water supply
system.
Where the use of a cold-water dip tube installed in a tapping in
the top and extending to a point close to the bottom of the hotwater storage tank is prohibited, the cold-water supply line should
be connected to a tapping as close to the bottom as possible.
If the cold water enters the tank at a point considerably above
the bottom, the water below that point will be in a more or less
static state, which may be conducive to more rapid deposition of
lime or other scale on the tank bottom.
Lime or other scale on the tank bottom retards the transfer of
heat to the water if the heater is of the underfired type, which
impairs its efficiency.
Lighting and Operating Instructions
Lighting and operating instructions are supplied by the manufacturer
and should be read and thoroughly understood before attempting to
adjust the rate of gas input and the thermostat or other automatic
controls, particularly if the serviceperson is not completely familiar
with the design and construction of such controls.
Before leaving the premises, it is imperative that the serviceperson hang the operating instructions at a point convenient to the
heater where it will be available for ready reference whenever
needed by the owner or operating personnel.
232 Chapter 4
The return warranty registration card, if provided, should also
be properly filled in by the serviceperson and handed to the owner
for mailing to the manufacturer. In many instances, warranty provisions are invalidated if the registration card is not returned to the
manufacturer.
Installation and Maintenance Checklist
The water temperature control in a residential water heater should
be set as low as possible and still provide satisfactory hot water at
the faucets. This adjustment for low water temperature prolongs
Install pressure and
temperature relief valves
per instructions on heater.
Check for proper flue size
and connection to outside vent.
Refer to local codes.
Relief opening must be
kept clear of obstructions.
Install cold water inlet
shut off valve upstream
of connecting union.
INLET — if sweat connection
do not heat check for
presence of dip tube.
HOT WATER OUTLET
Check anode rod for
deterioration. Replace if
magnesium dissipated.
GAS LINE
Use clean deburred pipe.
Proper thread size.
Avoid excessive lubrication.
Avoid excessive penetration
of valve.
Install upstream
shut off valve.
Check all joints for leaks correct as necessary.
Check clearances
to walls per applicable
codes and requirements.
Check for proper
updraft while operating.
Read and follow lighting
instructions explicitly.
Turn temperature dial
to cycle off. Check if
main burner shuts off.
ADJUST PILOT FLAME.
Check for leaks with soap
or leak detecting fluid.
DO NOT USE FLAME
Drain water until
clear— once a month.
CHECK OUTLET PRESSURE
Install drip leg to catch
scale, dirt and oil.
Check thermocouple and
E.C.O. connections
(Internal or remote E.C.O.).
Be sure pilot and
thermocouple are properly
positioned as recommended
and firmly in place.
Check automatic pilot operation.
Check for presence of E.C.O. device
(AGA requirement).
Recommend water heater location so that
controls are not exposed to moisture.
Figure 4-55
Adjust air shutters if so equipped
for blue gas flame.
Check codes for air availability requirements.
Water heater service guide. (Courtesy Robertshaw Controls Co.)
Water Heaters 233
the life of the tank and prevents stacking. The temperature dial is
adjustable and should be used to meet varying conditions and
requirements. For control maintenance, it is best to call a qualified
serviceperson. Instructions in the manufacturer’s field information
bulletin should be followed when servicing or repairing water
heater controls. Figure 4-55 provides a general checklist for water
heater installation and maintenance.
Troubleshooting Gas-Fired Water Heaters
Table 4-1 covers many of the more common symptoms and possible causes of operating problems associated with gas-fired water
heaters.
Table 4-1
Troubleshooting Gas-Fired Water Heaters
Symptom and Possible Cause
Possible Remedy
Water too hot.
(a) Thermostat setting too high.
(b) Leaking thermostat valve.
(c) Pilot too high.
(d) Thermostat out of calibration.
(e) Pilot outage.
(a)
(b)
(c)
(d)
Set thermostat lower.
Clean valve or replace.
Adjust pilot lower.
Recalibrate or replace
thermostat.
(e) Set thermostat lower and
reignite pilot.
Not enough hot water or water temperature too low.
(a) Thermostat setting too low.
(a) Set thermostat higher. Caution:
Do not set thermostat higher
than 120°F.
(b) Thermostat out of calibration. (b) Recalibrate or replace
thermostat.
(c) Undersized heater for
(c) Replace with larger heater.
hot-water demand.
(d) Clogged burner orifice.
(d) Inspect and clean.
(e) Undersized burner orifice.
(e) Change orifice to correct size.
(f) Gas pressure too low.
(f) Readjust regulator (if so
equipped); check gas supply
pressure and manifold
pressure.
(g) Clogged flue.
(g) Inspect and clean.
(continued)
234 Chapter 4
Table 4-1 (continued)
Symptom and Possible Cause
Possible Remedy
(h) Draft venting problem.
(h) Check for downdraft and
updraft venting and correct as
required; check for any drafts
blowing out pilot light.
(i) Replace thermostat.
(j) Inspect and replace.
(k) Replace dip tube.
(i) Defective thermostat.
(j) Gas control problem.
(k) Defective dip tube.
No hot water.
(a) No gas supply to burner.
(b) Pilot out.
(a) Turn on gas supply.
(b) See Failure to Ignite and
Pilot Will Not Stay Lit.
Delayed or slow hot-water recovery.
(a) Clogged flue.
(b) Incorrect gas pressure.
(c) Clogged burner orifice.
(d) Excessive drafts.
(a) Clean flue chamber.
(b) Check gas pressure and adjust.
(c) Inspect, clean, or
replace as necessary.
(d) Locate and eliminate drafts.
Burner flame too high.
(a) Pressure regulator
set too high.
(b) Defective regulator.
(c) Burner orifice too large.
(a) Reset.
(b) Replace.
(c) Replace with correct size.
Noisy burner flame.
(a) Too much primary air.
(b) Noisy pilot.
(c) Burr in orifice.
(d) Dirty burner orifice.
(a)
(b)
(c)
(d)
Check and adjust.
Reduce pilot gas.
Remove burr or replace orifice.
Inspect and clean.
(a)
(b)
(c)
(d)
Check and adjust.
Inspect and clean.
Realign.
Clean.
Yellow-tipped burner flame.
(a) Too little primary air.
(b) Dirty burner orifice.
(c) Misaligned burner orifices.
(d) Clogged draft hood.
Water Heaters 235
Table 4-1 (continued)
Symptom and Possible Cause
Possible Remedy
Floating burner flame.
(a) Blocked venting or clogged
flue.
(b) Insufficient primary or
secondary air.
(c) Incorrect orifice.
(a) Inspect and clean.
(b) Increase air supply;
adjust air shutters.
(c) Install correct orifice.
Delayed ignition.
(a) Improper pilot location.
(b) Pilot flame too small.
(a) Reposition pilot.
(b) Check orifices; clean;
increase pilot gas.
(c) Burner ports clogged near pilot. (c) Clean ports.
(d) Low pressure.
(d) Adjust pressure regulator.
Unable to ignite pilot.
(a) Gas supply off.
(a) Open manual valve
to turn on gas supply.
(b) Thermostat out of calibration. (b) Recalibrate, repair, or replace.
(c) Defective thermocouple
(c) Check and replace.
and/or automatic pilot valve.
(d) Loose thermocouple
(d) Check and tighten
connection.
connection.
(e) Defective safety magnet
(e) Check magnet and replace
assembly.
gas valve.
(f) Gas-cock knob dial set
(f) Check lighting instructions
incorrectly.
and set gas-cock knob to
correct position.
(g) Clogged pilot burner orifice.
(g) Clean or replace.
(h) Air in gas line.
(h) Purge air from line.
(i) Defective gas valve.
(i) Replace gas valve.
(j) Clogged pilot tube.
(j) Clean or replace.
(k) Pinched pilot tube.
(k) Repair or replace.
Burner will not turn off.
(a) Thermostat set too high.
(b) Thermostat out of calibration.
(c) Dirt on thermostat valve seat.
(d) Defective thermostat.
(a)
(b)
(c)
(d)
Lower setting.
Recalibrate or replace.
Clean or replace.
Replace thermostat.
(continued)
236 Chapter 4
Table 4-1 (continued)
Symptom and Possible Cause
Possible Remedy
Pilot will not stay lit.
(a)
(b)
(c)
(d)
Too much primary air.
Dirt in pilot orifice.
Clogged flue.
Draft venting problem.
(e) Too much draft.
(a)
(b)
(c)
(d)
Check and adjust pilot shutter.
Open orifice.
Clean flue way.
Check downdraft and updraft
venting and correct as required;
check for any drafts blowing
out pilot light.
(e) Provide shielding or reduce
draft.
(f) Check magnet and replace
gas valve.
(g) Replace.
(f) Defective safety magnet
assembly.
(g) Automatic pilot magnet
valve defective.
(h) Loose thermocouple
(h) Tighten connection.
connection.
(i) Defective thermocouple.
(i) Replace.
(j) Thermocouple tip out of
(j) Move tip into flame.
pilot flame.
(k) Incorrect pilot-gas adjustment. (k) Adjust pilot gas.
(l) Incorrect pilot orifice size.
(l) Replace with correct size.
(m) Pilot burner orifice or supply (m) Inspect and clean pilot burner
tube partly clogged.
and supply tube.
Main burner will not stay lit.
(a) Clogged orifice.
(b) Low gas pressure.
(c) Pinched or damaged main
burner gas supply tube.
(d) Clogged main burner gas
supply tube.
(e) Defective magnetic assembly.
(f) Defective thermocouple.
(g) Loose thermocouple
connection.
(a) Clean or replace.
(b) Check gas supply pressure
and correct.
(c) Repair or replace.
(d) Clean or replace.
(e) Check and replace gas
control valve.
(f) Check and replace
thermocouple.
(g) Check and tighten connection
or replace if connection
damaged.
Water Heaters 237
Table 4-1 (continued)
Symptom and Possible Cause
Possible Remedy
(h) Defective main valve.
(i) Venting downdraft problem.
(j) Venting sizing problem.
(h) Replace gas control valve.
(i) Check and correct.
(j) Check and correct.
Noisy water heater operation.
(a) Scale or sediment at
bottom of tank.
(b) Loose baffles.
(a) Clean tank.
(b) Reset and tighten.
Excessive temperature/pressure relief valve operation.
(a) Excessive temperature.
(b) Excessive water pressure.
(a) Lower temperature setting. If
problem continues, check for
grounded element and correct
as necessary; replace defective
thermostat.
(b) Install specified pressurereducing valve on cold intake
side.
Rusty, black, or brown water.
(a) Excessive sediment
accumulation in tank.
(b) Elements covered with scale.
(c) Dissolved anode rod.
(a) Drain and clean tank, or
replace if necessary.
(b) Clean or replace elements.
(c) Replace anode rod.
Water below gas water heater (drops of water or puddles on floor).
(a) Normal condition for gas
water heaters if drops of water
or small puddles dry up.
(b) Small pinhole leak in
inner tank.
(c) Loose immersion thermostat
or anode rod.
(d) Defective joint at cold intake
or hot outlet on tank.
(e) Defective temperature/pressure
relief valve.
(a) Ignore.
(b) Replace water heater.
(c) Tighten or replace.
(d) Inspect and repair as necessary.
(e) Check and replace.
238 Chapter 4
Oil-Fired Water Heaters
Most of the oil-fired heaters used in residences and small buildings are of the
external, or floating, tank design (see
Figure 4-56). The products of the combustion process pass upward through the
flue passages located between the suspended hot-water storage tank and the
outer walls of the water heater. Multiflue
and internal flue oil-fired water heaters,
though less common, are also used (see
Figure 4-57).
As with gas-fired water heaters, an oil
heater must have an adequate draft for
proper combustion. Sometimes it is necessary to vent two oil-fired appliances
(for example, furnace and water heater)
Figure 4-56 External
into the same flue. When this situation
(floating) tank oil-fired
occurs, the two can be connected to the
water heater.
flue either with a “Y” connection or in
(Courtesy National Oil Fuel Institute)
such a way that both feed directly into
the flue (see Figure 4-58). When two oilfired appliances, such as a furnace and a
water heater, are connected to a single
vent, the controls can be wired to prevent
simultaneous operations and give priority
to the water heater (see Figure 4-59).
Oil-fired water heater controls are
similar to those used to control hotwater space-heating boilers. They are
also designed to regulate the temperature of the water in the water heater
storage tank. For example, the primary
control shown in Figures 4-60 and 4-61
is used in conjunction with an immersion aquastat and a remote sensor (cadmium detection cell) to simultaneously
regulate the water temperature and provide oil burner control. Both oil burner
malfunctions and water temperatures
that fall outside the rated temperature
Figure 4-57 Internal flue range of the heater will cause the primary control to start or stop the oil
oil-fired water heater.
burner as conditions require.
(Courtesy National Oil Fuel Institute)
Water Heaters 239
DRAFT
REGULATORS
HEATING
PLANT
"Y" CONNECTOR
SEPARATE STACK PIPES
AND DRAFT REGULATORS
HEATING
PLANT
WATER
HEATER
Figure 4-58
WATER
HEATER
Connecting the boiler and water heater flues to chimney.
(Courtesy National Oil Fuel Institute)
THERMOCOUPLE
SWITCHING RELAY
7
1
CAD CELL
2
T6
8T
CAD CELL
IGNITION
S
3
L1
BURNER
MOTOR
OIL VALVE
T
T
S
S
L2
CAD CELL RELAY
COMBINATION
WATER HEATER
AND OIL BURNER
PRIMARY CONTROL
G H
WATER HEATER CONTROLS
FURNACE CONTROLS
Wiring the water heater and heating plant so that they
do not operate simultaneously. (Courtesy National Oil Fuel Institute)
Figure 4-59
Pressure and temperature relief valves are vital for the protection
of the hot-water storage tank. These valves are described elsewhere
in this chapter (see Relief Valves).
When adjusting an oil-fired water heater, always adjust for a
smoke-free fire first, and then make the necessary adjustment for
efficient operation.
240 Chapter 4
TEMPERATURE
SET POINT KNOB
AQUASTAT TEMPERATURE
CONTROL (REPLACEABLE)
DIFFERENTIAL
ADJUSTMENT DIAL
RELAY (2K)
SWITCHING RELAY (1K)
TRANSFORMER
SAFETY SWITCH
WIRING TERMINALS
Honeywell R4166 combination water heater
and oil burner primary control. (Courtesy Honeywell Tradeline Controls)
Figure 4-60
Electric Water Heaters
Most electric water heaters used in residences are the automatic
storage type. Although some instantaneous heaters are in use, the
high electric power input required makes them uneconomical to
operate when compared with fuel-fired types.
An electric water heater generally consists of a vertical tank with
a primary heating element or resistor inserted near the bottom of
the tank. Some water heaters have a secondary heating element
located in the upper one-fourth of the tank (see Figure 4-62). The
number of heating elements used in the heater will depend on the size
of the storage tank. Large-capacity storage tanks will require two
heating elements.
The manual and thermostatic (automatic) controls are located
inside the storage tank. A water heater thermostat is designed to
automatically open or close the electrical circuit to the heating element(s) whenever the hot-water temperatures exceed or fall below
Water Heaters 241
SAFETY
SSH SWITCH
R4166 COMBINATION
AQUASTAT AND
PROTECTORELAY
CONTROL
1K
1K3
2K2
2K
1K1
2
3
L1 L2
POWER
SUPPLY
1
L1
(HOT)
L2
3
F
F
C 554A
CAD CELL
IGNITION
BURNER MOTOR
OIL VALVE
1
Provide disconnect means and overload protection as required.
2
Aquastat control breaks on temperature rise to set point.
3
R4166b only—high limit control breaks on temperature rise to
set point.
Internal diagram and typical wiring hookup of a
Honeywell R4166 combination water heater and oil burner
primary control. (Courtesy Honeywell Tradeline Controls)
Figure 4-61
the temperature range of the water heater. Depending on the size of
the storage tank, the water heater will be equipped with either one
or two thermostats.
The rated voltage for electric water heaters is 240 volts. The
thermostats controlling the primary and secondary heating elements are generally set at 150°F.
Several types of heating units are available for electric water
heaters, but the two most popular are probably the immersion element and the strap-on unit. The immersion element is inserted
242 Chapter 4
TO DRAIN
TOP THERMOSTAT
HEAT TRAP
TOP
HEATING
UNIT
HOT WATER
POWER
SUPPLY
LOWER THERMOSTAT
Components
of an electric-fired water
heater. (Courtesy 1965 ASHRAE Guide)
Figure 4-62
SAFETY VALVE
INSULATION
LOWER
HEATING
UNIT
COLD WATER
INLET WITH
DIFFUSER
OFF-PEAK
TIME SWITCH
DRAIN
through an opening in the side of the tank. The strap-on unit is
externally mounted on the surface of the tank.
A larger storage tank capacity is required for electric water
heaters than for fuel-fired types in order to compensate for the limited recovery rate. As a result, initial equipment costs are higher.
Care should be taken not to oversize or undersize the storage tank.
Incorrect sizing will result in an inefficient water heater.
Electric water heaters of the automatic storage type are generally
available in storage tank capacities ranging from 30 to 140 gallons.
The electric power input requirement will range from 1600 to 7000
watts.
Troubleshooting Electric Water Heaters
The troubleshooting list in Table 4-2 covers most of the problems
commonly encountered when operating electric water heaters.
Table 4-2
Troubleshooting Electric Water Heaters
Problem and Possible Cause
Suggested Remedy
No hot water.
(a) Blown fuse.
(b) Tripped circuit breaker.
(c) Tripped high-limit switch.
(d) Grounded thermostat.
(a) Replace fuse.
(b) Reset circuit breaker. Call
electrician if problem continues.
(c) Manually reset switch.
(d) Check and replace.
Water Heaters 243
Table 4-2 (continued)
Problem and Possible Cause
Suggested Remedy
(e) Upper thermostat defective.
(f) Thermostat out of calibration.
(g) Upper element defective.
(h) Loose wiring.
(i) Defective or damage wiring.
(j) Undersized service wire.
(e)
(f)
(g)
(h)
(i)
(j)
Replace.
Tighten/replace as necessary.
Replace.
Check, tighten, and replace.
Replace.
Replace.
Hot-water temperature too high.
(a) Thermostat setting too high.
(a) Lower thermostat setting to
desired temperature.
(b) Thermostat out of calibration. (b) Check and replace.
(c) Grounded or defective element. (c) Check and replace.
(d) Water heater thermostat
(d) Reposition thermostat with
not flush with tank.
its back touching the tank.
Water slow to heat.
(a) Undersized heating elements.
(b) Defective lower thermostat.
(a) Check wattage and replace.
(b) Replace.
Not enough hot water or temperature of water too low.
(a) Thermostat set too low.
(b) Incorrect wiring.
(c) Loose wiring.
(d) Lower element defective.
(e) Lower thermostat defective.
(f) Incorrectly wired thermostat.
(g) Grounded thermostat.
(h) Incorrect heating element
wattage.
(i) Water heater thermostat
not flush with tank.
(j) Scale of heating element.
(k) Damaged dip tube.
(a) Increase thermostat setting.
Caution: Do not set the
thermostat above 120°F.
(b) Check manufacturer’s wiring
diagram and rewire.
(c) Check; tighten or replace
as necessary.
(d) Replace.
(e) Replace.
(f) Replace.
(g) Replace.
(h) Check wattage and replace.
(i) Reposition thermostat with its
back touching the tank.
(j) Clean or replace.
(k) Replace dip tube.
(continued)
244 Chapter 4
Table 4-2 (continued)
Problem and Possible Cause
Suggested Remedy
(l) Water tank poorly grounded. (l) Check grounding and tighten.
(m) Undersized water heater.
(m) Resize for residence. Replace
if necessary.
Leaking water heater.
(a) Damaged or loose joints at
(a)
cold-water inlet and/or
hot-water outlet.
(b) Defective temperature/pressure (b)
relief valve.
(c) Defective heating elements.
(c)
(d) Defective anode rod or gaskets. (d)
(e) Hole in inner tank.
(e)
Check joints and repair.
Replace.
Replace.
Replace.
Replace water heater.
Excessive temperature/pressure relief valve operation.
(a) Excessive temperature.
(b) Excessive water pressure.
(a) Lower temperature setting. If
problem continues, check for
grounded element and correct
as necessary; replace defective
thermostat.
(b) Install specified pressurereducing valve on cold intake
side.
Rusty, black, or brown water.
(a) Excessive sediment
accumulation in tank.
(b) Elements covered with scale.
(c) Dissolved anode rod.
(a) Drain and clean tank, or
replace if necessary.
(b) Clean or replace elements.
(c) Replace anode rod.
Strong unpleasant odor.
(a) Dirty tank.
(b) Dissolved anode rod.
(a) Drain and clean tank with
chlorine bleach to remove
bacteria.
(b) Drain and clean tank; replace
anode rod.
Water Heaters 245
Manual Water Heaters
Manual water heaters, also referred to as circulating tank or side
arm heaters, are of the conventional design with the gas burner and
accompanying heating coils mounted on the side of the hot-water
storage tank as shown in Figure 4-63.
Manual water heaters are generally equipped with copper coils
161⁄2 to 20 feet in length and with either 3⁄4 - or 1-inch outside diameter. The coils are usually made of copper tubing of No. 20 Stubbs
gauge. Other designs are occasionally employed—for example, the
internal or underfired units intended to overcome liming in hardwater areas.
These heaters usually have between 20,000 and 30,000 Btu capacity, although the maximum sizes run up to 85,000 Btu capacity. The
PRESSURE RELIEF VALVE
COLD
WATER
HOT WATER
TO OPEN
SINK OR
DRAIN
6"
SPECIAL TAPPING
IN TANK MADE
WITH CIRCULAR
HACK SAW
CIRCULATING
PIPE
TO
FLUE
UNION
UNIONS
FROM FURNACE
OR RANGE COIL
HEATER
18"
6"
DRAIN
TO
FURNACE
OR
RANGE
COIL
TO
GAS
SUPPLY
Connection of a manual gas water heater
where interconnected with a waterback or range coil.
Figure 4-63
246 Chapter 4
smallest-size manual heater will deliver about 19 gallons of hot water
per hour. This size heater is generally ample for most homes in which
the conventional 30-gallon tank is used for storing the hot water.
The manual water heater was formerly widely employed because
of its comparatively low cost and economy in operation. As the
name implies, manual water heaters are nonautomatic and supply
hot water quickly by turning on and lighting the gas shortly before
the warm water is required. Automatic water heaters have largely
replaced the manual type because the former require little or no
attention when in operation.
Assembly and Installation of Manual Water Heaters
A great many installations of manual water heaters have given poor
service, not because of any fault in the heater, but mainly due to the
improper method of connecting the heater to the storage tank. This
lack of good service can be largely overcome if a few simple installation rules are followed.
All recently manufactured range boilers have tappings provided
in them for hot- and cold-water connections, specifically two tappings in the side of the tank 6 inches from the top and bottom as
shown in Figure 4-63 to accommodate the circulating water connections, which should be made of 3⁄4-inch or larger pipe. The bottom of the tank has a tapping for connection to the drain or
blow-off, which is used to drain water or sediment from the boiler.
Circulating pipes between the heater and tank should be made as
free from fittings and bends as possible.
The use of brass pipe on the hot-water circulating line from the
heater to the tank is recommended, particularly for high-temperature circulation.
When required, unions should be placed as close to the heater as
possible on the hot-water and cold-water circulating lines.
The placement of hot- and cold-water tappings 6 inches from the
top and bottom of the tank allows free circulation, which results in
relatively large-volume storage without overheating. It also eliminates short-circuiting of the water through the heater and provides
ample sediment storage below the circulating line, thus preventing
sediment from getting into the heating element.
Solar Water Heaters
Many of the valves and heating controls used with gas, oil, and
electric water heaters can also be used in solar water heating systems. These components are designed to protect and control a solar
water heating installation from a single source. A typical system is
Water Heaters 247
BALL-TYPE TEST COCK
SOLAR
COLLECTOR
VACUUM
RELIEF VALVE
TO
FIXTURES
TO
FIXTURES
SELF-CLOSING
PRESSURE/AND TEMPERATURE
RELIEF VALVE
WATERTEMPERING VALVE
DRAIN
CONTINUOUS-PRESSURE
BACKFLOW PREVENTER
LOW-PRESSURE
REDUCING VALVE
COLD
SUPPLY
WATER-PRESSUREREDUCING VALVE
DRAIN
PRESSURERELIEF VALVE
DRAIN
DRAIN
BRONZE
BALL VALVE
Figure 4-64
BRONZE
BALL VALVE
Typical solar water heating installation.
(Courtesy Watts Regulator Co.)
shown in Figure 4-64. A specially designed thermostatic element
(for 210°F to 250°F service) in a thermal bypass control should be
included in the system to divert high-temperature water to a cooling section (see Figure 4-65). This prevents structural damage to the
solar panels and improves system efficiency.
Figure 4-65
Thermostatic element for 210°F to 250°F service.
(Courtesy Watts Regulator Co.)
Chapter 5
Heating Swimming Pools
Heating systems have been added to both private and commercial
swimming pools for a variety of reasons, ranging from the simple
desire to increase body comfort with warmer water temperatures to
the more practical reason of extending the swimming season.
In many commercial buildings and larger residences equipped
with hot-water (hydronic) heating systems, the central boiler provides the heat for space heating, domestic hot water, and pool
water. In structures equipped with other heating systems (for example, forced warm-air), a pool heater operating independently of the
central heating unit is necessary to heat the pool water. The water
in a swimming pool may be heated in one of the three following
ways:
1. Solar heating
2. Radiant heating
3. Recycling
Solar heating relies on the use of solar panels to collect the heat
from the sun. The pool water is circulated through the panels where
it collects the heat from the sun and then carries it back down to the
pool. Many solar pool-heating systems have an auxiliary gas or
electric heater to augment the heat from the panels on days where
there is insufficient sunlight.
Pools can also be heated with a radiant heating system, but such
a system must be installed when the pool is constructed because it
entails embedding tubing (commonly 1⁄2-inch diameter) in the pool
itself. As shown in Figure 5-1, the tubing is buried close to the surface in the walls and floor of the pool. The hot water is fed through
a supply pipe from the boiler. The water returns to the boiler
through a return line. Water temperature in the pipes is controlled
by a thermostat, which usually is located on the return line.
Radiant heating systems for swimming pools are the most
expensive types to install because they require more pipe than other
heating systems. Furthermore, the construction feature of having
the copper tubing embedded in the walls and floor of the pool adds
to the installation cost.
249
250 Chapter 5
COPPER TUBING
BURIED IN CONCRETE
WALLS AND FLOOR
RADIANT HEAT
RETURN LINE
TO BOILER
HOT WATER FROM BOILER
Figure 5-1
Heating a swimming pool by the radiant heating method.
Most modern pool heating systems are based on the recycling
principle. The water is drawn from the pool by a pump, passed to
the heat exchanger in the boiler or pool heater, heated to the desired
temperature, and returned to the swimming pool.
When both a pool and its heating system are installed during the
original construction of the house or building, it is possible (and
advisable) to install a single boiler with more than one heat
exchanger. As a result, the boiler will have the capacity to provide
Heating Swimming Pools 251
hot water not only for the pool but also for space heating and
domestic hot-water needs. Three such systems for commercial
buildings are illustrated in Figures 5-2, 5-3, and 5-4. In these systems, the primary boiler water is maintained at the desired spaceheating water temperature by the operating aquastat in the boiler.
The temperature of the pool water is maintained by the opening
and closing of a pool temperature-control valve located in the circulation line between the filter and heater. This valve is controlled
by a pool temperature-control aquastat, which senses the temperature of the water being returned from the pool.
Pool heaters can also be installed independent of space heating
and domestic hot-water heating systems. This is usually the case
when a heating unit is installed at an existing pool.
A pool heater operates on the same principle as the domestic
hot-water heater, but the two differ considerably in their functions.
The hot-water heater is required to heat only 30 to 40 gallons of
water in a closed tank. The pool heater must heat thousands of gallons of water with a surface exposed to the outside air. Because
there is a high degree of heat loss from the large surface area of the
water to the colder air above it, a pool heater uses a considerable
amount of fuel to replace the lost heat and to maintain the pool
water at the desired temperature. The fact that water has a high
heat capacity contributes to the problem. As a result, it generally
takes a pool heater 20 to 24 hours to warm the water to the desired
temperature.
Classifying Pool Heaters
Pool heaters can be classified in a number of different ways. If they
are classified according to their basic operating principle, the following two types are recognized:
1. Direct-type pool heaters
2. Indirect-type pool heaters
In a direct-type pool heater (see Figure 5-5), the water from the
pool passes through the heating unit in pipes that are heated
directly by a gas or oil burner. In an indirect-type pool heater (see
Figure 5-6), the pipes containing the pool water pass through a
compartment in the heating unit, which also contains water. The
water in the compartment of the heating unit is heated by a gas or
oil burner located outside the water compartment. The heat of the
water is then transferred to the water in the pipes from the pool,
252
S
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OW
SH
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WA ERVI
TER CE
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CU
LA
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R
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ME TEM ATE
FLU CTIO
MO
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TW R
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H
HO ANGE
NN
T
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NS
ME EX
ER
PA K
DO HEAT
EX TAN
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TE
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DR
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A
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PO
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IN
SS ILL
W
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AC S
AIN
FRO
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DR
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SO
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BO
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RD
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Figure 5-2
Hot water radiation
unit heaters shown
but any conventional
type of space heating
radiation may be used.
Typical multipurpose water-heating system for pool heating, space heating, and hot-water service.
(Courtesy Bryan Steam Corp.)
TYPICAL SPACE HEATING
(OPTIONAL)
ION
A
GR
)
DIN
R(S
IT
UN
T
DIA
E
AT
HE
RD
OR
N
TA
S
A
BO
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SE
BA
G
TIN
CO
MAIN SWIMMING POOL
LOWER TEMPERATURE
A
E
BH
LA
POO
LD
RAI
E
AN
P
RS
ETE
N
OM
ERM
TH
FILTER PUMP
AND STRAINER
DRAFT DIVERTER OR
BAROMETRIC CONTROL
PO
O
CO L T
NT EM
RO PE
L V RA
AL TUR
VE E
SK
IM
DR MER
AIN
RS
LO
THERAPUTIC POOL
HIGHER TEMPERATURE
HE
WI ATER
TH
B
PL YPA
UG
S
CO S
CK
ION
NS
PA
EX TANK
DR
L
OO
P
BOILER
DRAIN
SPACE HEATING
CIRCULATOR
E
UR
AT
ER VE
MP AL
TE OL V
L
R
O
PO ONT
RS
C
ETE
OM
ERM
TH
DRAIN
R
ME
IM
SK
PO
INL OL
ETS
AIN
DRAIN
FILTER TANK
AIN
AIN
DR
FILTER
TANK
FILTER BYPASS
HEATER BYPASS WITH
OR BACKWASH
PLUG COCK
BRYAN MULTI- PURPOSE HEATER
POOL TEMPERATURE CONTROLS
SET AT DESIRED POOL TEMPERATURE
MP R
PU NE
ER TRAI
T
FIL D S
AN
FILTER BYPASS
AND BACKWASH
253
Typical multipurpose water-heating system for two pools of different temperatures and
space heating. (Courtesy Bryan Steam Corp.)
Figure 5-3
DR
254
,
ING
AT ,
HE TION
D
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AR
BO AD
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BA DIN
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PO NTRO TERS
CO OME
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BO L VA
M
L
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TE MP
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N
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DR
HE CULA
CIR
Bryan heater with two indirect
LY
PP
heat exchangers one for pool
SU
OIL
SS
heating and one for heating
A
R
P
SO
BY
domestic water (optional).
R
GA
E
K
AT OC
HE UG C
PL
Figure 5-4
N
UR
ET
R
ING
N
AI
DR
FILTER
BYPASS
OR
ASH
BACKW
SW
PO
SK
OL
IM
DR
DR MER
AIN
AIN
ER
AIN
STR
FILTER
TANK
AL
PIC
TY
NG
PO
OL
OL
INL
S
PO
M
TE
YS
RS
MI
ET
MP
PU
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ILT
IM
F
Typical multipurpose water-heating system for pool heating, space heating, and domestic hot water.
(Courtesy Bryan Steam Corp.)
Heating Swimming Pools 255
Figure 5-5 Operating principle
of a direct-type pool heater.
WATER FROM
POOL
WATER CHAMBER
HEAT EXCHANGER
WATER FROM
POOL
COMBUSTION CHAMBER
Figure 5-6
Operating principle of an indirect-type pool heater.
hence the name indirect pool heater. Because the coils of the heat
exchanger never come in direct contact with the combustion heat
(as is the case with direct-type pool heaters), scale and corrosion are
virtually eliminated.
Another means of classifying pool heaters is by the type of fuel
or energy source used to heat the water. The pool water can be
heated by natural gas or propane, oil, electricity, or solar radiation.
Note
When installing a conventional pool heating system, purchase a
heater with a high efficiency rating. It will save energy and result in
significantly lower fuel costs.
Gas-Fired Pool Heaters
Gas-fired indirect pool heaters (see Figure 5-7) are available in the
same Btu input/output ratings as the oil-fired types. They differ
only in certain items of standard equipment that relate directly to
256 Chapter 5
FROM POOL
MANUAL
AIR VENT
TO POOL
SECONDARY
RELIEF VALVE
POOL WATER
TEMPERATURE
CONTROL
TRIDICATOR
PRIMARY
RELIEF VALVE
COPPER TUBE
HEAT EXCHANGER
BOILER WATER
LIMIT CONTROL
BOILER FILL
POOL WATER
CONTROL
BOILER DRAIN
Figure 5-7
Hydrotherm gas-fired indirect pool heater. (Courtesy Hydrotherm, Inc.)
the type of fuel used. Gas-fired pool heaters will also differ according to the type of ignition system. There are two types of ignition
systems used in gas-fired pool heaters:
• Millivolt (or standing pilot) ignition systems
• Automatic spark ignition systems
A millivolt ignition system is one in which the pilot light is continuously burning. The heat from the pilot light is used to generate
a low-voltage electrical current. The electrical current produced by
the pilot light is strong enough to open and close the main gas valve
(also sometimes called a combination gas valve) as well as the controls and safety devices on the heater.
Note
A pilot light that is continuously lit is sometimes called a standing
pilot or standing pilot light.
An automatic spark ignition system (also sometimes called an
intermittent ignition system or simply an IID system) has a pilot
light that is lit only when the heater is operating. An external electrical source is used to spark the pilot and operate the controls and
safety devices on the heater.
In addition to the pilot light, a gas-fired pool heater also will
include a number of different components, safety devices, and controls. Those included in the heater will depend on the type of ignition system used as well as its make and model. They include the
following:
Heating Swimming Pools 257
• Pilot generator. A pilot generator (also sometimes called a
thermocouple) is the device in a millivolt ignition system that
converts the heat energy of the pilot flame to the electrical
energy required to operate the main gas valve. Pilot generators are not used in the automatic spark ignition systems.
• Control circuit. The control circuit consists of a series of
safety devices used to control the flow of electricity to the
main gas valve. If there is a malfunction somewhere in the
heater, one or more of these safety devices in the control circuit will interrupt the flow of electricity to the main gas valve
and prevent the burners from operating. The devices in the
control circuit include safety switches (see safety switches), a
fusible link (see gas burner tray), and a remote on-off switch.
• Safety switches. A variety of different types of switches are
used in gas-fired pool heaters for safety and operational
control purposes.
• Pressure switch. A device that prevents the heater from
starting until there is sufficient water pressure in the system.
• High-limit switch. A device that prevents the water temperature in the pool heater from exceeding a preset upper limit
(commonly 140ºF).
• Flow switch. A device that prevents the heater from starting
if there is not enough water flowing through the system.
• Fireman switch. A device that allows the circulator (pump)
to continue operating up to 15 minutes after the heater has
shut off. The additional pump running time allows the system to cool down.
• Bypass valve. The bypass valve is used to maintain a constant
flow of water through the heat exchanger. The cool water
protects the heat exchanger surfaces and other heater components from excessively high and potentially damaging temperatures. The bypass valve and the fireman switch provide
similar functions in a pool heater.
• Automatic gas valve. The automatic gas valve (also sometimes
called the main gas valve or combination valve) regulates the
flow of gas to the burner tray and pilot. It is controlled by the
heater control circuit.
• Gas-pressure regulator. A device that regulates the gas pressure. It is commonly combined with the main gas valve in the
same unit (hence the name combination gas valve).
258 Chapter 5
• Gas shutoff valve. A valve used to shut off the supply of gas to
the burners when a heater malfunction occurs.
• Thermostat. As in other heating systems, a thermostat is used
to control operation within a preset temperature range. When
the pool water temperature drops below a preset low-temperature limit setting, the thermostat switches on the pool heater.
When the temperature of the pool water reaches the upper
preset limit, it shuts off the pool heater.
Other gas-fired pool heater components, many of which are also
found on oil-fired, electric, and solar heaters, include the following:
• Heat exchanger. A device used to transfer heat from air, fluid,
or water contained in one circulating system to the air, fluid,
or water contained in an adjacent one without any intermixing. Heat exchangers are available in the form of flat plates or
fins, coils, or tubes and are made of a metal that easily
absorbs heat. Copper-finned heat exchangers are the type
most commonly used in pool heaters. These consist of closely
spaced flat fins attached to copper tubing.
• Header. The header (also called a manifold) is the component
that directs the flow of water in and out of the heat exchanger.
There is a header at each end of the heat exchanger. The front
header, through which the water flows into the heat
exchanger, contains a flow control assembly that is used to
mix the cool incoming water with the hot outgoing water as it
leaves the heat exchanger through the back header. This
ensures a temperature differential of 25ºF or less between the
temperatures of the incoming and outgoing water. This
reduced temperature differential prevents condensation, mineral deposits, and other problems associated with excessively
high temperature differentials.
• Gas burner assembly. A pool heater may have as many as 16
and as few as 6 burners, depending on the make and model.
The burner tubes are arranged in a parallel array and connected by a manifold pipe. A pilot light is mounted on the last
burner tube. The gas burner tray beneath the burners can be
removed from the cabinet for cleaning.
• Pool heater aquastat. A pool heater aquastat is used to control pool water temperatures and provide high-limit boiler
control. The high-limit control provides shutdown protection
to prevent boiler overheating. Some models are equipped with
automatic reset, while others are equipped with manual.
Heating Swimming Pools 259
A typical wiring diagram for a gas-fired indirect pool heater is
shown in Figure 5-8. The pool water control on the dual aquastat is
set at the desired pool temperature. The cold water from the pool
starts the boiler, which continues to produce heat until the pool
water temperature reaches the setting on the pool control. When
this point is reached, the boiler shuts off. The boiler water temperature is controlled by the water-limit control.
POOL WATER CONTROL
(SET AT DESIRED POOL
TEMPERATURE)
BOILER WATER
LIMIT CONTROL
(SET AT 220°–240°)
POWER PILE
TH PP
GAS VALVE
Typical wiring diagram for a gas-fired
indirect pool heater. (Courtesy Hydrotherm, Inc.)
Figure 5-8
Oil-Fired Pool Heaters
The oil-fired indirect pool heater illustrated in Figure 5-9 is available in several input ratings ranging from 175,000 Btu/h (1.25 gph
firing rate) to 280,000 Btu/h (2.00 gph firing rate) with No. 2 fuel
oil. The corresponding output ratings range from 133,000 Btu/h to
208,000 Btu/h, which gives this pool heater the capacity to heat
swimming pools containing 16,000 to 25,000 gallons of water.
These pool heaters have a 100-psi ASME pressure rating, which
makes possible their direct connection to city water lines without
the use of pressure-reducing valves. The heat exchanger consists of
multiple-pass finned copper tubes, which are designed for low-pressure drop and which can be removed for cleaning.
Figure 5-10 illustrates the recommended piping arrangement for
this particular pool heater. Note that the filter is installed on the
line from the pool between the pump (circulator) and the shutoff
valve. No provision for bypass piping is made between the pipes
leading to and from the pool. An example of bypass piping in a
pool heating installation for a similar oil-fired indirect heater is
shown in Figure 5-11.
The aforementioned pool heater is suitable for small residential
pools. A typical 25,000-gallon pool is approximately 18 feet wide
by 36 feet long if a rectangular-shaped pool is used as an example.
260 Chapter 5
MANUAL
AIR VENT
FROM POOL
TO POOL
SECONDARY
RELIEF VALVE
POOL WATER
TEMPERATURE
CONTROL
PRIMARY
RELIEF VALVE
TRICATOR
COPPER TUBE
HEAT EXCHANGER
BOILER FILL
DUAL
AQUASTAT
BOILER DRAIN
BURNER
CONTROL
POOL WATER AQUASTAT
(SET AT DESIRED POOL TEMP.)
BOILER HI-LIMIT
AQUASTAT
(SET AT 220°–240°)
H
115 V
G
FACTORY WIRED
FIELD WIRED
TRANSFORMER
BURNER
CONTROL
FLAME
DETECTOR
MOTOR
OIL BURNER
Figure 5-9
Oil-fired indirect-type pool heater with wiring diagram.
(Courtesy Hydrotherm, Inc.)
Pool heaters, whether oil-, gas-, or electric-fired, are available for
almost any size pool. It is simply a matter of matching the pool size
with the capacity of the pool heater. For example, Figure 5-9 shows
an indirect oil-fired pool heater used for commercial applications,
which is capable of heating a 105,000-gallon swimming pool. It has
an input rating of 1,155,000 Btu per hour with 8.25 gph firing rate.
This pool heater actually represents the combination of three heating modules; each has its own oil burner and modulating aquastat.
Electric Pool Heaters
An electric pool heater produces heat by forcing water to flow
around a submerged electric coil. Most of the components are
Heating Swimming Pools 261
TO POOL
CIRCULATOR
SHUT OFF VALVE
FROM POOL
FILTER
BOILER FILL
HYDROTHERM
PLEASURE-TEMP
BOILER DRAIN
Recommended piping arrangement for heater in
Figure 5-7. (Courtesy Hydrotherm, Inc.)
Figure 5-10
DIAPHRAGM TYPE
EXPANSION TANK
OR EQUIVALENT
TO POOL
FULL SIZE BY-PASS
POOL AQUASTAT
COIL
FILTER
PUMP
TRIDICATOR
FROM POOL
BOILER FILL
BUILT-IN STANDPIPE
PRESS. RELIEF
VALVE—30PSI
POOL
FILTER
DRAIN
HI-LIMIT
AQUASTAT
FILL VALVE
Figure 5-11 Piping diagram with bypass arrangement. (Courtesy Hydrotherm, Inc.)
similar to a gas or oil pool heater. The controls of an electric pool
heater are usually built into the unit. Some models have a separately mounted thermostat to control water temperature.
Electric pool heaters are used where space is too restricted for a
gas or oil heater, or where it is not possible to provide sufficient
ventilation. They are used more frequently to heat small spas or hot
tubs than pools.
The input of an electric-fired indirect pool heater is measured in
kilowatts; its output is measured in Btu. The pool heater shown in
Figure 5-12 is available in 11 different models ranging in input
capacity from 15 kW to 300 kW with a corresponding output of
50,000 Btu per hour to 1,000,000 Btu per hour. These pool heaters
are also available with 240 volts (single-phase) or 240/480 volts
(three-phase). A wiring diagram for an electric-fired indirect pool
heater is shown in Figure 5-13.
262
L
VA
MO
RE ENT
OR LEM
F
E
E
AC NCE
SP
W ISTA
LO
AL F RES
O
EF
ELI
AL
OV
EM
R R ER
FO ANG
E
AC XCH
E
SP
W EAT
LO
AL OF H
E
ELE
LV
VA
CT
A
RIC
LP
AN
EL
R
TO EXPANSION TANK
U
GA
GE
BREAK UNIONS WHEN
DRAINING OR VALVING
OF HEATER FROM POOL
NOTE:
If pvc (plastic) pipe is used provide
heat trap by extending metal piping
to floor line before connecting to
pvc and install positive check valve
as shown.
BYPASS WITH PLUG COCK IF FILTER
FLOW RATE EXCEEDS 756 P.M.
FILL
VALVE
ER
AT
W
W F
LO TOF
U
C
GLOBE VALVE
CHECK VALVE
DRAIN
L
FIL
Figure 5-12
R
TE
WA
FROM FILTER
TO POOL
Electric-fired pool heater. (Courtesy Bryan Steam Corp.)
Y
PL
P
SU
NOTE:
Panel size will vary depending on,
power available, controls, steps,
fusing, etc.
FUSE
POWER SUPPLY
FROM FUSED
WALL SWITCH
L-4031A COMBINATION
POOL TEMP & LIMIT
LOW WATER CUTOFF
CONTROL
ON-OFF SWITCH
Heating Swimming Pools 263
H
G
CONTROL PANEL
Figure 5-13
115/60/1
POWER
SOURCE
POWER ON LAMP
POOL ELEMENT LIMIT ELEMENT
IN BOILER
IN CONTROL
LINE
Wiring diagram for an electric-fired pool heater.
(Courtesy Bryan Steam Corp.)
Heat-Exchanger Pool Heaters
The heat-exchanger pool heater illustrated in Figure 5-14 is
designed for use in either steam or hot-water heating systems. It
is essentially a steel shell enclosing the copper tubes of the heat
exchanger. The hot water or steam is taken from the heating
main and circulated around the copper tubes inside the steel
shell. The pool water enters the heat exchanger in a pipe leading
from the pool filter and circulates inside the copper tubes. As it circulates, it is heated by the hot water or steam circulating around the
copper tubes. The heated water eventually leaves the heat
exchanger through a second exit point and is returned to the pool.
Figures 5-15 and 5-16 illustrate the modifications necessary for
use with either steam or hot water as the heat source. Basic construction is essentially the same in both cases, with the pool water
circulating through copper tubes (the heat exchanger) enclosed in a
steel shell. You will probably notice that different types of steel are
used in constructing the shell: 125-psi ASME steel for heat
exchangers using hot water as a heat source, and 15-psi ASME steel
for those using steam.
Both types of heat exchangers have temperature-control aquastats
activated by the temperature of the pool water entering the heat
exchanger. In heat exchangers that use water as a heat source, the
aquastat is connected to a circulating pump (see Figure 5-16). If
steam is the heat source, the aquastat is connected to a steam-control
valve. Both the circulating pump and the steam-control valve control
the rate of flow of the hot water or steam from the heating unit.
264 Chapter 5
RETURN
TO BOILER
HEAT SOURCE
TO
POOL
FROM
FILTER
POOL TEMPERATURE
CONTROL SWITCH
BOILER WATER
CIRCULATOR
FROM BOILER HEAT SOURCE
Figure 5-14
Heat-exchanger pool heater. (Courtesy Bryan Steam Corp.)
When steam is used as the heat source, the heat exchanger should
also be equipped with a steam trap and a line running to the condensation main. The steam valve sizing is based on 2-psi minimum steam
pressure and 0-psi return pressure. A steam strainer should be placed
in the steam supply line just before it reaches the control valve.
Circulating pump sizing in units that use water as a heat source
should be based on a maximum temperature drop through the heat
exchanger of 30°F and a maximum head loss in piping between the
hot-water boiler and the heater of 10 feet H2O.
The Btu/h output for heat-exchanger pool heaters using water as
a heat source ranges from 200,000 to 4,200,000 Btu per hour. The
amount will depend on water temperature (180°F or 210°F) and
the size of the unit. Heaters using steam as a heat source are capable of generating an output of 400,000 to 3,600,000 Btu per hour.
Here the difference depends on the steam pressure used (2 lbs or 10
lbs) and the size of the unit.
Solar Pool Heaters
The principal components of a solar pool heating system are illustrated in Figure 5-17. In this system, the solar panels or collectors
Heating Swimming Pools 265
STEAM CONTROL VALVE
POOL TEMPERATURE
CONTROL AQUASTAT
STEAM STRAINER
STEAM
SUPPLY
COPPER HEAT EXCHANGE
TO POOL
STEEL SHELL
15 PSI ASME
FROM
POOL
STEAM TRAP
TO CONDENSATE MAIN
Heat-exchanger pool heater using steam as a heat
source. (Courtesy Bryan Steam Corp.)
Figure 5-15
POOL TEMPERATURE
CONTROL AQUASTAT
RETURN WATER COPPER
HEAT EXCHANGER
TO POOL
FROM POOL
STEEL SHELL 125 PSI ASME
HOT WATER FROM CENTRAL
HEATING SYSTEM
HEAT SOURCE
CIRCULATING PUMP
Heat-exchanger pool heater using water as a heat
source. (Courtesy Bryan Steam Corp.)
Figure 5-16
266 Chapter 5
SOLAR PANEL
END CAP
COUPLER
VACUUM RELIEF VALVE
TEMP SENSOR
SOLAR
CONTROL
UNIT
FLOW METER
3-WAY VALVE
MOTORIZED
ONE WAY
CHECK VALVE
BALL
VALVE
FILTER
TEMP SENSOR
ONE WAY
CHECK VALVE
WATER RETURN TO POOL
OR GAS HEATER
POOL PUMP
Figure 5-17
Solar pool schematic. (Courtesy GO Solar Company)
function as the heater. There is no component similar to the heaters
used in the more conventional pool heating systems. Note, however, that an auxiliary heater may be included in the system as a
backup to the solar collectors when there is not enough sunlight to
warm the water.
In operation, water is automatically pumped through the solar
collectors where it picks up the heat from the sun. A solar sensor is
used to measure the heat on the panel. If the panels are cold, the
solar sensor causes the water to bypass the panels and flow directly
to the auxiliary heater (commonly a gas or electric heater) where it
is heated and sent to the pool. If the solar sensor detects heat on
the panels, it opens a valve to send the water directly to the solar
panels where it is heated and then returned to the pool. At the
same time, a bypass ball valve closes and isolates the auxiliary
heater.
The temperature of the pool water is measured by a water sensor. Both the solar sensor and water sensor are connected to a controller that governs the operation of a three-way valve. A check
valve in the piping leading from the three-way valve can be used to
Heating Swimming Pools 267
isolate the pump, filter, and water sensor from other components in
a solar heating system. The isolation valves installed in the solar
panel supply and return lines are optional. The former is a ball
valve, the latter a check valve.
The solar collectors are made from polypropylene or a similarly
formulated material designed to withstand extreme exposure to
weather conditions and pollution. The panel material is also unaffected by pool chemicals and will not corrode or rust. Each panel is
constructed in a tube and curved web design to trap the heat as the
sun moves across the sky.
Heat Pump Pool Heaters
A heat pump also can be used to heat the water in a swimming
pool. A heat pump is a much more expensive piece of equipment
than a conventional pool heater, but it is more energy efficient,
requires less maintenance and repair, and has a longer service life.
Heat is generated when pressure is exerted by the compressor on
a nonflammable, noncorrosive gas. The heat in the gas is transferred
to water flowing through the heat exchanger. The warm water flows
to the pool, and the cooled gas returns to the compressor where it is
recompressed and reheated before repeating the cycle.
High-efficiency electric heat pump pool heaters are available
with coefficients of performance (COPs) in the 6.0 to 8.0 range.
Heat pumps not graded as high-efficiency units will produce a coefficient of performance of approximately 4.0.
Note
The coefficient of performance may be defined as the ratio of the
transferred energy to the electric energy used in the process—in
other words, the total useful output (heat energy in the case of a pool
heater) divided by the total energy input used to produce the heat.
Sizing Pool Heaters
The two principal methods used for sizing pool heaters are as follows:
1. The surface-area method
2. The time-rise method
Table 5-1 contains all the necessary data for determining the
required pool heater size with either method. The listed output ratings are for Bryan pool heaters.
The sizing data in Table 5-2 is based on heat loss from the surface of the heater with an assumed wind velocity of 31⁄2 mph. This
268
Table 5-1
Surface-Area Method
Sizing the Pool Heater (Ratings Given in 1000 Btu/h)
Time-Rise Method
Pool
Pool Size
Surface
(Rectangular) Area
Difference between Desired Water Temperature and
Average AirTemperature for Recommended Heater
Sized on Surface Area
Width Length (ft2)
10°
15°
20°
25°
30°
40°
15
16
16
18
18
18
20
20
20
20
25
25
30
30
30
35
150
150
150
150
250
250
250
30
32
36
36
40
42
40
42
45
50
50
60
60
70
75
75
450
512
576
648
720
756
800
840
900
1000
1250
1500
1800
2100
2250
2625
350
250
350
450
250
450
350
250
350
350
450
450
650
650
650
450
650
650
850
850
900
1200
1200
1500
Recommended Heater
Pool
Sized on Pool Capacity
Gallonage to Raise Temp. 1°F
(approx.) per Hour (approx.)
17,000
20,000
23,000
25,000
30,000
31,000
34,000
35,000
37,000
40,000
50,000
62,000
79,000
84,000
92,000
107,000
250
350
450
650
850
900
1200
1500
1800
40
42
42
45
50
60
60
65
75
75
80
80
75
75
80
90
100
100
110
120
130
160
175
200
3000
3150
3465
4050
5000
6000
6600
7800
9750
12,000
14,000
16,000
(Courtesy Bryan Steam Corporation)
450
850
900
850
650
850
900
1200
1500
1800
2100
1500
1200
1200
1500
1500
2100
2450
2700
3200
1800
2100
2450
3200
3750
4300
123,000
137,000
143,000
2100
184,000
2700
217,000
3200
250,000
3750
275,000
4300
320,000
4850
400,000
Two 2700 490,000
Two 3200 575,000
Two 4300 655,000
1800
1500
1800
2100
2450
2100
2450
2700
3200
3200
3750
4300
4850
4850
Two 2700
Two 2700 Two 3200
2100
2450
3200
3750
4300
Two 2700
Two 3200
Two 3750
Two 4300
269
270 Chapter 5
Table 5-2 Wind Velocity and Recommended Pool
Heater Capacity
Approximate
Pool Gallonage
Wind Velocity
Recommended Pool
Heater Capacity
17,000 gal
17,000 gal
17,000 gal
31⁄2 mph
5 mph
10 mph
250,000 Btu
375,000 Btu
500,000 Btu
is the average wind velocity for a pool protected from direct wind
exposure by trees, shrubs, fences, and buildings. An exposed pool
will mean that the required pool heater capacity (that is, the input
ratings listed in Table 5-1) must be increased. Generally it is recommended that the input rating be increased by 1.25 for a 5-mph wind
velocity and 2.0 for a 10-mph wind velocity.
The Surface-Area Method
The surface-area method of sizing a pool heater is based on the surface area (in square feet) of the pool and the temperature difference
(in degrees Fahrenheit) between the desired water temperature and
the average air temperature. The procedure is as follows:
1. Determine the mean average air temperature for the coldest
2.
3.
4.
5.
month in which the pool is to be used.
Determine the desired pool water temperature.
Find the difference between the air temperature (step 1) and
the water temperature (step 2).
Calculate the pool surface area in square feet.
In Table 5-1, find the surface area closest to your pool size.
Move horizontally in a straight line across to the column that
represents the temperature difference for your pool. The point
at which the horizontal line and the temperature column
intersect will be the required Btu per hour input rating for
your pool heater.
The surface-area method can be illustrated with a simple example. Let’s suppose that you have a small 15-foot × 30-foot pool with
a 17,000-gallon capacity. You want to maintain a pool water temperature of 70°F (step 2), and the mean average air temperature for
the coldest month in which the pool is to be used is 50°F (step 1).
What will be the required input rating of your pool heater?
Heating Swimming Pools 271
Your temperature difference required for sizing the heater is 20°
(70° – 50°F). The pool surface area is 450 square feet (15 × 30 feet).
Moving horizontally across the top line in Table 5-1, you arrive at
the 20° column and learn that the required input rating for a pool
heater meeting these criteria is 150,000 Btu per hour.
Another, less precise form of the surface-area method is to multiply the surface area of the pool by 15 and then by the temperature
difference between the pool water and the air. Using the same data
as before, the following results are obtained:
450 ft2 15 20° ⫽ 135,000 Btu per hour
The Time-Rise Method
The first step in the time-rise method of sizing a pool heater is to
determine the pool capacity in gallons of water (pool gallonage).
This only needs to be an approximate figure and is commonly
rounded off to the nearest thousand (for example, 17,000 gal,
20,000 gal, 23,000 gal). In Table 5-1, the extreme right-hand column lists pool heaters recommended for different pool capacities.
The sizing in this chart is based on the number of Btu required to
raise the pool temperature approximately 1°F per hour.
Sizing Indoor Pool Heaters
If the swimming pool is located inside a heated building, the surface
temperature of the water is naturally not affected by the colder outdoor air temperatures. A simple rule-of-thumb method for sizing an
indoor pool heater is as follows:
1. Determine the surface area of the pool (for example, 30 ft ⫻
40 ft ⫽ 1200 ft2).
2. Multiply the surface area by 125 Btu (1200 ft2 ⫻ 125 Btu ⫽
150,000 Btu per hour input).
Installing Pool Heaters
Installing a pool heater requires knowledge of plumbing, electrical
work, gas or oil burner operation, and ventilation. Pool heaters
should be installed only by qualified and experienced personnel,
and their installation must comply with local codes and ordinances.
Pool heaters are shipped with a complete set of instructions for
installing and starting the unit. If the instructions are missing, the
manufacturer should be contacted for a replacement set. The following installation recommendations apply to most pool heaters:
272 Chapter 5
1. Install the pool heater on a level concrete slab or a pad of con-
crete block or brick. The slab or pad must be at least 4 inches
high. If concrete blocks are used, align them so that all open
cells are pointed in the same direction with the cells at the
edge of the pad left open. Cover the top of a concrete block
pad with 24-gauge (or thicker) sheet metal.
Note
Never install a pool heater on a combustible material, such as
wood boards or plywood.
2. Maintain proper clearances on all sides of an outdoor pool
heater. Consult the owner’s manual for the clearances specified by the pool heater manufacturer. Maintaining minimum
required clearances around the pool heater will ensure efficient combustion and proper ventilation of the combustion
gases (gas-fired and oil-fired heaters).
Note
The American National Standards Institute (ANSI) has established
a standard set of clearances for outdoor pool heaters based on
the external temperature of the heaters (see ANSI 2223.1).
3. Indoor pool heaters must be properly vented to the outdoors.
They also must have sufficient intake air for proper combustion.
Consult the owner’s manual for specific venting requirements.
Warning
Incorrect venting of an indoor pool heater can result in carbon
monoxide poisoning. Incorrect venting can also result in fire.
4. An indoor gas-fired pool heater must be equipped with a draft
hood to further ensure that potentially harmful combustion
gases are expelled outdoors. The vent pipe is directly connected to the draft hood. The diameter of the draft hood is
based on recommendations from the National Fuel Gas Code.
It may vary among different pool heater makes and models.
5. To provide proper draft, the discharge opening of the flue
pipe must extend at least 2 feet above the surface of the roof
or its highest point within a 10-foot radius of the point where
it extends through the roof.
6. Install a barrier (for example, closed wooden fence, trees and
bushes) around a pool if it is subjected to sustained high winds.
Sustained winds across the surface of the water will increase the
heat loss from the pool. This will require increasing the heater
Heating Swimming Pools 273
size to maintain the desired water temperature. The heater itself
should be protected from high winds with a windbreak.
Pool Heater Repair and Maintenance
Follow the guidelines in the manufacturer’s manual when servicing
or repairing a pool heater or related equipment. Some manufacturers also permit the downloading of manuals from their online web
site. If a manual is unavailable and you do not have the necessary
experience to do the work without one, call the pool heater manufacturer or a local dealer for help.
The following suggestions for servicing and repairing pool
heaters apply to all makes and models:
1. Perform a major inspection and servicing of the pool, pool
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
heater, pump, and related components just before putting the
pool into operation and just after closing it down if the pool is
used only part of the year.
Perform periodic inspections and maintenance if the pool is
used throughout the year.
Replace worn parts with new ones. Do not attempt to reuse
them or make temporary repairs.
Inspect and clean or replace pool filters on a regular basis.
Inspect the pool heater for sooting (a combustion problem).
Inspect the pool heater for water leaks (all heaters), gas leaks
(gas-fired units), and oil leaks (oil-fired units).
Check all pipe connections for tightness and corrosion.
Check wiring for damaged wires and loose connections.
Check for proper burner flame characteristics on gas-fired
and oil-fired heaters. The pilot flame of a gas-fired heater
should also be included when making this inspection.
Inspect the heat exchanger for scaling.
Remove leaves and other debris from the top of the pool heater.
Note
Always shut off the pool heater and allow it time to cool down
before servicing it or making repairs.
Caution
To avoid injury from electrical shock, always shut off the electrical
power before servicing the line voltage controls. Never leave a
jumper wire in place to fix a heater or the operating and safety
controls will be bypassed.
274 Chapter 5
Warning
If gas odors are detected when repairing or servicing a gas-fired
pool heater, immediately contact your local utility for instructions.
If the pool is located indoors, leave the house and make the call
from a neighbor’s telephone.
Troubleshooting Pool Heaters and Equipment
Always review the pool heater manufacturer’s installation and/or
operating manual for recommended troubleshooting procedures. If
no manual is available, it may be possible to download one for the
specific pool heater or equipment from the manufacturer’s online
web address. As a last resort, Tables 5-3, 5-4, and 5-5 list frequent
problems, their symptoms, and possible remedies.
Table 5-3
Troubleshooting Gas-Fired Pool Heaters
Symptom and Possible Cause
Possible Remedy
Heater cycles on and off continuously.
(a) Low water level in pool.
(b) Dirty filter.
(c) Pressure switch out of
adjustment.
(d) External bypass setting needs
adjustment.
(e) Closed valve.
(a) Raise water level.
(b) Backwash or replace filter.
(c) Adjust pressure switch.
(d) Adjust bypass setting.
(e) Locate, repair, or replace
valve.
(f) Thermostat calibration incorrect. (f) Recalibrate or replace
thermostat.
Heater not producing enough heat.
(a) Gas cock in wrong position
and cutting off gas supply.
(b) Pilot light out.
(c) Pilot light at off setting.
(a) Check and change position
of gas cock.
(b) Relight pilot. If burners still
fail to light, call for service.
(c) Turn to on position and
relight pilot.
Weak burner flame.
(a) Burner intake ports clogged.
(b) Low gas pressure.
(a) Remove blockage.
(b) Adjust gas pressure.
Heating Swimming Pools 275
Table 5-3 (continued)
Symptom and Possible Cause
Possible Remedy
Pilot out (millivolt system).
(a) Restricted pilot.
(b) Weak or defective pilot generator.
(c) Low gas pressure.
(d) No gas.
(a) Clean pilot and restart heater.
(b) Replace pilot generator.
(c) Adjust gas pressure.
(d) Check gas supply. Call local
utility.
Pilot will not light.
(a) No fuel.
(b) Fuel tank empty (propane gas).
(c) Low gas pressure.
(a) Turn on gas.
(b) Fill tank.
(c) Adjust gas pressure or repair
as required.
(d) Clogged or damaged pilot tubing. (d) Clean or replace.
(e) Insufficient air supply.
(e) Correct as necessary.
(f) Improper venting.
(f ) Correct as necessary.
Pilot requires frequent relighting.
(a) Faulty thermocouple/pilot
generator.
(b) Loose connection between
thermocouple and gas valve.
(c) Loose coil connection.
(d) Electrical short in wiring between
thermocouple and gas valve or
coil.
(a) Replace.
(b) Tighten connection. Replace
if damaged.
(c) Tighten connection. Replace
if damaged.
(d) Determine cause of electrical
short and repair.
Noisy heater.
(a) Restriction in system.
(b) Blockage in gas line.
(c) Scale buildup in heat exchanger.
(d) Incorrectly adjusted pressure
switch.
(e) Low gas pressure.
(a) Locate restriction and remove.
(b) Locate and remove blockage.
(c) Remove scale from heat
exchanger tubes or replace
heat exchanger.
(d) Adjust pressure switch.
(e) Adjust gas pressure or repair
as required.
(continued)
276 Chapter 5
Table 5-3 (continued)
Symptom and Possible Cause
Possible Remedy
Soot forming in combustion chamber.
(a) Insufficient air supply.
(b) Too much water flowing
through heater.
(c) Heater run time too short.
(d) Gas valve regulator adjustment.
(e) Burner inlet throat or venturi
blocked.
(a) Check clearances and correct
(outdoor heater); check for
sufficient intake (combustion)
air and correct venting and
correct (indoor heater).
Clean soot from heat
exchanger.
(b) Correct water flow. Clean
soot from heat exchanger.
(c) Adjust time clock to allow
heater to run long enough to
heat the water. Clean soot
from heat exchanger.
(d) Test for correct gas pressure.
Adjust regulator or gas valve.
(e) Locate blockage and remove.
Heater leaking water.
(a) Leaking gasket.
(a)
(b) Loose connection to pressure
(b)
switch.
(c) Oversized pump causing excessive (c)
water flow through heater.
(d) Soot deposits in heat exchange.
(d)
(e) Damaged bypass valve.
Locate and replace gasket.
Tighten connection.
Replace with correctly sized
pump.
Correct problem. Clean heat
exchanger tubes.
(e) Replace valve.
Scale forming in combustion chamber.
(a) Problem with water chemistry.
(a) Check pH level, alkalinity,
and calcium hardness of
water. Bring within levels
recommended by heater
manufacturer.
(b) Improper bypass valve adjustment. (b) Adjust bypass valve. If
problem persists, repair or
replace valve.
Heating Swimming Pools 277
Table 5-4
Troubleshooting Oil-Fired Pool Heaters
Symptom and Possible Cause
Possible Remedy
Burner will not start (motor and transformer will not start).
(a) No power to heater.
(b) Heater control circuit defect.
(c) Loose wires or worn insulation
in the wire harness of the heater
control circuit.
(d) Defective control (pressure
switch, high-limit control,
safety switch, thermostat,
or time clock switch).
(e) Restriction in the fuel line.
(f) Binding fuel pump.
(g) Defective high-limit switch.
(h) Dirty or defective cad cell.
(i) Loose wiring below primary
control and ignition transformer.
(a) Check reset buttons on
motor and primary control.
(b) Connect a jumper wire
across the two terminals of
the cad cell. If the burner
starts, the problem is in
either the heater control
circuit wiring or one of the
controls.
(c) Inspect and correct as
necessary.
(d) Test each control with a
jumper wire. Replace
defective control when
located.
(e) Check fuel line and repair as
necessary.
(f) Repair or replace fuel pump.
(g) Turn off power to the heater
and short out the high-limit
switch in the line voltage
circuit. Try to restart the
burner. If it starts, the highlimit switch is defective and
must be replaced.
(h) Remove one cad cell wire
from the primary control. If
burner starts, replace
defective cad cell.
(i) Locate and repair.
Burner shuts off but restarts when primary control button is pressed.
(a) Dirty or defective cad cell.
(b) Poor combustion caused by
fouled nozzle.
(a) Clean or replace as necessary.
(b) Clean or replace nozzle.
(continued)
278 Chapter 5
Table 5-4 (continued)
Symptom and Possible Cause
Possible Remedy
(c) Oil level in storage tank too low. (c) Fill tank to appropriate level.
(d) Fuel line oil leaks.
(d) Locate and repair leaks.
(e) Nozzle pressure less than
(e) Determine cause and correct
100 psig.
nozzle pressure.
Table 5-5
Troubleshooting Pool Pumps and Filters
Symptom and Possible Cause
Possible Remedy
Pump does not run.
(a) Tripped circuit breaker.
(b) Blown fuse.
(c) Incorrect timer setting.
(d) Pump motor binding.
(a) Rest circuit breaker.
(b) Replace fuse.
(c) Check and reset for correct time.
(d) Oil motor.
Pump will not prime.
(a) Damaged impeller or motor
shaft.
(b) Water leaks in suction line.
(c) Valves in wrong position.
(a) Repair or replace pump.
(b) Repair or replace suction line.
(c) Change position of valves.
Excessive high or low filter water pressure.
(a) Water leak.
(b) Dirty or clogged filter.
(c) Valves in wrong position.
(a) Find leak and repair.
(b) Back-flush filter or replace it.
(c) Change position of valves.
Caution
These troubleshooting procedures may require connections to
electrical terminals and jumper wires to check and determine the
cause of an operating problem. To avoid injury from electrical
shock, always shut off the electrical power before servicing the
line voltage controls. Never leave a jumper wire in place to fix a
heater or the operating and safety controls will be bypassed.
Heating Swimming Pools 279
Caution
Never attempt to troubleshoot or service a pump or pump motor
if you are standing on a wet or damp surface or if your hands are
wet. The electrical connection can cause serious shock, injury, or
even death.
Note
A pump may start unexpectedly if it is equipped with an automatic
resetting thermal protector.
Chapter 6
Ventilation Principles
Ventilation is the process of moving air from one space to an
entirely separate space and is primarily a matter of air volume. It
should not be confused with circulation, which is the moving of air
around and within a confined space. In contrast to ventilation, circulation is a matter of air velocity. Ventilated air may or may not
have been conditioned, and it may be supplied to or removed from
the spaces by either natural or mechanical means.
The ventilation of a structure is important not only for the
health of its occupants but for their comfort as well. The proper
ventilation of a structure will replace stale, warm air in the interior
with fresh cooler air from the outdoors. It will reduce or eliminate
odors, remove excess moisture, and lower humidity levels, especially in the basement, attic, and crawl spaces.
For many years, proper ventilation was not considered as important as it is today. Houses were not very well insulated, and outside
air could be easily drawn into the structure not only through open
windows and doors but also through the walls themselves. Older
houses were said to breathe because air could move in and out of
them without much difficulty.
The fuel crisis of the 1970s and the rapid increase in energy costs
made the public aware that we had to have more efficient combustion appliances (for example, furnaces, boilers, water heaters) and
that structures had to be more tightly constructed and insulated.
Although the latter move did result in a reduction in heat loss and
gain, it also produced new problems such as trapped moisture, stale
air, and even health problems. For example, in tightly constructed
and insulated houses, vent fans, clothes dryers, and kitchen exhaust
fans can create a negative pressure, drawing air into the house through
holes in the framing, chimneys, and even exhaust flues. This can cause
backdrafting in combustion appliances, which can be a serious health
hazard.
If ventilation is inadequate and more air is exhausted from the
house than can be drawn in through natural ventilation, the result
is depressurization, which causes toxic combustion gases to be
released through cracks or poorly connected ducts in the heating
and cooling system. It is important that a balance be maintained
between air being exhausted and air being drawn into the house.
281
282 Chapter 6
There are two types of ventilation: passive ventilation and mechanical ventilation. The former only uses openings (vents) in the roof and
walls to allow heat to escape. The latter uses mechanical ventilators,
such as exhaust fans, attic fans, and whole-house fans in combination
with vents to remove the air from the house. Exhaust and attic fans
are covered in Chapter 7 (“Ventilation and Exhaust Fans”).
The Motive Force
The force that moves the air in a room or building may be due to
natural causes or mechanical means. In the first case, the ventilation is called natural ventilation. This kind of ventilation finds
application in industrial plants, public buildings, schools, garages,
dwellings, and farm buildings. The two natural forces available for
moving air into, through, and out of buildings are (1) induction
and (2) thermal effect. The inductive action is due to the wind
force, whereas the thermal effect is due to the difference in temperature inside and outside a building (this being in fact the same as
the chimney effect). The air movement may be caused by either of
these forces acting alone or by a combination of the two, depending on atmospheric conditions, building design, and location.
The nature of the ventilating results obtained by natural means
will vary from time to time because of variation in the velocity and
direction of the wind and the temperature difference.
The wind ventilating effect depends on its velocity. In almost all
localities, summer wind velocities are lower than those in the winter.
There are relatively few places where the wind velocity falls below
one-half of the average for many hours per month. Accordingly, if a
natural ventilating system is proportioned for wind velocities of onehalf the average seasonal velocity, it should prove satisfactory in
almost every case.
When considering the use of natural wind forces for producing
ventilation, three conditions must be considered:
1. The average wind velocity.
2. The prevailing wind direction.
3. Local wind interference by buildings, halls, or other obstruc-
tions.
Inductive Action of the Wind
When the wind blows without encountering any obstruction to
change its direction, its movement may be represented by a series of
parallel arrows, as in Figure 6-1. The arrows indicate the direction
Ventilation Principles 283
Natural flow of
wind when there is no
obstruction to change its
direction.
10
Figure 6-1
9
8
7
NATURAL FLOW
6
5
OF THE WIND
PRESSURE CONSTANT
4
3
2
1
10
9
8
DISTURBED
ATMOSPHERIC PRESSURE
CONSTANT
of flow. Under such conditions, the pressure may be considered as
constant throughout the airstream.
If the airstream meets an obstruction of any kind, such as a
house or ventilator, these parallel air lines will be pushed aside as in
Figure 6-2, crowding each other at points A and B, curving back on
the sides of the obstruction and curving inward past points C and D
to their original parallel positions.
B
C
OBSTRUCTION
PLAN
A
D
VACUUM
7
6
5
The results of an
airstream when it meets an
obstruction such as a house
or ventilator.
Figure 6-2
4
3
2
1
A vacuum is formed here as indicated by the suction lines (that
is, the arrows that curve back and inward toward the space occupied by the vacuum). This vacuum (or reduction in pressure) is
what causes inductive action.
A ventilator can be constructed in such a way as to make this
inductive action effective for ventilation. Figure 6-3 shows the two
essential parts of a simple ventilator: the head and connecting flue.
The head is open at one end and closed at the other and in actual
construction is pivoted to rotate, guided by a vane so that the
closed end always faces the wind.
As shown in Figure 6-3, the closed end forms an obstruction,
which changes the direction of the wind expanding at the closed
end and converging at the open end, producing a vacuum inside the
284 Chapter 6
OBSTRUCTION (HEAD OF VENTILATOR)
ELEVATION
INDU
CTI
ION
ACT
VE
VACUUM
LOW PRESSURE
HIGH PRESSURE
CONNECTING FLUE
Two essential parts of a ventilator
showing the results of wind action.
Figure 6-3
head, which induces an upward flow of the air through the flue
and out through the head. This is inductive action of the wind.
The stack or flue effect (see Figure 6-4) produced within a building when the outdoor temperature is lower than the indoor temperature is due to the difference in weight of the warm column of air
within the building and the cooler air outside. The flow due to the
stack (flue) effect is proportional to the square root of the draft
ELEVATION
B
a
LIGHT WARM AIR GOING OUT
OPEN WINDOWS
A
b
HEAVY COLD
AIR COMING IN
Figure 6-4
Illustrating the stack effect in a two-story structure.
Ventilation Principles 285
head. The formula for determining the rate of flow is as follows:
Q 9.4A 2h (t t0)
where Q airflow, cubic feet per minute.
A free area of inlets or outlets (assumed equal), square
feet.
h height from inlets to outlets, feet.
t average temperature of indoor air at height h, °F.
t0 temperature of outdoor air, °F.
9.4 constant of proportionality, including a value of 65
percent for effectiveness of openings. This should be
reduced to 50 percent (constant 7.2) if conditions are
not favorable.
Induced Draft
A closed flue (stack) or chimney will induce a draft or draw air. In
other words, it will cause the air to rise from the bottom level (or
room level) to the top. Consider the schematic of a stack shown in
Figure 6-5. The air is cool at the bottom of the stack and hot at
the top. Each unit of air in traversing the stack expands as the
temperature increases and becomes lighter. Assuming that cube A
in Figure 6-5 represents 1 lb of air and that the initial volume
undergoes first eight expansions and then sixteen, the corresponding
weight of the initial volume (1 lb) decreases to 1⁄8 lb and then to 1⁄16
lb. Accordingly the sum of the weights of unit volume in ascending
is 1 1⁄8 1⁄16 or 13⁄16 lbs. On the outside of the stack the volume
and weight of each unit of air remain the same so that considering
three units a, b, c of decreasing weights in the stack, there are three
units of a⬘, b⬘, c⬘ of constant weight outside the stack, the total
weight outside the stack being 3 lbs and only 13⁄16 lbs inside the stack.
As a result of the downward force (3 lbs) outside the stack being
greater than that in the stack, the heavy units a⬘, b⬘, c⬘ push the lighter
units a, b, c up and out of the stack, thus inducing a draft as indicated
by the lever scales in Figure 6-5. For purposes of explanation, induced
draft may be considered virtually the same as thermal effect.
Combined Force of Wind Effect
and Thermal Effect
It should be noted that when the forces of wind effect and thermal
effect are acting together (even when both forces are acting together
without interference), the resulting airflow is not equal to the sum
286 Chapter 6
113/16 LBS.
LIGHT AIR
3 LBS.
C
1/16
HEAVY AIR
LB.
1 LB.
a1
STACK
HOT
c
8 EXPANSIONS
B
1/8
1 LB.
LB.
WARM
b
b1
INITIAL
VOLUME
A
1 LB.
13/16 LBS.
Figure 6-5
a
c1
1 LB.
COOL
3 LBS.
The principle of induced draft.
of the two estimated quantities. The flow through any opening is
proportional to the square root of the sum of the heads acting upon
the opening.
When the two heads are equal in value and the ventilating openings are operated so as to coordinate them, the total airflow
through the building is about 10 percent greater than that produced
by either head acting independently under conditions ideal to it.
This percentage decreases rapidly as one head increases over the
other, and the larger will predominate.
Ventilation Principles 287
The wind velocity and direction, the outdoor temperature, or the
indoor distribution cannot be predicted with certainty, and refinement in calculations is not justified; consequently, a simplified
method can be used. This may be done by using the equations and
calculating the flows produced by each force separately under conditions of openings best suited for coordination of the forces.
Mechanical Ventilation
Mechanical ventilation is the process of supplying or removing air
by mechanical means. In other words, it represents a form of forced
ventilation. Some form of mechanical ventilation is necessary when
the volume of air required to ventilate a space cannot be delivered
adequately by natural means. As a result, it may be necessary to
add a fan (or fans) to the ventilation system in order to obtain the
required rate of air change.
Mechanical ventilation involves the use not only of fans but also
of ducts in some larger systems. The selection, installation, and
operation of fans are described in Chapter 7 (“Fan Selection and
Operation”). All aspects of duct sizing, the resistance to airflow,
and other related aspects are described in considerable detail in
Chapter 7 of Volume 2 (“Ducts and Duct Systems”).
Air Ventilation Requirements
The volume of air required for proper ventilation is determined by
the size of the space to be ventilated and the number of times per
hour that the air in the space is to be changed. Table 6-1 gives some
recommended rates of air change for various types of spaces. The
volume of air required to ventilate a given space is determined by
dividing the volume of the space by the number of minutes shown
for that space in the “rate of change” column in Table 6-1.
In many cases, existing local regulations or codes will govern the
ventilating requirements. Some of these codes are based on a specified amount of air per person and others on the air required per
foot of floor area. The table should thus serve only as a guide to
average conditions; where local codes or regulations are involved,
they should be taken into consideration.
If the number of persons occupying a given space is larger than
would be normal for such a space, the air should be changed more
often than shown in the table. It is recommended that an air
exchange rate of 40 cubic feet per minute per person be allowed for
extremely crowded spaces.
If the cooling effect of rapid air movement is needed in localities
that have high temperatures or humidities, the number of air
changes shown in Table 6-1 should be doubled.
288 Chapter 6
Table 6-1
Fresh Air Requirements
Type of Building or Room
Attic spaces (for cooling)
Boiler rooms
Churches, auditoriums
College classrooms
Dining rooms (hotel)
Engine rooms
Factory buildings (ordinary
manufacturing)
Factory buildings (extreme fumes
or moisture)
Foundries
Galvanizing plants
Garages (repair)
Garages (storage)
Homes (night cooling)
Hospitals (general)
Hospitals (children’s)
Hospitals (contagious diseases)
Kitchens (hotel)
Kitchens (restaurant)
Libraries (public)
Laundries
Mills (paper)
Mills (textile—general buildings)
Mills (textile—dyehouses)
Offices (public)
Offices (private)
Pickling plants
Pump rooms
Restaurants
Schools (grade)
Schools (high)
Shops (machine)
Shops (paint)
Shops (railroad)
Minimum Air
Changes per
Hour
12–15
15–20
8
CFA per
Minute per
Occupant
20–30
25–35
5
4–6
2–4
10–15
15–20
20–30*
20–30
4–6
9–17
40–50
35–40
80–90
10–20
10–20
4
10–15
15–20*
4
15–20*
3
4
10–15†
5
8–12
15–25
30–35
5
15–20*
5
Ventilation Principles 289
Table 6-1 (continued)
Type of Building or Room
Shops (woodworking)
Substations (electric)
Theatres
Turbine rooms (electric)
Warehouses
Waiting rooms (public)
Minimum Air
Changes per
Hour
CFA per
Minute per
Occupant
5
5–10
10–15
5–10
2
4
*Hoods should be installed over vats or machines.
†
Unit heaters should be directed on vats to keep fumes superheated.
Roof Ventilators
The function of a roof ventilator is to provide a storm- and weatherproof air outlet. For maximum flow by induction, the ventilator
should be located on that part of the roof where it will receive the
full wind without interference.
One must exercise great care when installing ventilators. If the
ventilators are installed within the vacuum region created by the
wind passing over the building or in a light court, or on a low building between two buildings, their performance will be seriously influenced. Their normal ejector action, if any, may be completely lost.
The base of a ventilator should be a tapering cone shape. This
design provides the effect of a bell mouth nozzle, which gives considerably higher flow than that of a square entrance orifice.
Air inlet openings located at low levels in the building should be
at least equal to, and preferably larger than, the combined throat
areas of all roof ventilators.
The advantages of natural ventilation units are that they may be
used to supplement power-driven supply fans, and under favorable
conditions it may be possible to shut down the power-driven units.
Types of Roof Ventilators
Roof ventilators are manufactured in a variety of shapes and
designs. Because of this variety, it is possible to classify roof ventilators under a number of broad categories, including the following:
1. Stationary head
2. Revolving
290 Chapter 6
3. Turbine
4. Ridge
5. Siphonage
Some of the examples illustrated in the paragraphs that follow
are no longer manufactured, but they will be encountered on older
buildings. For this reason, they are included in this chapter.
Stationary-Head Ventilators
More ventilators are of this type than any other, and when well
designed, it is usually considered the most efficient type of gravity
ventilator. The chief advantages of stationary-head ventilators are
as follows:
1.
2.
3.
4.
Higher exhaustive capacity under all wind conditions.
No moving parts.
Quiet operation.
No upkeep.
A stationary head ventilator is illustrated in Figure 6-6.
Figure 6-6
Stationary-head
ventilator.
Revolving Ventilators
A typical revolving ventilator is shown in Figure 6-7. This type of
ventilator swings on a pivot, aided by the wind vane so that its
open end points away from the wind. The inductive action of the
wind, in passing around the head, draws air out of the building. In
Ventilation Principles 291
Revolving ventilator.
The top portion pivots.
Figure 6-7
general, this is not as efficient as the stationary-head ventilator,
although it has general use.
A major disadvantage of the revolving ventilator is its low capacity in still air. Furthermore, if the pivot bearings stick so that the
head cannot follow the wind, it fails to exhaust air (in some cases
even admitting air, rain, or snow). The revolving ventilator also frequently becomes noisy, creaking when changing direction. Constant
attention is required to overcome these disadvantages.
Turbine Ventilators
Figure 6-8 represents one type of turbine ventilator. On its top is a
series of vanes that, from the force of the wind, causes the entire top
to rotate. Fastened to the top on the inside and placed in the air
outlet openings is a series of propeller blades. The wind rotates this
head, the blades drawing air up the shaft and exhausting it through
the blade opening. The basic limitation of the turbine ventilator is
that its blades draw the air outward as the top revolves. Its principal
disadvantages include the following:
1. Low capacities in quiet air.
2. Lowered capacity if the pivot bearings do not turn freely.
3. The tendency to become noisy (as does any heavy rotating
body that cannot accurately be kept in balance).
4. Required service attention in oiling, cleaning, and eventually
replacing bearings.
292 Chapter 6
Turbine ventilator.
The blades draw air outward as
the top revolves.
Figure 6-8
Another type of turbine ventilator (see Figure 6-9) consists of a
globe-shaped head containing vane blades. It, too, is designed to
draw air out of the structure as the globe-shaped head rotates. The
basic components of a globe-head turbine ventilator are shown in
Figure 6-10.
Turbine ventilators with globe-shaped heads also have a number
of disadvantages. For example, wind impact on the vanes allows
outside air to enter the head on the windward side that must be
exhausted, together with the air from the building on the leeward
Figure 6-9
ventilator.
Globe-head turbine
Ventilation Principles 293
ANCHORED ROTOR HEAD
SEAMLESS ROTOR CROWN PLATE
PRELUBRICATED BALL BEARING ASSY
RIGIDIZED ROTOR BLADES
ROTOR SHAFT
SEALED SHAFT AND BEARING CASING
BRONZE, SELF-LUBRICATED
OILITE BEARING
SPINDLE SUPPORT ASSEMBLY
ROTOR COLLOR
SWEDGED AIR SHAFT
Figure 6-10
Construction details of a turbine ventilator.
(Courtesy Penn Ventilator Co., Inc.)
side. This decreases its efficiency inasmuch as the head must handle
both volumes of air. Furthermore, this type of ventilator is apt not
to be rainproof when the wind is not turning it. Like all revolving
ventilators, its moving parts involve a service problem in oiling,
keeping bearings free, and the replacement of worn parts.
Ridge Ventilators
Figure 6-11 shows a sectional view of a ridge ventilator, which is
installed along the entire roof ridge of the space to be ventilated.
Basically, it consists of a valve in the top of the building, which
lets the warm air out as it rises to the roof air outlet distribution
along the length of the structure. Then, too, it has a pleasing uniform
appearance.
Figure 6-11
Ridge ventilator.
294 Chapter 6
Its major disadvantage is that it does not take full advantage of
wind action unless the wind direction is almost directly across it.
This type of ventilator also involves a somewhat cumbersome
damper and a rather difficult problem in building modernization.
Siphonage Ventilators
The siphonage ventilator (see Figure 6-12) acts by induction, drawing the building air upward. Wind causes a flow of air upward
through a duct that is concentric to and parallel with the ventilator
shaft extending from the building. Both of these air passages terminate in the ventilator head, and the upward flow of the outside air
creates a siphonage action drawing the building airstreams exhausting through the head. This ventilator is simply a stationary unit
with an auxiliary air passageway to obtain the siphonage action.
Figure 6-12
Siphonage
ventilator.
The head of the siphonage ventilator
must be designed to eject not only the
building air but also the siphon stream.
This tends to retard airflow from the
building due to the fact that egress from
the head is usually somewhat restricted.
Fan Ventilators
A typical fan ventilator is shown in
Figure 6-13. The principal advantage of
this type of ventilator is that the fan greatly
increases the ventilating capacity when the Figure 6-13 Sectional
fan is in operation. Fan ventilators also view showing fan
have a number of other advantages when ventilator.
Ventilation Principles 295
the fan is not in use and have great capacity when the fan is operated. Fan ventilators can be used on any building, regardless of
access to wind flow, and can be spotted directly over any point at
which ventilation is badly needed. These ventilators can also be used
on ductwork flues to give greater capacities when friction losses are
relatively large. It should be noted that a fan ventilator is a forceddraft rather than an induced-draft ventilator.
Components of a Roof Ventilator
The basic components of a typical roof ventilator are shown in
Figure 6-14 and may be listed as follows:
1.
2.
3.
4.
5.
6.
Base
Barrel
Top
Windband
Airshaft
Dampers
Component parts of
a roof ventilator.
Figure 6-14
FINIAL
WINDBAND
TOP
LOUVERS
BARREL OR
AIR SHAFT
BASE
The base serves as the connection between the roof and the ventilator proper. A trough is usually provided around the inside bottom edge of the base to collect any condensation occurring in the
ventilator and draw it out to the roof.
As bases are made to fit either a round or square opening and to
conform to the shape and slope of the roof, they are essentially tailor-made for each installation.
296 Chapter 6
After leaving the base, the air passes through the barrel (or neck)
of the ventilator, which is merely the lower section of the head. It
then enters the head proper and is exhausted to the outside air
through the openings between louvers. The top, of course, covers
the opening in the roof.
The windband is the vertical band encircling the ventilator head.
The airshaft is the entire passageway through the ventilator from
the roof to the top of the barrel.
The dampers are mechanical devices for closing the airshaft.
They assume a number of forms and are referred to according to
type as the sliding sleeve, inverted cone, butterfly, and louver.
Motive Force to Cause Air Circulation
Two agencies form the motive force to cause air circulation:
(1) temperature differences inside and outside the building resulting
in a chimney effect, and (2) inductive action caused by wind blowing against the ventilator.
Capacity of Ventilators
The following factors must be taken into consideration in making a
selection of the proper ventilator for any specific problem:
1.
2.
3.
4.
Mean temperature difference.
Stack height (chimney effect).
Inductive action of the wind.
Area of opening in the ventilator.
The mean temperature difference refers to the average temperature difference between the air inside and outside the building (see
Figure 6-15). If the ventilating problem is essentially a winter one, this
difference may be as much as 40˚F, while in summer, when doors and
windows are open, this difference will probably drop to about 10˚F.
Mean
temperature difference inside
and outside.
Figure 6-15
MEAN
TEMPERATURE
DIFFERENCE
OUTSIDE
TEMPERATURE
INSIDE TEMPERATURE
Ventilation Principles 297
Stack height (see Figure 6-16) is the height of the column of
warm air that causes the chimney action of the ventilator. It is measured in feet from the floor of the building to the top of the ventilator barrel.
The inductive action of the wind (see Figure 6-17) is the effect of
the wind as it passes over the ventilator in inducing a circulation
out of the building.
The area of the opening in the ventilator (see Figure 6-18) is
determined by the rated size of the ventilator, expressed as the
inside diameter of the barrel in inches.
Stack height upon
which the chimney effect depends.
Figure 6-16
STACK HEIGHT
The suction
action of the wind as it passes
over the ventilator.
Figure 6-17
WIND VELOCITY
Diameter of the
base, which governs the
capacity of gravity ventilation.
Figure 6-18
DIAMETER
298 Chapter 6
Design and Placement of Inlet Air Openings
The purpose of a roof ventilator is to let air escape from the top of
a building. This naturally means that a like amount of air must be
admitted to the building to take the place of that exhausted. The
nature, size, and location of these inlet openings are of importance
in determining the effectiveness of the ventilating system.
Inlet air openings are frequently constructed in the form of louvered
openings located near the floor line, but they also often consist of the
building windows. In general, there are three factors that should be
considered when planning for an effective ventilating system:
1. The relationship between the area of the air intakes and the
airshaft areas.
2. The distribution of inlet air openings.
3. The height at which air inlets are placed.
The area of the air intakes should at all times be twice that of the
combined airshaft area of all ventilators (see Figure 6-19). By keeping
Open areas at B
should be twice that of A.
Figure 6-19
A
A
B
B
Ventilation Principles 299
this relationship, the full capacity of the ventilators will be realized,
and the velocity of the incoming air will be low, thereby lessening
the danger from drafts in the building. Any backdraft down the
ventilator itself will also be eliminated.
These inlet air openings should also be distributed in such a way
as to allow the admission of fresh air to all parts of the building.
They should be located as close to the floor as possible in order to
bring the incoming fresh air into the breathing zone.
Fresh Air Requirements
Table 6-1 lists necessary air changes for various rooms and buildings and thus offers a guide as to the amount of air required for efficient ventilation. This information should be used in connection
with the ventilator capacity tables in the proper selection of the
number and size of units required.
Where two figures are given for one type of building, use the
smaller figure when conditions are normal and the larger figure
when they are abnormal. Certain buildings are better figured on a
cfm (cubic feet per minute) per occupant basis. Their requirements
are given in this manner.
Ventilator Bases
The ventilator base is the connection between the other elements
of the ventilator and the roof. It must be designed so as to fit the
contour of the roof and the opening on which it is mounted. Its
design and construction is important, particularly in ventilator
sizes and types where weight and wind resistance are high.
Ventilator manufacturers provide a wide variety of different ventilator
base sizes. In their literature, illustrated base designs (see Figure 6-20)
are cross-referenced with dimensional tables for the convenience of
the buyer.
Gauges of metal are used that ensure rigidity and strength.
Reinforcement is added where needed. Flashing flanges are amply
wide to ensure rigid, weather-tight joints that will not leak when
properly fastened and flashed to the roof. All seams are well riveted, soldered, or doped (the latter in asbestos-protected steel) to
ensure storm-tight joints. All connections to the roof and to the
next adjacent ventilator unit (the head in a gravity unit or the fan in
a fan unit) are designed for 75-mph wind velocity as standard or
100 mph optional.
Since the outside sheet-metal surfaces of ventilators are exposed to
atmospheric temperatures and the inside surfaces to room temperature, there is frequently a tendency for condensation to form on the
300 Chapter 6
C
A
D
H-2
B-2
F-2
T
C
C
A
A
H-1
F-1
C
A
B-1
F-1
E
F-1
ROUND BASE FLAT
12"
C
C
C
A
H-2
D
B-2
F-1
SQUARE BASE FLAT
ROUND BASE RIDGE
A
D
E
B-1
12
B-1
ROUND BASE SLOPE
A
F-1
H-1
H-1
E
12"
B-2
SQUARE BASE SLOPE
H-2
D H-2
F-1
E
12"
B-2
SQUARE BASE RIDGE
Standard ventilator bases.The letters refer to dimension
on manufacturers’ tables.
Figure 6-20
inside surfaces. In order to minimize the possibility of condensation
drip into the ventilated space, condensation gutters may be provided
to drain the water to the outside of the ventilator. These condensation
gutters are usually located at the extreme lower edge of the base
where as little water as possible can get past them.
The round ventilator bases in Figure 6-21 are standard but can
be omitted if a duct is to be fitted into the lower end of the base
with which the gutter would interfere. Examples of spare bases are
shown in Figure 6-22, but these are special. In either type, drains
Ventilation Principles 301
Figure 6-21
Round-base
DRAIN
ventilators.
ROUND BASE
SWEDGES
ROUND BASE
CONDENSATE GUTTERS
ROUND BASE
STIFFENER ANGLES
Figure 6-22
Square-base
ventilators.
DRAIN
SQUARE BASE
STIFFENER ANGLES
SQUARE BASE
CONDENSATE GUTTERS
SQUARE BASE
SWEDGES
from the gutter to the roof are ample for drainage and to prevent
clogging.
In ventilator sizes and types where weights are not great, bases
are lapped into the next adjacent unit above. In order to properly
position the units and to add stiffness, a wedge is provided in the
base against which the next adjacent unit seats.
302 Chapter 6
Angle Rings
In larger ventilator sizes where added strength, rigidity, and ease of
erection are important, angle rings have been used to connect the
base to the next adjacent unit (ventilator head, fan section, or stack).
In certain instances a one-ring connection (see Figure 6-23) is
used with the upper edge of the base lapping into the next adjacent
unit, which rests upon the angle ring. The bolted connection is
made through the sheet-metal lap. The lap connection is ample to
ensure proper bearing for connection screws or bolts. When angle
rings are provided, wedges are not used.
Figure 6-23
One-ring
connection.
Sometimes a two-ring connection (see Figure 6-24) is used, one
ring at the top of the base, another at the bottom of the adjacent
unit. The two rings form a flanged connection and are bolted
together. In every instance where angle rings are used, they are riveted to the bases to develop the full design strength of the assembly
for velocities of 75 mph standard or 100 mph optional.
Figure 6-24
connection.
Two-ring
Ventilation Principles 303
Stiffener Angles
Stiffener angles are provided in conjunction with angle rings in certain applications where the sheet metal needs reinforcing. These lie
vertically along the outside of the base surface at quarter points and
extend from the angle ring at the top to the outer edge of the roof
flange at the bottom. They are riveted to the base sheet metal and
welded to the angle ring. Bolted connections through portions of
the stiffener that lie along the roof flange to the curb or framing
members below provide rigid structural members through which
load is carried to the roof structure.
Where applicable and with certain types of dampers, a small
clip can be supplied and riveted to the base (see Figure 6-25). The
damper chain drops through this clip and can be locked at any
point to properly position the damper. This clip is useful when the
damper is to be operated from a point directly below the ventilator since it avoids the use of pulleys and complicated chain
arrangements.
Figure 6-25
Base chain clip.
Prefabricated Roof Curbs
Prefabricated roof curbs (bases) for ventilators are available from
a number of manufacturers. One of the advantages of the prefabricated type over those constructed at the site is the fact that they
are generally cheaper. This, of course, is due to their being massproduced. Although commonly designed for flat-roof installation, prefabricated roof curbs can also be built for installation on
the ridge or single slope of a roof. Figures 6-26 and 6-27 illustrate some of the design features incorporated in a prefabricated
roof curb.
304 Chapter 6
WOOD-NAILER
(OPTIONAL ACCESSORY)
INTEGRAL FIBERGLASS
INSULATION
FIELD FLASHING
(BY OTHERS)
INSULATION
(BY OTHERS)
BUILT-IN CANT STRIP
ROOF DECK
(BY OTHERS)
Figure 6-26
P
V
il
I
Prefabricated roof curb designed for flat-roof installation.
(Courtesy Penn Ventilator Co., Inc.)
Figure 6-27
Prefabricated roof curb featuring self-flashing design.
(Courtesy Penn Ventilator Co., Inc.)
Ventilator Dampers
Ventilator dampers (see Figure 6-28) are made in a variety of types,
from the single-disc butterfly to the multiblade louver, which has
been designed to allow a flexible and reliable means of air movement control. A tight seal can be obtained through the use of a
damper ring, which prevents the passage of air when the damper is
closed.
Some dampers can be controlled only by hand chain; others may
be remotely operated through the use of damper control motors of
the electric or compressed-air type.
Ventilation Principles 305
OPEN
Figure 6-28
Various forms
of dampers.
OPEN
ED
OS
CL
CLOSED
OPEN
BUTTERFLY
OPEN
CLOSED
SLIDING SLEEVE
CLOSED
OPEN
CONE
LOUVRE
The principal types of ventilator dampers are as follows:
1.
2.
3.
4.
5.
Sliding sleeve
Fire-retarding cone
Single butterfly
Divided butterfly
Louver
Louver Dampers
Figure 6-28 shows the general appearance of a louver damper. It is
considered the best type for airflow. Louver dampers offer little
resistance to the passage of air and in a partially open position create little turbulence in the airstream. In multiblade louvers, the
blades on one half open up, and those on the other half open down.
The center blade is double the width, and its edges are connected
to adjacent blades by clips and bars. The spacing of the blades
along the connecting bars has been closely studied to ensure that
the blade edges seat tightly on the damper ring when closed. This
damper ring also allows all the blade pivot bearings to be placed
inside the ventilator shaft, away from the weather. It also eliminates
holes through the airshaft that might leak air and rain. Blades are
regularly weighted so that the damper closes automatically. Any type
of control may be used.
306 Chapter 6
Sliding Sleeve Dampers
The sliding sleeve damper is frequently used for gravity ventilators.
In construction it closely fits the under circumference of the ventilator airshaft and operates vertically. It occupies almost no space in
the airshaft and offers no resistance or turbulence to the airstream
in any position. Its normal position is open, and with a fusible link
it can be used as an automatic-opening damper where there is need
for such a control unit.
Sliding sleeve dampers have one principal advantage. Because
of their vertical sides, there is no tendency for dust or dirt to
accumulate.
The sliding sleeve damper is operated by chain only. Radial spiders keep the damper cylindrical to the operating chain attached to
the hub of the spider, passing upward through a pulley fastened
below the finial and then down past the spider hub, where a spring
clip is located. The spring clip enables the damper to be positioned
at any point between open and closed.
Sliding Cone Dampers
As shown in Figure 6-28, a sliding cone damper consists of a cone
with apex down and with a flared outer rim that seats on the upper
edge of the airshaft when closed. This directs the airstream to the
outlet openings of the ventilator, lessens turbulence in the ventilator
head, and consequently increases capacity.
From the apex of the damper, the operating chain passes upward
to a pulley located below the finial, then downward through a slot
in the cone to a pulley located on the inside of the airshaft, and then
through the base to the building below.
When used in connection with the fusible link, this damper becomes
an automatically closing, fire-retarding unit.
Butterfly Dampers
The two butterfly dampers used in roof ventilators are (1) the
single-disc damper and (2) the divided-disc damper. They receive
their name from the butterfly-wing appearance of the metal disc
used to open or close the air passage.
The single-disc butterfly damper seats tightly against the ring
channel, preventing air leakage when closed. When operated by
hand chain, these dampers are normally counterweighted to close
but can be supplied weighted to open when required.
The divided-disc butterfly damper is used for sizes that prevent
the use of a single disc. The divided halves (or wings) of the disc
swing upward, pivoted on two rods whose ends bear in the damper
ring channel on which the damper edges seat tightly.
Ventilation Principles 307
Butterfly dampers, single- and divided-disc, are the only dampers
that can be successfully used in ventilators constructed of asbestosprotected steel. In this material, the damper ring is omitted and the
damper pivot rods are mounted on brackets secured to the airshaft
wall.
Method of Calculating Number and Size of
Ventilators Required
The number and size of ventilators required by a particular building can be calculated by taking the following steps:
1. Determine the gross volume of the interior of the building in
2.
3.
4.
5.
6.
cubic feet by multiplying its length by its width and by its
height.
Determine the number of air changes per hour required for
the building in question. This can be found by referring to the
tables given in the Typical Installation section.
Find the total number of cubic feet of air per hour necessary
for the ventilators to exhaust by multiplying the number of
changes per hour by the volume of each change, or 1 2.
Reduce this to cubic feet per minute by dividing by 60.
The effective range of a gravity ventilator is about 10 to 15 feet
in the direction of the length of the building and 15 to 25 feet in
the direction of the width of the building, where air is being
admitted on the sides. The next step, therefore, is to space the
units along the roof, using these restrictions, determining in this
manner the number of ventilators that will be required.
If the building is divided into bays, one unit is usually
placed in each bay, provided the bays are not over 20 feet
long. If there are no bays, one ventilator every 20 feet should
be sufficient for buildings up to 50 feet in width. In wider
buildings, the ventilators should be so arranged as to maintain approximately 20-foot spacing. If there are any spots
where there is urgent need of ventilation, such as a machine or
vat emitting fumes or dust, they should be cared for by ventilators placed above them. Such a layout will provide the number of ventilators required for the building.
Next, determine the exhaustive capacity required of each ventilator by dividing the total amount of air per minute to be
exhausted by the number of ventilators to be used, or 4⁄5. This
is the capacity for which you should look in the capacity
tables obtained from the manufacturer.
308 Chapter 6
7. Determine the conditions under which the ventilators will
operate, that is, stack height, mean temperature difference,
and wind velocity. These factors, their use, and their probable
values have already been explained.
8. Turn to the manufacturer’s capacity tables and look under the
proper columns of temperature difference, stack height, and
wind velocity, as determined in step 7, to find a capacity in
cfm that will fulfill the requirement as determined in step 6.
This capacity is listed under the size that should be selected.
Ventilator Calculation Examples
Assume a building used as an automobile storage garage 50 feet
wide by 150 feet long by 20 feet high to the eaves, 26 feet to the
ridge of the roof.
1. Volume of space from the eaves down is 50 20 150 150,000 cubic feet. Volume of space from the eaves up is 50 3 150 22,500 cubic feet. Total volume 172,500 cubic
feet.
2. From the table of air change requirements, you will find that
storage garages require four changes per hour for proper ventilation. Total air to be exhausted is then 172,500 4 690,000 cubic feet per hour, or 690,000 60 11,500 cfm.
3. Spacing ventilators along the roof as indicated in Figure 6-29,
with the aforementioned rules in mind, the resultant number
of ventilators would be seven, spaced 15 feet from each end
15'
20'
20'
20'
20'
20'
20'
15'
6'
20'
'
50
150'
Typical building illustrating method of calculating number
and size of ventilators required.
Figure 6-29
Ventilation Principles 309
and 20 feet apart. Each ventilator would need to exhaust
11,500 7 1643 cfm.
4. Suppose we have a mean temperature difference of 10°F, an
average wind velocity of 5 mph, and a stack height of 26 feet
(floor to roof ridge).
5. Turning to the capacity tables under that of the 30-inch cone
damper unit in the proper columns for the factors given in
step 4, we find that the capacity is 1750 cfm, which exceeds
our requisite of 1643 cfm obtained in step 3. Even though this
is a trifle higher than necessary, it should be used, inasmuch as
the next size smaller would be too far under the required
capacity. This can be seen by referring to the 24-inch unit, the
capacity of which is 1165 cfm.
We have therefore determined that to properly ventilate this
building, seven 30-inch cone damper ventilators will be necessary,
located on the ridge of the roof and spaced 20 feet apart and 15 feet
from each end.
Air Leakage
Air leakage is the passage of air in and out of various cracks or
openings in buildings. It is also sometimes referred to as infiltration.
Air leaking into a building may be caused by wind pressure or by
differences in temperature inside and outside of the building. In the
former case, the wind builds up a pressure on one or two sides of a
building, causing air to leak into the building. As shown in Figure
6-2 previously, the action of the wind on the opposite side or sides
produces a vacuum that draws air out of the building. Thus, as
shown in Figure 6-4 previously, a plan view of a single-room building is shown having a window and a door on one side and a window on the opposite side. The details are greatly exaggerated so
that you can see the cracks.
Note that when the wind hits the A side of the building, its momentum (dynamic inertia) builds up a pressure higher than inside the
building, which causes the air to leak through any cracks present, as
indicated by the arrows.
As the wind traverses the length of the building, the air currents as
they continue past the side C converge and produce a vacuum along
side C by induction. Because the pressure on the outside of C is lower
than inside the building, air leaks out as indicated by the arrows.
Air leakage due to temperature difference or thermal effect is usually referred to as stack or chimney effect. Air leakage due to cold air
outside and warm air inside takes place when the building contains
310 Chapter 6
cracks or openings at different levels. This results in the cold and
heavy air entering at low level and pushing the warm and light air
out at high levels, the same as draft taking place in a chimney.
Thus, in Figure 6-4, assume a two-story building having a window open on each floor. Evidently when the temperature inside the
building is higher than outside, the heavy cold air from outside will
enter the building through window A and push the warm light air
through window B, as indicated by arrow a; as it cools, it will
increase in weight and circulate downward, as indicated by arrow b.
Although not appreciable in low buildings, this air leakage is
considerable in high buildings unless sealing between various floors
and rooms is adequate.
A reasonable amount of air leakage is actually beneficial to health.
Any attempt to seal a building drum-tight will cause the inside air
to become stale and putrid. Emphasis should be placed on the reduction of heat transmission rather than the absolute elimination of air
leakage.
The application of storm sash to poorly filtered windows will
generally result in a reduction of air leakage of up to 50 percent. An
equal effect can be obtained by properly installed weather stripping.
Garage Ventilation
The importance of garage ventilation cannot be overestimated
because of the ever-present danger of carbon monoxide poisoning.
During warm weather, there is usually adequate ventilation because
doors and windows are kept open. In cold weather, however, people close up openings tight as a drum, with considerable danger.
Nobody can breathe the resulting carbon monoxide concentration
long without being knocked out—hence the importance of proper
ventilation in cold weather, regardless of physical comfort.
Where it is impractical to operate an adequate natural ventilation
system, a mechanical system should be used that will provide for
either the supply of 1 cubic foot of air per minute from out of doors
for each square foot of floor area or the removal of the same amount,
discharging it to the outside as a means of flushing the garage.
The following points should be carefully reviewed when considering a ventilating system capable of removing carbon monoxide
from an enclosed area:
1. Upward ventilation results in a lower concentration of carbon
monoxide at the breathing line and a lower temperature
above the breathing line than does downward ventilation for
the same rate of carbon monoxide production and air change
and the same temperature at the 30-inch level.
Ventilation Principles 311
2. A lower rate of air change and a smaller heating load are
required with upward ventilation than with downward ventilation.
3. In the average case, upward ventilation results in a lower concentration of carbon monoxide in the occupied portion of a
garage than is had with complete mixing of the exhaust gases
and the air supplied. However, the variations in concentration
from point to point, together with the possible failure of the
advantages of upward ventilation to accrue, suggest the basing of garage ventilation on complete mixing and an air
change sufficient to dilute the exhaust gases to the allowable
concentration of carbon monoxide.
4. The rate of carbon monoxide production by an idling car is
shown to vary from 25 to 50 cubic feet per hour, with an
average rate of 35 cubic feet per hour.
5. An air change of 350,000 cubic feet per hour per idling car is
required to keep the carbon monoxide concentration down to
one part in 10,000 parts of air.
Ventilation of Kitchens
In estimating the requirements for the ventilation of kitchens, the
following two methods should be considered:
1. It is customary to allow a complete change of air every 2 min-
utes.
2. In many cases it is desirable to have all the extracted air leave
via hoods or canopies located over ranges, steam tables, urns,
dishwashers, and so on.
The first method applies only to average conditions, and modification from this average should be made depending on the kitchen
size and the heat- and vapor-producing equipment.
In the second method, the air volume should be calculated from
the hood entrance velocity rather than the air-change method.
Light cooking requires an entrance velocity of only 50 feet per
minute, while severe conditions may run to 150 feet per minute or
higher.
The size of a hood will depend on its dimensions. For example, a
hood 3 feet by 8 feet would have an area of 24 square feet using an
average velocity of 100 feet per minute.
Where quiet operation is essential, the blower should be selected
on the basis of a low outlet velocity. This will also result in lower
operating costs.
312 Chapter 6
If space is limited and noise is not a factor, smaller units with
higher outlet velocities may be necessary. This may result in a lower
initial cost.
General Ventilation Rules
The American Society of Heating and Ventilating Engineers offers
the following recommendations for designing and installing an adequate natural ventilation system:
1. Inlet openings in the building should be well distributed and
2.
3.
4.
5.
6.
7.
should be located on the windward side near the bottom,
while outlet openings are located on the leeward side near the
top. Outside air will then be supplied to the zone to be ventilated.
Inlet openings should not be obstructed by buildings, trees,
signboards, and so on, outside or by partitions inside.
Greatest flow per square foot of total openings is obtained by
using inlet and outlet openings of nearly equal areas.
In the design of window-ventilated buildings, where the direction of the wind is constant and dependable, the orientation
of the building, together with amount and grouping of ventilation openings, can be readily arranged to take full advantage of the force of the wind. Where the wind’s direction is
variable, the openings should be arranged in sidewalls and
monitors so that, as far as possible, there will be approximately equal areas on all sides. Thus, no matter what the
wind’s direction, there will always be some openings directly
exposed to the pressure force and others to a suction force,
and effective movement through the building will be ensured.
Direct shortcuts between openings on two sides at a high level
may clear the air at that level without producing any appreciable ventilation at the level of occupancy.
In order for temperature difference to produce a motive force,
there must be vertical distance between openings. That is, if
there are a number of openings available in a building, but all
are at the same level, there will be no motive head produced
by temperature difference, no matter how great that difference might be.
In order for the forces of temperature difference to operate
to maximum advantage, the vertical distance between inlet
and outlet openings should be as great as possible.
Ventilation Principles 313
8.
9.
10.
11.
12.
13.
Openings in the vicinity of the neutral zone are less effective
for ventilation.
In the use of monitors, windows on the windward side should
usually be kept closed, because if they are open, the inflow
tendency of the wind counteracts the outflow tendency of
temperature difference. Openings on the leeward side of the
monitor result in cooperation of wind and temperature difference.
In an industrial building where furnaces that give off heat and
fumes are to be installed, it is better to locate them in the end
of the building exposed to the prevailing wind. The strong
suction effect of the wind at the roof near the windward end
will then cooperate with temperature difference to provide for
the most active and satisfactory removal of the heat and gasladen air.
In case it is impossible to locate furnaces in the windward
end, that part of the building in which they are to be located
should be built higher than the rest so that the wind, in
splashing, will create a suction. The additional height also
increases the effect of temperature difference to cooperate
with the wind.
The intensity of suction or the vacuum produced by the jump
of the wind is greatest just behind the building face. The area
of suction does not vary with the wind velocity, but the flow
due to suction is directly proportional to wind velocity.
Openings much larger than the calculated areas are sometimes desirable, especially when changes in occupancy are
possible or to provide for extremely hot days. In the former
case, free openings should be located at the level of occupancy
for psychological reasons.
In single-story industrial buildings, particularly those covering
large areas, natural ventilation must be accomplished by taking
air in and out of the roof openings. Openings in the pressure
zones can be used for inflow, and openings in the suction
zone, or openings in zones of less pressure, can be used for
outflow. The ventilation is accomplished by the manipulation
of openings to get airflow through the zones to be ventilated.
Chapter 7
Ventilation and Exhaust Fans
Both ventilation and air circulation utilize fans to move the air.
Ventilation is concerned with the moving of a volume of air from
one space to another. It does not involve the weight of air but the
volume of air in cubic feet moved per minute (cfm). The circulation of air, on the other hand, is concerned with the velocity at
which air moves around a confined space and is expressed in feet
per minute (fpm).
This chapter is concerned primarily with introducing the reader
to the problems of fan selection and operation. Several sections of
this chapter provide detailed instructions for fan sizing. Because the
selection of a fan and the design of a duct system are mutually
dependent, Chapter 7 of Volume 2 (“Ducts and Duct Systems”)
should also be consulted.
Codes and Standards
Always consult local codes and standards before designing or
attempting to install a fan system. Other sources of information on
codes and standards pertaining to fans and fan systems are as follows:
1. The Air Moving and Conditioning Association (AMCA).
2. The National Association of Fan Manufacturers (NAFM).
3. The American Society of Heating, Refrigerating and Air-
Conditioning Engineers (ASHRAE).
4. Home Ventilation Institute (HVI).
Definitions
A number of terms and definitions largely related to fan selection
and operation should be examined and learned for a clearer understanding of the materials in this chapter. Most of the terms and definitions contained in this section are provided by the Air Moving
and Conditioning Association.
Air horsepower (AHP). The work done in moving a given volume (or weight) of air at a given speed. Air horsepower is
also referred to as the Morse power output of a fan.
Area (A). The square feet of any plane surface or cross section.
315
316 Chapter 7
Area of duct. The product of the height and width of the duct
multiplied by the air velocity equals the cubic feet of air per
minute flowing through the duct.
Brake horsepower (BHP). The work done by an electric motor
in driving the fan, measured as horsepower delivered to the
fan shaft. In belt-drive units, the total workload is equal to
the workload of the electric motor plus the drive losses
from belts and pulleys. The brake horsepower is always a
higher number than air horsepower (AHP). Brake horsepower is also referred to as the horsepower input of the fan.
Cubic feet per minute (cfm). The physical volume of air moved
by a fan per minute expressed as fan outlet conditions.
Density. The actual weight of air in pounds per cubic foot
(0.075 at 70°F and 29.92 inches barometric pressure).
Fan inlet area. The inside area of the inlet collar.
Fan outlet area. The inside area of the fan outlet.
Mechanical efficiency (ME). A decimal number or a percentage
representing the ratio of air horsepower (AHP) to brake
horsepower (BHP) of a fan. It will always be less than
1.000 or 100 percent and may be expressed as follows:
ME AHP
BHP
Outlet velocity (OV). The outlet velocity of a fan measured in
feet per minute.
Revolutions per minute (RPM). The speed at which a fan or
motor turns.
Standard air. Air at 70°F and 29.92 inches barometric pressure
weighing 0.075 lbs per cubic foot.
Static efficiency (SE). The static efficiency of a fan is the
mechanical efficiency multiplied by the ratio of static pressure to the total pressure.
Static pressure (SP). The static pressure of a fan is the total
pressure diminished by the fan velocity pressure. It is measured in inches of water (see velocity pressure).
Tip speed (TS). Also referred to as the peripheral velocity of
wheel. It is determined by multiplying the circumference of
the wheel by the rpm.
Ventilation and Exhaust Fans 317
TP ⫽
⫻ wheel diameter in feet ⫻ RPM
12
⫻ wheel diameter in feet ⫻ RPM
The tip speed should not exceed 3300 rpm if a quiet operation is
to be obtained.
Total pressure (TP). Any fan produces a total pressure (TP),
which is the sum of the static pressure (SP) and the velocity
pressure (VP). Total pressure represents the rise of pressure
from fan inlet to fan outlet.
Velocity. The speed in feet per minute (fpm) at which air is
moving at any location (for example, through a duct, inlet
damper, outlet damper, or fan discharge point). When the
performance data for air-handling equipment are given in
feet per minute (fpm), conversion to cubic feet per minute
can be made by multiplying the fpm by the duct area:
Air velocity ⫽ 1000 FPM
Duct size ⫽ 8 in. ⫻ 20 in. ⫽ 160 sq. in.
Duct area 160 ⫼ 144 ⫽ 1.11 sq. ft.
Air flow 1000 FPM 1.11 sq. ft. 1110 CFM
Velocity pressure (VP). Velocity pressure results only when air
is in motion, and it is measured in inches of water. Oneinch water gauge corresponds to 4005 fpm (standard air)
velocity. The following formula is used for determining
velocity pressure:
VP c
Air Velocity 2
d
4005
Types of Fans
The various mechanical devices used to move the air in heating,
ventilating, and air-conditioning installations are known as fans,
blowers, exhausts, or propellers.
Every fan is equipped with an impeller, which forces (impels) the
airflow. The manner in which air flows through the impeller provides the basis for the following two general classifications of fans:
318 Chapter 7
1. Centrifugal fans
2. Axial-flow fans
In a centrifugal (or radial flow) fan (see
Figure 7-1), the air flows radially (that is,
diverging from the center) through the
impeller, which is mounted in a scroll-type
housing. Centrifugal fans are further subdivided into a number of different types
depending on several design variations,
Figure 7-1 Centrifugal such as the forward or backward inclinafan principles.
tion of the blade.
An axial-flow fan is mounted within a
cylinder or ring, and the air flows axially (that is, parallel to the
main axis) through the impeller. Depending on the design of the
enclosure and impeller, axial-flow fans can be subdivided into the
following types:
1. Tubeaxial fans
2. Vaneaxial fans
3. Propeller fans
A tubeaxial fan consists of an axial-flow wheel within a cylinder
(see Figure 7-2). These fans are available in a number of different
types depending on the design and construction of the impeller blades.
A vaneaxial fan also consists of an axial-flow wheel but differs
from a tubeaxial fan in that it uses a set of vanes to guide the airflow and increase efficiency (see Figure 7-3).
A propeller fan consists of a propeller or disc wheel within a ring
casing or plate. These fans are by far the simplest in construction
and operate best against low resistance (see Figure 7-4).
Figure 7-2
principles.
MOTOR
Tubeaxial fan
Ventilation and Exhaust Fans 319
Figure 7-3
Vaneaxial fan principles.
GUIDE VANE
MOTOR
GUIDE VANE
Furnace Blowers
The blower used in a forced warm-air furnace is
similar to the centrifugal fan used in ducts and
other types of applications. Most blowers are
designed with a belt drive, although some are
equipped with a direct drive to the motor.
Furnace blowers are described in considerable
detail in the several chapters dealing with specific
types of furnaces. See, for example, Chapter 11
of Volume 1 (“Gas-Fired Furnaces”).
MOTOR
Basic Fan Laws
The performance of fans and their relationship to the ventilation system are governed by
definite principles of fluid dynamics. An
understanding of these principles is useful to Figure 7-4
anyone designing a ventilation system Propeller fan.
because they make possible the prediction of
effects resulting from altered operating conditions. The principles (and formulas) associated with fan and ventilation system engineering are referred to collectively as basic
fan laws.
The basic fan laws used in calculating fan performance depend
on the fact that the mechanical efficiency (ME) of a fan remains
constant throughout its useful range of operating speeds (that is,
the fan rpm). They also apply only to fans that are geometrically
similar.
A current edition of the ASHRAE Guide will contain detailed
explanations of the principles and formulas associated with basic
fan laws. A typical example is the production of fan speed (rpm),
static pressure (SP), and horsepower when the volume of air moved
320 Chapter 7
by the fan is varied. The following three principles and formulas are
involved:
1. Fan speed delivery will vary directly as the cfm ratio:
New RPM ⫽ Old RPM ⫻ c
New CFM
d
Old CFM
2. Fan (and system) pressures will vary directly as the square of
the rpm ratio:
New SP (or TP or VP) ⫽ c
New RPM 2
d ⫻Old SP (or TP or VP)
Old RPM
3. Brake horsepower (bhp) on the fan motor (or air horsepower
of the fan) will vary directly as the cube of the rpm ratio:
New RPM 3
New BHP (or AHP) ⫽ c
d ⫻ Old BHP (or AHP)
Old RPM
Example
A centrifugal fan delivers 10,000 cfm at a static pressure of 1.0 inch
when operating at a speed of 600 rpm and requires an input of 3 hp.
If 12,000 cfm is desired in the same installation, what will be the new
fan speed (rpm), static pressure (SP), and horsepower (bhp) input?
The three aforementioned formulas can be applied as follows:
1. New RPM ⫽ 600 ⫻ c
12,000
d
10,000
⫽ 600 ⫻ 1.2 ⫽ 720
2. New SP ⫽ c
720 2
d ⫻1
600
⫽ 1.44 ⫻ 1 ⫽ 1.44
3. New BHP ⫽ c
720 3
d ⫻3
600
1.7 ⫻ 3 ⫽ 5.1
The following three formulas also may prove useful in making
fan calculations:
Ventilation and Exhaust Fans 321
1. A (area) ⫻ V (velocity) ⫽ CFM
2. CFM ⫼ V ⫽ A
3. CFM ⫼ A ⫽ V
Series and Parallel Fan Operation
Two separate and independent fans can be operated either in series
or in parallel (see Figure 7-5). When two fans are operated in
series, the cfm is not doubled. Instead, the total airflow is limited
to the cfm capacity of one fan alone. Series operation is seldom
desirable except when it is necessary to maintain the following
conditions:
1. Constant pressure
2. Zero pressure
3. Constant vacuum
When fans are operated in parallel, they produce a total airflow
equal to the sum of their individual cfm capacities. Parallel fan
operation is necessary when a single fan is incapable of moving
the total volume of air required or when airflow distribution is a
factor.
EXHAUST
AIR FAN
SUPPLY
AIR FAN
SERIES
AIR
EXHAUST
AREAS
SUPPLY
AIR FAN
PARALLEL
Figure 7-5
Series and parallel fan operations.
322 Chapter 7
Fan Performance Curves
Fan performance curves are provided by fan manufacturers to
graphically illustrate the relationship of total pressure, static pressure, power input, mechanical efficiency, and static efficiency to
actual volume for the desired range of volumes at constant speed
and air density. A typical performance curve for a forward-curved
blade centrifugal fan is shown in Figure 7-6.
General Ventilation
General ventilation involves the moving of a volume of air from
one space to an entirely separate space, where concern for a concentrated source of heat or contamination is not a factor. In this
respect, it differs from local ventilation, which is used primarily to
control atmospheric contamination or excessive heat at its source
(see following section).
In general ventilation, the specific volume of air to be moved is
measured in cubic feet per minute (cfm). The two principal methods of determining the required cfm are as follows:
PERCENT OF BLOCKED TIGHT PRESSURE –
MAXIMUM HORSEPOWER – EFFICIENCY – SOUND LEVEL
1. Air-change method
2. Heat removal method
S O U N D LE
VEL
LATI
– RE
ITY
TENS
VE IN
110
TOTA
100
ST
AT
IC
90
80
70
60
50
40
H OR
30
20
L PR
ESSU
RE
PR
ES
SU
TOT RE
AL
STA
EFFIC
TIC
IENC
Y
EFF
ICI
R
E
EN
W
O
C
Y
SE P
ROTATION
10
0
0
10
20
30
40
50
60
70
PERCENT OF WIDE OPEN VOLUME
80
90
100
Typical performance curves for a forward-curved
blade centrifugal fan.
Figure 7-6
Ventilation and Exhaust Fans 323
Determining CFM by the Air-Change Method
In order to determine the required cfm for a structure of space by
the air-change method, the following data are necessary:
1. The total cubic feet of air space in the structure or space.
2. The required number of air changes necessary to give satisfac-
tory ventilation.
The total cubic feet of air space is easily determined by multiplying the dimensions of the structure of space. For example, a room
12 feet long and 10 feet wide with an 8-foot ceiling would have 960
cubic feet of air space (12 ft ⫻ 10 ft ⫻ 8 ft ⫽ 960 ft3).
The required number of air changes necessary to give satisfactory ventilation will depend on a variety of factors, including (1)
use, (2) number of people, (3) geographic location, and (4) height
of ceiling.
Usually local health department codes will specify the required
number of air changes for various installations. When there are no
code requirements, the data given in Table 7-1 are recommended.
Once the necessary data have been obtained, the following formula can be used to determine the cfm:
CFM ⫽
Building Volume in Cubic Feet
Minutes Air Change
Let’s use the space shown in Figure 7-7 to illustrate how the airchange method is used to determine cfm. First, let’s assume that the
space is being used as a bakery. In Table 7-1 you will note that a 2- to
3-minute air-change range is recommended for a bakery. The fact
that a range is given is important because the number selected for the
air-change method will depend on several variables. For example, a
30'
15'
EXHAUST
INTAKE
100'
Figure 7-7
Bakery building dimensions.
324 Chapter 7
Table 7-1 Average Air Changes Required per Minute for
Good Ventilation
Minutes per Change
Assembly halls
Auditoriums
Bakeries
Banks
Barns
Bars
Beauty parlors
Boiler rooms
Bowling alleys
Churches
Clubs
Dairies
Dance halls
Dining rooms
Dry cleaners
Engine rooms
Factories
Forge shops
Foundries
Garages
Generator rooms
Gymnasiums
Kitchens, hospitals
Kitchens, resident
Kitchens, restaurant
Laboratories
Laundries
Markets
Offices
Packing houses
Plating rooms
Pool rooms
Projection rooms
Recreation rooms
Residences
2–10
2–10
2–3
3–10
10–20
2–5
2–5
1–5
2–10
5–10
2–10
2–5
2–10
3–10
1–5
1–3
2–5
2–5
1–5
2–10
2–5
2–10
2–5
2–5
1–3
1–5
1–3
2–10
2–10
2–5
1–5
2–5
1–3
2–10
2–5
(continued)
Ventilation and Exhaust Fans 325
Table 7-1 (continued)
Minutes per Change
Sales rooms
Theaters
Toilets
Transformer rooms
Warehouses
2–10
2–8
2–5
1–5
2–10
higher number is used when the structure or space is located in a
warm climate, when the ceiling is a particularly low one, or when
there are a large number of people using a relatively small space.
Comfort cooling, on the other hand, may be obtained by using the
lowest figure in each stated range.
For the sake of our example, let’s assume that the bakery has not
been designed for comfort cooling. Furthermore, the ceilings are
higher than average (15 feet), and the structure is located in a warm
climate. With this information, the cfm can be determined in the
following manner:
1. 100 ft. ⫻ 30 ft. ⫻ ⫽ 45,000 cu. ft. of air space (Fig. 7-7).
2. 3-minute required air change (Table 7-1).
3. CFM ⫽
45,000
⫽ 15,000
3
Thus, 15,000 cfm are required to change the air in the bakery
every 3 minutes. Assuming a 300 fpm intake velocity, 50 square feet
of free air intake are needed.
Determining CFM by the Heat Removal Method
The heat removal method is useful for determining cfm in installations where the ventilation of sensible heat is required.
In order to determine cfm by this method, you need to know the
total Btu per minute, the average outdoor temperature, and the
desired inside temperature. This information is then used in the following formula:
CFM Total Btu per minute
0.0175 ⫻ Temp. Rise ⬚F
326 Chapter 7
Note that the cfm determined by the heat removal method deals
primarily with sensible heat, not with radiant heat. The cfm
obtained from the previous formula indicates the amount of air
that needs to be passed through a structure or space in order to
maintain the desired inside temperature.
Determining Air Intake
Adequate air intake area should be provided where fans are used to
exhaust the air. The same holds true for fans used to supply air to a
room (that is, adequate air exhaust area should be provided). The
size of the air intake (or air exhaust) area depends on the velocity
(fpm) of the entering or existing air and the total cfm required by the
structure or space. This may be expressed by the following formula:
A
CFM
FPM
where A square feet of free intake (or exhaust) area
cfm cubic feet per minute
fpm feet per minute
The bakery previously described requires 15,000 cfm. Assuming
a 300-fpm intake velocity, 50 square feet of free air intake area are
required.
Area 15,000 CFM
50
300 FPM
Doors and windows are suitable air intake areas if they are
located close enough to the floor and provide a full sweep through
the area to be ventilated. When you have determined the total free
air intake area by the aforementioned formula, deduct the area for
doors and windows that function as passageways for air. Fixed or
adjustable louvers can be installed over the other intake areas.
Screen Efficiency
It is frequently necessary to cover an air intake (or exhaust) area with
a bird or insect screen. These screens reduce the free intake area, but
the amount of the reduction will depend on the type of screen used. In
Figure 7-8, the net (effective) free area for each of three screens is
shown as a percentage. The small holes required by an insect screen
reduce the net free area to approximately 50 percent. The 1⁄2-inch
mesh screen, on the other hand, provides a net free area of 90 percent.
Ventilation and Exhaust Fans 327
1 /2 "
MESH
1/4"
80%
90%
Figure 7-8
MESH
INSECT SCREEN
50%
Net free air of various screens.
The reduction of the free intake area by screens can be compensated for by using a larger overall area.
Static Pressure
The static pressure of a fan may be defined as the total pressure
diminished by the fan velocity pressure.
Calculating the total external static pressure of a system is
important to the selection of a fan or blower because it must be
capable of handling the required volume of air (in terms of cfm)
against this pressure.
The total external static pressure is determined by adding the
static pressures of any of the air-handling components in a system
capable of offering resistance to the flow of air. A 10 percent
allowance of the sum of these static pressures is added to obtain the
total external static pressure.
The static pressures (that is, friction losses in inches of water)
used in determining the total external static pressure of an air-handling system will include the following:
1.
2.
3.
4.
5.
6.
Entrance loss
Friction loss through filters
Friction loss through tempering coils
Friction loss through air washer
Duct system resistance
Supply grille resistance
Most friction losses can be obtained from data tables provided
by manufacturers; however, duct loss is based on the longest run of
duct, and this will vary from one installation to another.
In determining the length of duct, start at the point where the
air enters the system and include all ducts in the main supply duct
to the end of the system. An example of this type of calculation is
shown in Table 7-2. The sum (406 ft) is then multiplied by the
328 Chapter 7
Table 7-2
Total Length of Duct for an Installation
Equivalent Length of
Straight Duct (ft)
1 gooseneck at roof (double elbow 18⬙ ⫻ 63⬙)
28 feet straight duct to basement
1 elbow (18⬙ ⫻ 63⬙) to transition piece
40 feet straight duct
1 elbow (63⬙ ⫻ 18⬙)
60 feet straight duct
1 elbow (63⬙ ⫻ 18⬙)
15 feet straight duct
1 elbow (63⬙ ⫻ 18⬙)
39
28
20
40
68
60
68
15
68
406
resistance for the ducts. For example, if the resistance is found to
be 0.1 inch per 100 feet, the static pressure for the total run of duct
will be 0.406 inch (that is, 406 ft ⫼ 100 ft ⫽ 4.06 ft ⫻ 0.1 in ⫽
0.406 in).
Local Ventilation
Local ventilation is used to control atmospheric contamination or
excessive heat at its source with a minimum of airflow and power
consumption. It is not used to move a volume of air from one space
to another for human comfort.
Air velocity is an important factor in local ventilation. Air must
move fast enough past the contaminant source to capture fumes,
grease, dust, paint spray, and other materials and carry them into
an exhaust hood.
Both the capture velocity of the air at the contaminant source
and the velocity at the discharge duct must be considered when
designing a localized ventilation system. It is important to remember that capture velocities will differ depending on the contaminant. Table 7-3 lists the capture velocities for contaminants found
in a variety of booths (that is, enclosures designed to isolate areas
used for special purposes).
The selection of a suitable fan for a local ventilation system
requires knowledge of the required fan cfm capacity and the static
pressure (SP) at which the fan must work. Once these facts are
known, you have all the necessary information required for sizing
the fan from the manufacturer’s rating tables.
Ventilation and Exhaust Fans 329
Table 7-3
Capture Velocities for Various Types of Booths
Capture
Velocity (fpm)
Process
Type of Hood
Aluminum furnace
150–200
200–250
200–250
250–300
100–150
150
1500–2000
100–150
200–250
150–200
125–150
100–175
250–300
200–250
225–250
250 cfm
per foot of
tank surface
Canopy hood
125–175
Enclosed booth, open one side 150–200
Enclosed hood, open one side
Canopy or island hood
Brass furnace
Enclosed hood, open one side
Canopy hood
Chemical lab
Enclosed hood, front opening
Degreasing
Canopy hood
Slotted sides, 2⬙–4⬙ slots
Electric welding
Open front booth
Portable hood, open face
Foundry shakeout
Open front booth
Kitchen ranges
Canopy hoods
Paint spraying
Open front booth
Paper-drying machine Canopy hood
Pickling tanks
Canopy hood
Plating tanks
Canopy hood
Slotted sides
Steam tanks
Soldering booth
Courtesy Hayes-Albion Corporation
The required fan cfm capacity is determined by multiplying the
open face area of any booth by the capture (face) velocity (fpm) of
the air at the source of contamination.
CFM Face Area (sq. ft.) ⫻ Face Velocity (FPM)
The total open face area of any booth is determined by its physical size and the required access to the work area. If a booth is
designed with several open face areas, all of them must be calculated and added together.
Capture (face) velocities (fpm) can be determined for various
types of booths from data available from manufacturers and other
sources. An example of such data is illustrated in Table 7-3.
The precise calculation of static pressure (SP) is not necessary for
the sizing of a fan (or fans) in a local ventilation installation. An
330 Chapter 7
approximate calculation of static pressure will usually suffice, and
the following steps are suggested for making such a calculation:
1. Assume the losses in the exhaust hood itself to be 0.05 inch to
0.10 inch SP.
2. Size the cross-sectional area of the main duct to ensure 14002000 fpm velocity.
Duct Area (sq. ft.) CFM
FPM
3. Keep all ductwork as short and straight as possible and avoid
4.
5.
6.
7.
elbows and sharp turns (see Figure 7-9).
Determine the total straight duct length.
Add the equivalent straight duct length for each turn (see
Table 7-4), and add it to step 4.
Multiply the sum of steps 4 and 5 by 0.0025 inch to determine an approximate static pressure for the ductwork.
The static pressure for filters usually can be obtained from the
filter manufacturer. If this is not possible, assume 0.25 inch SP
for clean filters and 0.50 inch for dirty filters.
DUCT WITH BEND
GRACEFUL ELBOW REDUCE FRICTION
CORRECT WAY
STRAIGHT DUCT
INCREASE AT FAN
CORRECT WAY
ANGLE TOO SHARP
INCORRECT WAY
Figure 7-9
INCORRECT WAY
Various designs to avoid when designing a duct system.
Ventilation and Exhaust Fans 331
Table 7-4 Equivalent Lengths of Straight Pipe
90° Elbow* Centerline Radius
Dia. of Pipe
3⬙
4⬙
5⬙
6⬙
7⬙
8⬙
10⬙
12⬙
14⬙
16⬙
18⬙
20⬙
24⬙
30⬙
36⬙
40⬙
48⬙
1.5 D
5
6
9
12
13
15
20
25
30
30
41
46
57
74
93
105
130
2.0 D
2.5 D
3
4
6
7
9
10
14
17
21
24
28
32
40
51
64
72
89
3
4
5
6
7
8
11
14
17
20
23
26
32
41
52
59
73
R
D
*For 60° elbows-x.67; for 45° elbows-x.5.
(Courtesy Hayes-Albion Corporation)
8. Add the static pressures from steps 1, 6, and 7 to obtain the
approximate total static pressure for the installation.
9. Use the total static pressure for the installation and the
required cfm capacity for sizing the fan.
Caution
Always check local building and safety codes for regulations pertaining to hazardous conditions. For extremely critical installations, such as those dealing with acids, poisons, or toxic fumes,
consult the fan manufacturer for engineering analysis. It is
strongly recommended that you do not attempt to make these
calculations yourself. Finally, never undersize a fan. If you have any
doubts about the correct size or horsepower, then select the
next size larger.
332 Chapter 7
Exhaust-Hood Design Recommendations
A properly designed exhaust hood (see Figure 7-10) is an important
part of a local ventilation system. The following recommendations
are offered as design guidelines:
1. Use the shortest duct run possible.
2. Avoid the use of elbows and transitions.
3. Size the exhaust hood to provide a minimum 100 fpm face
velocity (150 fpm for island-type work).
4. Provide sufficient hood overhang on all sides to overlap work
area.
5. Use more than one exhaust fan on very large hoods.
6. Use as many individual hood and duct systems as possible
(that is, try to avoid grouping hoods together on the same
duct system).
7. Use filters where required. Velocities over filters should be sized
in accordance with filter manufacturer’s recommendations.
8. Provide makeup air units.
30° – 45°
0.4 D
Figure 7-10
D
Recommended hood design. (Courtesy Penn Ventilator Co., Inc.)
Ventilation and Exhaust Fans 333
Fan Motors
Most fans used in heating, ventilating, and air-conditioning installations are powered by electric motors. Because of the small size of
many of these fans, the majority are equipped with direct-connected motors. A V-belt drive arrangement is used with larger fans,
particularly centrifugal fans used in forced warm-air furnaces or
the larger ventilating units found in commercial and industrial
installations.
It is the general rule to select a fan one size larger than the fan
requirements for the installation. This is particularly so in installations that may require the movement of large volumes of air for
short intervals.
The advantage of fans equipped with a belt-drive arrangement is
that adjustments can be made for different speeds. It is simply a
matter of changing the pulley size. A belt drive is especially desirable when the required horsepower requirement is in doubt.
A fan wheel directly connected to the motor shaft is the best
arrangement, but this is only feasible with the smaller centrifugal
fans and propeller fans under 60 inches in diameter.
A direct-connected fan is generally driven by a single-phase AC
motor of the split-phase, capacitor, or shaded-pole type. The capacitor motor is recommended when there are current limitations. Its
major advantage is its greater efficiency electrically. The major disadvantage of such motors is that they are usually designed to operate at only one speed. A damper arrangement can be used to
throttle the air when it becomes necessary to vary the air volume or
pressure of the fan.
The variation of pressure and air volume in larger fan installations (for example, mechanical draft fans) can be accomplished by
means of a constant-speed, direct-connected motor equipped with
movable guide vanes in the fan inlet.
The National Electrical Manufacturer’s Association (NEMA)
has recently revised motor voltage designations to conform to system voltages now present throughout the country. Single-phase
motor voltages should now be specified as 115 volts or 230 volts
instead of the 110-volt or 220-volt designations formerly in effect.
Polyphase voltages should be expressed as 208 volts or 230/460
volts instead of the 220/440 voltages formerly in effect. Motors
for special voltages such as 177, 480, or 575 volts are available
from many fan manufacturers on special order. Fan motors have
been designed to operate satisfactorily over the range of plus or
minus 10 percent of the nameplate voltage ratings. Always check
the fan motor nameplate voltage ratings before installing the motor.
334 Chapter 7
Tables 7-5 and 7-6 list nominal full-load ampere ratings for single-phase and three-phase motor voltages. The amperes given are
approximate values only and represent averages compiled from
tables of leading motor manufacturers. Compare these with the
specific amperages listed for Airmaster fans in Table 7-7.
Table 7-5
Nominal Full-Load Ampere Ratings for
Single-Phase Motors
Full-Load Current
HP
RPM
115 V
1
1550
1050
1725
1140
860
1550
1725
1140
860
1725
1140
860
1725
1140
860
1725
1140
860
1725
1140
860
1725
1140
860
1725
1140
860
1.0
1.0
2.0
2.4
3.2
2.4
2.8
3.4
4.0
3.2
3.84
4.5
4.6
6.15
7.5
5.2
6.25
7.35
7.4
9.15
12.8
10.2
12.5
15.1
13.0
15.1
15.9
⁄25
⁄25
1
⁄12
1
1
⁄10
⁄8
1
1
⁄6
1
⁄4
1
⁄3
1
⁄2
3
⁄4
1
(Courtesy Penn Ventilator Company, Inc.)
230 V
0.5
0.5
1.0
1.2
1.6
1.2
1.4
1.7
2.0
1.6
1.92
2.25
2.3
3.07
3.75
2.6
3.13
3.67
3.7
4.57
6.4
5.1
6.25
7.55
6.5
7.55
7.95
Ventilation and Exhaust Fans 335
Table 7-6
Nominal Full-Load Ampere Ratings for
Three-Phase Motors
Full-Load Current
HP
1
⁄4
1
⁄3
1
⁄2
3
⁄4
1
11⁄2
2
3
5
71⁄2
RPM
115 V
230 V
1725
1140
860
1725
1140
860
1725
1140
860
1725
1140
860
1725
1140
860
1725
1140
860
1725
1140
860
1725
1140
860
1725
1140
860
1725
1140
860
0.95
1.4
1.6
1.19
1.59
1.8
1.72
2.15
2.38
2.46
2.92
3.26
3.19
3.7
4.12
4.61
5.18
5.75
5.98
6.50
7.28
8.70
9.25
10.3
14.0
14.6
16.2
20.3
20.9
23.0
0.48
0.7
0.8
0.6
0.8
0.9
0.86
1.08
1.19
1.23
1.46
1.63
1.6
1.85
2.06
2.31
2.59
2.88
2.99
3.25
3.64
4.35
4.62
5.15
7.0
7.3
8.1
10.2
10.5
11.5
(Courtesy Penn Ventilator Company, Inc.)
336 Chapter 7
Table 7-7 Ampere Rating Table for Airmaster Fans
RPM
HP
1
Syn. Speed
⁄30 1050
⁄25 1050
1
⁄20 1550
1140
1050
1
⁄15 1550
1
⁄12 1550
860
1
⁄8 1800
1200
860
1
⁄6 1800
1200
860
1
⁄4 1800
1200
900
1
⁄3 1800
1200
900
1
⁄2 1800
1200
900
3
⁄4 1800
1200
900
1
1800
1200
900
11⁄2 1800
1200
900
2
1800
1200
900
1
3-Phase, 60 Cycle AC
Single-Phase AC
220 Volts
440 Volts
550 Volts
110 Volts
220 Volts
—
—
—
—
—
—
—
—
—
—
—
—
—
—
0.96
1.16
1.45
1.16
1.43
1.75
1.68
2.07
2.90
2.33
2.85
3.45
3.05
3.54
3.74
4.28
4.85
5.81
5.76
6.35
7.21
—
—
—
—
—
—
—
—
—
—
—
—
—
—
0.48
0.58
0.73
0.58
0.72
0.88
0.84
1.04
1.45
1.17
1.43
1.73
1.53
1.77
1.87
2.14
2.43
2.91
2.88
3.18
3.61
—
—
—
—
—
—
—
—
—
—
—
—
—
—
0.38
0.46
0.58
0.47
0.58
0.71
0.67
0.83
1.16
0.93
1.14
1.38
1.22
1.42
1.50
1.71
1.94
2.32
2.30
2.54
2.88
1.90
2.00
2.30
2.40
3.10
3.20
3.80
2.80
2.80
3.40
5.40
3.00
3.60
5.60
4.12
5.50
6.50
5.00
6.00
8.40
7.16
10.00
—
9.86
11.90
—
10.60
12.30
12.90
14.80
16.80
20.00
20.00
22.00
25.00
—
—
—
—
—
—
—
—
1.40
1.70
2.70
1.50
1.80
2.80
2.06
2.75
3.25
2.50
3.00
4.20
3.58
5.02
—
4.94
5.96
—
5.28
6.12
6.48
7.40
8.40
10.10
10.00
11.00
12.50
(continued)
Ventilation and Exhaust Fans 337
Table 7-7 (continued)
RPM
HP
3
5
71⁄2
3-Phase, 60 Cycle AC
Syn. Speed
220 Volts
440 Volts
900
1800
1200
900
1800
1200
900
1800
1200
900
7.21
8.29
8.92
10.20
13.20
13.10
15.60
19.30
20.30
23.80
3.61
4.14
4.46
5.09
6.60
7.05
7.80
9.70
10.20
11.90
550 Volts
2.88
3.32
3.56
4.08
5.28
5.64
6.24
7.72
8.12
9.51
Single-Phase AC
110 Volts
220 Volts
25.00
28.80
30.80
35.40
45.60
48.80
54.00
67.00
70.20
82.40
12.50
14.30
15.40
17.60
22.80
24.40
27.00
33.40
35.20
41.20
(Courtesy Hayes-Albion Corporation)
Overload relay heaters should not be selected solely on the
basis of the data listed in Tables 7-5 and 7-6. Heaters must be
selected in accordance with the actual motor current as shown
on the nameplate. It is also important that ambient temperatures
of the area in which the motor control is located be taken into
consideration when making heater selections. Ambient compensated overload relays are available for abnormal temperature
conditions.
Typical connection diagrams for two-speed, three-phase motors
are illustrated in Figures 7-11 and 7-12. Two-speed motors are
available for most fan lines. Because all two-speed motors are
always single-voltage, it is necessary to specify the available line
voltage phase and frequency when ordering.
Examples of fans equipped with the belt-drive arrangement and
direct-connected motors are shown in Figures 7-13 and 7-14.
Troubleshooting Fans
Fan motors are electrically powered (see Table 7-8). Always turn
off the electricity before attempting to service or repair a fan.
Failure to do so could result in serious injury or even death because
high voltages are involved. Electrical tests on fan motors should be
done by a qualified electrician.
Fan motors mounted in the airstream are cooled by a portion of
the air drawn around them. This acts to hold motor temperatures
338 Chapter 7
THREE-PHASE, TWO-SPEED, ONE-WINDING
VARIABLE TORQUE
T4
T1
T3
T2
T5
T6
SPEED
L1
L2
L3
OPEN
LOW
T1
T2
T3
ALL OTHERS
TOGETHER
HIGH
T6
T4
T5
T1 , T2 , T3
Connection diagram for three-phase, two-speed,
one-winding variable-torque motors. (Courtesy Penn Ventilator Co., Inc.)
Figure 7-11
THREE-PHASE, TWO-SPEED, TWO-WINDING
VARIABLE TORQUE
T1
T11
T3
T2
SPEED
L1
L2
T12
T13
L3
OPEN
LOW
T1
T2
T3
T11 , T12 , T13
HIGH
T11
T12
T13
T1 , T2 , T3
Connection diagram for three-phase, two-speed,
two-winding variable-torque motors. (Courtesy Penn Ventilator Co., Inc.)
Figure 7-12
down and makes it possible for the motor to run continuously at
substantial brake horsepower (bhp) overloads without exceeding
its rated temperature rise.
The actual brake horsepower load has little relation to its nameplate horsepower as long as it remains at or below its rated maximum
Ventilation and Exhaust Fans 339
Belt-driven
propeller fan assembly.
Figure 7-13
(Courtesy Hayes-Albion Corp.)
Fan with directconnected motor.
Figure 7-14
(Courtesy Penn Ventilator Co., Inc.)
temperatures. It is temperature rise that is crucial to the breakdown
or burning out of a fan motor (even though it may be physically
underloaded).
A fan motor will normally run at a temperature too hot to hold a
hand against it, but this will still be at or below the manufacturer’s
temperature rise limit as stated on the nameplate. When a fan motor
340 Chapter 7
Table 7-8 Fan Maintenance and Troubleshooting
Symptom and Possible Cause
Possible Remedy
Fan motor hums but blades do not rotate.
(a) Motor overheated from
thermal overload.
(b) Defective motor.
(a) Turn off fan and wait 20
minutes. If motor is not
defective, it will restart after
cooling off.
(b) Turn off electricity and check
motor starting capacitor.
Fan motor will not start.
(a) Fan unplugged at attic outlet.
(b) Blown fuse or tripped circuit
breaker.
(c) Thermostat set too low.
(d) Defective fan motor starting
capacitor.
(e) Defective fan motor.
(a) Plug fan into outlet.
(b) Replace fuse or reset circuit
breaker. Call electrician if
problem continues.
(c) Turn thermostat to higher
setting.
(d) Test and replace if necessary.
(e) Replace fan motor.
Noisy fan.
(a) Tighten connection or replace.
(b) Tighten.
(c) Tighten if loose connection,
replace if defective, or clean if
dirt accumulation on one blade
is causing imbalance.
(d) Repair or replace motor.
(d) Defective motor bearing.
(e) Not insulated against vibration. (e) Insert foam or rubber pad
between fan motor and
structure surface.
(f) Lubricate motor bearings.
(f) Motor bearing needs
lubrication.
(a) Loose fan blade.
(b) Loose fan motor mounting.
(c) Unbalanced fan blade.
does overheat or burn out, it is usually for one of the following
reasons:
1. Defective motor.
2. Line voltage too high or too low for the rated motor voltage
(more than plus or minus 10 percent voltage deviation is
considered excessive).
Ventilation and Exhaust Fans 341
3. The belts on belt-driven fans may be too tight or too loose,
causing slippage and consequent loss of the cooling effect of
air passing around the motor.
4. Improper pulleys on belt-driven fans will result in too high a
fan rpm, which causes overloading.
5. Backward- and forward-curved wheel centrifugal fans or roof
ventilators running backward will guarantee an overload condition. Remember that all centrifugal fans blow in one direction only, regardless of rotation; propeller fans that run
backward blow backward.
6. Propeller fans may be starved for air as a result of insufficient
intake (or outlet) area. The fans are literally starved for air,
which causes the static pressure to rise and the brake horsepower
load on the motor to increase. The air that flows around the
motor is also reduced, causing the motor to overheat. Attic fans
are frequently damaged as a result of inadequate outlet area.
Fan Selection
The following information is generally required for the selection of
a suitable fan:
1.
2.
3.
4.
5.
6.
7.
8.
Volume of air required (cfm)
Static pressure (SP)
Type of application or service
Maximum tolerable noise level
Nature of load and available drive
Ambient and airstream temperature
Mounting arrangement of the system
Available line voltage
The volume of air required refers to the volume of air that must
be moved by the fan to meet the needs of the building or space. It is
expressed in cubic feet per minute and is determined by dividing the
total cubic feet of air space by the required number of air changes
necessary to give proper ventilation.
The static pressure of a fan may be defined as the total pressure
diminished by the fan velocity. In other words, it is the resistance
offered by the system (ducts, air intakes, and so on) to the flow of
air. After the duct sizes have been determined, it is necessary to calculate the static pressure of the system so that the proper fan can
be selected which will handle the desired volume of air (that is, the
342 Chapter 7
required cfm) against the static pressure of the system. The various
fan manufacturers provide tables indicating the operating characteristics of various-size fans against a wide range of static pressures.
These tables list static pressures for different sizes of various fans.
The type of application (or service) is often an important consideration in what kind of fan is used in an installation. For example,
a duct system will offer sufficient resistance to require a centrifugal,
tubeaxial, or vaneaxial fan. A propeller fan is usually recommended
for an installation without a duct system. Other factors, such as the
volume of air that must be moved, the allowable noise level, the air
temperature, use for general or local ventilation, and cost, are also
important considerations in fan selection.
The maximum tolerable noise level is the highest acceptable
noise level associated with air exchange equipment. The fan should
be of suitable size and capacity to obtain a reasonable operating
speed without overworking.
The nature of load and available drive is an important factor in
controlling the noise level. High-speed motors are usually quieter
than low-speed ones. Either belt- or direct-drive units are used in
fan installations, and a high-speed motor connected to the fan with
a V-belt offers the quietest operation.
The dry-bulb temperature of either ambient air or exhauststream air (ambient or airstream temperature) is a determining factor in selecting a suitable fan. Most fans operate satisfactorily at
temperatures up to about 104°F (40°C). Special fans that can operate at higher temperatures are also available. For example, standard
belt-driven tubeaxial fans are usable for temperatures up to 200°F
(where the motor is out of the airstream).
The mounting arrangement of the system is directly determined
by the application or service of the fan. Certain types of fans will
prove to be more suitable than others, depending on the kind of
installation. Fan manufacturers often offer useful recommendations
for mounting arrangements.
The available line voltage will determine the size and type of fan
motor most suitable for the installation. Motor voltage designations
conform to the following system of voltages now used throughout
the country: 115 volts, 230 volts, and 460 volts. Motors for special
voltages (that is, 117, 480, or 575 volts) are available on special
order.
Fan manufacturers provide information and assistance in selecting the most suitable fan or fans for your installation. Remember
that ventilation requirements vary under different climatic conditions, and it is impossible to provide exact rules for determining the
Ventilation and Exhaust Fans 343
Table 7.9
Minimum Fan Capacity (CFM) for Various Sections
of the Country
Minimum Fan Capacity Needed
For Satisfactory Results (CFM)
Approx.
Volume of
House (ft3)
North
Central
3000
4000
5000
6000
7000
8000
9000
10,000
11,000
12,000 24⬙
13,000
14,000
15,000
16,000
17,000
18,000
19,000
20,000
21,000
22,000
1000
1320
1650
2000
2310
2540
3000
3330
3630
4000
4290
4620
5000
5280
5610
6000
6270
6660
7000
7260
2000
2640
3300
4000
4620
5280
6000
6660
7260
8000
8580
9240
10,000
10,560
11,220
12,000
12,540
13,320
14,000
14,520
24⬙
36⬙
30⬙
South
24⬙
3000
4000
5000
6000
30⬙
7000
36⬘
8000
9000
10,000
11,000
12,000
48⬙ 13,000
14,000
42⬙
15,000
16,000
17,000
18,000
19,000
20,000
21,000
22,000
30⬙
42⬙
(Courtesy Hayes-Albion Corporation)
variables of local climate and topography (see Table 7-9). Allowances
must be made for these climatic variables.
The following suggestions are offered only as a general guide to
the selection of a fan and should not be construed as applying in
every situation.
1. Use a 1⁄2 hp, 1⁄3 hp, or 1⁄4 hp 860-rpm direct-drive fan on
three-phase motor voltages whenever possible to eliminate the
possibility of single-phase magnetic hum.
2. A belt-driven fan is less expensive, less noisy, more flexible, and
more adaptable to capacity change than the direct-drive type.
344 Chapter 7
3. Prolonged motor life can be expected of direct-driven fans
using other than shaded-pole motors. For that reason, 1550rpm and 1050-rpm motors should be avoided when very
heavy duty and/or extremely long motor life is required.
4. Use a propeller fan when operation offers little or no resistance, or when there is no duct system.
5. Use a centrifugal or axial-flow fan when a duct system is
involved.
6. Never try to force air through ducts smaller than the area of
the fan.
Fan Installation
The following recommendations are offered as guidelines for
proper fan installation.
1. Install the fan and air intake openings at opposite ends of the
2.
3.
4.
5.
6.
7.
8.
enclosure so that the intake air passes lengthwise through the
area being ventilated (see Figure 7-15).
When possible, install exhaust fans or air outlets on the leeward side so that the air leaves with the prevailing winds (see
Figure 7-16).
When possible, install ventilation (supply) fans or air intakes
on the windward side so that the entering air utilizes pressure
produced by prevailing winds (see Figure 7-17).
Provide a net intake area at least 30 percent greater than the
exhaust fan opening.
When filters are used, increase the net intake area to allow
minimum pressure loss from resistance of the filter.
Steam, heat, or odors should be exhausted by fans using
totally enclosed motors mounted near the ceiling. The air
intakes should be located near the floor (see Figure 7-18).
An explosion-proof motor with a spark-proof fan should be
used when the exhaust air is hazardous.
Spring-mount fans and connect them to the wall opening by a
canvas boot when extremely quiet operation is required.
Fan Installation Checklist
A properly installed fan motor (unless defective) will operate efficiently and will never overheat or burn out. To ensure proper installation, the following guidelines are suggested:
Ventilation and Exhaust Fans 345
SHOPS, STORES,
OFFICES
FRONT
FRONT
REAR
PLAN VIEW
REAR
CORRECT WAY
INCORRECT WAY
FRONT
GRILLE
RESTAURANTS
GRILLE
RANGE
RANGE
PARTITION
PARTITION
PLAN VIEW
FRONT
REAR
REAR
INCORRECT WAY
CORRECT WAY
VENTILATING
BLIND ROOM
PLAN VIEW
FRONT
DUCT
REAR
VENTILATING ROOM
WITH FALSE CEILING
CEILING
SIDE ELEVATION
REAR
FRONT
Figure 7-15
Locations of fans and air intake openings.
(Courtesy Hayes-Albion Corp.)
WIND DIRECTION
SUPPLY AIR
INTAKE
EXHAUST
FAN
Exhaust fan installed on the leeward side, away from
prevailing winds.
Figure 7-16
346 Chapter 7
WIND DIRECTION
SUPPLY AIR
FAN
Supply air fan installed on the windward side, with the
prevailing winds.
Figure 7-17
AUTOMOBILE PAINT SHOP
PENTHOUSE UNIT
INTAKE
HOOD OR
DROP
CURTAIN
INTAKE
VATS
WALL OR PARTITION
SIDE ELEVATION
ONE STORY BUILDING
HOOD OR
DROP
CURTAIN
FAN
VATS
Figure 7-18
SPACE FOR AUTO BEING
SPRAY PAINTED
FUME AND HEAT REMOVAL
EXHAUST OPENING SHOULD
BE APPROX. 41⁄2 FEET
ABOVE FLOOR
SIDE ELEVATION
Recommended locations for exhaust openings.
(Courtesy Hayes-Albion Corp.)
1. Check the line current to be sure it is not more than plus or
minus 10 percent voltage deviation.
2. Check belt tension for looseness after the first or second day
of operation.
3. Check to be sure the fan is running in the right direction.
4. Inspect and lubricate fans subject to heavy usage. Do this
after the first 15,000 hours or 5 years of service (whichever
comes first).
Ventilation and Exhaust Fans 347
5. Use open, drip-proof motors where fan motors are installed
outside the airstream.
6. Use enclosed, nonventilated, air-over motors where fan
motors are mounted in the airstream to reduce obstruction by
dirt, grease, or other contaminants.
Air Volume Control
Sometimes it becomes necessary to vary the air volume handled by
a fan. The following methods can be used for this purpose:
1.
2.
3.
4.
5.
6.
7.
Dampers placed in the duct system.
Changing the pulley on the fan motor.
Changing the pulley on the fan.
Using variable-speed pulleys.
Using variable-speed motors.
Using variable inlet vanes on fans.
Reduction or increase of speed through power control.
Noise Control
In order to decrease the noise associated with the air exchange
equipment, the following recommendations should be observed:
1. The equipment should be located a reasonable distance from
important rooms.
2. The fans should be of proper size and capacity to obtain reasonable operating speed.
3. The equipment should be mounted on resilient bases made
from a sound-dampening material.
4. When possible, the quieter high-speed AC motors with beltdriven fans should be used.
Fan Applications
Many different fans are used in ventilation and air-circulation systems, and these fans are classified on the basis of certain design and
operating characteristics. Fan applications, on the other hand, are
classified by the specific function they serve in the ventilation or aircirculation system. Among the numerous fan applications used for
ventilation and air circulation are the following:
1. Attic fans
2. Exhaust fans
348 Chapter 7
3.
4.
5.
6.
Circulating fans
Kitchen fans
Cooling tower fans
Unitary system fans
Attic fans are generally propeller types used during the summer
to draw the cool night air through the structure and discharge it
from the attic. The air can be discharged through windows or
grilles or directly through an attic exhaust fan. The air is circulated,
not conditioned.
Exhaust fans are used in local ventilation to remove contaminants at their source, or as a general means of discharging air from
a space (for example, attic exhaust fans, wall fans, bathroom fans).
Hood exhaust fans used with a duct system are generally centrifugal types. Because wall fans operate against very low resistance or
no resistance at all, they are most commonly propeller types.
Circulating fans and kitchen fans are propeller types used for air
circulation purposes. Cooling tower fans are also generally propeller types, although centrifugal fans have also been used in installations requiring a forced draft.
Unitary system fans are centrifugal or propeller fans used in unit
ventilators, unit heaters, unit humidifiers, and similar types of equipment. A propeller fan is used in these units when no ductwork exists.
Attic Ventilating Fans
A noninsulated attic on a hot summer day will experience temperatures as high as 130˚F to 150˚F. This accumulated heat seeps down
through the ceiling and raises the temperatures in the rooms below,
making living and sleeping areas very uncomfortable. This hot air
from an uninsulated attic also increases the load on the air conditioner, which will raise the energy costs during the summer months.
After sunset, the outside temperature sinks to pleasant cool levels,
but the indoor air (especially in the upstairs bedrooms of a twostory house) remains uncomfortably hot with temperature readings
that can reach as high as 85˚F. This condition results from the fact
that a house loses accumulated heat at a very slow rate.
This condition can be alleviated considerably by installing an
attic ventilating fan. Such a fan placed in the attic will cool the air
by replacement; that is, it will ventilate rather than condition. An
attic ventilating fan can reduce temperatures in the attic by as much
as 20 to 30 percent, and by approximately 10 to 15 percent in the
bedrooms immediately below the attic.
Ventilation and Exhaust Fans 349
Attic ventilating fans are controlled by a thermostat located in
the attic or in the fan housing. The thermostat turns the fan on at a
preset temperature and shuts it off when the temperature is lowered
to the minimum setting in the thermostat preset temperature range.
Many attic fans are equipped with a firestat, which will shut off the
fan if there is a fire in the house.
In areas where high humidity is a problem, the fan should be
equipped with a humidistat to remove excess moisture from the
attic during the winter months. Moisture accumulating in the attic
will contribute to the formation of ice dams on the roof. Ice will
also form on the rafter surfaces inside the attic, which may lead to
rot and damage to the roof framing.
Because of the low static pressures involved (usually less than
0.125 inch), disc or propeller fans with the blade mounted
directly on the motor shaft are generally recommended for attic
installation. It is recommended that these fans have quiet operating characteristics and sufficient capacity to give at least 30 air
changes per hour.
The two general types of attic fans in common use in houses and
other buildings are the following:
1. Boxed-in fans
2. Centrifugal fans
The boxed-in attic fan is installed within the attic in a box or
suitable housing, located directly over a ceiling grille or in a bulkhead enclosing an attic stair. This type of fan can be connected to
individual room grilles by means of a duct system.
In operation, outside cool air entering through the windows in
the downstairs rooms is discharged into the attic space and escapes
to the outside through louvers, dormer windows, or screened openings under the eaves. A general arrangement showing a typical
installation of this type of fan is illustrated in Figure 7-19.
The installation of a multiblade centrifugal attic fan is shown in
Figure 7-20. At the inlet side, the fan is connected to exhaust ducts
leading to grilles, which are placed in the ceiling of the two bedrooms. The air exchange is accomplished by admitting fresh air
through open windows, moving it up through the suction side of
the fan, and finally discharging it through louvers.
The fan shown in Figure 7-21 is of the centrifugal curved-blade
type, mounted on a light angle-iron frame, which supports the fan
wheel, shaft, and bearings, with the motor that supplies the motive
power to the fan through a belt drive.
350 Chapter 7
EXHAUST
FAN (LOCATED
IN ATTIC)
DOOR OPEN
AIR INLET
WINDOW
DOOR OPEN
DOOR
OPEN
AIR
INLET
WINDOW
DOOR O
PEN
Figure 7-19
Attic ventilation system.
The air inlet in this installation is placed close to a circular opening that is cut in an airtight board partition, which serves to divide
the attic space into a suction and discharge chamber. The air is
admitted through open windows and doors and then drawn up the
attic stairway through the fan into the discharge chamber, from
which it flows through the attic open window.
For best results, the outlet area for an attic fan should be 11⁄2
times the area of the fan. Satisfactory results will be obtained as
long as the area is at least equal to the blade area of the fan.
Recommended dimensions for attic fan exhaust outlets are given in
Table 7-9.
Tables 7-10, 7-11, and 7-12 provide data for square- and triangular-type louvers used with various fan diameters. These tables
Ventilation and Exhaust Fans 351
AIR DISCHARGE
CENTRIFUGAL FAN
AIR
INLET
MOTOR
DUCT
DUCT
GRILLE
GRILLE
AIR INLET
(WINDOW OPEN)
AIR INLET
Figure 7-20
BEDROOM
AIR
INLET
BEDROOM
Multiblade centrifugal attic fan connected to exhaust ducts.
CENTRIFUGAL FAN
ATTIC
DOOR
BOARD
PARTITION
MOTOR
AIR OUTLET
DOOR
ANGLE
IRON
FRAME
DOOR
AIR INLET THROUGH
WINDOWS
Figure 7-21
Centrifugal curved-blade fan.
352 Chapter 7
Table 7-10 Recommended Dimensions for Attic Fan
Exhaust Outlets
Recommended Dimensions of Attic Fan Exhaust Outlet
Fan Diameter
Air Delivery Range (cfm) *Free Outlet Area Needed (ft2)
24⬙
30⬙
36⬙
42⬙
48⬙
3500/5000
4500/8500
8000/12000
10000/15500
12000/20000
4.70
7.35
10.06
14.40
18.85
*1.5 times fan area
(Courtesy Hayes-Albion Corporation)
Table 7-11 Data for Square-Type Louvers
Minimum Size of Square Outlet (inches)
Metal Shutters
Wood Slats
Fan
Diameter
Automatic (90%
Open Area)
Fixed (70%
Open Area)
Fixed (60%
Open Area)
24⬙
30⬙
36⬙
42⬙
48⬙
26 ⫻ 26
32 ⫻ 32
38 ⫻ 38
44 ⫻ 44
50 ⫻ 50
32 ⫻ 32
39 ⫻ 39
45 ⫻ 45
54 ⫻ 54
62 ⫻ 62
34 ⫻ 34
42 ⫻ 42
49 ⫻ 49
60 ⫻ 60
68 ⫻ 68
(Courtesy Hayes-Albion Corporation)
include the net free areas for 1-inch mesh wire screening.
Remember that in order to keep insects and other foreign objects
out of the attic, the exhaust air outlets should be covered with
1
⁄2-inch or 1-inch wire mesh screen. The fan should be boxed-in on
the intake side with conventional fly screening. This screening has
Ventilation and Exhaust Fans 353
Table 7-12 Data for Triangular-Type Louvers
Fan
Diameter
*Height of Triangular Louvers (for different roof pitches)
6
7
8
⁄12 Pitch
⁄12 Pitch
⁄12 Pitch
⁄12 Pitch
One Louver
One Louver
One Louver
One Louver
24⬙
30⬙
36⬙
42⬙
48⬙
2⬘0⬙
2⬘6⬙
3⬘0⬙
3⬘3⬙
3⬘10⬙
5
2⬘2⬙
2⬘9⬙
3⬘3⬙
3⬘9⬙
4⬘3⬙
2⬘4⬙
3⬘0⬙
3⬘6⬙
4⬘1⬙
4⬘7⬙
2⬘6⬙
3⬘3⬙
3⬘9⬙
4⬘4⬙
4⬘9⬙
*Heights given are for one triangular louvered opening only; when two openings are used, reduce heights by
approximately 80%.
(Courtesy Hayes-Albion Corp.)
Fan mounted at the attic window with the ceiling
opening in central hallway. (Courtesy Hayes-Albion Corp.)
Figure 7-22
354 Chapter 7
only 50 percent free area; therefore, the boxing must have a total
area twice that of the inlet opening.
The location of the attic fan always depends on the design of the
structure. In a house having a suitably sized window in an attic end
wall or dormer, the best results (and fewest construction problems)
can usually be obtained by mounting the fan directly against the
window (see Figure 7-22). An automatic shutter should be installed
outside the window for window-mounted fans. If the window is
opened and the fan is mounted inside the opening, louvers should be
installed a few inches in front of the fan to keep rain out of the attic.
In one-floor houses, the ceiling openings can be installed in any
convenient central location (see Figure 7-23). In houses of two or
more stories, the opening is generally located in the ceiling of the
top-floor hallway. Again, a central location is usually best. The ceiling opening and its accompanying grille or shutter must be of sufficient size to avoid excessive resistance to airflow, permitting the
airstream to pass through at a moderate, quiet velocity.
Figure 7-23
Fan mounted in ceiling hallway. (Courtesy Hayes-Albion Corp.)
Some attic fans require periodic lubrication of their motor bearings. Check the fan manufacturer’s installation and operating
instructions for the recommended lubrication schedule. Lubricate
the bearings by pouring oil into the oil cups. Fan motors with
sealed bearings do not require lubrication.
Clean the fan housing and blades in the spring before the beginning of the cooling season. The screens on the fan vent, soffits, and
attic vents should also be cleaned at this time. Blocked vents will
prevent air from being drawn into or exhausted from the attic.
Ventilation and Exhaust Fans 355
Exhaust Fans
Exhaust fans are small, electrically operated fans used to remove
odors, heat, and moisture from kitchens and bathrooms. They are
commonly mounted in the wall or ceiling. Kitchens also will have
an exhaust fan in the range hood over the stove.
Exhaust fans require very little maintenance. Wash the fan
housing and fan blades every 6 months. Check the fan in the range
hood for a grease filter. This should be cleaned every 3 months or
more often depending on how much cooking is being done.
Kitchen Exhaust Fans
In estimating the requirements for ventilating kitchens, it is customary to allow a complete change of air every 2 minutes. In many
cases, it is also desirable to have all the extracted air leave via hoods
or canopies located over ranges, steam tables, dishwashers, and
similar sources of localized heat and contaminants.
Allowing for a complete change of air every 2 minutes only
applies to average conditions, and modifications from this average
should be made on the basis of the kitchen size and the type of heatand vapor-producing equipment.
An entrance velocity at the hood opening of 100 fpm is considered satisfactory as an allowance for average conditions. For very
light cooking, an entrance velocity of only 50 fpm is usually sufficient. Heavy cooking may require an entrance velocity of 150 fpm
or higher.
Exhaust hoods are usually located overhead in the majority of
kitchen exhaust systems. They should be placed directly over the heatand vapor-producing equipment and approximately 80 inches from
the floor line to allow sufficient head clearance.
An overhead exhaust hood should be larger in horizontal area
than the source of the heat or fumes. When located not over 2 feet
above the range, the hood should be 6 inches larger in all directions
than the overall dimensions of the range when the distance exceeds
2 feet. Thus, a range 2 feet by 7 feet with a clearance of 2 feet would
require a hood 3 feet by 8 feet. Such a hood would have an area of
24 square feet. Using an average entrance velocity at the hood of
100 fpm, the volume of air to be handled would be 2400 cfm.
The area of the branch duct leading from the hood should be
made 1⁄16 of the hood area (that is, 24 square feet ⫼ 16) or 1.5 square
feet. With the hood located 4 feet above the range, the dimensions
would be 4 feet by 9 feet with a branch duct area of 2.25 square feet.
If a supply system is required, the amount of exhaust air should
be greater than the volume of supply air to prevent undesirable
356 Chapter 7
cooking odors spreading to adjoining rooms. The supply air is usually figured on the basis of 75 percent of the exhaust air.
Bathroom Exhaust Fans
An air change every 3 minutes, or 20 complete changes per hour, is
desirable for bathroom ventilation. Systems of this type should be
entirely different and separated from other ventilating systems.
Bathrooms located on the inside of a structure require ducts to
exhaust air to the outside.
Compact fans are especially recommended for use in bathroom
exhaust systems. Their compact design requires a minimum of space,
and they are capable of operating against the resistance of the system.
Note
In tightly constructed and insulated houses, vent fans, clothes dryers,
and kitchen exhaust fans can create a negative pressure that draws
air into the house through holes in the framing, chimneys, and even
exhaust flues.This can cause backdrafting in combustion appliances,
which can be a serious health hazard. While the bathroom can be
maintained at a negative pressure to control odor problems, the
remainder of the house should be maintained at a slightly positive
pressure. In hot, humid climates, it is best to operate the exhaust fan
only when the bathroom is in use, so that the negative pressure does
not draw humid outside air into the building cavities.
Whole-House Ventilation
Whole-house ventilation is a ventilating system in which a large
centrally located fan provides natural air-conditioning. In very dry
climates where hot days and very cool nights are the norm, wholehouse ventilating fans often provide a suitable replacement for airconditioning. Cooler outside air is drawn in through the windows
on the lower floors during the night and forced out through the
attic vents (see Figure 7-24). This system produces a steady supply
of filtered, fresh air to all the living spaces of the house. It works
most efficiently when the outdoor temperature is below 82˚F. A
whole-house ventilation system can also reduce air-conditioning
costs by using it instead of the air conditioner to cool the house
between the heating and cooling seasons, or by using it to ventilate
the house before turning on the air conditioner.
Note
Whole-house ventilation is not very suitable for humid climates
because it draws excess moisture into the house.
In cold climates, the type of whole-house ventilator used in the
system is commonly designed to capture some of the heat from the
Ventilation and Exhaust Fans 357
EXHAUST AIR
OUTLET
ROOM AIR EXHAUST DUCTS
EXHAUST
FAN
SUPPLY FAN
FRESH AIR INLET
BALANCED VENTILATION
ROOM AIR EXHAUST DUCTS
HEAT RECOVERY
VENTILATOR
EXHAUST AIR OUTLET
FRESH AIR INLET
BALANCED HEAT-RECOVERY VENTILATION
Figure 7-24
Typical whole-house ventilation systems.
(Courtesy U.S. Department of Energy)
358 Chapter 7
air before it is exhausted from the attic. These are sometimes called
air-to-air heat exchangers or heat recovery ventilators (HRVs).
These air-to-air heat exchangers are designed to recover as much as
80 percent of the heat energy from the indoor air before it leaves
the attic.
Some whole-house ventilators are designed to add or remove
moisture from the air. These units are sometimes called energy
recovery ventilators (ERVs). An energy recovery ventilator operates
by balancing the humidity levels between the air drawn into the
structure and the air exhausted from the attic. During the winter
when the outdoor air is drier, moisture is added to the air by the
unit as it is drawn into the house. In the summer when the air is
more humid, the energy recovery ventilator removes moisture from
the air before it is blown out of the attic.
The fans used in whole-house ventilation are much larger
than the standard attic ventilating fans because they are required
to move much more air. These are high-velocity cooling fans
commonly installed in a hallway ceiling directly beneath the
attic. Because some of these fans are too large to be installed
between ceiling joists, a box frame is constructed on top of the
joists to house them. The box frame must be built by the homeowner or building contractor because it is not provided by the
fan manufacturer.
These fans are either belt-driven or direct drive. Belt-driven fans
are the quieter of the two, but they require belt replacement every 2
or 3 years. Direct-drive fans are almost maintenance-free.
Note
Low-velocity whole-house ventilating fans should not be confused
with the high-velocity types used in whole-house ventilation systems. The former are used only to provide a continuous stream of
fresh air and remove indoor pollutants.
A whole-house ventilation fan is switched on when the outside
temperature falls below the indoor temperature and continues to
operate throughout the night. The fan can be operated both manually and automatically through centrally located controls. Many
installations have only a wall-mounted manual on-off switch.
Warning
Windows must be open when operating a whole-house ventilator
in order to prevent backdrafting. Depressurization can be prevented if the total open area of the windows is approximately
equal to the total net free area of the attic.
Ventilation and Exhaust Fans 359
Select a whole-house ventilator large enough to deliver 20 air
changes per hour (ACH). A typical sizing method for these fans is
to divide the volume of the house (width ⫻ height ⫻ length) by 3 to
obtain the air changes per hour for the fan.
Whole-house ventilators require very little maintenance. If the
unit is equipped with a filter, it will have to be periodically cleaned
or replaced. Inspect the fan blades from time to time and clean
them when there is a noticeable buildup of dirt or grease.
Chapter 8
Air-Conditioning
Although it is a commonly held belief, it is incorrect to regard airconditioning as simply the cooling of air. Conditioning the air of a
space means to change it in whatever way necessary to improve the
comfort of those living or working there. This may mean warming
air to a livable temperature and holding it there; cooling the air;
adding or subtracting moisture; filtering out contaminants such as
dust, bacteria, and toxic gases; and maintaining a proper distribution and movement of the air. In general, air-conditioning includes
the following processes:
1.
2.
3.
4.
5.
6.
Heating
Cooling
Humidification
Dehumidification
Cleaning and filtering
Air movement (circulation)
Each of these processes contributes in some way to the improvement of those conditions that affect the comfort and health of an
individual. For example, air nearly always contains certain impurities, such as ammonia, sulphurous acid, and carbon dioxide. The
last named is a product of exhalation from the lungs and the combustion process in internal combustion engines. It is so universally
present (about in the same proportions everywhere, except where
concentrated by some local conditions) that it may be regarded as
a normal part the air. Air-conditioning is an efficient means of
eliminating carbon dioxide from the air. The same is true of other
impurities. Some dry strainer filters used in air-conditioning systems are capable of removing 99.98 percent of radioactive dust
from the air.
To understand how an air-conditioning system works and how
to calculate cooling loads, you should have a basic understanding
of the physical properties of air and how its moisture content, temperature, and pressure will influence your calculations. These topics
and the associated terminology are described in the following
sections.
361
362 Chapter 8
Properties of Air
Air is composed of water vapor and dry air. These two components
are combined in such a way that neither loses its distinct characteristics. A number of different terms are used to describe the qualities
or properties of air, but the two terms essential in heating and cooling calculations are humidity and temperature.
Humidity
Humidity is a general term used to refer to the water vapor (moisture) content of air. When this term is used, it is usually in reference
to the sensation (or lack of sensation) of moisture in the air. For
purposes of heating and cooling calculations, the more narrowly
defined terms of absolute humidity, relative humidity, and specific
humidity are used.
Water vapor is actually steam at low temperatures and, consequently, low pressures; hence its properties are those of steam.
According to Dalton’s law, in any mechanical mixture of gases,
each gas has a partial pressure of its own, which is entirely independent of the partial pressures of the other gases of the mixture.
Note
In all air-conditioning calculations it should be understood that the
dry air and water vapor composing the atmosphere are separate
entities, each with its own characteristics. Water vapor is not
dissolved in the air in the sense that it loses its own individuality
and merely serves to moisten the air.
Air is capable of holding, as a mechanical mixture within itself,
varying quantities of water vapor, depending on its temperature.
When air absorbs moisture; that is, when it is humidified, the latent
heat of evaporation must be supplied either from the air or from
another source. And conversely, when the moisture from the air is
condensed, the latent heat of condensation (equivalent to the latent
heat of evaporation) is recovered.
Air is said to be saturated when it contains all the water vapor it
can hold. If partly saturated air is reduced in temperature until the
amount of moisture present corresponds to the amount that the air
is capable of holding at the given temperature, it will become saturated air.
If the temperature of the air is still further reduced, its ability to
hold moisture will be reduced accordingly. As a result, the excess
moisture will be condensed, which means that it will be converted
from a vapor to a liquid. This is the reverse of the process that
occurred as the air absorbed the moisture.
Air-Conditioning 363
Converting liquid water into water vapor requires a great quantity of heat. The heat necessary for this process is used only in performing the conversion, the temperature of the liquid and the vapor
being the same at the end of the process. If the conversion is from
liquid to vapor, this involves the latent heat of evaporation. The
latent heat of condensation is involved if the conversion is from
vapor to liquid.
Cold air is saturated when it contains very small quantities of
water vapor, whereas warm air is not saturated until it contains
larger quantities of vapor. For example, air at zero degrees
Fahrenheit is saturated when it contains but one-half of one grain
(1/7000 lb) of water vapor per cubic foot. Air at 70°F is saturated
when it contains 8 grains of vapor per cubic foot, while at 83°F, 12
grains per cubic foot are required to saturate.
Absolute Humidity
Absolute humidity is the actual mass of water vapor in one cubic
foot of air (that is, the weight of water vapor per unit volume of air)
and is expressed in grains or pounds per cubic foot (1 lb 7000
grains), or grams per cubic centimeter. Absolute humidity is
equivalent to the density of the air.
Specific Humidity
Specific humidity is the weight of water vapor per pound of dry air.
Do not confuse specific humidity with relative humidity. The latter
term indicates the percentage of water vapor, the former the weight.
Relative Humidity
Relative humidity is the ratio of absolute humidity to the maximum
possible density of water vapor in the air at the same temperature.
In other words, it is a percentage or ratio of water vapor in the mixture of dry air and water vapor at a certain temperature relative to
the maximum quantity that the volume of air could possibly carry
at that temperature. The relative humidity at any given temperature
can be obtained by first using a sling psychrometer to determine the
amount of moisture (that is, water vapor) actually present in the air
and then dividing this figure by the amount of moisture that the air
can hold at that temperature, and multiplying the result by 100 in
order to obtain the percentage factor.
Drying Effect of Air
The drying effect of air varies approximately inversely with its relative humidity. In other words, the drying effect decreases as the relative humidity increases. It should be noted that it is relative
humidity that determines the drying effect of air, and this effect
364 Chapter 8
depends on both the temperature and the water content of the air
since relative humidity depends on both these factors.
The quantity of heat that dry air contains is very small because
its specific heat is low (0.2415 for ordinary purposes), which means
that 1 lb of air falling 1°F will yield only 0.2415 of the heat that
would be available from 1 lb of water reduced one degree in temperature. The presence of water vapor in the air materially
increases the total heating capacity of the air because of the latent
heat of the vapor itself.
Most hygroscopic materials in the presence of dry air, even at
high, dry-bulb temperatures, may actually be cooled rather than
heated. This occurs because the dry air immediately begins to evaporate moisture form the material.
The Dew Point
The dew point is the temperature of saturation for a given atmospheric pressure. In other words, for a given atmospheric pressure
(barometer), it is the temperature at which moisture begins to condense in the form of tiny droplets, or dew.
The saturation temperature for any given quantity of water
vapor in the atmosphere is known as the dew point. Any reduction
in temperature below the dew point will result in condensation of
some of the water vapor present, with a consequent liberation of
the latent heat of the vapor, which must be absorbed before any further condensation can take place.
If the vapor pressure of the water vapor in a given space is the
same as the vapor pressure of saturated steam at the prevailing drybulb temperature, the space contains all the water vapor it can hold
at that temperature. The term saturated water vapor is applied to
water in this state.
Humidification
Humidification may be defined as the addition of moisture to the
air. The conditioning machine that functions to add moisture to
the air is called a humidifier. A humidifier is commonly a lowpressure, low-temperature boiler in which the water is evaporated
and the vapor (low-pressure steam) thus formed is caused to mix
with air.
In a sense, water functions as a natural humidifier by acting as
the medium that conveys heat to the air and as the source of the
water vapor required to saturate the heated air. Contrast this with
what takes place in a humidifier unit. A machine functions as a
humidifier when the temperature of the spray water is above that at
which the moisture in the air will condense.
Air-Conditioning 365
Dehumidification
Dehumidification may be defined as the removal of moisture from
the air. A machine that functions to remove moisture from the air is
called a dehumidifier.
The removal of moisture from the air is accomplished by condensation, which takes place when the temperature of the air is
lowered below its dew point. The condensation thus formed falls
into the tank of the conditioning machine. In this case the water
acts solely as a conveyor of heat from the air (in addition to its
cleansing action) and, as such, the finely divided mist is extraordinarily effective (practically 100 percent).
Some conditioning machines can function both as humidifiers or
dehumidifiers. This can often be done without alteration to the unit
except that the valves in the control line from the dew point thermostat on some designs are adjusted to connect the steam control
of the water heater for winter operation, and to connect the threeway mixing valve to the water supply line for summer operation.
Whether the requirement is humidification or dehumidification,
the unit always operates under accurate automatic control, maintaining the required indoor conditions winter and summer, regardless of the outdoor weather.
Temperature
Temperature is a general term used to describe the sensation (or
lack of sensation) of heat in the air. Among the more specific terms
used in the heating and cooling calculations to describe the air
temperature are dry-bulb temperature and wet-bulb temperature.
Note
Sometimes both temperature and humidity are used in conjunction with one another as a calculation factor, and the temperature-humidity index is an example of this. By definition, the
temperature-humidity index (formerly called the discomfort index)
is a numerical indicator of human discomfort resulting from
temperature and moisture. It is calculated by adding the indoor
dry-bulb and the indoor wet-bulb thermometer readings, multiplying the sum by 0.4 and adding 15. The results you obtain are
the same as those used for the effective temperature index (see
Standards of Comfort). This can be worked out from the data
provided in Table 8-1.
Dry-Bulb and Wet-Bulb Temperatures
Dry-bulb temperature is the actual temperature of air as measured by
an ordinary thermometer. Wet-bulb temperature is the temperature at
366 Chapter 8
Table 8-1 Recommended Scale of Interior Effective
Temperatures for Various Outside Dry-Bulb Conditions
Degrees
Outside
Degrees Inside
Dry-Bulb
Dry-Bulb
Wet-Bulb
Dew Point
Effective
Temperature
100
95
90
85
80
75
70
82.5
81.0
79.5
78.1
76.7
75.3
74.0
69.0
67.7
66.5
65.3
64.0
63.0
62.0
62.3
60.8
59.5
58.0
56.6
55.6
54.5
76.0
74.8
73.6
72.5
71.3
70.2
69.0
which the air would become saturated if moisture were added to it
without the addition or subtraction of heat. It is the temperature of
evaporation. In actual practice, the wet-bulb temperature reflects
humidity conditions in the area. A high wet-bulb reading, for
example, means that the humidity is also high.
The wet-bulb temperature in conjunction with the dry-bulb temperature is an exact measure of both the humidity of the air and its
heat content. In air-conditioning the dry-bulb temperature and the
wet-bulb temperature must both be controlled if the effects of air
are to be regulated.
If the bulb of an ordinary thermometer is surrounded with a moistened wick and placed in a current of air and superheated water vapor,
it will be found that a reading at some point below the dry-bulb temperature is obtained. The minimum reading thus obtained is the wetbulb temperature of the air. The reduction in temperature is caused by
the sensible heat being withdrawn from the air to vaporize the water
surrounding the wet bulb, thus raising the dew point of the air.
Note
The point of equilibrium at which the withdrawn sensible heat
balances with the heat of vaporization necessary to bring the dew
point up to the same point is the wet-bulb temperature.
In this transformation of energy from sensible heat of vaporization,
there is no change in the total amount of energy in the mixture. For
this reason, the wet-bulb temperature, once fixed, is an indication
of the total heat in any mixture of air and water vapor.
Air-Conditioning 367
The daily temperature range is the difference between the maximum and minimum dry-bulb temperatures during a 24-hour period
on a typical day for a heating or cooling system. It is used in determining the factors used in making Btu tabulations. The Btu tabulation
cooling form illustrated in Figure 8-9 shows their use. In Figure 8-9
you will note that the tables labeled “wall factors” and “ceiling factors” each have a column reserved for four different degrees of
daily temperature range (that is, 15°F, 20°F, 25°F, and 30°F).
Reading across from left to right, the different daily temperature
ranges intersect with a number of other columns representing differences in the dry-bulb temperatures. The selection used will depend on
the type (or absence) of insulation.
Wet-Bulb Depression
Because outdoor summer air is rarely fully saturated, there is usually a considerable difference between its dry-bulb and its wet-bulb
temperatures. This difference is referred to as wet bulb depression
and is greatest during the summer.
As previously mentioned, the wet-bulb temperature is that temperature to which air would be cooled by evaporation if the air was
brought into contact with water and allowed to absorb sufficient
water vapor to become saturated. For example, if the outdoor summer air is drawn through a humidifier and completely saturated, its
dry-bulb temperature will be reduced to its wet-bulb temperature, and
the air will leave the humidifier at the outdoor wet-bulb temperature.
This cooling is accomplished entirely by evaporation and is due to the
latent heat required to convert the liquid water vapor. This conversion
occurs the instant the air is brought into contact with the mist in the
spray chamber of the humidifier, the heat being taken from the air.
The spray water in a humidifier is used over and over again, only
that quantity being added which is actually absorbed by the air. Thus,
without any additional expense, a humidifier will perform the function of cooling the air through the wet-bulb depression in the summer.
The extent of the wet-bulb depression in some localities is as much
as 25° or 30°. Even in localities adjacent to large bodies of water
where the humidity is high and the wet-bulb depression correspondingly low, the latter will quite commonly range from 10° to 15°.
In the vicinity of New York, for instance, the maximum outdoor
wet-bulb temperature is about 78°. On such a day the dry-bulb
temperature would probably be about 90°, making the wet-bulb
depression 12° (90° 78° 12°).
In Denver, on the other hand, the maximum outdoor wet-bulb
temperature is usually less than 78°. Because the coincident drybulb temperature is usually much higher then 90°, it results in a
368 Chapter 8
greater wet-bulb depression, which means that more cooling can be
accomplished by evaporation.
Sensible and Latent Heat
The distinction between dry air and the moisture content of air and
between dry-bulb and wet-bulb temperatures is extended to the two
types of heat carried by the entering air and the air already contained in the space: sensible and latent heat.
Sensible Heat
Sensible heat is the amount of heat in air that can be measured by
an ordinary thermometer (that is, a dry-bulb thermometer). The
daily weather report gives us sensible heat temperatures, but it does
not represent the total heat we experience. It constitutes a portion
of the heat resulting from air infiltration and ventilation, and internal heat sources such as people, electric lights, and electric motors.
Sensible heat also results from heat leakage (or heat loss in the case
of heating calculations) and solar radiation.
Latent Heat
Latent heat is the amount of heat contained in the water vapor
(moisture) of the air. It constitutes a portion of the heat resulting
from infiltration and ventilation and any internal sources capable
of adding water vapor to the air (for example, cooking vapors,
steam, people). The amount of latent heat in the air can be determined by using a psychrometric chart (see Appendix E,
“Psychrometric Charts”). The amount of excess latent heat so
determined will indicate the amount of moisture that must be
removed from the air in order to obtain comfortable conditions.
Both sensible heat gain and latent heat gain are expressed in Btu.
When the total of the two are added together, their sum represents
the total heat gain in Btu that must be removed from the air each
hour by the air conditioner.
Sensible heat gain (or load) is represented by a change in the drybulb temperature readings, whereas latent heat gain is represented
by a change in the web-bulb temperature.
Pressure
Atmospheric air is air at the pressure of the standard atmosphere.
Standard atmosphere is considered to be air at a pressure of 29.921
inches of mercury, which is equal to 14.696 pounds per square inch
(usually written 14.7 psi). In any air-conditioning system, atmospheric air is regarded as being air at the atmospheric pressure at
the point of installation.
Standard atmospheric pressure at sea level is 29.921 inches of
mercury. Since most pressure gauges indicate gauge pressure or
Air-Conditioning 369
pounds per square inch, a barometer reading can be converted into
gauge pressure by multiplying inches of mercury by 0.49116 psi.
Thus, a barometer reading of 29.921 inches is equivalent to a gauge
pressure of 14.696 psi (29.921 0.49116 14.696, or 14.7 psi).
So 0.49116 psi is a constant value for 1 inch of mercury and is
determined by dividing the pressure in pounds per square inch by
the barometer readings in inches of mercury (that is, 14.696 ⫼
29.921 0.49116). Table 8-2 gives the atmospheric pressure for
various readings of the barometer.
The pressure of the atmosphere does not remain constant in any
one place. It continually varies depending on the conditions of the
weather and the elevation. With respect to elevation, atmospheric
pressure will decrease approximately 1⁄2 lb for each 1000 feet of
ascent. Table 8-2 illustrates the effect of altitude and weather (the
barometer reading) on atmospheric pressure.
Table 8-2
Atmospheric Pressure and Barometer Readings
for Various Altitudes
Altitude above Sea
Level (Feet)
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
5500
6000
6500
7000
7500
8000
8500
9000
9500
Atmospheric Pressure
(Pounds per Square Inch)
Barometer Reading
(Inches of Mercury)
14.69
14.42
14.16
13.91
13.66
13.41
13.16
12.92
12.68
12.45
12.22
11.99
11.77
11.55
11.33
11.12
10.91
10.70
10.50
10.30
29.92
29.38
28.86
28.33
27.82
27.31
26.81
26.32
25.84
25.36
24.89
24.43
23.98
23.53
23.09
22.65
22.22
21.80
21.38
20.98
(continued)
370 Chapter 8
Table 8-2 (continued )
Altitude above Sea
Level (Feet)
Atmospheric Pressure
(Pounds per Square Inch)
Barometer Reading
(Inches of Mercury)
10,000
10,500
11,000
11,500
12,000
12,500
13,000
13,500
14,000
14,500
15,000
10.10
9.90
9.71
9.52
9.34
9.15
8.97
8.80
8.62
8.45
8.28
20.58
20.18
19.75
19.40
19.03
18.65
18.29
17.93
17.57
17.22
16.88
Absolute pressure is pressure measured from true zero or the
point of no pressure. It is important to distinguish absolute pressure
from gauge pressure, whose scale starts at atmospheric pressure.
For example, when the hand of a steam gauge is at zero, the absolute pressure existing in the boiler is approximately 14.7 psi. Thus,
5 lbs pressure measured by a steam gauge (that is, gauge pressure) is
equal to 5 lbs plus 14.7 lbs, or 19.7 psi of absolute pressure.
Compression and Cooling
The objective of the use of compression in air-conditioning is to
cool the air being conditioned. It is important to note, however,
that it is not the air that is compressed, but the refrigerant gas used
in the coils of the air-conditioning unit. The low temperature is produced by the expansion and contraction of the refrigerant gas.
When a gas is compressed, both its pressure and temperature are
changed in accordance with Boyle’s and Charles’s laws.
The English scientist Robert Boyle (1627–1691) determined that
the absolute pressure of a gas at constant temperature varies
inversely as its volume. Somewhat later, the French scientist Jacques
Charles (1745–1823) established that the volume of a gas is proportional to its absolute temperature when the volume is kept at constant pressure. These findings came to be known as Boyle’s and
Charles’s laws respectively. In Tables 8-3 and 8-4 a series of relations
based on these two laws are tabulated for convenient reference.
A more simplified explanation of the interrelationship of these
two laws may be gained with the aid of the cylinder illustrated in
Air-Conditioning 371
Table 8-3
Summary of Boyle’s Law
1. Pressure volume formula
PV PV . . . . . . . .(1)
P
PV . . . . . . . .(2)
V
V
PV . . . . . . . .(3)
P
2. Compression constant
PV constant . . . . . .(4)
3. Pressure at any point
constant . . . . .(5)
P
V
4. Volume at any point
constant . . . . .(6)
V
P
where,
R ratio or number of
compressions
Vi initial volume
Vf final volume
R Pi ⫼ Pf Vi ⫼ Vf . . .(8)
6. Initial pressure of compression
Pi R ⫼ Pf
. . . . . . . . . . .(9)
where,
Pi initial pressure absolute
Pf final pressure absolute
7. Final pressure of compression
Pf Pi ⫼ R
5. Ratio of compression
R V ⫼ V . . . . . .(7)
i
f
Table 8-4
Summary of Charles’s Law
1. At constant volume
P
V
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .(1)
T
T
where, P initial pressure absolute
P⬘ final pressure absolute
T initial temperature absolute
T⬘ final temperature absolute
2. At constant pressure
V
V
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .(2)
T
T
where
V initial volume (usually in cubic feet)
V⬘ final volume (usually in cubic feet)
372 Chapter 8
Figure 8-1. If the cylinder is filled with air at atmospheric pressure
(14.7 psi) represented by volume A, and piston B is moved to
reduce the volume by, say, 1⁄3 of A, as represented by B, then
according to Boyle’s law, the pressure will be tripled (14.7 3 44.1 lbs absolute or 44.1 14.7 29.4 gauge pressure). According
to Charles’s law, a pressure gauge on a cylinder would at this point
indicate a higher pressure than 29.4 gauge pressure because of the
increase in temperature produced by compressing the air. This is
called adiabatic compression if no heat is lost or received externally.
A
B
1/
3
VOL.
UNITY VOLUME
Figure 8-1
The interrelationship of Boyle’s and Charles’s laws.
Measuring the Physical Properties of Air
A number of instruments are used for measuring the physical properties of air. These include the following:
1.
2.
3.
4.
The thermometer
The barometer
The psychrometer
The pressure gauge
A thermometer (see Figures 8-2 and 8-3) is a device used to measure temperature, and consists of a glass tube terminating in a bulb
charged with mercury or colored alcohol. It measures the temperature by the contraction or expansion of the liquid with temperature
Air-Conditioning 373
100
changes, causing the liquid to rise or recede in
the tube. The scale of an ordinary thermometer,
either Fahrenheit or Celsius, is simply an arbitrary standard by means of which comparisons
can be established.
An ordinary thermometer is used to measure
dry-bulb temperature. Dry-bulb temperature is
the degree or intensity of heat. In other words,
dry-bulb temperature measures the degree of
effort that the heat will exert to move from one
position to another.
A specially designed thermometer is used to
measure wet-bulb temperature. The latter represents the temperature at which the air becomes
saturated if moisture is added to it without a
change of heat. The bulb of an ordinary thermometer is surrounded with a moistened wick,
placed in a current of air, and superheated with
water vapor. Essentially this represents a wetbulb thermometer.
A barometer (see Figure 8-4) is an instrument
designed to measure atmospheric pressure. Early
barometers consisted of a 30-inch-long glass
tube open at one end and filled with mercury.
The open end was submerged in a bowl of mercury, and the mercury in the glass tube would
assume a level in accordance with the existing
Figure 8-2 A
atmospheric pressure. Thus, the height of the
pencil-style stack
mercury column in the tube is a measure of the
thermometer.
atmospheric pressure. Standard atmospheric
pressure at sea level is 29.921 inches of mercury.
A psychrometer (or sling psychrometer) is an instrument used to
measure relative humidity. It consists of a dry-bulb (for air temperature) and a wet-bulb thermometer mounted side by side. The reading
on the wet-bulb thermometer is determined by the rate at which the
moisture evaporates from its bulb. If the psychrometer is working correctly, the reading on the wet-bulb thermometer will be lower than the
one on the dry-bulb thermometer. The difference between the two
readings serves as a basis for determining the relative humidity.
Pressure gauges (see Figures 8-5, 8-6, and 8-7) are used to measure pressure. A high-pressure gauge (see Figure 8-5) is used to
measure pressures ranging from zero to 300 or 400 psig. A compound gauge (see Figure 8-6) is used to measure low pressures
200
300
400
500
600
700
800
900 950
374 Chapter 8
212°
210
BOILING POINT
100°
200
OF WATER
80
90
70
190
180
80
170
60
70
160
50
130
120
110
80 DIVISIONS
60
140
100 DIVISIONS
180 DIVISIONS
150
50
40
30
100
90
30
80
20
70
20
60
50
40
32°
40
10
10
FREEZING
0°
POINT OF
0°
WATER
25
20
10
0°
FAHRENHEIT
Figure 8-3
MERCURY FILLED BULBS
CENTIGRADE
REAUMUR
Various thermometer scales.
above atmospheric pressure in psig and below atmospheric pressure
in vacuum in inches of mercury.
Cleaning and Filtering the Air
The purpose of cleaning and filtering the air is to remove dust and
other contaminants that could be harmful to the health or discomforting. Many bacteria that cause diseases are carried on dust particles.
Cleaning and filtering may be accomplished with equipment
using one of the following four methods:
Air-Conditioning 375
INCHES OF
MERCURY
STANDARD
ATMOSPHERE
31
29.921
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
0
1.
2.
3.
4.
ABSOLUTE PRESSURE
PER SQ. IN.
15.226
14.696
14
Mercurial
barometer illustrating the
relationship between inches
of mercury and absolute
pressure in pounds per
square inch.
Figure 8-4
13
12
11
10
9
8
7
6
5
4
3
2
0
Filtering
Washing
Combined filtering and washing
Electrostatic field
Filters trap particles by bringing them in contact with specially
coated surfaces or by straining them through dry materials of particularly close texture. The filters used in air-conditioning equipment may be either dry or wet (viscous) types. Depending on the
type used, air-cleaning filters may be replaceable or periodically
376 Chapter 8
A highpressure gauge.
Figure 8-5
(Courtesy Ernst Gage Co.)
cleaned. In the latter case, either manual or
automatic cleaning is possible.
Air washers form a part of the cooling and
humidifying apparatus of the air-conditioning system. They operate by passing the air
first through fine sprays of water and then
past baffle plates upon the wetted surface of
which is deposited whatever dust and dirt not
caught by the sprays.
Electronic air cleaners employ an electrostatic ionizing field to remove dust particles
from the air. The particles are given an electrical charge when passing through the field
and are subsequently attracted to metal plates
having an opposite polarity.
Cleaning and filtering processes are
described in greater detail in Chapter 12
(“Air Cleaners and Filters”).
Standards of Comfort
The influence of air temperature, moisture,
and movement on physical comfort has
been very thoroughly investigated. Once
again, the most authoritative sources of
information on this subject are the results
of research conducted by the American
Figure 8-6 A
compound gauge that Society of Heating, Refrigeration, and AirConditioning Engineers. The most current
measures both
pressure and vacuum. edition of the ASHRAE Guide should be
consulted for details because some revisions
(Courtesy Ernst Gage Co.)
have been made.
The sensations of warmth or cold experienced by the human
body depend not only on the dry-bulb temperature but also on the
moisture content of the air. Cooling applications that remove only
the sensible heat fall short of establishing comfortable conditions
if the latent heat gain is particularly high. The air will be cooler
under these conditions, but it will feel damp and uncomfortable. In
order to meet minimal standards of comfort, both sensible and
latent heat must be reduced to an acceptable level.
The average comfort conditions in summer and winter are considerably different, although the two zones overlap to some degree.
This difference is caused largely by differences in clothing, and the
natural inclination of the body to acclimate itself to somewhat
higher temperatures in the summer.
Air-Conditioning 377
GAUGE
PRESSURE
D
ZERO
ABSOLUTE
PRESSURE
GAUGE
VACUUM
GAUGE
A
C
E
B
ZERO
ZERO
29.921 INS.
14.696
(LBS. PER SQ. IN.)
Figure 8-7
Gauge illustrating absolute and zero pressure.
(Courtesy Ernst Gage Co.)
The effective temperature is an arbitration index of the degree of
warmth or cold as apparent to the human body, and takes into
account the temperature, moisture content, and motion of the surrounding air.
Effective temperatures are not strictly a degree of heat; at least
not in the same sense that dry-bulb temperatures are. For instance,
the effective temperature could be lowered by increasing the rate of
airflow even though wet- and dry-bulb temperatures remain the
same. Consequently, effective temperature is more correctly defined
as the body sensation of warmth or cold resulting from the combined effect of temperature, humidity, and air movement. For space
cooling and heating, however, the air movement factor is considered a constant at approximately 20 feet per minute, and under this
condition effective temperature is determined by the wet-bulb and
dry-bulb thermometer readings only.
The Comfort Chart
The comfort chart (see Figure 8-8) is an empirically determined
effective temperature index that has been published by the ASHRAE
since 1950.
The purpose of the comfort chart is to indicate the percentage of
people feeling comfortable at various effective temperatures in the
winter and summer. This serves only as an approximate standard
of comfort, because individual reactions to warmth and cold are
much too variable, but it is the most precise and scientific form of
measurement available.
378 Chapter 8
%
AIR MOVEMENT OR TURBULENCE
15 TO 25 FT. PER MIN.
90
70%
%
80
60%
L
RE
75
SU
80
80
M
M
ER
85
90
IT
Y
50%
40%
60
50
40
30
20
70
20%
65
10
10%
60
75
10
20
30
40
50
60
70
80
90
100
TS BLE
EC
BJ ORTA
U
F S MF
T O CO
EN ING
C
L
R
PE FEE
55 DEG. EFFECTIVE
TEMP. LINE
WET-BULB TEMPERATURE F
60
VE
ID
30%
P
F ER
E
EL CEN
IN T
G
CO OF S
M UB
FO J
R E
T
AB CTS
LE
70
0
10 90
80 0
7
I
AT
M
HU
55
70
50
65
60
40
55
50
ER
NT
WI
60
70
80
90
100
DRY-BULB TEMPERATURE F
Figure 8-8
Comfort chart for still air. (Courtesy ASHRAE 1960 Guide)
From the chart, one can obtain an approximate idea of the various effective temperatures at which a majority of people will feel
comfortable (that is, the summer and winter comfort zones).
Most air-conditioning systems are designed with a recommended
indoor design relative humidity of about 50 percent or slightly
lower. Budget jobs will range as high as 60 percent relative humidity. The indoor dry-bulb temperature will range from 75°F or
slightly below to about 80°F, depending on the degree of occupancy
and whether it is a budget job or not. In any event, the indoor
design conditions should fall within the comfort zone.
Air-Conditioning 379
More information about the use of the comfort chart is included
in Appendix E (“Psychrometric Charts”).
Cooling Load Estimate Form
Air-conditioning equipment manufacturers often provide their local
representatives with forms for making cooling load estimates.
Along with these forms they also provide tables, slide charts, tabulation sheets, and other aids for computing the cooling load.
Typical tabulation sheets and cooling load estimate forms are
shown in Figures 8-9 and 8-10. These forms contain lists of factors
that represent approximate values for a variety of different items (for
example, walls, ceilings, people). For example, the form illustrated in
Figure 8-9 requires that you select the appropriate design dry-bulb
temperature and its column of factors. After calculating the area (in
square feet) of the structural section, you must multiply this figure by
its factor to determine the Btu per hour of heat gain and enter the
result in the column on the extreme right.
Because a manufacturer’s cooling estimate form will probably not
be available, it may be necessary to create your own. If this should be
the case, then provisions should be made on the cooling estimate form
for distinguishing between sensible and latent heat sources.
Your cooling load estimate form should contain the following
basic categories of heat gain:
A. Sensible heat gain
1. Heat leakage
2. Solar radiation
3. Internal heat sources
4. Infiltration
5. Ventilation
6. Electric lights
7. Electric motors
8. People
9. Appliances
B. Latent heat gain
1. Infiltration
2. Ventilation
3. People
380 Chapter 8
BTU TABULATION
AMANA REFRIGERATION INC., AMANA, IOWA
(BASED ON 24 HOUR PER)
Job Name
Date
Location
Computed By
LIVING ROOM
ROOM
DINING ROOM
KITCHEN
BED ROOM 1
Room Size (LxWxH)
Linear Ft. Exposed Wall
Floor Ceiling Area
Windows
AREA
OR QUAN
BTUH
AREA
OR QUAN
BTUH
AREA
OR QUAN
BTUH
AREA
OR QUAN
BTUH
DIRECTION
FACTOR
Shade
Walls
Sunlit
Ceiling
Cooking
1200
People
380
1
3
Room Sensible Heat
Room CFM
WALL FACTORS
WINDOW & DOOR FACTORS
Temp. Diff. F
North
NE & NW
East &&West
East
West
SE & SW
South
15
12
23
32
35
26
20
18
29
38
41
32
25
25
36
44
48
39
Above factors assume shades or venetian blinds. If no shades double factors.
30
31
42
51
55
45
Temp. Diff. F
No Insul.
15 Daily
11⁄2" Insul.
Temp.
Range
3" Insul.
No Insul.
20 Daily
Temp.
11⁄2" Insul.
Range
3" Insul.
No Insul.
25 Daily
11⁄2" Insul.
Temp.
3" Insul.
Range
Light Color
15
3.6
2.1
1.5
2.7
1.5
1.1
1.4
0.9
0.6
20
5.4
3.0
2.1
4.5
2.6
1.8
3.6
2.1
1.5
25
7.2
4.0
2.9
6.5
3.6
2.6
5.4
3.0
2.1
30
9.0
5.1
3.6
8.2
4.7
3.3
7.4
4.1
2.9
For masonry walls multiply factors x 1.2. For
⁄2 Value in Table.
1
For outside shading or awnings multiply factor x .60.
For double glazed or storm windows
multiply factor x .80.
NOTES:
PEOPLE LOAD — One Person in each
bedroom and three persons in living room.
ROOF OVERHANG — South walls only.
36" overhang provides complete shade to
wall and windows. Use shade values for
windows and walls.
DOORS — Treat all outside doors as windows.
Figure 8-9
CEILING FACTORS
15 Daily
Temp.
Range
20 Daily
Temp.
Range
25 Daily
Temp.
Range
Temp. Diff. F
2" Insul.
4" Insul.
6" Insul.
2" Insul.
4" Insul.
6" Insul.
2" Insul.
4" Insul.
6" Insul.
15
5.7
3.6
3.2
5.0
3.2
2.9
4.4
2.9
2.6
Factors assume dark color roof with attic having vents.
If light color roof — take 75" of values in tables.
If no vents in attic space double values.
Btu tabulation cooling form. (Courtesy Amana Refrigeration, Inc.)
C. Ventilation heat gain (from outside sources)
1. Sensible heat
2. Latent heat
The sum of these categories will represent the total heat gain
expressed in Btu per hour. A balance must be established between
Air-Conditioning 381
COOLING (Residential)
Outside Design Temp
(DAY OPERATION OF EQUIPMENT)
Inside Design Temp
Temp Diff.
Outside Humidity Factor
Daily Temp Range
BATH
BED ROOM 2
BTUH
TOTALS
AREA
OR QUAN
BTUH
AREA
OR QUAN
BTUH
AREA
OR QUAN
20
6.9
3.0
2.6
6.0
3.2
2.3
5.1
2.7
2.0
25
8.9
4.7
3.3
7.8
4.2
3.0
6.9
3.6
2.6
30
10.7
5.1
4.1
9.8
5.1
3.6
8.9
4.7
3.3
North or Shaded Wall Figure
20
6.9
4.4
4.0
6.2
3.7
3.5
5.5
3.6
3.2
25
8.7
5.1
4.6
7.5
4.7
4.2
6.9
4.4
4.0
AREA
OR QUAN
BTUH
HOUSE TOTAL SENS. BTUH
Dark Color
15
5.1
2.7
2.0
4.2
2.1
1.5
3.3
1.7
1.2
BTUH
30
9.6
5.7
5.1
8.6
5.4
4.9
7.6
5.0
4.5
DUCT. GAIN
%
VENTILATION LOAD BTUH
TOTAL SENSIBLE BTUH
GRAND TOT. = TOT. SENS. x HUM. FACTOR
% DUCT GAIN
2 Story
1 Story
11⁄2 Story
4
8
6
Ducts Insulated
15
12
Ducts not Insulated
18
NOTE: All ducts in attic spaces must be insulated with
3" minimum thickness insulation with vapor barrier.
Ducts in crawl spaces and damp basements must be
covered with 2" minimum thickness insulation with
vapor barrier.
Do not figure duct gain for concrete slab under floor
ducts
HUMIDITY FACTORS
Outside Hum.
Factor
Below 40
1.25
40 to 45
1.30
Above 45
1.35
VENTILATION LOAD
House Volume Cu. Ft. (LxWxH) x .40 BTUH/ CU. Ft.
Figure 8-9
(continued)
this hourly heat gain within the conditioned space and the hourly
capacity of the air-conditioning unit to remove this heat gain in
order to maintain the inside design temperature.
Figure 8-11 is a floor plan (not drawn to scale) of a house that
will serve as a basis for most of the cooling calculations used in this
chapter.
382 Chapter 8
Customer .....................................................................................
Address ...............................................................................
Buyer ...........................................................................................
Installation by .....................................................................
Estimate Number .......................................................................
Estimate by ....................................... Date ......................
Equipment Selected .................................................................;
Model ........................................; Size ..............................
Direction House Faces ......................; Gross Floor Area ..........................sq ft ; Gross Inside Volume ........................... cu ft
Degrees
North Latitude
...............
Design Conditions:
Dry-Bulb
Temperature (F)
...............
BTU/HR
(Area x
Factor)
FACTOR
(Circle the factors applicable.)
AREA
(sq ft)
ITEM
Wet-Bulb
Temperature (F)
...............
For glass block, reduce factors by 50%;
for storm windows or double-glass,
reduce factors by 15%.
Outside
No
Inside
Awnings
Shading
Shades
1. (a) WINDOWS, Gain from Sun
(Figure all windows for each
exposure, but use only the
exposure with the largest
load.)
Northeast
East
Southeast
South
Southwest
West
Northwest
Load for Each
Exposure
(Area x Factor)
.................
60
.................
25
20
100
.................
40
25
.................
Use
75
................. only
30
20
.................
.................
75
.................
35
20
the
.................
110
45
30
................. largest
150
................. load.
65
45
.................
120
.................
50
35
.................
For calculating gain from sun through windows under overhanging roofs, see example given in Instructions.
90
DESIGN DRY-BULB TEMPERATURE (F)
92
95
97 100 102 105 110
.................
.................
13
7
15
8
.................
4
4
5
6
6
7
.................
.................
3
2
3
2
4
2
4
2
5
3
5
3
PARTITIONS
(Between conditioned and un.................
conditioned space)
2
2
3
3
4
4
.................
.................
.................
.................
18
9
5
3
18
11
5
3
19
12
5
4
20
14
5
4
21
16
6
4
.................
.................
.................
.................
28
14
8
6
29
14
9
6
30
15
9
6
31
16
9
6
.................
3
3
4
.................
.................
2
3
2
3
.................
2
2
(b) WINDOWS, Heat Gain
(Total of all windows)
Single-glass
Double-glass or glass block
2.
WALLS
No insulation (brick veneer,
frame, stucco, etc.)
1 in. insulation or 25/32 in.
insulation sheathing
2 in. or more insulation
3.
4.
5.
6.
7.
8.
9.
ROOFS
(a) Pitched or flat with vented
air space, and:
No insulation
No insulation, with attic fan
2 in. insulation
4 in. insulation
(b) Flat with no air space, and:
No insulation
1 in. or 25/32 in. insulation
11⁄2 in. insulation
3 in. insulation
CEILING
(Under unconditioned rooms
only)
FLOORS
(Omit if over basement, enclosed crawl space, or slab.)
Over unconditioned room
Over open crawl space
OUTSIDE AIR
Total sq ft of floor area
PEOPLE
(Use minimum of 5 people)
SUB-TOTAL
19
9
22
10
25
11
30
13
42
19
.................
.................
8
9
10
.................
6
3
7
4
9
4
.................
.................
5
6
7
.................
21
17
6
4
22
19
6
4
24
22
7
5
25
25
7
5
.................
.................
.................
.................
33
16
10
7
34
17
10
7
35
18
11
7
38
19
11
8
40
20
12
8
.................
.................
.................
.................
4
5
5
6
7
8
.................
2
4
3
5
3
5
4
6
4
7
5
8
6
9
.................
.................
2
2
3
3
4
4
5
.................
............(number of people) x 200
LATENT HEAT ALLOWANCE
30 per cent of Item 9
11.
TOTAL
Sum of Items 9 and 10
Residential cooling load estimate form.
(Courtesy Amana Refrigeration, Inc.)
115
36
16
10.
Figure 8-10
27
12
.................
.................
Air-Conditioning 383
SOUTH
15'
3' × 4'
3' × 4'
10'
6'
ROOM # 1
15' × 15'
3' × 4'
10'
3' × 4'
ROOM # 4
ROOM # 2
10' × 10'
18'
20'
ROOM # 3
10' × 10'
CLOSET
BATH
REFR.
CLOSET
RANGE
2'
25'
10'
Figure 8-11
Floor plan of a one-story residence constructed on
concrete slab.
The house is located 30° north, and complete exposure to the
sun occurs at 1:00 P.M. The structure contains 740 square feet of
floor space divided into four rooms and a bath. There are ten 3 × 4
windows, with four of them facing south. The indoor design temperature is 80°F.
Indoor-Outdoor Design Conditions
The indoor and outdoor design conditions must be established
before any cooling load calculations can be made. This will be the
first step in your procedure. As you will see, the difference between
the indoor and outdoor design temperatures will eventually serve as
a basis for selecting the correct size air conditioner.
Designing a system to meet the maximum outdoor summer temperature is generally not necessary because these temperatures either
rarely occur or occur for a comparatively short duration of time. It
is the general practice to design the system for slightly less severe
conditions and thereby save on equipment and installation costs.
384 Chapter 8
Ventilation Requirements
Each conditioned space requires a specific amount of outside fresh
air to be circulated through it in order to remove objectionable
odors (for example, cooking odors, tobacco smoke, body odors)
and to maintain comfort standards.
Ventilation standards indicating recommended air changes for a
variety of space usages and occupancy have been established by the
ASHRAE. Local codes are often based on ASHRAE research and
data. These ventilation standards are easy and convenient to use,
but are objected to by some authorities because the sources of contamination seldom bear any relationship to cubic area.
The air-conditioning system must be capable of supplying
enough outside fresh air to maintain air purity and comfort standards. The ventilation requirements for a given structure or space
are based either on the desired number of air changes or the number of occupants. The volume rate of ventilation air is expressed in
cubic feet per minute (cfm).
According to the ASHRAE, the outside fresh air requirement for
both residences and apartments ranges from 10 cfm (minimum) to
20 cfm (recommended). Fresh air requirements for other types of
structures are listed in Table 8-5.
Table 8-5
Type of Building or Room
Attic spaces (for cooling)
Boiler room
Churches, auditoriums
College classrooms
Dining rooms (hotel)
Engine rooms
Factory buildings (ordinary
manufacturing)
Factory buildings (extreme
fumes or moisture)
Foundries
Galvanizing plants
Garages (repair)
Garages (storage)
Fresh Air Requirements
Minimum Air
Changes per Hour
12–15
15–20
8
5
4–6
2–4
10–15
15–20
20–30
20–30
4–6
Cubic Feet of Air
per Minute per
Occupant
20–30
25–30
Air-Conditioning 385
Table 8-5 (continued)
Type of Building or Room
Homes (night cooling)
Hospitals (general)
Hospitals (children’s)
Hospitals (contagious diseases)
Kitchens (hotel)
Kitchens (restaurant)
Libraries (public)
Laundries
Mills (paper)
Mills (textile—general buildings)
Mills (textile dyehouses)
Offices (public)
Offices (private)
Pickling plants
Pump rooms
Restaurants
Schools (grade)
Schools (high)
Shops (machine)
Shops (paint)
Shops (railroad)
Shops (woodworking)
Substations (electric)
Theaters
Turbine rooms (electric)
Warehouses
Waiting rooms (public)
Minimum Air
Changes per Hour
Cubic Feet of Air
per Minute per
Occupant
9–17
40–50
35–40
80–90
10–20
10–20
4
10–15
15–20
4
15–20
3
4
10–15
5
8–12
15–25
30–35
5
15–20
5
5
5–10
10–15
5–10
2
4
The amount of outside fresh air required for each air change per
hour equals the amount of inside air that must be removed from the
structure or space during the same time span. The following formula
can be used to determine the amount of air supplied per minute:
CFM area in cubic feet
minutes of air change
386 Chapter 8
The floor plan of the residence shown in Figure 8-11 contains
740 square feet. The height of each room is 7 feet, which gives an
area of 5180 cubic feet.
Table 7-1 in Chapter 7 (“Ventilation and Exhaust Fans”) lists
the number of average air changes per minute required for good
ventilation for a number of different applications. You will note
that each listed air change ranges from a minimum to a maximum
number of changes. The rate of air change you select will depend on
the following:
1. Geographical location
2. Occupancy
3. Ceiling height
Warmer climates and larger numbers of occupants require a
greater rate of air change. Conversely, an 8-foot ceiling will require
more ventilation than a 15-foot ceiling.
Using a 3-minute rate of air change for the residence illustrated
in Figure 8-11, the required number of air changes necessary to give
proper ventilation can be determined as follows:
CFM 5180 cu. ft.
1726.7
3
Thus, 1726.7 cfm is needed to change the air every 3 minutes (or
20 air changes every hour).
Always check the local health department codes or local building
codes for required ventilation standards first. If none exist, use the
recommended air changes listed in this table, or data available from
ASHRAE research.
Cooling a Structure
The aspect of air-conditioning most familiar to us is the reduction of
indoor temperatures to a comfortable level. There are a number of different sources of indoor heat, some are external and some are internal.
External Sources of Heat
The principal sources of heat from outside the structure are solar
radiation, heat leakage, infiltration, and ventilation.
Heat Leakage
Heat leakage refers to the amount of heat flow through structural sections and is stated in Btu per hour, per degree Fahrenheit, per square
foot of exposed surface. A significant portion of the total heat gain
of a space is due to heat from the outside of a structure or from a
Air-Conditioning 387
nonconditioned space passing (that is, leaking) through walls, ceilings,
floors, and roofs to the interior of the structure.
The coefficient of heat transmission (U-factor) is the specific
value used in determining the amount of heat leakage. It has
already been described in Chapter 4 (“Heating Calculations”) in
Volume 1 in the section Heat Loss. Actually the only difference
between heat leakage and heat loss is the direction of heat flow.
Both are concerned with the same thermal properties of construction materials and the rate at which heat flows through them.
Insofar as heat leakage is concerned, the direction of heat flow is
from the outside to the inside of the structure. In the case of heat
loss, the reverse is true.
The formula used for calculating heat leakage is identical to the
one used for heat loss, and may be stated as follows:
Q ⫽ UA(to t i)
where,
Q Amount of heat transmission in Btu/h
U Overall coefficient of heat transfer (U-factor) between the
adjacent space and the conditioned space (stated in Btu per
hour, per square foot, per degree Fahrenheit)
to Air dry-rule temperature in degrees Fahrenheit of adjacent
space or outdoors
ti Air dry-bulb temperature in degrees Fahrenheit of conditioned space of the structure
Heat Gain from Solar Radiation
A portion of the heat gain in the interior of a structure can be
attributed to solar radiation coming in through the windows. To
disregard this factor when calculating the total loads of the structure can result in serious error. It is particularly important to consider the type of shading because this will determine the amount of
heat gained from solar radiation.
One method of determining heat gain from solar radiation
through window glass is illustrated by the following equation:
Total
Instantaneous
Area of
Factor
Heat
Heat
Heat
Window for
Gain by ⫹ Gain by
Gain
Glass
Shading
Solar
Convection
Through
Radiation and
Window
Radiation
Glass
388 Chapter 8
The ASHRAE has conducted extensive research into all aspects
of solar radiation, and makes the results of this research available
through its publications. As you saw earlier, Tables 8-3 and 8-4
were adapted by permission from the ASHRAE 1960 Guide to
illustrate the aforementioned equation for determining total instantaneous heat gain through window glass.
Calculating the amount of heat gain due to solar radiation
through a glass window can be even more clearly illustrated by
using the above equation to solve a problem. Let us assume that
you have a residence containing four 3 × 4 windows facing south.
The structure is located 30° north, and complete exposure to the
sun occurs at 1:00 P.M. The indoor temperature is 80°F. The windows are shaded by dark brown canvas awnings that are open at the
sides. As you will note by looking carefully at Tables 8-6 and 8-7,
each of these points in the description of the structure is important
in the solution. The total instantaneous heat gain through these
windows can be determined as follows:
1.
2.
3.
4.
Window glass area 3 × 4 12 square feet
Factor for shading 0.25
Heat gain by solar radiation 45 Btu/h per square foot
Heat gain by convection and radiation 17 Btu/h per square
foot
Total instantaneous heat gain through the four windows can be
found as follows:
12 (0.25 45 17)
12 28.25
339 Btu/h (for one window) 4 windows
1356 Btu/h
In Table 8-7, note that the shading factors are given not only for
such items as shading screens and awnings located on the outside of
the structure but also for window shades, venetian blinds, and
draperies located on the inside. It is always recommended that windows of air-conditioned spaces be shaded in some manner.
Heat Gain from Infiltration and Ventilation
A certain amount of warm outdoor air will enter the interior of a
structure by means of infiltration and ventilation. Both phenomena
are described in considerable detail in Chapter 6 (“Ventilation
Table 8-6 Heat Gain Due to Solar Radiation (Single Sheet of Unshaded Common Window Glass)
Sun Time
A.M.
S
P.M.
T
30° north
6 A.M.
7
8
9
10
11
12
40° north
5 A.M.
6
7
8
9
10
11
12
Latitude
Instantaneous Heat Gain in Btu per Hour (ft2)
N
NE
E
SE
S
SW
W
NW
Horiz.
6 P.M.
5
4
3
2
1
25
23
16
16
17
18
18
98
155
148
106
54
20
19
108
190
205
180
128
59
19
52
110
136
136
116
78
35
5
10
14
21
34
45
49
5
10
13
15
17
19
35
5
10
13
15
16
18
19
5
10
13
15
16
18
19
17
71
137
195
241
267
276
7 P.M.
6
5
4
3
2
1
3
26
16
14
15
16
17
17
7
116
149
129
79
31
18
17
6
131
195
205
180
127
58
19
2
67
124
156
162
148
113
64
0
7
11
18
42
69
90
98
0
6
10
12
14
16
23
64
0
6
10
12
14
16
17
19
0
6
10
12
14
16
17
17
1
25
77
137
188
229
252
259
(continued)
389
390
Table 8-6 (continued)
Sun Time
Latitude
50° north
A.M.
S
P.M.
T
5 A.M.
6
7
8
9
10
11
12
7 P.M.
6
5
4
3
2
1
c
P.M. S
(Courtesy ASHRAE 1960 Guide)
Instantaneous Heat Gain in Btu per Hour (ft2)
N
NE
E
SE
S
SW
W
20
25
12
13
14
15
16
16
N
54
128
139
107
54
18
16
16
NE
54
148
197
202
176
124
57
18
E
20
81
136
171
183
174
143
96
SE
3
8
12
32
72
110
136
144
S
3
7
10
12
14
16
42
96
SW
3
7
10
12
14
15
16
18
W
NW
3
7
10
12
14
15
16
16
NW
Horiz.
6
34
80
129
173
206
227
234
Horiz.
Air-Conditioning 391
Table 8-7
Shade Factors for Various Types of Shading
Type of Shading
Canvas awning sides open
Canvas awning top and sides
tight against building
Inside roller shade, fully drawn
Inside roller shade, fully drawn
Inside roller shade, fully drawn
Inside roller shade, half drawn
Inside roller shade, half drawn
Inside roller shade, half drawn
Inside venetian blind, slats set
at 45°
Inside venetian blind, slats set
at 45°
Inside venetian blind, slats
at 45°
Inside venetian blind, slats set
at 45°
Outside venetian blind, slats
set at 45°
Outside venetian blind, slats set
at 45° extended as awning
fully covering window
Outside venetian blind, slats set
at 45° extended as awning
covering 2/3 of window
Outside shading screen, solar
altitude 10°
Outside shading screen, solar
altitude 20°
Outside shading screen, solar
altitude 30°
Outside shading screen, solar
altitude, above 40°
(Courtesy ASHRAE 1960 Guide)
Finish on Side
Exposed to Sun
Shade
Factor
Dark or medium
Dark or medium
0.25
0.35
White, cream
Medium
Dark
White, cream
Medium
Dark
White, cream
0.41
0.62
0.81
0.71
0.81
0.91
0.56
Diffuse reflecting
aluminum metal
Medium
0.45
0.65
Dark
0.75
White, cream
0.15
White, cream
0.15
White, cream
0.43
Dark
Green tint
0.52
0.46
0.40
0.35
0.25
0.24
0.15
0.22
392 Chapter 8
Principles”) and in the section Ventilation Standards in this chapter.
These materials should be read before proceeding any further.
Insofar as cooling load calculations are concerned, infiltration
(that is, natural ventilation) is the leakage of warmer outdoor air
into the interior of a structure usually as the result of wind pressure.
This occurs primarily through cracks around windows and doors.
As a result, the crack method is considered the most accurate means
of calculating heat leakage by air infiltration (see the appropriate
section of Chapter 4 in Volume 1 (“Heating Calculations”). A ruleof-thumb method for calculating heat leakage around doors located
in exterior walls is to allow twice the window heat leakage.
Some authorities feel that infiltration will fulfill the ventilation
requirements of small structures (for example, houses, offices, and
small shops) and that no special provisions need be made for a
mechanical ventilating system. Unfortunately, there is little or no
infiltration on days during which the outdoor air is perfectly still.
The amount of ventilation is generally determined by the number of air changes (inside air replaced by air from the outdoors)
required by a structure. This is most commonly based on the number of occupants and building use. In structures having air-conditioning, most of the outdoor air used for ventilation will pass
through the air-conditioning unit. A small portion of the air will
bypass the air-conditioning coils and add to the sensible and latent
heat levels of the interior spaces of the structure. The temperature
and humidity of the air that does pass over the cooling coils of the
unit are reduced to room conditions or below.
Internal Sources of Heat
A number of heat sources within a structure contribute to heat gain
independently from outside sources. The most important internal
heat gain sources are the following:
1.
2.
3.
4.
5.
People
Electric lighting
Appliances
Electric motors
Steam
The occupants of conditioned spaces give off both sensible and
latent heat. The amount of heat gain will depend on a number of
variables, including (1) the duration of occupancy, (2) the number
of people, and (3) their principal activity. Table 8-8 lists estimated
heat gains from a variety of activities performed by individuals.
Table 8-8
Rate of Heat Gain from Occupants of Conditioned Spaces
Degree of Activity
Typical Application
Seated at rest
Theater—matinee
Theater—devening
Offices, hotels, apartments
Offices, hotels, apartments
Department store, retail
store, dime store
Drugstore, bank
Seated, very light work
Moderately active office work
Standing, light work, walking
slowly
Walking, seated
Standing, walking slowly
Sedentary work
Light bench work
Moderate dancing
Walking 3 mph, moderately
heavy work
Bowling
Heavy work
(Courtesy ASHRAE 1960 Guide)
Total Heat
Adults,
Male (Btu/h)
Total Heat
Adjusted
(Btu/h)
Sensible
Heat
(Btu/h)
Latent
Heat
(Btu/h)
390
390
450
475
550
330
350
400
450
450
180
195
195
200
200
150
155
205
250
250
550
500
200
300
Restaurant
Factory
Dance hall
Factory
490
800
900
1000
550
750
850
1000
220
220
245
300
330
530
605
700
Bowling alley
Factory
1500
1450
465
985
393
394 Chapter 8
Calculating Infiltration and Ventilation
Heat Gain
It has been shown that outdoor air enters a structure by means of
both infiltration and ventilation. Because air is composed of a mixture of dry air and moisture particles, the heat gain produced by the
entering air will be expressed in terms of both its sensible heat gain
and its latent heat gain in Btu per hour.
The sensible and latent heat gain resulting from entering air represents only a small portion of the total heat gain involved in determining the design cooling load of a structure. For many applications,
however, the calculation of this portion of the heat gain is crucial
to a well-designed system. The following formulas, adapted from
ASHRAE materials, are used for making these calculations:
(1) QS cfm 1.08 (to ti)
(2) QL cfm 0.68 (wo wi)
(3) QT QS ⫹ QL
where,
QS ⫽ Sensible load
QL ⫽ Latent load
QT ⫽ Total load
cfm ⫽ Rate of entry of outdoor air (cubic feet per minute)
to ⫽ Dry-bulb temperature of outside (entering) air
ti ⫽ Dry-bulb temperature of inside air
wo ⫽ Outdoor wet-bulb temperature
wi ⫽ Indoor wet-bulb temperature
In order to use these formulas, it is first essential to determine
the outdoor and indoor design conditions (that is, the dry-bulb and
wet-bulb temperatures) and the maximum rate of entering air (in
cubic feet per minute).
Rule-of-Thumb Methods for Sizing
Air Conditioners
Manufacturers of air-conditioning equipment and mail order houses
(for example, Sears, Montgomery Ward) that sell air-conditioning
equipment through their catalogs provide rule-of-thumb methods for
calculating the size of the air conditioner required by a structure. The
Btu calculation formulas are based on recommended coefficient factors for different types of construction and conditions. The responsibility for calculating the cooling load (and ultimately selecting a
suitable air conditioner) lies with the purchaser of the equipment.
The problem of using any rule-of-thumb method is that the results
are not precise. In other words, the results represent an approximate
Air-Conditioning 395
estimate; not the results one would expect from an engineer’s calculations. There is always the danger of oversizing or undersizing the air
conditioner. Under normal conditions, however, this method of calculating the size of a central air conditioner is reasonably accurate.
The Btu tabulation and cooling estimate forms illustrated in
Figures 8-9 and 8-10 are typical examples of the forms provided by
manufacturers of air-conditioning equipment. Note that these
forms not only provide coefficient factors for various types of construction but also recommend standard loads for different activities. For example, the cooling load estimate form shown in Figure
8-10 provides for a latent heat allowance of 30 percent of the total
heat gain from all other sources. Another example of this practice is
the commonly used standard load of 1500 Btu for kitchen activities. People are usually given a 200 Btu allowance per person, and
residences are calculated on the basis of two people per bedroom.
Thus, a three-bedroom house would have a 1200 Btu allowance for
six people (3 2 6 200 1200 Btu).
The Btu calculation formulas used with the various rule-of-thumb
methods also provide for temperature and humidity adjustments
where conditions differ from the recommended levels. This is sometimes accomplished by providing humidity factors and a range of
dry-bulb temperature differences (see Figure 8-9) or by providing
humidity and temperature adjustment allowances. In the latter
case, the coefficient factors are usually based on a specific wet-bulb
temperature and dry-bulb temperature difference. If, for example,
the former were 75°F and your wet-bulb reading were 80°F, the
instructions might require that you add 10 percent of the total heat
gain of the structure for the humidity adjustment. Similar allowances
are provided for temperature adjustments.
One of the easier and more popular rule-of-thumb methods
employed for calculating the size of large central air conditioners is
to use one ton of refrigeration for each 500–700 square feet of floor
area, or each 5000–7000 cubic feet of space. A ton of refrigeration
is equivalent to 12,000 Btu per hour. This figure is based on the fact
that 1 lb of melting ice will absorb 144 Btu of heat over a 24-hour
period. Therefore, a ton of ice will absorb 288,000 Btu during the
same period of time (that is, 144 Btu 2000 lbs) (288,000 ⫼ 24
hours 1 ton of refrigeration).
HVAC Contractor’s Cooling Load Estimate
If you are not satisfied with your own cooling load estimate, you
should invite several air-conditioning contractors to give their bids.
This is particularly true if you are considering a central air-conditioning system. For a central air-conditioning system, each contractor
396 Chapter 8
should include the estimated Btu per hour required to cool the
structure. Each of the bids should be fairly close in estimated Btu
and cost. Your choice will be based largely on availability of
replacement parts, the reputation of the local dealer for quick and
reliable service, and the estimated Btu output. You will naturally
want an air-conditioning system that will efficiently remove the
required amount of heat. If this proves to be more expensive than
another type, you would be wise to choose the more expensive one
because your operating costs will be cheaper over the long run. Any
contractor’s bid that shows a wide variation from the others either
in cost or estimated Btu required to cool the structure should be
regarded with some suspicion. It may simply be an attempt to win
the contract. Most reliable bids will be fairly close.
Using the ACCA Design Manuals for Sizing
Air-Conditioning Systems
The Air-Conditioning Contractors of America (ACCA) publishes a
series of manuals used by contractors to size heating and cooling
loads. These manuals are updated regularly to match changes in
HVAC technology and construction materials. These manuals are
available for purchase from the ACCA web site (or their mailing
address) by both members and nonmembers. Check the ACCA listing in Appendix A (“Professional and Trade Associations”).
• Manual J Residential Load Calculation (8th Edition). Manual
J provides the contractor with the industry-standard residential
load calculation method, required by most building codes
around the country. The revised and expanded eighth edition
procedures produce improved equipment sizing loads for
single-family detached homes, small multiunit structures,
condominiums, town houses, and manufactured homes.
• Manual S Residential Equipment Selection. Manual S is an
essential companion to Manual J. It describes how to select
and size heating and cooling equipment to meet Manual J
loads based on local climate and ambient conditions at the
building site. Manual S covers sizing strategies for all types of
cooling and heating equipment, as well as how to use comprehensive manufacturer’s performance data on sensible, latent,
or heating capacity for various operating conditions.
• Manual C What Makes a Good Air-Conditioning System?
Manual C provides an overview of appropriate air-handling
characteristics for an efficient and comfortable HVAC system.
Air-Conditioning 397
• Manual D Residential Duct Systems. Manual D describes the
different types of residential duct systems, their selection, and
their application. Design criteria for duct systems are included
in this manual.
Note
Use the ACCA Manual N for sizing the heating or cooling equipment in commercial or industrial buildings. Typically, these structures are larger than homes, are constructed differently, and have
correspondingly greater internal HVAC loads. Using an HVAC
load calculation method designed for homes can result in oversizing or undersizing the HVAC equipment.
Central Air-Conditioning
The term central air-conditioning refers not so much to the method
of cooling used in a structure as it does to the type of installation
and its location. A central air-conditioning system is one that is generally centrally located in a structure in order to simultaneously
serve a number of rooms and spaces.
The following sections describe first the different cooling methods used in central air-conditioning systems and then the various
central air-conditioning applications used in homes and light commercial buildings.
Cooling Methods
Central air-conditioning can be accomplished by means of a variety
of different cooling methods. The following are described in this
chapter:
1.
2.
3.
4.
5.
6.
Evaporative cooling
Cold-water coil cooling
Gas compression refrigeration
Gas absorption refrigeration
Thermoelectric refrigeration
Cooling with steam
In a majority of air-conditioning installations, and almost exclusively in the smaller horsepower range found in residences and
small commercial buildings, the vapor or gas compression method
of cooling is used (see Gas Compression Refrigeration).
A comparatively recent entry into the field of residential air-conditioning is thermoelectric refrigeration. This method of cooling is
based on the thermocouple principle; the cool air is produced by
398 Chapter 8
the cold junctions of a number of thermocouples wired in series (see
Thermoelectric Refrigeration).
Absorption refrigeration and cooling with steam are cooling
methods generally found in large commercial and industrial
applications (see Gas Absorption Refrigeration and Cooling with
Steam).
Evaporative Cooling
An evaporative cooling system cools the indoor air by lowering its
dry-bulb temperature. In effect, it cools by evaporation, and it
accomplishes this function by means of an evaporative cooler.
Figures 8-12, 8-13, and 8-14 show the basic components of three
evaporative coolers.
INLET AND OUTLET
FLANGED FOR DUCT
CONNECTION
ROTOR—LAYERS OF
CRIMPED AND FLAT
METAL SCREENS
AIR FLOW
ROTOR
HOUSING
GEAR MOTOR
OVERFLOW
AUTOMATIC
DRAIN VALVE
WATER
TANK
DRAIN
CONNECTION
WATER LEVEL
Figure 8-12
FLOAT-OPERATED FILL VALVE
AND WATER CONNECTION
Typical rotary evaporative cooler.
(Courtesy 1965 ASHRAE Guide)
As shown in Figure 8-15, an evaporative cooler consists of a
blower and blower motor, water pump, water distribution tubes,
water pads, and a cabinet with louvered sides. In operation, the
blower draws air through the louvers of the cabinet where it comes
into contact with the moisture in the pads. The air passes through
these moist water pads and into the interior of the structure.
Air-Conditioning 399
SPRAY SECTION
BLOWER SECTION
TOP BAFFLE
FLEXIBLE CANVAS
CONNECTION
SIDE BAFFLE
EVAPORATIVE PAD
ELIMINATOR PAD
AIR FLOW
WATER SLINGER
RESILIENT MOUNTING
Figure 8-13
Typical spray evaporative cooler.
(Courtesy 1965 ASHRAE Guide)
WATER DISTRIBUTION
SYSTEM
ELECTRIC MOTOR
BLOWER
SHREDDED ASPEN
WOOD PADS COOLING
MEDIUM
WATER RECIRCULATING
PUMP
WATER TANK
WATER OVERFLOW
AND DRAIN
FLOAT VALVE
Figure 8-14
Typical drip evaporative cooler.
(Courtesy 1965 ASHRAE Guide)
WATER LEVEL
400 Chapter 8
DISTRIBUTION
TUBES
BLOWER
MOTOR
WATER
PADS
PUMP
PUMP
BLOWER
Figure 8-15
Evaporative cooler. (Courtesy Honeywell Tradeline Controls)
The water in the pads absorbs heat from the air as it passes
through them. This causes a portion of the water to evaporate and
lowers the dry-bulb temperature of the air as it enters the room or
space. It is this lower dry-bulb temperature that produces the cooling effect.
In an evaporative cooling system, the water is recirculated and
used over and over again. Only enough water is added to replace
the amount lost by evaporation. The pump supplies water to the
pads through the distribution tubes.
The air is never recirculated because it contains too much moisture once it has passed through the evaporative cooler. New air
must always be drawn from the outdoors.
An evaporative cooling system is generally not very effective in a
humid climate because the outdoor air is not dry enough. Evaporative
coolers have been used for years with excellent results in New
Mexico, Arizona, Nevada, and similar areas with dry climates.
Air-Conditioning 401
Cold-Water Coil Cooling
Indoor air temperatures can also be reduced by passing warm
room air over a cold surface, such as a water-cooled coil, and then
recirculating it back into the room. When a water-cooled coil is
used for this purpose, the system is referred to as cold-water coil
cooling (see Figure 8-16).
COLD AIR
TO ROOMS
WARM AIR
FROM ROOMS
PUMP
SUPPLY WATER
FROM DEEP WELL
35° TO 55°F
Figure 8-16
DISCHARGE WATER
10° TO 15°F WARMER
THAN SUPPLY WATER
Cold-water coil cooling. (Courtesy Honeywell Tradeline Controls)
A water-cooled coil is effective only when there is a sufficient supply of cold water. The temperature of the water should range from
35° to 55°F, and the most common source is a deep well. A pump
supplies the cold water to the coil where it picks up heat from the air
passing through it. This warmer water is then discharged to a storm
sewer, dry well, or some other outdoor receiver. The discharge water
is approximately 10° to 15°F warmer than the supply water.
Gas Compression Refrigeration
A gas compression refrigeration air-conditioning system operates on
the direct-expansion cooling principle. Basically the system consists
of a compressor, condenser coil, receiver, expansion device, and
evaporator coil. A refrigerant flowing through the system is affected
by temperature and pressure acting simultaneously in such a way
that heat is transferred from one place to another. In other words,
heat is removed from the room air for cooling and added to it for
heating.
Mechanical Refrigeration Cycle
The mechanical refrigeration cycle is illustrated schematically in
Figure 8-17. The liquid refrigerant is contained initially in the
402 Chapter 8
COMPRESSOR
CONDENSER
COIL
EVAPORATOR
COIL
EXPANSION POINT
Figure 8-17
RECEIVER
Mechanical refrigeration cycle. (Courtesy Honeywell Tradeline Controls)
receiver, which is usually located in the lower section of the condenser, although it can be a separate tank. The compressor, acting
as a pump, forces the liquid refrigerant under high pressure through
the liquid line to the expansion device.
The function of the expansion device is to regulate the flow of
refrigerant into the evaporator coil. This expansion device may be
in the form of an expansion valve or a capillary tube.
As the high-pressure liquid refrigerant is forced through the
expansion device, it expands into a larger volume in the evaporator,
thus reducing its pressure and consequently its boiling temperature.
Under this low pressure, the liquid refrigerant boils until it becomes
a vapor. During this change of state, the refrigerant absorbs heat
from the warm air flowing across the outside of the evaporator.
After the refrigerant has boiled or vaporized, thus removing its
quota of heat, it is of no more value in the evaporator coil and must
be removed to make way for more liquid refrigerant. Instead of
being exhausted to the outdoor air, the low-pressure heat-laden
refrigerant vapor is pumped out of the evaporator through the
Air-Conditioning 403
suction line to the compressor. The compressor then compresses the
refrigerant vapor, increasing its temperature and pressure and
forces it along to the condenser.
At the condenser, the hot refrigerant vapor is cooled by lower
temperature air passing over the condenser coils, thus absorbing
some of the refrigerant heat. As a result, the air temperature
increases and the refrigerant temperature decreases until the refrigerant is cooled to its saturation condition. At this condition, the
vapor will condense to a liquid. The liquid, still under high pressure, flows to the expansion device, thus completing the cycle.
Note that cold is never created during the mechanical refrigeration cycle. Instead, heat is merely transferred from one place to
another. When the refrigerant passes through the evaporator, it
absorbs heat from the room air, thereby cooling it. When the
higher-temperature refrigerant passes through the condenser, it
gives up heat to the air entering the room, thereby warming it.
Gas Absorption Refrigeration
The gas absorption refrigeration method of cooling uses heat as its
energy instead of electricity. This heat can be in the form of steam
from a gas-fired or oil-fired atmospheric steam generator, or it can
come from a gas or oil burner applied directly to the refrigeration
generator. Normally, water is used as the refrigerant and lithium
bromide as an absorbent. The absorption unit operates under a
vacuum that gives the water a boiling temperature low enough for
comfort cooling.
The absorption refrigeration system shown in Figure 8-18 is
charged with lithium bromide and water, the lithium bromide being
the absorbent and the water the refrigerant. This solution is contained within the refrigeration generator.
As steam heat is applied to the generator, a part of the refrigerant
(water) is evaporated or boiled out of the solution. As this water
vapor is driven off, absorbent solution is raised by vapor lift action
to the separating chamber (5) above the generator.
Refrigerant (water) and absorbent separate in the vapor separating chamber (5), the refrigerant vapor rises to the condenser (6),
and the separated absorbent solution flows down through a tube
(8) to the liquid heat exchanger and thence to the absorber.
The refrigerant (water vapor) passes from the separating chamber
to the condenser through a tube (6), where it is condensed to a liquid
by the cooling action of water flowing through the condenser tubes.
The cooling water that flows through the condenser is brought from
some external source, such as a cooling tower, city main, or well.
404 Chapter 8
12
HEATING COIL
CONDENSER
HUMIDIFIER
ATMOSPHERIC
VENT
COOLING COIL
7
6
SEPARATOR
11
5
8
1
WATER LEVEL
CONTROL
ABSORBER
STEAM
DIVERTER
VALVE
8
10
ATMOSPHERIC
STEAM
GENERATOR
2
CONDENSTATE RETURN PUMP
Figure 8-18
3
HEAT
EXCHANGER
4
9
9
COOLING
WATER
REFRIGERATION
GENERATOR
Gas absorption refrigeration unit.
The refrigerant vapor thus condensed to water within the condenser then flows through a tube (7) into the cooling coil. This tube
contains a restriction that offers a resistance and therefore a pressure barrier to separate the slightly higher absolute pressure in
the condenser from the lower pressure within the cooling coil.
The refrigerant (water) entering the cooling coil vaporizes due to
the lower absolute pressure (high vacuum) that exists within it. The
high vacuum within the evaporator lowers the boiling temperature
of water sufficiently to produce the refrigeration effect.
The evaporator or cooling coil is constructed with finned horizontal tubes, and the air being cooled flows horizontally over the coil
surface. Evaporation of the refrigerant takes place within the cooling
coil, the heat of evaporation for the refrigerant is extracted from the
air stream, and cooling and dehumidifying are accomplished.
In the absorber, the solution absorbs the refrigerant vapors that
were formed in the evaporator directly adjacent. To explain the
presence of the absorbent at this point, it is necessary to divert
attention back to the generator. The absorbent was separated from
the refrigerant by boiling action. The absorbent then drains from
Air-Conditioning 405
the separator (5) down to the liquid heat exchanger and then to the
absorber through the tube (8) designed for this purpose. The flow
of solution in this circuit can actually exist by gravity action only
because the absorber is slightly below the level of the separating
chamber.
It must be understood at this point that lithium bromide in either
dry or solution form has a very strong affinity for water vapor. It is
because of this principle that the refrigerant vapor is absorbed back
into solution again. Because the rate of absorption is increased at
lower temperatures, a water-cooling coil is provided within the
absorber shell.
The resultant mixture of refrigerant and absorbent drains back
through the heat exchanger through another tube (9) to the refrigeration generator where it is again separated into its two component parts to repeat the cycle.
The liquid heat exchanger serves to increase operating efficiency.
The absorbent solution leaves the refrigeration generator at a relatively high temperature. Because its affinity for water vapor is
increased as its temperature is reduced, precooling is desirable
before it enters the absorber. Conversely, the combined solution of
refrigerant and absorbent leaving the absorber and flowing toward
the generator is relatively cool.
Because heat is applied in the generator to drive off water vapor,
it is desirable to preheat this liquid before it enters the generator.
With counterflow action in the liquid heat exchanger, both precooling and preheating are accomplished within the solution circuit.
As stated previously, a high vacuum exists throughout all circuits. However, a slightly higher absolute pressure exists in the generator and condenser than in the cooling coil and absorber. This
difference in pressure is maintained by a difference in height of the
solution columns (or restrictor) in the various connecting tubes.
The effect of heat applied to the refrigeration generator raises the
absorbent solution to the vapor separator located at the top of the
generator. The absorbent solution is able to flow from the generator to the absorber by gravity, aided by the slight pressure differential between the two chambers.
In the absorber, water vapor is taken into the solution, which
then flows back to the bottom of the generator. Because the pressure in the absorber is slightly below that in the generator, solution
flow from a low-pressure area to one of relatively higher pressure is
accomplished by the higher elevation of the absorber.
The water vapor (refrigerant) released from the generator rises to
the condenser, where it is condensed to a liquid. Elevation of the
406 Chapter 8
condenser permits gravity flow of the refrigerant to the evaporator,
aided by the slight pressure differential between the two chambers.
Thus, by taking advantage of differences in fluid temperatures, density, and height of columns, continuous movement in the same direction throughout all circuits is accomplished without moving parts.
The cooling-water circuit can be traced in Figure 8-18 by noting
that it enters the absorber coil at point 10. Flow is then directed
through tube 11 to the condenser and leaves the unit at point 12.
Figure 8-19 shows a schematic sectional diagram of a typical
absorption year-round air conditioner. Inlet air enters a plenum
chamber that contains filter elements. The air, after having been
AIR
FILTERS
COOLING
COIL
HEATING
COIL
HUMIDIFIER
CENTRIFUGAL
FAN
FLOW
RESTRICTOR
BYPASS
DAMPER
STEAM DIVERTER VALVE
CONDENSTATE
DRAIN
STEAM GENERATOR
GAS BURNERS
Figure 8-19
Typical absorption year-round air conditioner.
Air-Conditioning 407
cleaned, passes through the cooling coil (evaporator) and heating
coil, and is then returned to the rooms or spaces being cooled.
During the cooling cycle, the room air is cooled and dehumidified.
Heat is extracted from the air and moisture is condensed on the cooling coil. Thus, both functions of cooling and dehumidification are
performed simultaneously. During the heating cycle, the air is warmed
by the steam heating coil, and moisture is added by the humidifier.
Steam is provided for both heating and cooling cycles by the
steam generator located in the base of the conditioner. Steam at
atmospheric pressure flows from the generator into a two-position
steam diverter valve, which automatically directs the flow of steam
to either the heating coil or the absorption refrigeration unit. The
steam diverter valve is positioned by an electric motor governed by
a remote heating and refrigeration switch.
After the air leaves the heating coil, it passes through the humidifier, which functions during the heating cycle only. The humidifier,
in this installation, consists of a number of horizontal trays, each
equipped with an overflow tube that feeds water to the next lower
tray. This arrangement provides a large evaporative surface for positive humidification. Water is supplied at a predetermined and controlled rate of flow to the humidifier trays.
The air is drawn through the unit by a centrifugal fan that delivers the heated or cooled air through a duct-distributing system to
the various rooms or spaces being conditioned. Because less air is
normally required for winter heating than for summer cooling, a
flow-restricting device is mounted in the fan scroll and functions on
the heating cycle to automatically reduce the flow of air by adding
resistance. This device usually consists of a pivoted blade, and its
location is indicated by the dotted line in Figure 8-19.
When maximum air delivery is desired, the air-restricting device
is positioned tightly against the inside column of the fan scroll.
When the restrictor is pivoted toward the fan wheel, thereby reducing normal wheel clearance, a resistance is thus imposed which
alters fan performance to reduce air delivery. The airflow-restricting device is moved automatically between predetermined summer
and winter positions by the motor that governs its operation.
Correct air distribution practices dictate a need in some cases for
the handling of a greater quantity of air on the cooling cycle than
required by the refrigeration unit for full-rated cooling capacity.
Should this excess air be needed, the amount in excess of rated
quantity should be handled through the bypass, thus ensuring correct cooling coil performance. The bypass damper is located in the
air circuit just beyond the cooling coil. During the heating season,
408 Chapter 8
the bypass damper will automatically be repositioned by the controlling motor to the closed position.
Thermoelectric Refrigeration
Thermoelectric refrigeration is a cooling method developed comparatively recently for use in residential air-conditioning, although
the operating principle is not new. Thermoelectric refrigeration has
been used for years as a cooling method for small refrigerators. It is
also the cooling used on nuclear submarines.
Thermoelectric refrigeration is based on the thermocouple principle. In a thermoelectric refrigeration cooling system, electricity in
the form of direct current power is applied to the thermocouple and
heat is produced. The heat is transferred from one junction to the
other producing a hot and cold junction. The direction of current
flow determines which junction is hot and which is cold. If the
power supply connections are reversed, the positions of the hot and
cold junctions are also reversed.
The amount of cooling or heating that can be produced with a
single thermocouple is small. For that reason, a number of thermocouples are wired in a series to produce the quantity of heating and
cooling required by the installation.
The schematic of a typical thermoelectric cooling system
shown in Figure 8-20 illustrates how direct current power is
applied to a number of thermocouples wired in series. Heat is
transferred from one side to the other depending on the direction
of current flow.
COLD
P
N
P
N
P
BLOWER
AIR
FLOW
N
P
INSULATING
N
AIR
FLOW
HOT
FINS
BARRIER
BLOWER
DC POWER
SUPPLY
Typical thermoelectric refrigeration
cooling system. (Courtesy Honeywell Tradeline Controls)
Figure 8-20
Cooling with Steam
Cooling with steam is based on the well-known fact that the boiling
point of any liquid depends on the pressure to which it is subjected.
By lowering the pressure, the boiling point is also lowered. When a
liquid at a certain temperature and corresponding boiling point is
Air-Conditioning 409
sprayed into a closed vessel in which the pressure is lower, the entering liquid is above its boiling point at the new reduced pressure, and
rapid evaporation takes place.
The basic components of a typical steam cooling system are
shown in Figure 8-21. In operation, the water to be cooled, returning from the air-conditioning or other heat-exchanging apparatus
at a temperature of 50°F, is sprayed into the evaporator. Because of
the large surface of the spray, the boiling (or flashing) is very rapid
and the unevaporated water falls to the bottom of the evaporator
chilled to 40°F. At this temperature it is withdrawn from the evaporator by the chilled water pump and pumped to the heat-exchanging
apparatus to again absorb heat, thus completing the cycle.
STEAM
HEADER
CONDENSER WATER
OUTLET 98°F
STARTING NOZZLES
BOOSTER EJECTOR
RUNNING NOZZLES
COLD TANK
SPRAY
PIPES
CHILLED WATER
INLET 55°F
50°F 29.637" VACUUM
28 IN. VACUUM
SECOND STAGE
EJECTOR
LIQUID LEVEL
CONTROL
CHILLED WATER PUMP
AIR
OFF-TAKE
BOOSTER CONDENSER
SECOND STAGE
CONDENSER
CONDENSTATE
PUMP
VENT
CONDENSTATE
OUTLET 99°F
DRAIN TO MAIN
CONDENSER
CHILLED WATER
OUTLET 50°F
Figure 8-21
FIRST STAGE
CONDENSER
FIRST STAGE
EJECTOR
CONDENSER COOLING
WATER 80°F
Basic components of a steam cooling system.
(Courtesy 1965 ASHRAE Guide)
In the booster ejector, steam flowing at high velocity through nozzles located in the ejector head is expanded in the venturi-shaped
diffuser. The kinetic energy of the steam is in part utilized in imparting velocity to the water vapor liberated in the evaporator and in
compressing this vapor over a compression range from the evaporator pressure to the condenser pressure. In this compression, the temperature of the water vapor is raised so that it can be readily
condensed by condensing water at temperatures normally available.
410 Chapter 8
The initial evacuation and constant purging of air and other
noncondensable gases is handled by a secondary group of ejectors
and condensers. These are relatively small in size, but of the greatest importance, and normally consist of two steam-operated ejectors in series, each with its own condenser in which condensing
water condenses the propelling water and entrained vapor.
Condensers used in a steam cooling system may be either of the surface type, with water passing through condenser tubes over which
the mixture of operating steam and water vapor flows, or of the jet
or barometric type, with condensing water sprayed directly into the
steam mixture.
The amount of condensing water and condensing surface
employed is such that the vapor temperature in the condenser is
normally 5°F above the condensing water discharge temperature.
This fixes the terminal pressure condition to which the steam mixture is compressed. The initial pressure condition (in the evaporator) is determined by the chilled water temperature desired.
Variation in either of these two conditions affects the compression
range and therefore the amount of operating steam required.
Central Air-Conditioning Applications
There are many different ways to apply central air-conditioning to
a structure. The method used depends on a number of factors, but
the type of heating system is probably the dominant one. The following are the most common types of cooling applications:
1.
2.
3.
4.
5.
Water chiller cooling
Split-system cooling
Year-round air-conditioning
Central cooling packages
Cooling coils
Water Chiller Cooling
A water chiller is used to add cooling and dehumidification to
steam or hot-water heating systems. A refrigeration-type water
chiller consists of a compressor, condenser, thermal expansion
valve, and evaporator coil. The water is cooled in the evaporator
coil and pumped through the system.
A typical system in which a water chiller is used is shown in
Figure 8-22. The boiler and water chiller are installed as separate
units, each with its own circulator (pump), or with one circulator in
the return line. Hot water from the boiler is circulated through the
Air-Conditioning 411
COMBINATION HEATING
AND COOLING UNITS
CONDENSATION
DRAIN LINE
CIRCULATING
PUMP
BOILER
DRAIN
HOT OR CHILLED WATER
WATER
CHILLER
THREE-WAY VALVE
Figure 8-22
Water chiller and boiler installed as separate units.
(Courtesy 1965 ASHRAE Guide)
convectors for heating, and cold water is circulated through the
same piping from the water chiller for cooling purposes.
Each convector unit contains a blower to force the air across the
convector coil (see Figure 8-23). Water condensed from the coil
during the cooling operation is trapped in a drip pan and discarded
through a drain connected to the convector. Some convectors also
contain a filter for air cleaning. The room convectors in a water
chiller cooling system are usually designed for individual control.
The same piping carries both the chilled and hot water to the
room convectors, but it must be insulated to minimize condensation during the cooling operation.
Water chillers are available as separate units or as a part of a
complete package containing the boiler. Separate water chiller units
are used when cooling must be applied to an existing steam or hot
water heating system.
Split-System Cooling
Another method of applying central air-conditioning to a steam or
hot-water heating system is to add forced-air cooling. This type of
cooling application is sometimes referred to as a split-system installation—that is to say, a system split or divided between one type of
heating (conventional steam or hot water) and another type of
412 Chapter 8
COOL-HEAT CONVECTOR COIL
CONDITIONED AIR
CONDENSTATE DRIP PAN
FAN & MOTOR
FILTER
RETURN AIR
WALL
Figure 8-23
Air forced by convector across convector coil.
(Courtesy Honeywell Tradeline Controls)
cooling (forced air). This results in some confusion because the
term split system is also used to refer to the separation of components in a year-round central air-conditioning system using forced
warm-air heating and cooling (see Location of Equipment).
Three typical methods of applying forced-air cooling to a steam
or hot-water heating system are shown in Figure 8-24.
Year-Round Air-Conditioning
In a year-round air-conditioning system, the heating and cooling units
are combined in a single cabinet (see Figure 8-25). This combined
package heats, cools, humidifies, dehumidifies, and filters the air in the
structure as required. The unit may have an air-cooled, a water-cooled,
or an evaporative-type condenser. The arrangement of the ductwork
will depend in part on the type of condenser used in the unit.
Air-Conditioning 413
COOLING
UNIT
COOL AIR GRILLE
IN EACH ROOM
RETURN AIR GRILLE
IN CENTER HALL
DROPPED CEILING
IN CENTER HALL
ATTIC INSTALLATION
RETURN AIR
DUCTS IN ATTIC
CRAWL SPACE
COOL AIR
TO ROOMS
COOLING UNIT
CONDENSER AIR
INLET
RETURN AIR
UTILITY ROOM
BASEMENT
Methods of applying forced-air cooling to steam or
hot-water heating systems. (Courtesy Honeywell Tradeline Controls)
Figure 8-24
DAMPERS
HEAT
COOLING
COIL
HEAT
COOL
FURNACE
HEAT
EXCHANGER
COOL
FURNACE
HEAT
EXCHANGER
DAMPER
COOLING
COIL
FAN
FAN
FILTER
Figure 8-25
FILTER
REFRIGERATION
EQUIPMENT
REFRIGERATION
EQUIPMENT
Heating and cooling units contained in a single cabinet.
(Courtesy Honeywell Tradeline Controls)
414 Chapter 8
Central Cooling Packages
A central cooling package is a unit designed for central air-conditioning applications. It consists of a cooling coil and the refrigeration
equipment and will provide the necessary cooling and dehumidification as conditions require. These units are available with their
own fans and filters, or they may be installed to use the filter and
blower of the existing heating equipment (see Figure 8-26).
DAMPERS
HEAT
HEAT
COOL
DIVERTING DAMPERS
(BLOW-OPEN TYPE)
COOL
HEAT
EXCHANGER
HEAT
EXCHANGER
FAN
COOLING
COIL
CO
FAN
REFRIG
EQUIPMENT
HEATING
PLANT
COOLING
PLANT
FAN
IN
OL
GC
OIL
REFRIG
EQUIP
FILTER
FILTER
COOLING UNIT USES FILTER
AND BLOWER IN HEATING UNIT
Figure 8-26
FILTER
HEATING
PLANT
COOLING
PLANT
COOLING UNIT PROVIDES ITS
OWN FILTER AND BLOWER
Central cooling package.
The method used to install a central cooling package will depend
on whether the unit has an air-cooled or water-cooled condenser. If
an air-cooled condenser is used, provisions must be made to carry
outdoor air to and away from the condenser. Typical installations
in which an air-cooled condenser is used are shown in Figure 8-27.
Figure 8-28 illustrates some typical methods of applying a central
cooling package in which a water-cooled condenser is used.
A typical remote or split system is shown in Figure 8-29. In this
installation, the compressor and air-cooled condenser unit are
located outdoors. The evaporator coil, fan, and heating appliance
are located indoors in the conditioned space.
Air-Conditioning 415
COOLING
UNIT
DOWNFLOW
FURNACE
COOLING
UNIT
UPFLOW
FURNACE
Applications of central cooling package having an
air-cooled condenser. (Courtesy Honeywell Tradeline Controls)
Figure 8-27
416 Chapter 8
COOLING UNIT
UPFLOW
FURNACE
COOLING UNIT
TO ADDITIONAL
ROOMS
Figure 8-27
(continued)
Air-Conditioning 417
COOLING UNIT MOUNTED IN BASEMENT
PLENUM OF UP-FLOW FURNACE
COOLING UNIT MOUNTED IN CRAWL-SPACE
PLENUM OF DOWN-FLOW FURNACE
COOLING UNIT ADDED TO PLENUM
OF HORIZONTAL-FLOW FURNACE
Applications of a central cooling package having a watercooled condenser. (Courtesy Honeywell Tradeline Controls)
Figure 8-28
Cooling Coils
Cooling can be applied to a warm-air heating system by installing
an evaporator coil or a cold-water coil in the ductwork. The evaporator coil is the low-side section of a mechanical refrigeration system. As shown in Figure 8-30, the evaporator coil is installed in the
ductwork above the furnace. It is connected by refrigerant piping to
the condenser coil and compressor installed outdoors.
A thermostatic expansion valve and condensation drip pan (with
drain) are included with the evaporator coil. Sometimes a fan is
added to the coil to supplement the furnace blower.
A cold-water coil may be used instead of an evaporator coil in
the ductwork. Cold water is supplied to the coil by a water chiller,
418 Chapter 8
RETURN
AIR DUCT
SUPPLY
DUCT
POWER
HUMIDIFIER
REFRIGERATION
LINES
CONDENSING
UNIT
EVAPORATOR
COIL
WARM-AIR
FURNACE
ELECTRONIC AIR
CONDITIONER
Figure 8-29
Typical remote split-type air-conditioning system.
(Courtesy Mueller Climatrol Corp.)
which can be located in the basement, a utility room, or outdoors.
If the water chiller is installed outdoors, a gas engine can be used to
drive the compressor (see Figure 8-31).
Hydronic Forced-Air Systems
In a hydronic forced-air system, the water is first heated in a boiler
(sometimes called a hydronic furnace in these systems) or water
heater and then circulated through the coils of a liquid-to-air heat
exchanger connected to the furnace air handler. Heat is transferred
from the water in the coils to the air inside the air-handler compartment. A blower forces the warm air through ducts to outlets inside
the rooms. Cool air is produced by a chilled water or DX coil inside
or on top of the blower cabinet. The cool air is distributed by the
blower through the same ductwork used by the warm air.
Condensation is collected by a condensate pump.
Hybrid Systems
A hybrid heating and cooling system consists of a radiant hydronic
heating system working in conjunction with a separate cooling system. Hot water is produced by a hydronic boiler, water heater, or
combination water heater. The cooling system is added to an existing
Air-Conditioning 419
REMOTE
CONDENSER
SECTION (HIGH SIDE)
CONDENSER
COIL
FAN
CONDITIONED
AIR TO
ROOM
CONDENSER
COOLING AIR
REFRIGERANT PIPING
(INSULATED)
EVAPORATOR
(LOW SIDE)
SECTION
GROUND
LEVEL
COMPRESSOR
CONDENSATE
DRAIN
HEAT PLANT
FURNACE
HEAT
EXCHANGER
FILTER
RETURN
AIR
BLOWER
Evaporator coil installed in ductwork of a warm-air
heating system. (Courtesy Honeywell Tradeline Controls)
Figure 8-30
hydronic system, when augmenting or upgrading the mechanical system of an older house or building. Some of the systems used to provide cool air to an existing hydronic heating system are described in
the following paragraphs.
Indirect/Direct Evaporative Coolers
A high-efficiency indirect/direct evaporative cooler designed with a
hydronic option can be used to supply cool air to a house with an
existing hydronic heating system. The evaporative cooler has a
Seasonal Energy Efficiency Ratio (SEER) of 36, which is three times
the minimum SEER efficiency rating for air conditioners. Air cooled
by direct and indirect evaporation can generate approximately the
same amount of cooling as a 3-ton air conditioner. The cool air is
delivered directly to the interior of the house or through a short duct.
420 Chapter 8
COMPRESSOR
CONDENSER
COLD-WATER PIPING
GAS
ENGINE
GAS ENGINE
COMPRESSOR
PACKAGE
EXHAUST
FAN
CONDITIONED AIR TO ROOM
COLD-WATER COILS
CONDENSATE DRAIN
PUMP
FURNACE HEAT
EXCHANGER
OIL
WATER
CHILLER
HEAT PLANT
GROUND
LEVEL
RETURN
AIR
FILTER
BLOWER
Cold-water coil used with outdoor gas engine
compressor. (Courtesy Honeywell Tradeline Controls)
Figure 8-31
Ductless Split System
As the name suggests, the ductless split system does not require ductwork. The system consists of an indoor air handler and an outdoor
condenser, connected by refrigerant tubing extending through a 3-inch
hole in the wall. Decorative units can be mounted on the floor, wall,
ceiling or recessed (drop) ceiling. The system can consist of a single
zone with one condenser and one air handler, or a multizone system
with one condenser containing two or more compressors connected to
one, three, or four air handlers. The ductless split system is capable of
producing 9000 Btu to 48,000 Btu, depending on the application.
Fan Coil and Flexible Ducts
The conditioned air is produced by a fan coil located in the attic, an
attic crawl space, the basement, or a closet. If the air-conditioning
unit is placed in the attic or an attic crawl space, a 5-ton one is
Air-Conditioning 421
small enough to insert between 16-inch on centers ceiling joists
without cutting any framing. The distribution system consists of
flexible 2-inch-diameter tubing running inside walls and floors and
around internal framing obstructions. The conditioned air is delivered to the rooms through a 2-inch opening in the ceiling.
Residential Chiller with Ceiling-Mounted Panels
Chilled water is run through ceiling-mounted panels that exchange
heat with the warm air in the room. The heated water is then carried down to the chiller where it is again cooled and returned to
the ceiling. The system uses small ducts to feed fresh air directly
into the house or building.
Room Air Conditioners
Room air conditioners are designed to cool a single room or space
in a structure. The most commonly used type of room air conditioner is the window-mounted unit. These air conditioners are
available for installation in single-hung windows, double-hung
windows, horizontal sliding windows, and casement windows.
Make sure to read carefully the specifications printed on the
shipping container before purchasing a window air conditioner.
The specifications should list the air conditioner’s dimensions, the
type of window installation, and its Btu output. Room air conditioners are also available for through-the-wall installation in exterior walls. A sleeve is provided for the wall mounting.
Chapter 9
Air-Conditioning Equipment
The gas compression method of mechanical refrigeration used in
conjunction with an air-cooled condenser is probably the most
common cooling system used in residences and small commercial
buildings. For that reason, this chapter is devoted almost exclusively to a description of mechanical refrigeration equipment.
A typical central air-conditioning system cools the house with an
indoor coil (evaporator) working in conjunction with an outdoor
coil (condenser) and a pump (compressor). The evaporator and
condenser coils are commonly constructed of copper tubing and
aluminum fins. A pump (compressor) forces a refrigerant (heat
transfer fluid) through the tubing coils and fins. When the refrigerant reaches the indoor coil (evaporator), it evaporates and pulls the
heat out of the indoor air. At this point, the refrigerant fluid has
changed to a gas. The hot refrigerant gas is then pumped back
through the copper tubing and aluminum fins of the outdoor condenser where it changes (condenses) back into a liquid, releasing its
heat to the air passing over the metal tubing and fins.
Mechanical Refrigeration Equipment
The equipment of a gas compression mechanical refrigeration system
can be divided into mechanical and electrical components. The electrical components are described below (see Electrical Components)
and in Chapter 6 (“Other Automatic Controls”) in Volume 2. The
principal mechanical components include the following:
1.
2.
3.
4.
5.
Compressor
Condenser
Receiver
Evaporator
Liquid refrigerant controls
Air Conditioner Efficiency Ratings
The energy efficiency of an air conditioner is determined by the number
of Btu per hour (Btu/h) removed for each watt of power drawn. The
method used to rate the energy efficiency of a central air conditioner
differs from that used for a room air conditioner.
(continued)
423
424 Chapter 9
Air Conditioner Efficiency Ratings (continued)
• Central Air Conditioners. The energy efficiency of the cooling
equipment used in a residential or light commercial central airconditioning system is expressed in terms of its Seasonal Energy
Efficiency Ratio (SEER). In other words, the efficiency of the central air-conditioning equipment is defined in terms of the cooling
effect in Btu per hour divided by the power use in watts for the
seasonal average day (SEER). New air-conditioning equipment
should have a SEER rating of 10 or better. The ratings go as high
as 17.The ratings of equipment manufactured before the new
efficiency ratings went into effect were 8 or lower.
• Room Air Conditioners. The energy efficiency of a room air
conditioner is expressed in terms of its Energy Efficiency Ratio
(EER); that is to say, it is defined in terms of the cooling effect in
Btu per hour divided by the power use in watts for the peak day
(EER). An energy-efficient room air conditioner will have an EER
rating of 8 or higher. One with a 10 rating is recommended for
hot climates.
Some air conditioner manufacturers also participate in the voluntary EnergyStar labeling program. Air-conditioning equipment
with an EnergyStar label means that they possess high EER and
SEER ratings.
Energy efficiency ratings are posted on an energy guide label,
which is attached to the equipment.
Compressors
A compressor is a pumping device used in a mechanical refrigeration
system to receive and compress low-pressure refrigerant vapor into a
smaller volume at higher pressure. Thus, the primary function of a
compressor is to establish a pressure difference in the system to create a flow of the refrigerant from one part of the system to the other.
Compressors are manufactured in many different sizes for a variety of different applications. Most residential compressors are
reciprocating-type, scroll-type units, or rotary-type units, depending on how the refrigerant is compressed. The scroll compressors
are a more recent design.
A reciprocating compressor (also sometimes called a piston
compressor) uses a piston moving inside a cylinder to compress
the refrigerant (see Figures 9-1 and 9-2). The operation of a piston
Air-Conditioning Equipment 425
compressor is similar to that of the reciprocating pistons in an
automotive engine. It is a positive-displacement compressor with
the piston (or pistons) moving in a straight line but alternately in
opposite directions. Both open and hermetic reciprocating compressors are manufactured for use in refrigeration systems.
OUTDOOR
COIL FAN
DISCHARGE AIR
INLET AIR
COMPRESSOR
INLET
AIR
INLET
AIR
VAPOR LINE
CONNECTION
VAPOR &
LIQUID LINE
CONNECTION
INLET AIR
SIDE VIEW
LIQUID LINE
CONNECTION
TOP VIEW
Side and top views of Lennox HP29 reciprocating
compressor. (Courtesy Lennox Industries Inc.)
Figure 9-1
OUTDOOR
FAN/MOTOR
CONTROL
BOX
DISCHARGE
MUFFLER
DEFROST
THERMOSTAT
REVERSING
VALVE
COMPRESSOR
CHECK/EXPANSION
VALVE
BI-FLOW
FILTER DRIER
Cutaway view of Lennox HP29 reciprocating
compressor. (Courtesy Lennox Industries Inc.)
Figure 9-2
426 Chapter 9
A scroll compressor uses two spiral-shaped scrolls to compress the
refrigerant (see Figures 9-3 and 9-4). One scroll remains stationary
while the other orbits around it in a rotary motion. The moving scroll
compresses the refrigerant by forcing it into an increasingly smaller
space. At this point, the gas, now compressed to a high pressure, is
discharged from a port in the stationary scroll to the condenser.
Scroll compressors are quieter than piston compressors because they
contain only one moving part (the single rotating scroll).
DISCHARGE
SUCTION
Figure 9-3
DISCHARGE
PRESSURE
Details of scroll compressor. (Courtesy Lennox Industries Inc.)
DISCHARGE
STATIONARY SCROLL
SUCTION
TIPS SEALED BY
DISCHARGE PRESSURE
Figure 9-4
ORBITING SCROLL
Cross-section of scrolls. (Courtesy Lennox Industries Inc.)
Air-Conditioning Equipment 427
A rotary compressor is a hermetically sealed, direct-drive compressor that compresses the gas by movement of the roll in relation
to the pump chamber. Rotary compressors are manufactured in
large quantities for use in residential cooling systems (see Figures
9-5 and 9-6).
MOTOR ROTOR
MOTOR STATOR
TERMINAL BOX
CRANK SHAFT
PISTON
VALVE
SPRING
SUSPENSION
VALVE
CONNECTING ROD
Figure 9-5
(Courtesy Trane Co.)
Cutaway view of a typical rotary compressor.
428 Chapter 9
ECCENTRIC SHAFT
DISCHARGE
VALVE
ROLLER
SLIDING
VANE
PUMP
CASING
COMPRESSOR BODY
Figure 9-6
Eccentric shaft and roller of a rotary compressor.
(Courtesy Mueller Climatrol Corp.)
Air-Conditioning Equipment 429
A centrifugal compressor is a non-positive-displacement compressor that relies in part on centrifugal effect for pressure rise.
Compression of the refrigerant is accomplished by means of centrifugal force. As a result, this type of compressor is generally used in
installations having large refrigerant volumes and low pressure differentials. The compressors used in residential and light commercial cooling systems may be classified on the basis of how accessible they are
for field service and repair. The following three types are recognized:
1. Open-type compressors
2. Hermetic compressors
3. Semihermetic compressors
As shown in Figure 9-7, an open-type compressor is usually
driven by a separately mounted electric motor. Both the compressor
and motor are easily accessible for field service and repair.
DISCHARGE
SUCTION
FAN BELT
PULLEY
OIL
Diagram on an open-type
compressor. (Courtesy Honeywell Tradeline Controls)
Figure 9-7
The hermetic compressor shown in Figure 9-8 differs from the open
type in being completely sealed, usually by welding. No provision is
made for service access. The compressors used in residential and lightcommercial construction are hermetic compressors. A hermetic compressor is so called because its components are sealed inside a welded
housing. The housing (or can) contains an electric motor and a pump.
Compressors can be reciprocating, scroll, rotary, disc, or screw types.
Note
A sealed (hermetic) compressor must be replaced if it fails because
it cannot be repaired on site. After it is replaced, filter dryers must
be installed to remove any moisture and/or acid in the system.
430 Chapter 9
SUCTION
MOTOR
WELDED
DISCHARGE
OIL
Figure 9-8
Diagram of a hermetic compressor.
(Courtesy Honeywell Tradeline Controls)
Both single-speed and two-speed compressors are used in residential heat pumps. A single-speed compressor is the most common
type. It operates at full capacity regardless of the actual heating and
cooling needs of the structure. A two-speed compressor, on the other
hand, operates at a capacity that approximates the actual heating
and cooling needs at any given moment. A two-speed compressor is,
therefore, much more energy efficient than a single-speed one. It also
is subject to less wear because its operation is not continuous.
The semihermetic compressor is similar in construction to the
hermetic type, except that field service and repairs are possible on
the former through bolted access plates.
Both the compressor and electric motor are sealed in the same
casing in hermetic and semihermetic compressors. As a result, the
motors are cooled by a refrigerant that flows through and around
the motors. Quick-trip overload relays provide additional protection against overheating should the refrigerant flow be cut off.
Semihermetic and hermetic compressor motors of a given size
are designed and constructed to operate on a heavier current without overheating. Hermetically sealing the compressor and electric
motor in the same casing also results in a greater output. The principal disadvantage of a hermetic compressor is that it must be
replaced with a new unit when it malfunctions. Because this usually
occurs in the cooling season, the homeowner may be without airconditioning for a day or so when it is most needed.
Troubleshooting Compressors
When a compressor is suspected of being defective, a complete
analysis should be made of the system before the compressor is
replaced. In some cases, the symptoms encountered in servicing an
Air-Conditioning Equipment 431
air conditioner may lead the serviceperson to suspect the compressor when actually the trouble is in another section of the system.
For example, noise and knocking are often attributed to a faulty
compressor when the trouble may be a loose compressor flywheel,
incorrect belt alignment, air in the system, or a large quantity of oil
being pumped through the compressor because of liquid refrigerant
in the crankcase.
Table 9-1 lists the most common operating problems associated
with air-conditioning compressors. For each observable symptom,
a possible cause and remedy are suggested.
Table 9-1
Troubleshooting Compressors
Symptom and Possible Cause
Possible Remedy
Compressor does not start; no hum.
(a) Open power switch.
(b) Fuse blown.
(c) Broken electrical connection.
(d) Overload stuck.
(e) Frozen compressor or motor
bearings.
(f) High head pressure; cut out
open due to high pressure.
(g) Central contacts in open
position.
(h) Open circuit in compressor
stator.
(i) Thermostat set too high.
(j) Solenoid valve closed.
(a) Close switch.
(b) Replace fuse.
(c) Check circuit and repair.
(d) Wait for reset; check current.
(e) Replace the compressor.
(f) Push high-pressure button and
check for air circulation in
condenser.
(g) Repair and check control.
(h) Replace the compressor.
(i) Reset to proper level.
(j) Examine holding coil; if
burned out, replace.
Compressor starts but motor will not get off of starting windings; high
amperage and rattle in the compressor.
(a) Compressor improperly wired. (a) Check wiring against wiring
diagram; rewire if necessary.
(b) Low line voltage.
(b) Check line voltage and correct
(decrease load on line or
increase wire size).
(c) Relay defective.
(c) Replace relay.
(d) Run capacitor defective.
(d) Replace run capacitor.
(continued)
432 Chapter 9
Table 9-1 (continued)
Symptom and Possible Cause
Possible Remedy
(e) Compressor motor starting
(e) Replace compressor.
and running windings shorted.
(f) High discharge pressure.
(f) Correct excessive high pressure.
(g) Starting capacitor weak.
(g) Check capacitor; replace if
necessary.
(h) Tight compressor.
(h) Check oil level and correct, or
replace compressor.
Compressor will not start; hums and trips on overload.
(a) Compressor improperly
wired.
(b) Low line voltage.
(c) Starting capacitor
defective.
(d) Relay contacts not closing.
(e) Grounded compressor
motor or motor with open
winding.
(f) High discharge pressure.
(g) Tight compressor.
(a) Check wiring against wiring
diagram; rewire if necessary.
(b) Check line voltage and correct.
(c) Replace capacitor.
(d) Check contact points; replace
if defective.
(e) Replace compressor.
(f) Check excessive high pressure.
Check air.
(g) Check oil level and correct, or
replace compressor.
Compressor starts and runs but short cycles.
(a) Low line voltage.
(b) Additional current passing
through overload
protector.
(c) Suction pressure high.
(d) High discharge pressure.
(e) Run capacitor defective.
(f) Compressor too hot;
inadequate motor cooling.
(g) Compressor motor
windings shorted.
(a) Check line voltage; correct.
(b) Check wiring diagram;
fan motors may be
connected to the wrong
side of the protector.
(c) Check compressor for possibility
of misapplication.
(d) Correct excessive high
pressure.
(e) Check capacitor and replace.
(f) Check refrigerant charge; add
if necessary.
(g) Replace compressor.
(continued)
Air-Conditioning Equipment 433
Table 9-1 (continued)
Symptom and Possible Cause
Possible Remedy
(h) Overload protector
defective.
(h) Check current, give reset time;
if it does not come back, replace
compressor.
(i) Check oil level and correct, or
replace compressor.
(j) Replace compressor.
(i) Compressor tight.
(j) Discharge valve defective.
Compressor short cycling.
(a) Thermostat differential
set too closely.
(b) Dirty air filter.
(c) Refrigerant charge
too low.
(d) Dirty strainer or dryer
in liquid line.
(e) Restricted capillary tube
or expansion valve.
(f) Dirty condenser.
(g) Too much refrigerant.
(h) Air in system.
(i) Compressor valve leaking.
(j) Overload protector
cutting out.
(a) Widen differential.
(b) Replace.
(c) Recharge system with
correct charge.
(d) Replace.
(e) Replace.
(f) Clean condenser.
(g) Discharge some refrigerant.
(h) Purge system.
(i) Replace compressor.
(j) Check current and give reset
time; if it does not come back,
replace compressor.
Compressor runs continuously.
(a) Shortage of refrigerant.
(b) Compressor too small
for load.
(c) Discharge valve leaking
badly.
(a) Test at refrigerant test cock; if
short of gas, add proper
amount. Test for leaks.
(b) Increase capacity by increasing
speed or using larger compressor.
(c) Test valve; if leaking, remove
head of compressor and repair
or service.
Compressor noisy.
(a) Vibration because unit
not bolted down properly.
(a) Examine bolts and correct.
(continued)
434 Chapter 9
Table 9-1 (continued)
Symptom and Possible Cause
Possible Remedy
(b) Too much oil in
circulation, causing
hydraulic knock.
(c) Slugging due to flooding
back of refrigerant.
(d) Wear of parts such as
piston, piston pins.
(b) Check oil level and check
for oil in refrigerant test
cock; correct.
(c) Expansion valve is open too
wide. Close.
(d) Locate cause. Repair or
replace compressor.
High suction pressure.
(a) Overfeeding of expansion
valve.
(b) Compressor too small for
evaporator or load.
(c) Leaky suction valves.
(a) Regulate expansion; check
bulb attachment.
(b) Check capacity. Try to
increase speed or replace with
larger-size compressor.
(c) Remove head and examine
valve discs or rings; replace if
worn.
Low suction pressure.
(a) Restricted liquid line and
expansion valve or
suction screens.
(b) Compressor too big for
evaporator.
(c) Insufficient gas in system.
(d) Too much oil circulating in
system.
(e) Improper adjustment of
expansion valves.
(a) Pump down; remove,
examine, and clean screens.
(b) Check capacity against load;
reduce speed if necessary.
(c) Check for gas shortage at test
cock.
(d) Remove oil.
(e) Adjust valve to give more flow.
If opening valve does not
correct, increase size to give
greater capacity.
Each compressor should be equipped with internal devices to
provide protection against the following operating problems:
1.
2.
3.
4.
Motor overload
Locked rotor
Extreme voltage supply
Excessive winding temperature
Air-Conditioning Equipment 435
5. Excessive pressure
6. Loss of refrigerant charge
7. Compressor cycling
If these devices are operating properly, the compressor will provide efficient and trouble-free service.
Compressor Replacement
Before replacing a hermetic compressor, be sure to check other possible causes of system malfunction (see Troubleshooting
Compressors). Do not replace the compressor unless you are absolutely certain it is the source of the trouble.
Many manufacturers will provide instructions for replacing the
compressor along with their installation, servicing, and operating
literature. Carefully read these instructions before attempting to
disconnect the compressor.
Disconnect the power supply, remove the fuses, and check the
liquid refrigerant for oil discoloration or an acrid odor. These are
indications that a compressor burnout has contaminated the system. If the system is not properly cleaned up, the replacement compressor will also burn out.
The system can be checked for contamination by discharging a
small amount of refrigerant and oil through the high-side port onto
a clean white cloth and checking it for discoloration and odor.
Perform the same test on the low-side gauge port. If the system
shows signs of contamination, discharge the remainder of the refrigerant through the liquid line gauge port (on a factory-charged system) or the high-side gauge port (on a field-charged system). Inspect
the refrigerant lines to determine the exact extent of contamination.
Examine the refrigerant lines connected to the evaporator for
contamination. A rapid compressor burnout will usually leave the
evaporator coil unaffected. If the burnout has been particularly
slow and the refrigerant and oil have been circulated through the
system, the evaporator will also be contaminated. A contaminated
evaporator can be cleaned by flushing it with a refrigerant.
Electric Motors
The electric motors used to power mechanical refrigeration equipment are commonly of the following two types:
1. Single-phase induction motors
2. Three-phase induction motors
436 Chapter 9
The single-phase induction motors are usually classified by the
method used to start them. Among the more common ones are the
following:
1.
2.
3.
4.
Split-phase motors
Capacitor-start motors
Permanent-split capacitor motors
Capacitor-start, capacitor-run motors
Capacitor-start and capacitor-start, capacitor-run motors are
described in Chapter 6 (“Other Automatic Controls”) in Volume 2.
Either capacitor-start, capacitor-run or three-phase induction
motors can be used to power compressors. The latter are normally
used when three-phase current is available.
Troubleshooting Electrical Motors
Table 9-2 lists the most common operating problems associated
with electric motors. For each symptom, a possible cause and remedy are suggested.
Table 9-2
Troubleshooting Electrical Motors
Symptom and Possible Cause
Possible Remedy
Motor blows fuses, trips overload.
(a) Fuses and/or overload too
small.
(b) Poor switch contacts.
(c) Low voltage.
(d) Leaky discharge valve.
(e) Overloaded motor.
(a) Install larger sizes if necessary
within safe limit for motor.
(b) Check and replace contacts.
Replace entire switch if
necessary.
(c) Check voltages with meter; if
more than 10 percent low,
notify power company to
correct condition.
(d) Replace.
(e) Check bhp load against backpressure and compressor speed; if
motor is too small, increase size.
Motor hot.
(a) Low voltage.
(a) Check voltage with meter; if
more than 10 percent low,
notify power company to correct condition.
(continued)
Air-Conditioning Equipment 437
Table 9-2 (continued)
Symptom and Possible Cause
Possible Remedy
(b) Bearings need oil.
(c) Overloaded motor.
(b) Oil bearings to reduce friction.
(c) Check bhp load against backpressure and compressor speed; if
motor is too small, increase size.
Gas Engines
A four-cylinder water-cooled gas engine using natural gas as the
fuel can be used to power the compressor (and sometimes the condenser fan). It is normally mounted in a weatherproof cabinet outside the residence where venting is not a problem. Because an
internal combustion engine must be vented, electric motors are by
far the most popular type used for powering mechanical refrigeration equipment.
Electrical Components
The principal electrical components of a mechanical refrigeration
system include the following:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Electric compressor motor
Compressor contactor or relay
Compressor starter
Overload protector
Capacitor
Potential relay
Pressure switch
Evaporator fan motor
Condenser fan motor
Evaporator fan relay
The wiring diagram in Figure 9-9 illustrates the relationship of
these various components. Switches, relays, and capacitors have
already been described in considerable detail in Chapter 6 (“Other
Automatic Controls”) in Volume 2.
The room thermostat is sometimes included when the electrical
components of a refrigeration system are listed. The reader is
referred to Chapter 4 (“Thermostats and Humidistats”) in Volume
2 for detailed information about thermostats.
438 Chapter 9
HUMIDIFIER
T87 THERMOSTAT
AND Q539 SUBBASE
X1
CHECK LIGHT
G
W
R
Y
H46D
HUMIDISTAT
ODOR
CONTROL
R8230, R8225 OR R8222
ISOLATING RELAY
TRANSFORMER
POWER
SUPPLY
HEATING
CONTROL
BLACK
R8210, R8214 OR R8508
CONTACTOR
R8222D DPDT RELAY
POWER
SUPPLY
FAN SWITCH
F50
ELECTRONIC
AIR CLEANER
R8093 THERMAL DELAY RELAY
BROWN
L
H
L1
R8231 IMPEDANCE RELAY
CONDENSER FAN MOTOR
P430/P431
HIGH/LOW
PRESSURE CONTROL
POWER SUPPLY
C
L2
SINGLE PHASE
COMPRESSION MOTOR
TWO SPEED FAN
Impedance relay, thermal delay relay, isolating relay, heat
control, electronic air cleaner, and humidity controls added to a basic
cooling control system. (Courtesy Honeywell Tradeline Controls)
Figure 9-9
Troubleshooting Electrical Components
Table 9-3 lists the most common problems associated with the
operation of the electrical components in air-conditioning equipment.
For each symptom, a possible cause and remedy are suggested.
Table 9-3
Troubleshooting Electrical Components
Symptom and Possible Cause
Possible Remedy
Starting capacitor is open, shorted, or burned out.
(a) Relay contacts not operating
properly.
(b) Improper capacitor.
(c) Low voltage.
(d) Improper relay.
(e) Short cycling.
(a) Clean contacts or replace.
(b) Check for proper MFD rating
and voltage.
(c) Check and correct.
(d) Check and replace.
(e) Replace starting capacitor.
(continued)
Air-Conditioning Equipment 439
Table 9-3 (continued)
Symptom and Possible Cause
Possible Remedy
Running capacitor is open, shorted, or burned out.
(a) Improper capacitor.
(b) Excessive high line voltage.
(a) Check for proper MFD rating
and voltage.
(b) Correct line voltage to not more
than 10 percent of rated motor
voltage.
Relay is shorted or burned out.
(a) Line voltage is too low or
too high.
(b) Incorrect running capacitor.
(c) Loose relay.
(d) Short cycling.
(a) Check and correct.
(b) Replace with correct MFD
capacitor.
(c) Tighten relay.
(d) Replace relay.
Condenser
A condenser is a device that is used to liquefy gas by cooling. In
operation, hot discharge gas (refrigerant vapor) from the compressor enters the condenser coil at the top and, as it is condensed, drains out of the condenser to a receiver located at a
lower level.
The condenser coil is located along with the compressor and
controlling devices in the condensing unit. In a remote or splitsystem air-conditioning installation, the condensing unit is located
outdoors (see Figure 9-10). Condensers are available in a variety of
designs, including plain tube, finned tube, and plate type, and as
series-pass and parallel-pass units. A number of different condensers are illustrated in Figures 9-11, 9-12, 9-13, and 9-14.
Condensers may be classified with respect to the cooling method
used into the following three types:
1. Air-cooled condensers
2. Water-cooled condensers
3. Combined air- and water-cooled condensers
An air-cooled condenser consists of a coil of ample surface
across which air is blown by a fan or induced by natural draft (see
Figure 9-15). This type of condenser is universally used in smallcapacity refrigerating units.
440 Chapter 9
EVAPORATOR COIL
FURNACE
CONDENSING UNIT
REFRIGERANT LINES
Location of the condensing unit in a remote
or split-system air-conditioning installation.
Figure 9-10
FAN AND
MOTOR ASSEMBLY
CONDENSER COIL
COMPRESSOR
WIRING AND
CONTROL BOX
REFRIGERANT
LINE
CONNECTIONS
Figure 9-11
Lennox HSW4 series air-conditioning condenser unit.
(Courtesy Lennox Air Conditioning and Heating)
Air-Conditioning Equipment 441
CONDENSER
COIL
COMPRESSOR
Figure 9-12
WIRING AND
CONTROL BOX
CONDENSER
COIL GRILLE
FAN AND
MOTOR ASSEMBLY
REFRIGERANT LINE CONNECTIONS
Lennox HS8 series air-conditioning condenser unit.
(Courtesy Lennox Air Conditioning and Heating)
A water-cooled condenser is similar to a steam surface condenser
in that cooling is accomplished by water alone that circulates
through tubes or coils enclosed in a shell. The refrigerant circulates
through the annular space between the tubes or coils. Because of its
construction, a water-cooled condenser is also sometimes called a
double-pipe condenser (see Figure 9-16).
Maximum temperature differences can be obtained by connecting the condenser for counterflow. This type of arrangement usually
gives the best operating results.
Shell-and-tube construction is recommended for a small condensing unit. In medium-size units, shell-and-coil construction
works very well (see Figures 9-17 and 9-18).
A combined air- and water-cooled condenser, more commonly
known as an evaporative condenser, consists of a coil cooled by water
sprayed from above and cold air entering from below (see Figure 9-19).
442 Chapter 9
HEATING REVERSING
VALVE
AIR FLOW
REVERSING VALVE
SOLENOID
COMPRESSOR
COMPRESSOR
CAPACITOR
LOW PRESS
SERVICE PORT
HEATING CAPILLARY
AND CHECK VALVE
(THIS AREA)
DEFROST TIMER
DEFROST RELAY
CONTRACTOR
FAN MOTOR
CONTROL
PANEL
230 V 60 CY
24 V
LIQUID FITTING
Figure 9-13
MANUAL HI PRESS, SW.
SUCTION FITTING
Bard 36HPQ1 condensing unit. (Courtesy Bard Mfg. Co.)
As water evaporates from the coil, it brings about a cooling
effect, which condenses the refrigerant within the coil. The hot
refrigerant gas within the coil is thus changed to the liquid state by
the combined action of the sprayed water and the large volume of
moving air supplied by the fan. The water that does not evaporate
is recirculated by means of a pump.
Because an evaporative condenser is not wasteful of water, large
compressor installations are possible in areas where water is scarce.
Tests have shown that the amount of water required will not exceed
0.03 gpm per ton of refrigeration. Evaporative condensers also
eliminate wastewater disposal problems and provide the most economical means of cooling refrigerant gases.
Air-cooled condensers, like evaporators, should be kept free from
dirt, lint, and other foreign materials because they tend to reduce the
airflow around tubes and fins if they are allowed to accumulate.
Condenser Service and Maintenance
The aluminum fins on condenser coils are easily bent and can block
airflow through the coil. A tool called a fin comb is available at
Air-Conditioning Equipment 443
Climatrol
938-1 dual-compressor
condensing unit.
Figure 9-14
(Courtesy Mueller Climatrol Corp.)
air-conditioning equipment wholesalers that will comb these fins
back into nearly original condition.
REFRIGERANT
GAS IN
CONDENSER
FAN
Troubleshooting Condensers
Common operating problems associated with air-conditioning condensers are listed in Table 9-4. For
each symptom, a possible cause and
remedy are suggested.
Receiver
REFRIGERANT
LIQUID OUT
Figure 9-15
Air-cooled
condenser.
(Courtesy Honeywell Tradeline Controls)
As the name suggests, the receiver is
the reservoir for any excess liquid
refrigerant not being used in the system. The liquid receiver must be large
enough to hold the total amount of
444 Chapter 9
WATER
OUT
REFRIGERANT
GAS IN
REMOVABLE
END
REFRIGERANT
LIQUID OUT
Figure 9-16
WATER
IN
Double-pipe condenser.
(Courtesy Honeywell Tradeline Controls)
REFRIGERANT
GAS IN
REMOVABLE
HEADS
BAFFLES
WATER
OUT
WATER
IN
REFRIGERANT
LIQUID OUT
FINNED TUBES
HELD IN END
SHEETS
Figure 9-17
Shell-and-tube condenser.
(Courtesy Honeywell Tradeline Controls)
REFRIGERANT
GAS IN
WATER
OUT
COIL
REFRIGERANT
LIQUID OUT
WATER
IN
Figure 9-18
Shell-and-coil condenser.
(Courtesy Honeywell Tradeline Controls)
Air-Conditioning Equipment 445
CONDENSING
COIL
EVAPORATOR
EVAPORATIVE
CONDENSER
AIR IN
COMPRESSOR
Figure 9-19
Evaporative condenser. (Courtesy Honeywell Tradeline Controls)
Table 9-4
Troubleshooting Condensers
Symptom and Possible Cause
Possible Remedy
Compressor pressure too high.
(a) Air in system.
(b) Dirty condenser.
(c) Refrigerant too high.
(d) Unit location too hot.
(e) Condenser air off.
(a) Purge system.
(b) Clean condenser.
(c) Discharge some refrigerant.
(d) Change unit location.
(e) Check condenser motor
connections for burnout.
Condenser pressure too low.
(a) Refrigerant charge too low.
(b) Compressor discharge or
suction valves defective.
(c) Entering temperature to
evaporator low.
(a) Check for leak, repair, and
recharge with correct amount of
refrigerant.
(b) Replace compressor.
(c) Raise temperature.
446 Chapter 9
COLD WATER
COIL
ROOM COOLING
UNIT
BLOWER
TO DRAIN
COLD WATER
PIPING
HEAT EXCHANGER
(EVAPORATOR COIL)
REFRIGERANT
PIPING
WATER CHILLER
PACKAGE
Figure 9-20
Evaporator coil. (Courtesy Coleman Co.)
Figure 9-21
Evaporator coil and water chiller.
(Courtesy Honeywell Tradeline Controls)
Air-Conditioning Equipment 447
refrigerant used in the system. Receivers are commonly constructed
of drawn steel shells welded together to form a single unit.
Evaporator
An evaporator is a device used in either mechanical- or absorptiontype refrigeration systems to transfer or absorb heat from the air
surrounding the evaporator to the refrigerant. In so doing, the liquid refrigerant is evaporated or boiled off as it passes through the
evaporator.
Evaporators are made of copper tubing with or without closely
spaced aluminum fins designed to increase the heat transfer surface.
Because of its function (that is, removing heat from room air) and
construction, an evaporator is also referred to as an evaporator
coil, cooling coil, blower coil, or direct-expansion coil.
Figure 9-20 illustrates a typical evaporator coil used in the bonnet or plenum of a warm-air furnace. The coil capacity must be
matched to the condensing unit for efficient cooling. This is particularly important to remember when converting an existing heating
system to year-round air-conditioning.
An evaporator coil may also be placed in the heat exchanger of a
water chiller as shown in Figure 9-21. The water cooled in the
water chiller is piped to the cold-water coil over which the room air
is circulated. The coil may be duct mounted (in a warm-air heating
system) or located in a room cooling unit (in a forced hot-water
heating system).
Evaporator Service and Maintenance
The aluminum fins on evaporator coils, like those on the condenser
coils, are also easily bent. If bent, they can block the flow of air
through the coil. The same tool used to straighten the fins on the
condenser tubing can be used to return the evaporator fins to their
original position.
Troubleshooting Evaporators
An evaporator must be kept clean and free of dirt and dust so that
the flow of air through the tubes remains unrestricted. If the evaporator is damaged or leaking to such an extent that it cannot be successfully repaired, it should be replaced by a new assembly. If
repairs or replacement are necessary, the complete coil assembly
must be removed from the system.
Before removing a damaged or leaking evaporator, the refrigerant lines must first be disconnected and the evaporator retaining
bolts (if used) loosened and removed.
448 Chapter 9
The new evaporator is bolted or otherwise secured in place and
connected to the refrigerant lines. After all connections are made,
the entire system is evacuated, recharged with refrigerant, and
tested for leaks.
Refrigerants
A refrigerant is any substance that produces a refrigerating effect by
absorbing heat as it expands or vaporizes. A desirable refrigerant
should possess chemical, physical, and thermodynamic properties that
permit efficient and safe operation in refrigerating systems. Among
the properties possessed by a good refrigerant are the following:
1.
2.
3.
4.
5.
6.
7.
8.
Low boiling point
Nontoxic and nonirritating
Nonexplosive
Nonflammable
Mixes well with oil
Operation on a positive pressure
High latent heat value
Not affected by moisture
Two of the most commonly used refrigerants in older equipment
are R-12 (Freon 12) and R-22 (Freon 22). These are clear, almost
colorless liquids at temperatures below their boiling points.
R-12 has a boiling point of –21.8°F at atmospheric pressure and
is characterized by moderate pressure differentials between suction
and discharge. A moderate volume of R-12 is required per ton of
refrigeration.
R-22 has a boiling point of –41.4°F at atmospheric pressure. In
contrast to R-12, it has a considerably higher pressure differential
between suction and discharge. As a result, it requires a smaller volume of refrigerant per ton of refrigeration.
R-410A is gradually replacing older refrigerants because it does
not possess the ozone-depleting chemical properties of the latter.
Refrigerant R-410A is known by such trade names as PuronTM,
Dupont Suva, and Genetron AZ20. Many HVAC manufacturers
are already using the new refrigerant in new air-conditioning
equipment.
Older air-conditioning equipment and systems cannot be
retrofitted with R-410A. If an older refrigerant was used, it must be
removed, cleaned, and reused. Because R-410A runs operating
pressures higher than older refrigerants, new sets of hoses and
refrigerant gauges are required for installation, service, and repair.
Air-Conditioning Equipment 449
Note
The efficiency of an air conditioner is greatest when the refrigerant charge exactly matches the manufacturer’s specification and is
neither undercharged nor overcharged. If the air conditioner is on
refrigerant (undercharged) and not leaking, refrigerant should be
added by a trained HVAC technician. If the air conditioner is leaking refrigerant, do not add refrigerant. Have a trained HVAC technician fix the leak, test the repair, and then charge the system with
the correct amount of refrigerant.
Liquid Refrigerant Control Devices
Each refrigeration system may be described in terms of a low side
and a high side of operating pressure. The low side is that part of the
refrigeration system that normally operates under low pressure (as
opposed to the high side). It is identified as that part of a refrigeration
system lying between the expansion valve and the intake valve in the
compressor, and includes the evaporating or cooling surface, the
intake line, and the compressor crankcase—in other words, that part
of the refrigeration equipment under intake pressure. The term low
side is sometimes used to designate the evaporator coils.
The high side is that part of the refrigeration system operating
under high pressure. The term high side is sometimes used to designate the condensing unit.
Some form of expansion device is necessary to control the flow
of liquid refrigerant between the low and high sides of a refrigeration system. The following expansion devices are designed to provide automatic control of refrigerant flow:
1.
2.
3.
4.
Automatic expansion valves
Thermostatic expansion valves
Float valves
Capillary tubes
Automatic Expansion Valves
An automatic expansion valve is a pressure-actuated diaphragm
valve used to maintain a constant pressure in the evaporator of a
direct-expansion mechanical refrigeration system (see Figure 9-22).
It accomplishes this function by regulating the flow of refrigerant
from the liquid line into the evaporator. In this way, the evaporator
is always supplied with the proper amount of refrigerant to meet
conditions. An automatic expansion valve does not respond well to
load fluctuations. For this reason, it is not recommended for use in
air-conditioning (see Thermostatic Expansion Valves).
450 Chapter 9
MANUAL
ADJUSTMENT
Automatic
expansion valve.
Figure 9-22
SPRING
BELLOWS
DIAPHRAGM
VENT TUBE
PUSH ROD
OUTLET
SEAT
CHECK BALL
SPRING
STRAINER
INLET
Thermostatic Expansion Valves
The thermostatic expansion valve is designed to automatically control the flow of liquid refrigerant entering the evaporator coil. The
valve mechanism must operate freely and without restriction in
order to allow the proper amount of refrigerant to enter the evaporator (see Figures 9-23 and 9-24).
Failure of any part of the thermostatic expansion valve will
affect the refrigerating capacity of the unit and the cooling capacity
of the system. Faulty operation of the expansion valve may be
caused by mechanically frozen internal parts clogging the strainer
or valve orifice, or by failure of the regulating sensor bulb, which
operates the needle valve.
If the expansion valve is frozen partly open, the capacity of the
unit will be affected because the flow of refrigerant is restricted. If
the expansion valve is frozen in a fully open position, the liquid
refrigerant may flow through the entire system, causing very cold
inlet line, high inlet pressure, pounding of the compressor, and a
cold compressor head.
Air-Conditioning Equipment 451
Figure 9-23
Typical thermostatic expansion valve.
452 Chapter 9
THERMOSTATIC
EXPANSION
VALVE
DIAPHRAGM A
TUBE C
SPRING B
EQUALIZER PORTS D
LIQUID
LINE FROM
RECEIVER
EVAPORATOR
RESTRICTION F
COIL
REMOTE
BULB E
Figure 9-24
SUCTION
LINE TO
COMPRESSOR
Thermostatic expansion valve operating principle.
(Courtesy Honeywell Tradeline Controls)
The pressure in the sensor bulb or feeler of the expansion valve
must be somewhat higher than the pressure in the evaporator,
which means that the inlet line where the bulb is clamped must be at
a higher temperature than that within the evaporator. Accordingly,
the vapor in the inlet line at this point must be in a somewhat
superheated state. This superheat should be at the minimum that
will allow the valve to regulate the flow of refrigerant.
For higher-temperature work, such as comfort cooling work, the
amount of superheating will vary between 5° and 10°. For lowertemperature work, such as product cooling work, the superheating
will vary between 4° and 6° or in some cases even lower.
Excessive superheat indicates a lack of sufficient refrigerant
flowing through the expansion valve, a condition that reduces the
capacity of the evaporator.
The sensitivity and response of the thermostatic expansion valve is
largely dependent on the proper installation of the sensor (feeler) bulb.
The sensor bulb should always be firmly attached to the inlet line.
When properly installed and adjusted, the thermostatic expansion valve will maintain all the evaporator surface effective and in
contact with the boiling refrigerant regardless of the change in load
on the evaporator, provided of course that the evaporator valve has
sufficient capacity for peak loads.
Air-Conditioning Equipment 453
Under normal operating conditions, the sensor (feeler) bulb will
cause the thermostatic expansion valve to close during the shutdown period. There are, however, certain conditions that will affect
this and may cause overflooding of the evaporator. For this reason,
the inlet lines should be trapped.
If the evaporator in an air-conditioning system is connected to
outside air or where it may receive air at a temperature lower than
that surrounding the sensor (feeler) bulb, the difference in temperature between the evaporator and the bulb will cause the valve to
open and overflood the low side. Under such conditions, it is
essential that the liquid line be equipped with a solenoid valve to
positively shut off the refrigerant during the shutdown period.
Float Valves
A float valve is one actuated by a float immersed in a liquid container
(see Figure 9-25). Both low-side and high-side float valves are used
to control the flow of liquid refrigerant in a refrigeration system.
GASKET
EXP
INLET FOR
LEVEL CONTROL
OUTLET FOR
EXPANSION
CONTROL
VALVE PORTS
GASKETS
END VIEW
GASKET
EQUALIZING CONNECTION
PIVOT
FLOAT
BALANCE WEIGHT
CUSHING SPRING
FLOAT IS WIRED FAST TO THIS
NIPPLE DURING SHIPMENT
Figure 9-25
EQUALIZING CONNECTION
Float valve construction details. (Courtesy Frick Company)
REMOVABLE HEAD
LEVEL
INLET FOR
EXPANSION.
OUTLET FOR
LEVEL
CONTROL
454 Chapter 9
A low-side float valve is one that is operated by a low-pressure
liquid. It opens at a low level and closes when the liquid is at a high
level. In other words, when there is no liquid in the evaporator, the
float and lever arm are positioned so that the valve is left open.
When liquid refrigerant under pressure from the compressor again
enters the float chamber, the float rises until a predetermined level
is reached and the valve is closed.
A high-side float valve is one that is operated by a high-side pressure. The valve opens on an increase of the liquid level in the float
chamber and admits liquid to the low side.
Capillary Tubes
A capillary tube is a tube of small internal diameter used in refrigeration air-conditioning systems as an expansion device between
the high-pressure and low-pressure sides. It can also be used to
transmit pressure from the sensor bulb of some temperature controls to the operating element (see Figure 9-26).
CAPILLARY
TUBE
LIQUID LINE
FROM RECEIVER
EVAPORATOR
COIL
SUCTION LINE
TO COMPRESSOR
Capillary tube and connections to mechanical
refrigeration system. (Courtesy Honeywell Tradeline Controls)
Figure 9-26
The use of a capillary tube as a liquid refrigerant expansion device
is largely limited to completely assembled factory refrigeration units
because the bore diameters and the length of the tube are critical to
its efficiency. The pressure reduction that occurs between the condenser and evaporator results from the pressure drop or friction loss
in the long, small-diameter passage provided by the capillary tube.
No pressure-reducing valve is necessary between the high-side and
low-side pressure zones when a capillary system is used.
Refrigerant Piping
The refrigerant travels between the various components of a
mechanical refrigeration unit or system in small-diameter copper
tubing sometimes referred to as the refrigerant lines.
Air-Conditioning Equipment 455
The suction line is the piping between the evaporator and compressor inlet. Its function is to carry the refrigerant vapor to the
compressor. It is important that the suction line be correctly sized for
a practical pressure drop at full load. Under minimum load conditions, the suction line should be able to return oil from the evaporator
to the compressor. Two other desirable features that should be
incorporated in the design of a suction line are the following:
1. The prevention of oil drainage into a non-operating evapora-
tor from an operating one.
2. The prevention of liquid drainage into a shut-down compressor.
The liquid line is the piping that carries the liquid refrigerant
from the condenser or receiver to a pressure-reducing device.
The refrigerant piping (lines) should be carefully checked to
make certain they will function properly. All connections should be
examined for leaks, and all bends should be checked to make certain the tubing has not been squeezed together. A squeezed or
pinched line will restrict the flow of refrigerant.
The slope of the suction line is also important in remote or splitsystem installations. When the evaporator coil is higher than the
condensing unit, the suction line should be sloped with a continuous fall of at least 1⁄4 inch per foot toward the condensing unit.
If the evaporator coil is higher than the condensing unit and the
excess line is coiled, the excess tubing must be coiled horizontally in
such a way that the flow of refrigerant is from the top to the bottom of the coil and toward the condensing unit in a continuous fall
(see Figure 9-27).
Refrigerant Piping Service and Maintenance
Check the liquid and suction lines to make certain that they do not
contact one another. Heat will transfer to the suction line if there is
bare contact between the two.
Figure 9-27
Flow of refrigerant toward the condensing unit.
(Courtesy Coleman Co.)
456 Chapter 9
Check refrigerant line connections for proper seat at the evaporator coil. These are nonreusable connecting valves that must be
100 percent seated for effective operation. If these valves have not
been 100 percent seated, then the metal diaphragm will obstruct
the line and restrict the flow of refrigerant. If this condition is suspected, use a wrench on the stationary fitting of the valve as shown
in Figure 9-28 while tightening the nut with another wrench.
BACK
UP
TIGHTEN
CONNECTION
Figure 9-28
Using wrenches to tighten connection. (Courtesy Coleman Co.)
Troubleshooting Refrigerant Piping
Table 9-5 lists the most common operating problems associated
with the refrigerant piping. For each observable symptom, a possible cause and remedy are suggested.
Table 9-5
Troubleshooting Refrigerant Piping
Symptom and Possible Cause
Possible Remedy
Frosted or sweaty suction line.
(a) Capillary tube or expansion
(a) Check the size and bore of
valve passes excess refrigerant.
capillary tube. Readjust the
expansion valve.
(b) Expansion valve is stuck.
(b) Clean valve; replace if necessary.
(c) Evaporator fan not running.
(c) Repair or replace.
(d) Overcharge of refrigerant.
(d) Correct.
(e) Ambient temperature too low. (e) Block the condenser to increase
the suction pressure or stop the
unit.
(continued)
Air-Conditioning Equipment 457
Table 9-5 (continued)
Symptom and Possible Cause
Possible Remedy
Hot liquid line.
(a) Low refrigerant charge.
(b) Expansion valve stuck or
open too wide.
(a) Fix leak and recharge.
(b) Clean valve and replace if
necessary.
Frosted or sweating liquid line.
(a) Restriction in dryer.
(a) Replace dryer.
Frost on expansion valve or on capillary tube.
(a) Ice plugging capillary tube
or expansion valve.
(a) Apply hot wet cloth to
capillary tube or expansion
valve; a suction pressure
increase indicates moisture
present. Replace dryer.
Filters and Dryers
Filters and dryers are devices that provide very important functions
in a mechanical refrigeration system. A filter is a device used to
remove particles from the liquid refrigerant and from the oil by
straining the fluid. For this reason, it is also sometimes referred to as
a strainer. If a filter or strainer were not used, these particles trapped
in the fluid could block small passages in the thermostatic valve or
capillary tube, thereby seriously affecting the operation of the cooling system, or they could eventually damage mechanical parts.
A dryer is a device designed to remove moisture from the refrigerant in a mechanical refrigeration system. It is also referred to as a
dehydrator or a drier (a spelling variant used by some authorities).
A typical combination filter-dryer is shown in Figure 9-29. The
desiccant surrounding the filter core is usually a silica gel and functions
as a drying agent. This unit is usually installed in the liquid line (either
at the liquid receiver outlet or at the expansion valve outlet).
Filters and dryers are not included with small-capacity cooling
units (residential types) that are filled and hermetically sealed at the
factory. Filters and dryers are usually installed in systems where the
refrigerant circuit is designed for field service.
Pressure-Limiting Controls
Certain pressure-limiting controls are used in cooling systems to
protect them from extremes in refrigeration suction and discharge
line pressures. Whenever the pressures in the system deviate from
458 Chapter 9
SCREEN CORE
STEEL SHEEL
INLET
OUTLET
DESICCANT
COTTON YARN
Figure 9-29
Combination filter-dryer. (Courtesy Honeywell Tradeline Controls)
the normal operating range, the
pressure control breaks the circuit
to the compressor until the pressure
returns to normal. High-side and
low-side pressure switches are
described in Chapter 6 (“Other
Automatic Controls”) in Volume 2.
Water-Regulating Valves
Temperature-actuated water-regulating valves are used on water-cooled
condensers to maintain condensing
pressures within the desired range.
This is accomplished by increasing or
decreasing the rate of water flow as
required by conditions in the system.
Most water-regulating valves may be
classed as either direct acting or pilot
operated.
In the case of a direct-acting valve,
the deflection of the bellows caused by
an increase in refrigerant pressure overcomes the force of the springs and
pushes the disc away from the seat,
allowing water to flow. When the unit
shuts down, the refrigerant pressure
Figure 9-30 Diagram of a
becomes less than the spring pressure
direct-acting water-regulating
and the water valve closes off (see
valve.
Figure 9-30).
In the pilot-operated valve, the main plunger to which the disc is
attached is actuated by water pressure. Opening and closing the pilot
Air-Conditioning Equipment 459
port causes the differential pressure across the hollow plunger to vary.
The amount of water that will flow through any given size and type of
orifice will depend on the pressure differential across the orifice.
Water-regulating valves are rated at a certain quantity of flow
under a given pressure differential and the amount of valve opening. The amount of opening is controlled by refrigerant pressure,
but if the pressure differential is insufficient, no amount of opening
will provide the necessary water for the condenser.
Automatic Controls
Refrigeration and air-conditioning systems consist of refrigeration
equipment and an electrical control circuit. These components are
interconnected to produce and control the required cooling.
Wiring diagrams of some typical automatic cooling control circuits
used in refrigeration and air-conditioning systems are illustrated in
Figures 9-31 and 9-32.
A cooling control circuit can be divided into the following principal components:
1.
2.
3.
4.
Basic controller or thermostat
Limit control
Primary control
Power supply
The relationships and functions of these various control system
components are illustrated in Figure 9-31. Detailed descriptions of
these components are given in a number of different chapters, especially Chapters 4 and 6 in Volume 2. Refer to the index for additional information.
Note
The compressor and fan controls are subject to early failure in an
oversized air-conditioning system because the air conditioner is
forced to turn on and off frequently. The corrosion of wires and
terminals is also a problem in many systems. Regularly check all
electrical wiring and contacts for loose connections, corrosion,
and damage.
System Troubleshooting
Table 9-6 lists the most common operating problems associated
with the system as a whole. For each problem and symptom, a possible cause and remedy are suggested.
460 Chapter 9
T87 THERMOSTAT
AND Q539 SUBBASE
G
R
Y
R8226A, R8227A OR R8239A
FAN CENTER
FAN SWITCH
G
R
W
POWER SUPPLY 1
Y
FAN RELAY COIL
C
TRANSFORMER
R8210A OR R850B
CONTACTOR
POWER
SUPPLY
P430/P431
HIGH/LOW
PRESSURE
CONTROLS
CONDENSER FAN MOTOR
L
H
TWO-SPEED
FAN MOTOR
POWER SUPPLY 1
C
1
SINGLE-PHASE
COMPRESSOR
Power supply. Provide disconnect means and overload protection, as required.
Basic cooling control system with system power supplied
by fan center transformer. (Courtesy Honeywell Tradeline Controls)
Figure 9-31
General Servicing and Maintenance
It must be thoroughly understood that the greatest precautions must
be taken to exclude air and moisture from a refrigeration system and
that it should not be opened to the atmosphere without first removing
the refrigerant from that part of the system to be serviced or repaired.
Caution
Always shut off the electrical power to the air conditioner at the
disconnect switch before performing any maintenance or repairs.
The air conditioner may have multiple power supplies.
Air-Conditioning Equipment 461
L1
L2
120 V. 60 Hz. OR
208/240 V. 60 Hz
EAC
BLACK
BROWN
ODOR CONTROL
FAN MOTOR
H
C
HIGH SPEED
DPDT
FAN RELAY
LOW SPEED
SPDT SWITCH
L
FAN SWITCH
HUMIDIFIER
HUMIDISTAT
TRANSFORMER
LIMIT
24 V AC
THERMAL RELAY
PRESSURE CONTROLS
IMPEDANCE
RELAY
CONTACTOR COIL
IMPEDANCE
RELAY COIL
R
Y
THERMAL DELAY HEATER
G
CHECK
LIGHT
FAN RELAY COIL
W
ISOLATION RELAY COIL
X1
IMPEDANCE RELAY
L3
L1
208/240 V. 60 Hz
COMPRESSOR MOTOR
L1 T1
CONTACTOR
L3 T3
CONTACTOR
CONDENSER FAN MOTOR
Ladder diagram of basic cooling system
control circuit. (Courtesy Honeywell Tradeline Controls)
Figure 9-32
462 Chapter 9
Table 9-6 System Troubleshooting
Symptom and Possible Cause
Possible Remedy
Unit operates continuously.
(a) Shortage of refrigerant.
(b) Control contacts frozen
or stuck closed.
(c) Insufficient air or dirty
condenser.
(d) Air conditioner space poorly
insulated or excess load in
structure.
(e) Compressor valves defective.
(f) Restriction in refrigerant
system.
(g) Filter dirty.
(h) Air bypassing the coil or
service load.
(a) Fix leak and recharge.
(b) Clean points or replace.
(c) Check and correct.
(d) Replace with larger unit.
(e) Replace compressor.
(f) Check and correct.
(g) Clean or replace.
(h) Check return air; keep windows
and doors closed.
Space temperature too high; not enough cooling.
(a) Refrigerant charge low.
(b) Control set too high.
(c) Cap tube, expansion valve,
or dryer plugged.
(d) Iced or dirty coils.
(e) Unit too small.
(f) Insufficient air circulation.
(g) Cap tube or expansion valve
not allowing enough
refrigerant.
(h) Cooling coils too small.
(i) Restrictions or small gas lines.
(j) High and low pressures
approaching each other;
defective compressor valves.
(k) Low line voltage.
(l) Dirty air filter.
(m)Dirty condenser.
(n) Air circulator size too small.
(o) Ductwork too small.
(a) Check for leaks and recharge.
(b) Reset control.
(c) Repair or replace.
(d)
(e)
(f)
(g)
Defrost or clean.
Replace with larger unit.
Correct air circulation.
Reset or replace.
(h) Replace.
(i) Correct restrictions; increase
line size.
(j) Replace compressor.
(k)
(l)
(m)
(n)
Check line voltage and correct.
Replace.
Clean condenser.
Replace with larger air `
circulator.
(o) Increase size of ductwork.
(continued)
Air-Conditioning Equipment 463
Table 9-6 (continued)
Symptom and Possible Cause
Possible Remedy
Noisy unit.
(a) Tubing rattle.
(b) Fan blade causing vibration.
(c)
(d)
(e)
(f)
(a) Fix so it is free from contact.
(b) Check for bend; replace if
necessary.
Refrigerant overcharged or
(c) Check for correct refrigerant
oil too high.
charge and maintain oil level.
If necessary, replace expansion
valves or capillary tube.
Loose parts or mountings.
(d) Fix and tighten.
Motor bearings worn.
(e) Replace motor.
Lack of oil in the compressor. (f) Add required oil.
No air delivery out of register.
(a) System not set for summer
cooling.
(b) Fan motor not operating.
(c) Open power switch.
(d) Fuse blown.
(e) Broken connection.
(f) Register closed.
(g) Evaporator fan motor leads
not connected to line voltage.
(a) Read operating instructions
and make required adjustment.
(b) Repair or replace.
(c) Close switch.
(d) Replace with same-size fuse.
(e) Check circuit and repair.
(f) Open register.
(g) Connect the leads.
Regular Maintenance
Extend the service life and operating efficiency of the air-conditioning equipment and system by providing regular maintenance. A regular maintenance schedule should include the following:
• Clean the indoor evaporator coils.
• Clean the outdoor condenser coils. Use a water hose to flush
the outdoor condenser coils.
• Check the coils for leaks with a leak detector.
• Clean or replace the indoor unit filter.
• Check wiring and contacts for loose connections, corrosion,
and/or damage.
• Check the amp draw at the outdoor fan motor and the indoor
blower motor and compare the values to those on the unit
nameplate.
464 Chapter 9
• Check the voltage at the indoor and outdoor units with the
units operating.
• Check the system for the correct amount of refrigerant.
• Inspect the condensate drain line for blockage and clean as
necessary.
• Check the ducts for leaks and repair if found.
• Oil motors and check belts for tightness and wear.
• Check for the correct electrical control sequence.
Pumping Down
Whenever a refrigeration system is to be opened to the atmosphere
for service operations or repairs, it is necessary to remove the refrigerant from that part of the system to be opened. By pumping down
the system prior to servicing, the refrigerant can be saved.
The manufacturer of the equipment will usually include detailed
instructions concerning the pump-down procedure. Read and follow these instructions carefully.
Pumping down the system usually involves confining the refrigerant to the receiver by closing off the liquid line stop valve and
(with a gauge attached to the intake stop valve) operating the compressor. By doing this, all the gas is drawn back to the compressor
and condensed in the condenser but is prevented from going further
by the liquid line stop valve.
The compressor should be run until the suction pressure is
reduced to holding steady at approximately 2 to 5 lbs pressure. Do
not draw a vacuum on the system. A vacuum will cause moisture to
be drawn into the system when it is opened.
Purging
Purging refers to the release of air or noncondensable gases from a
system, usually through a cock placed on or near the top of the
receiver. This term is also applied to the sweeping of air out of a
newly installed part or connection by releasing refrigerant gas into
the part and allowing it to escape from the open end, thus pushing
the air ahead of it.
Follow the instructions for purging contained in the manufacturer’s installation and operating literature.
Evacuating the System
Sometimes it becomes necessary to remove the entire refrigerant
charge from the system. This operation is referred to as evacuating
the system and is accomplished as follows:
Air-Conditioning Equipment 465
1. Close the discharge service valve stem by turning it clockwise
and remove the gauge connection plug.
2. Open the inlet service valve by turning the stem counterclock-
wise and attach a compound gauge to the inlet service valve.
3. Close the valve 1⁄2 turn clockwise and start the unit discharg-
ing through the open gauge connection in the discharging service valve.
Warning
Capture the evacuated refrigerant. It is illegal to release the refrigerant to the atmosphere.
If a vacuum is pumped too rapidly, the compressor will have a
tendency to pump oil out of the compressor crankcase. Attach a
copper tube to the gauge port and bend it so that any oil pumped
out may be drained into a container. During this operation, the
compressor may knock.
If knocking occurs, stop the compressor for about a minute and
then restart. Continue the process until the gauge indicates a 20inch vacuum or better. At this point, leaks in the system may be
detected by putting sufficient oil in the container to cover the end
of the tubing and continuing the pumping operation. When the
system is entirely evacuated, no more bubbles should appear in
the oil container. After the system is fully evacuated, replace the
discharge gauge connection plug or attach a pressure gauge as
desired.
Charging
Charging is the addition of refrigerant to a system from an external
drum. There are a number of ways to add a refrigerant charge to a
system, but the safest method usually is to introduce the refrigerant
through the liquid line. The procedure may be outlined as follows:
1. Connect the refrigerant cylinder to the liquid line port at the
2.
3.
4.
5.
condenser or compressor.
Purge the connecting line and tighten the last connection.
Disconnect the compressor so that it will not run during the
charging operation.
Turn on the blower to the condenser.
Warm the refrigerant cylinder by placing it in a bucket of
warm water (see Figure 9-33). Do not immerse any refrigerant
connections.
466 Chapter 9
DRUM
VALVE
1⁄
4
" COPPER TUBING
SUCTION
GAUGE
SUCTION
SERVICE VALVE
WARM
WATER
Figure 9-33
Warming the refrigerant cylinder.
6. Remove the cylinder from the water when you are satisfied it
has been thoroughly warmed.
7. Wipe the cylinder dry and invert it.
8. Open the cylinder valve and the charging port valve.
The refrigerant should flow very readily into the high-pressure
side of the system if steps 1–8 were carefully followed.
After the system has been charged, close the refrigerant cylinder
valve, allow 2 or 3 minutes to pass, and disconnect the cylinder.
Reconnect the compressor and operate the unit, using gauges to
determine if the charge is sufficient.
Always exercise caution when making connections or disconnections on the liquid line. This line is under high pressure, and
the refrigerant is in a liquid form. Guard against refrigerant spraying into the face and eyes. Any minor leakage that may occur
around the refrigeration hose in disconnection will be cold and at
high pressure. To minimize pressures, liquid line disconnections
should be made after the unit has been shut down for at least 5
minutes.
If the refrigerant charge is introduced in the low-pressure side of
the system, the charging cylinder should always be kept in a vertical
Air-Conditioning Equipment 467
position. This precaution prevents the refrigerant liquid from flowing into the crankcase of the compressor.
Never heat a refrigerant cylinder with a torch or any other type
of flame. Warming a cylinder in this manner generates excessive
pressures, which can result in an explosion. Always use warm
water to heat a refrigerant cylinder.
Silver-Brazing Repairs
For the repair of tubing condensers, evaporators, and parts made
of light metal, silver brazing is the ideal process. It was formerly
known as silver soldering, a term still frequently used. The term
silver soldering is used to avoid confusing the use of silver-brazing
alloys with the soft solders. Some silver-brazing alloys contain a
certain amount of silver alloyed with copper and zinc. Others contain silver, copper, and phosphors. These alloys are available in
forms having melting temperatures ranging from 1175°F to 1500°F.
The use of silver-brazing alloys enables the serviceperson to
obtain strong joints without danger of burning or overheating the
base metals. Apart from the skill acquired through practice, the two
most important requirements of a good silver-brazing job are clean
surfaces and enough heat to make the silver flow freely, but not so
much that the silver burns to form scale. The best source of heat is
an oxyacetylene or compressed-air and illuminating gas torch.
The various operations to be performed in silver brazing are as
follows:
1.
2.
3.
4.
5.
Preparation
Preparing swaged joints
Preparing different-size tubing for connection
Applying the flux
Applying the brazing alloy
Silver brazing has very little tensile strength of its own. The total
strength of the joint is derived from the union of the two surfaces as
a result of the action of the alloys used. Accordingly, surfaces must
fit together tightly.
The tubing should be expanded or swaged to a depth at least
equal to its diameter for tubes up to 1⁄2 inch and not less than 1⁄2
inch deep for tubes of larger diameter. Special swaging blocks and
drifts that accurately size and shape the inside of the tube and the
outside of the expanded section are recommended for this operation where there is sufficient volume to warrant the investment. For
468 Chapter 9
occasional jobs, the tube can be held on a flare block and a swaging
drift driven into it to form the bell end.
Where two tubes of different sizes, such as 3⁄8 inch and 1⁄2 inch,
are to be joined, the smaller tube can be expanded by the previously
described method until the outside diameter of the smaller tube is
sized to fit snugly into the inside of the larger tube.
When the surfaces of the tube ends to be joined have been thoroughly cleaned with steel wool or sandpaper, they should be fitted
together and clamped, or firmly held together so that no movement
will occur while they are being brazed (see Figure 9-34).
SURFACE CLEANED
Figure 9-34
Surface preparation.The surface must be clean.
Apply enough flux with a brush to cover the surfaces to be
joined, but not so much that it will run down the tubing. Make certain, however, that the flux is inside the joint all the way around
(see Figure 9-35).
After the flux has been applied, the heat should be concentrated
on one side of the joint and the silver brazing applied (see Figures
9-36 and 9-37). The temperature of the parts to be joined should be
high enough to melt the silver by touching it to the heated surfaces
near the flame. When the silver melts, apply it to the heated surfaces near the flame, but not under the flame. Move the flame
around the heated surface, following it with silver until silver has
been applied to the entire joint. Do not use too much silver, and try
to keep it from running down inside the tubing. Apply only enough
heat to cause the silver-brazing alloy to flow freely in order to avoid
the formation of scale or the burning of the surfaces.
Most of the heat should be applied to the heavier parts of the
joint where it will be conducted through the metal to the location
where the silver alloy is to be applied.
Air-Conditioning Equipment 469
Figure 9-35
Applying flux with brush.
Figure 9-36
Applying heat.
470 Chapter 9
Figure 9-37
Applying brazing alloy.
Flames should never be applied directly to the point where brazing is being done. For thorough inspection of the joint, all flux must
be carefully removed. Pinholes may exist under the film of melted
brazing flux and are not readily noticed until the flux has been
removed.
Cleaning the joint can be done either by washing it with water
while the joint is still hot or by thoroughly brushing and scraping it
with a wire brush or emery cloth after the joint has cooled.
Where silver brazing is being done near an enameled or painted
surface, or such materials as wood, insulating material, and other
combustible surfaces, the surface should be protected with sheet
asbestos during the brazing operation.
Valves, controls, or other apparatus to which a tube is being
joined by silver brazing must be protected from damage by heat.
Either remove the internal parts of the valve or protect the entire
assembly with a wet cloth.
If a joint has previously been soldered with soft solder, all traces
of the soft solder must be removed because the tin in soft solder
amalgamates with copper at the temperature necessary for a silverbrazing operation.
Chapter 10
Heat Pumps
A heat pump is a refrigeration device used to transfer heat from one
room or space to another. The heat pump is designed to take heat
from a medium-temperature source, such as outdoor air, and convert it to higher-temperature heat for distribution within a structure.
By means of a specifically designed reversing valve, the heat pump
can also extract heat from the indoor air and expel it outdoors.
Because a heat pump system uses the reverse-cycle principle of
operation, its operating principle is sometimes referred to as reversecycle conditioning or reverse-cycle refrigeration. The latter term is
not correct because there are fundamental differences between the
operating principles of a heat pump and a true refrigeration unit. The
confusion probably stems from the fact that during the cooling cycle,
the operation of a heat pump is identical to that of the mechanical
refrigeration cycle in a packaged air-conditioning unit. The indoor
coil functions as an evaporator, cooling the indoor air. The outdoor
coil is a condenser, in which the hot refrigerant gas releases heat to
the outside air.
Heat Pump Operating Principles
The two principal phases of heat pump operation are the heating
and cooling cycles. A third phase, the defrost cycle, is used to protect
the coils from excessive frost buildup.
Heating Cycle
The heating cycle of a heat pump begins with the circulation of a
refrigerant through the outdoor coils (see Figure 10-1). Initially, the
refrigerant is in a low-pressure, low-temperature liquid state, but it
soon absorbs enough heat from the outdoor air to raise its temperature to the boiling point. Upon reaching the boiling point, the
refrigerant changes into a hot vapor or gas. This gas is then compressed by the compressor and circulated under higher pressure and
temperature through the indoor coils, where it comes into contact
with the cooler room air that circulates around the coils. The cooler
air causes the gas to cool, condense, and return to the liquid state.
The condensation of the refrigerant vapor releases heat to the
interior of the structure. After the refrigerant has returned to a liquid state, it passes through a special pressure-reducing device (an
471
472
WARM AIR SUPPLY
COIL
FAN
LIQUID REFRIGERANT
REFRIGERANT VAPOR
M
WAR
COMPRESSOR
OUTDOOR UNIT
Figure 10-1
Heat pump heating cycle. (Courtesy Lennox Air Conditioning and Heating)
COIL
RETURN AIR
BLOWER
INDOOR UNIT
Heat Pumps 473
expansion valve) and then back through the outdoor coils where
the heating cycle begins all over again. The temperature of the
room air that originally cooled the higher-temperature refrigerant
vapor is itself increased by the process of heat transfer and recirculated throughout the room to provide the necessary heat.
Note
A heat pump is designed to reverse the action or direction of heat
transfer depending on whether heating or cooling is desired.As a
result, the indoor and outdoor coils change their functions based
on the heating or cooling cycle. The outdoor coil becomes the
condenser in the cooling cycle and the evaporator in the heating
cycle.The indoor coil, on the other hand, becomes the evaporator
in the cooling cycle and the condenser coil in the heating cycle.
Cooling Cycle
In the cooling cycle, the reversing valve causes the flow of the refrigerant to be reversed. As a result, the compressor pumps the refrigerant
in the opposite direction so that the coils that heat the building or
space in cold weather cool it in warm weather. In other words, the
heat is extracted from the interior, cycled through the heat pump, and
then expelled outside the building or space during the condensation of
the refrigerant (that is, its change from a gaseous to a liquid state) (see
Figure 10-2).
Heat Sink
The heat given off by the process of condensation is received by the
heat sink. This is true for both the heating and cooling cycles. In the
former, the air of the rooms or spaces functions as the heat sink. In
the cooling cycle, the outside air, a water source (for example, a well,
a pond, or a sewage pipe) or the ground commonly serve as heat sinks
outside the structure.
Defrost Cycle
Because the outdoor air is relatively cool when the heat pump is on
the heating cycle, and the outdoor coil is acting as an evaporator,
frost forms on the surface of the coil under certain conditions of
temperature and relative humidity. Because this layer of frost on the
coils interferes with the efficient operation of the heat pump, it
must be removed. This is accomplished by putting the heat pump
through a defrost cycle.
In the defrost cycle, the action of the heat pump is reversed at
certain intervals and returned to the cooling cycle. This is done to
474
COOL AIR SUPPLY
FAN
LIQUID REFRIGERANT
REFRIGERANT VAPOR
COO
L CO
IL
RETURN AIR
COIL
BLOWER
COMPRESSOR
OUTDOOR UNIT
Figure 10-2
Heat pump cooling cycle. (Courtesy Lennox Air Conditioning and Heating)
INDOOR UNIT
Heat Pumps 475
ELECTRIC HEAT DURING DEFROST
R
DEFROST
THERMOSTAT
9
7
5
4
3
1
W2
DEFROST
RELAY
JUMPERS
Figure 10-3
4
3
5
1
DEFROST
TIMER
Defrost system wiring diagram. (Courtesy Bard Mfg. Co.)
temporarily heat the outdoor coil and melt the frost accumulation.
The temperature rise of the outdoor coil is hastened because the
operation of the outdoor fan stops when the system switches over
to the cooling cycle.
The system will remain in the cooling cycle until the coil temperature has risen to 57°F. The time of the defrost cycle will vary, depending on how much frost has collected on the coil. During this period,
the indoor motor continues to operate and blow cool air. This cold
condition can be eliminated by installing an electric heating element
(see Auxiliary Electric Heating Elements in this chapter). The heating
element is wired in conjunction with the second stage of a two-stage
thermostat and will come on automatically when the heat pump is in
the defrost cycle (terminals 9 and 7 on the defrost relay in Figure 10-3).
The defrost cycle control system consists of a thermostat, timer,
and relay. The defrost thermostat is located at the bottom of the outdoor coil where it can respond to temperature changes in the coil. It
makes contact (closes) when the temperature of the outdoor coil
drops to 32°F. This action of the thermostat causes the timer motor
(located in the unit electrical box) to start. After the accumulative
running periods reach either 30 minutes or 90 minutes (depending
on the type of cam installed in the timer), the timer energizes the
defrost relays, which reverses the reversing valve and stops the outdoor fan motor. The unit remains in the defrost cycle (cooling cycle)
until the temperature of the outdoor coil reaches 57°F. At that
temperature the coil is free of frost and the frost thermostat opens to
476 Chapter 10
30 MIN.
CAM
Figure 10-4
Thirty-minute cam. (Courtesy Heat Controller, Inc.)
stop the timer and return the unit to the heating cycle. The timer will
not run again until the outdoor coil temperature drops to 32°F. The
timer runs only when the thermostat contacts are closed.
A defrost timer is shipped with a 30-minute cam installed (see
Figure 10-4). With this cam, the unit will defrost once every 30
minutes (of accumulated running time) when the outdoor coil temperature is below 32°F. If there is little or no frost on the coil, the
defrost cycle will be correspondingly short (approximately 45 seconds
to 1 minute). A 90-minute cam is recommended.
Types of Heat Pumps
Heat pumps are often classified according to their heat source. The
three principal types used in residential and light commercial heating/cooling systems are: (1) air-source heat pumps, (2) groundsource heat pumps, and (3) water-source heat pumps.
Air-Source Heat Pumps
An air-source heat pump (also sometimes called an air-to-air heat
pump) relies on the outdoor air as the heat source. In other words,
it extracts the heat from the outdoor air and transfers it to the
rooms and spaces inside the structure. A major technical problem
associated with earlier air-source heat pumps was that the temperature of the outdoor air is commonly lowest when heat requirements
are highest—that is, during the cold winter months. When outdoor
temperatures drop below 0°F, the heat pump is largely ineffective.
For this reason, some sort of supplementary radiant heating system
Heat Pumps 477
was usually employed until outdoor air temperatures rose to a level
suitable for effective use of the heat pump.
Note
Air-source heat pumps operate most efficiently in areas where the
winter temperatures usually remain above 30°F. In climates where
the winter temperatures frequently drop below freezing, a backup
auxiliary heater must be used with an air-source heat pump. Groundsource heat pumps are more efficient and economical to operate
than conventional air-source units in areas with similar heating and
cooling loads.
Split-System Heat Pumps
Most air-source heat pumps used in residential and light-commercial
heating and cooling systems are split-system heat pumps. A splitsystem heat pump is so called because its components are divided
into two sections, one located indoors and the other outdoors. The
two sections are connected by refrigerant tubing. In most split-system
heat pumps, the evaporator coil, blower, and filter section are located
inside the structure, and the compressor, condenser coil, and fan are
located outdoors (see Figures 10-5, 10-6, and 10-7).
Figure 10-5
Outdoor heat pump unit. (Courtesy Lennox Air Conditioning and Heating)
478 Chapter 10
Figure 10-6
Indoor heat pump unit. (Courtesy Lennox Air Conditioning and Heating)
Sometimes the outdoor condensing section is installed on the
roof and the indoor section is suspended from the ceiling. This is a
very common type of installation in commercial buildings.
In residential installations, the outdoor section is usually placed
on a concrete slab next to the house and the indoor section is
located either in the attic (installed horizontally) or in a closet space
(installed vertically) on the same level as the outdoor unit.
Packaged Heat Pumps
Some air-source heat pumps are packaged units. A packaged heat
pump differs from the split-system heat pump by having the
condenser coil, evaporator coil, compressor, blower and motor,
Heat Pumps 479
Figure 10-7
Indoor unit for split system. (Courtesy Lennox Air Conditioning and Heating)
480 Chapter 10
Figure 10-8
Packaged heat pump unit. (Courtesy Lennox Air Conditioning and Heating)
automatic controls, and filter all located in the same box (see Figure
10-8). Some packaged heat pumps are used with ductwork to heat
and cool the entire house; others do not use ductwork because they
are designed to heat and cool only a single room and do not require
ducts. These heat pumps are also referred to as single-packaged
units, through-the-wall units, or self-contained heat pumps by various manufacturers.
Advantages and Disadvantages of Air-Source Heat Pumps
Most residential heat pumps are the air-source type installed as a
split system with the compressor and outdoor coil installed outside
the structure and the indoor coil installed inside. Because their use is
so widespread, replacement parts are easy to acquire and trained,
certified technicians are readily available in most areas of the country.
The air-source heat pump is less expensive to install than the
ground-source or water-source heat pumps. On the other hand, it is
noisier than either of the other types, is more difficult to conceal,
and requires more maintenance.
Heat Pumps 481
Ground-Source Heat Pumps
A ground-source heat pump uses the constant temperature of the earth
instead of the outdoor air as the heat-exchange medium (that is, the
heat source or heat sink depending on the heating or cooling cycle).
During the summer when cool interior temperatures are required, the
fluid circulating through the indoor coil of the heat pump collects the
heat from inside the structure and pumps it outdoors into a pipe system located below ground. The heat is then absorbed into the ground
through the piping and the fluid is recirculated back to the unit. In the
winter, the process is reversed. The system is based on the principle of
heat transference, whereby heat is transferred from one object (the
underground pipe) to another object (the ground) through direct contact. The temperature of the ground is a constant 55ºF.
Ground-Source Heat Pump Terminology
Ground-source heat pump technology has made spectacular
advances in recent years through research and development by various HVAC equipment manufacturers. The HVAC trade associations,
as well as the government, have also conducted extensive research in
this technology. As a result, the ground-source heat pump is identified
by many different names, which can be a bit confusing.The two most
widely used names for this appliance are ground-source heat pump and
geothermal heat pump. Other less commonly used names include the
following:
•
•
•
•
•
•
•
•
•
Water-source heat pump
Well-water heat pump
Direct-expansion heat pump
Geo-exchange heat pump
Groundwater heat pump
Earth-coupled heat pump
Ground-coupled heat pump
Open-loop heat pump
Closed-loop heat pump
The use of so many different names for the same appliance results
from attempts to accurately identify the appliance and its operating
principle or, in many cases, to exclusively associate a name with a specific equipment manufacturer. Eventually, only one name will emerge as
the industry standard. At this point, the names ground-source heat
pump and geothermal heat pump have the widest usage. Both are also
used to include water-source heat pumps, which are described separately in this chapter.
482 Chapter 10
Ground-Source Coupling System
A ground-source (geothermal) heat pump uses a closed-loop ground
coupling system as a heat exchanger. In a closed-loop ground coupling
system, a heat transfer fluid is circulated by a pump through a network
of buried high-strength plastic pipe. Because the loop system is closed,
there is no mixing of the fluid with groundwater and no buildup of
contaminating mineral deposits in the heat pump heat exchanger.
The configuration of the ground coupling will depend primarily
on installation cost and the available space. The following three
closed-loop systems are illustrated in Figure 10-9:
• Horizontal closed-loop system
• Spiral closed-loop system
• Vertical closed-loop system
Figure 10-9
Closed-loop ground coupling systems.
(Courtesy U.S. Department of Energy)
The horizontal loop is used only when there is adequate space.
The space surrounding the house or building must be great enough
to bury the pipe network without extending onto the neighbor’s
property. One to six pipes are buried at least 4 ft beneath the surface in trenches.
Heat Pumps 483
Horizontal loops are most commonly used in residential heat
pump systems where there is adequate space beneath lawns to bury
the pipes. They are not recommended for large-tonnage commercial
applications because the land area required for the ground loops is
much larger than the area of most city properties.
The spiral loop is a variation of the horizontal loop configuration. In this configuration, the pipe is unrolled in spirals and placed
in horizontal trenches. In the vertical closed-loop system, the pipe
loops are inserted in 75- to 300-ft-deep vertical dry wells.
Advantages and Disadvantages of Ground-Source Heat Pumps
The U.S. Environmental Protection Agency (EPA) rates the groundsource heat pump as being the most energy efficient and environmentally clean of all the heating and cooling systems available for
residential use. It is quieter and less costly to operate than an airsource heat pump. It also has lower maintenance requirements
because the outside elements (piping loops) are buried in the
ground and not exposed to weather extremes.
Ground-source heat pumps do not require defrost cycles or
crankcase heaters because there is not the same danger of outdoor
coil freezing as there is with air-source heat pumps. Furthermore,
there is less of a need for supplemental resistance heaters than is
required with air-source heat pumps.
Ground-source heat pumps obtain their heat from the ground
during the heating cycle. Because subsurface ground temperatures
remain fairly constant and uniform throughout the year, groundsource heat pumps are very efficient all year long.
The two principal disadvantages of a ground-source heat pump
are its high installation costs and the requirement for large areas in
which to bury the outdoor piping loops.
Water-Source Heat Pumps
Water-source heat pumps use water for both the heat source and the
heat sink. The water serves as a direct heat transfer medium in contrast to the heat transfer fluid used in closed-loop systems. The steady
cool temperature of the water offsets the seasonal temperature variations by serving as a reservoir of heat in the winter and as a drain of
heat in the summer. The compressor and controls of a water-source
heat pump are identical to those in a ground-source heat pump.
Water-Source Coupling System
A water-source heat pump uses both the open-loop and closedloop coupling systems. The open-loop coupling system uses local
groundwater from extraction wells or extraction and reinjection
wells (see Figure 10-10). In some systems, a single standing column
484 Chapter 10
Figure 10-10
Water-source heat pump open-loop coupling system.
(Courtesy U.S. Department of Energy)
well is used as the water source. A standing column well allows the
major part of the discharge water from the heat pump to be reinjected into the source well. This method eliminates the need for a
separate reinjection well.
A submerged closed-loop piping system is used with a watersource heat pump if the heat source and discharge area is a lake,
pond, or stream. Using a closed-loop system avoids the problem of
discharging the water back into the lake, pond, or stream, which
can be an environmental concern.
The water in the pipes of a water-source closed-loop system is
circulated between the source (that is, the lake, pond, or stream)
and a refrigerant-to-water heat exchanger and then back to the
source. The compressor pumps a refrigerant through separate coils
in the refrigerant-to-water heat exchanger. The heat transfer occurs
in the heat exchanger.
Advantages and Disadvantages of Water-Source Heat Pumps
Installing a water-source heat pump can be a problem in many
areas of the country because there are no uniform regulations
Heat Pumps 485
governing the discharge of the water after the heat has been
extracted. It could be an important environmental concern.
Always check any existing federal, state, and local codes and
requirements governing the installation and use of water-source
heat pumps. Some of the requirements governing their use include
the following:
• Local ordinances may require the water to be discharged
through a sewer or a second well. The former method requires
a hookup fee (which commonly includes the cost of trenching
and pipe laying) and an increased monthly sewer bill. The latter
method requires the expense of drilling a return well. Water
discharged to a return well also may require an EPA reporting
procedure.
• Return wells for discharge water must be installed by licensed
drillers. The drillers must submit well logs and well locations
to the Bureau of Topographic and Geologic Survey at the
Department of Conservation and Natural Resources.
• Water discharged to a lake, pond, or stream may require a
National Pollutant Discharge Elimination System (NPDES)
permit.
• A well used as a water source must have sufficient flow and
adequate temperature for the heat pump.
The principal advantage of a water-source heat pump is that
water temperatures are warmer and more stable than air during the
cold winter months, which makes it more efficient than the airsource heat pump. The two principal disadvantages of this type of
pump are its higher installation cost and the lack of uniformity
among federal, state, and local codes and regulations.
Other Types of Heat Pumps
Heat pumps and heat pump systems may also be defined by how
the compressor is driven, whether the heat pump is a dual-fuel unit,
and other factors.
Gas-Fired Heat Pumps
A gas-fired heat pump is driven by a small natural gas or propane
engine which, in turn, drives the compressor. One advantage of a
gas-fired heat pump is that the waste heat produced by the engine
can be used to supplement the heat output of the heat pump and
also to heat the domestic hot water.
486 Chapter 10
Gas-fired heat pumps are available for both residential and commercial applications. They are about as efficient as an air-source heat
pump, but they are not widely available and their use is cost-effective
only in areas where natural gas or propane cost less than electricity.
Dual-Fuel Heat Pump System
A dual-fuel heat pump system combines an air-source heat pump with
a gas furnace in the same heating and cooling system. Instead of using
electric resistance heaters, this system uses a gas furnace to back up
the heat pump when outdoor temperatures become excessively cold.
A conventional gas furnace provides more heat while consuming less
energy than electric resistance heating. As a result, a dual-fuel system
provides year-round comfort with reduced energy use.
The dual-fuel heat pump system operates just like a typical airsource heat pump under ordinary conditions. In the winter, the airsource heat pump extracts the heat from the outside air, compresses
it, and transfers it to an inside coil and blower located inside the
house. In the summer, the cycle is reversed. The heat is extracted
from the indoor air and sent to the outdoor coil where it is released
to the atmosphere. The gas furnace operates as a backup heater to
the heat pump only when the outdoor temperature drops below a
preset temperature setting.
Dual-Source Heat Pumps
A dual-source heat pump combines a geothermal heat pump and an
air-source heat pump in the same unit. This results in a heat pump
almost as efficient as the geothermal heat pump but with the advantage of being much less expensive to install.
Instead of using only one outdoor heat source and heat sink (that
is, air or ground), the dual-source heat pump uses both air and ground
sources for the condensing process in the cooling mode and the evaporating process in the heating mode. In the cooling mode, the liquid
refrigerant discharging from an air-source condenser is subcooled by
using a ground-source-cooled fluid. This fluid is then reused after the
subcooler to desuperheat, that is, to remove some of the superheat
from the hot gas before it goes into the air-source condenser.
The ground loop requirements are much smaller than for a conventional ground-source system, which reduces the initial installation cost. Some dual-source heat pump systems are installed with
dual compressors to provide additional heat during the coldest outdoor temperatures.
Dual-source heat pumps are of limited availability in the United
States. As a result, it is difficult to find contractors with the necessary experience to install and service them.
Heat Pumps 487
Ductless Heat Pumps
A ductless heat pump (also sometimes called a mini-split-system heat
pump) is essentially a heat pump without distribution ducts (see
Figure 10-11). The ductless heat pump is used primarily for cooling,
although in some applications both heating and cooling are possible.
Figure 10-11
Ductless heat pump system.
A typical ductless heat pump system consists of one outdoor unit
(and compressor) connected by refrigerant lines to more than one
small indoor unit. Refrigerant is piped from the outdoor unit
through small-diameter insulated refrigerant lines directly to individual rooms or zones. Cooled air is blown into the room by fans
located in the individual evaporator units. It is called a mini split
system because of the multiple small (“mini”) indoor units.
The indoor units are about 6 to 8 in deep and are commonly
mounted flush to the inside surface of an exterior wall. They can
also be mounted on a ceiling or inside a dropped ceiling. Wiring,
refrigerant lines, control cables, and the condensate drain all pass
through a small 3-in-diameter hole in the wall or ceiling.
Heat Pump Performance and Efficiency Ratings
A number of different methods are used to rate the performance
and efficiency of heat pumps. The two methods used to measure the
488 Chapter 10
cooling and heating efficiency of the heat pump are the Seasonal
Energy Efficiency Ratio (SEER) and the Heating Season Performance
Factor (HSPF).
Note
These rating methods were conducted under ideal laboratory
conditions; the ratings will commonly be lower on-site in different
parts of the country for the same types of equipment.
Seasonal Energy Efficiency Ratio (SEER)
The Seasonal Energy Efficiency Ratio is a measure of the cooling
efficiency of a heat pump. The higher the SEER number, the more
efficient the system is at converting electricity into cooling power.
The higher the SEER ratio, the higher the energy efficiency rating of
the heat pump. The U.S. Department of Energy has established a
minimum SEER rating for cooling of 10.0.
Heating Season Performance Factor (HSPF)
The Heating Season Performance Factor (HSPF) is a measure of the
overall heating efficiency of a heat pump. The higher the HSPF
number, the more efficiently the heat pump heats the house.
Coefficiency of Performance (COP)
The Coefficiency of Performance (COP) measures the rate of heat output to the amount of energy input. The highest possible COP number
is 3. A heat pump with a COP of 3 would mean that for every $1.00
of energy input, the heat pump would produce $3.00 worth of heat.
Energy Efficiency Rating (EER)
The Energy Efficiency Rating (EER) measures the cooling efficiency
of the heat pump. The higher the EER number, the higher the cooling efficiency of the heat pump.
Energy Star Rating
The Energy Star Rating is a voluntary rating system for HVAC
manufacturers whose heat pumps meet or exceed the EPA guidelines for energy efficiency.
Heat Pump System Components
Figures 10-12 and 10-13 illustrate the components in the outdoor
unit of two Lennox residential heat pumps. They can be grouped
into four categories:
1. Compressor section (outdoor unit).
2. Air-handler section (indoor unit).
Heat Pumps 489
THERMOMETERWELL
DUAL
CAPACITOR
DEFROST
TIMER
TD1-1, OR TOC
TIME DELAY
CONTACTOR
EXPANSION
VALVE
DEFROST
RELAY
TERMINAL
STRIP
DISTRIBUTOR
DEFROST
THERMOSTAT
LIQUID LINE
SERVICE VALVE
AND GAUGE PORT
FILTER/DRIER
WITH
INTERNAL CHECK VALVE
VAPOR LINE
SERVICE VALVE
AND
GAUGE PORT
EXPANSION VALVE
SENSING BULB
SERVICE LIGHT
THERMOSTAT
SUCTION GAUGE
PORT
HIGH PRESSURE
SWITCH
MUFFLER
REVERSING VALVE
AND SOLENOID
COMPRESSOR
TEMPERATURE
SENSOR
COMPRESSOR
COMPRESSOR
TERMINAL BOX
Figure 10-12
Lennox HP26 outdoor unit (early model).
(Courtesy Lennox Industries Inc.)
DEFROST CONTROL/TIMED-OFF CONTROL
CONTACTOR
DUAL CAPACITOR
GROUND LUG
TERMINAL STRIP
THERMOMETER WELL
HIGH PRESSURE
SWITCH
COMPRESSOR
VAPOR LINE
SERVICE VALVE
AND GAUGE PORT
BI FLOW
FILTER/DRIER
SUCTION GAUGE PORT
EXPANSION VALVE
WITH
INTERNAL CHECK VALVE
LIQUID LINE
SERVICE VALVE
AND GAUGE PORT
DEFROST
THERMOSTAT
TXV SENSING BULB
DISTRIBUTOR
REVERSING VALVE
AND SOLENOID
COMPRESSOR
TERMINAL BOX
MUFFLER
Figure 10-13
SERVICE LIGHT
THERMOSTAT
Lennox HP26 outdoor unit (late model).
(Courtesy Lennox Industries Inc.)
490 Chapter 10
3. Refrigerant lines.
4. Heat pump controls.
The compressor section of a heat pump contains the compressor
(or compressors), outdoor coil, fan(s) and motor(s), control system
box, and reversing valve. In addition, the compressor section will
also contain a refrigerant-distributing device and the defrosting
controls (automatic timer and terminating thermostat). The compressor section of a remote, or split-system, heat pump is located
outdoors.
The air-handler section consists of the indoor coil, blower and
blower motor, check valve, thermal expansion valve, refrigerant
distributing device, and the air filter(s).
The refrigerant lines are divided into a liquid line containing the
refrigerant in a liquid state and a vapor or suction line containing
the refrigerant vapor. During the cooling cycle, cool refrigerant
vapors are moving through the line to the compressor section.
During the heating cycle, hot vapors are moving in the opposite
direction.
The heat pump controls include the thermostat, reversing valve,
expansion/check valves, safety switches, and other components
that ensure safe operation and which direct and regulate the flow of
the liquid refrigerant.
Compressor
The compressor is used to receive the refrigerant vapor at low pressure and compress it into a smaller volume at higher pressure and
temperature. It then pumps the refrigerant vapor to one of the coils
for either the heating cycle or the cooling cycle operation.
The compressors used in residential and light-commercial construction are hermetic compressors. A hermetic compressor is so
called because its components are sealed inside a welded housing.
The housing (or can) contains an electric motor and a pump.
Note
A sealed (hermetic) compressor must be replaced if it fails because
it cannot be repaired on-site.After it is replaced, filter dryers must
be installed to remove any moisture and/or acid in the system.
Compressors can be reciprocating, scroll, rotary, disc, or screw
types. The reciprocating and scroll compressors are the types used
most commonly in residential and light-commercial heat pump
installations. See Chapter 9 (“Air-Conditioning Equipment”) for
additional information on compressors.
Heat Pumps 491
Indoor Coil and Blower
The indoor coil is the part of a split-system heat pump located
indoors. During the cooling cycle, the indoor coil cools and dehumidifies the air by converting liquid refrigerant into a gas, which
absorbs the heat from the air. The warmed refrigerant is then carried through a tube to the outdoor unit.
Note
During the cooling cycle, the heat pump draws heat from the air
inside the house or building. Moisture in the air will condense on
the indoor coil and must be drained to the outdoors through a
condensate drain. A condensate pump should be installed to
assist drainage because reliance on gravity alone will not provide
efficient drainage. Do NOT allow the condensate to drain into
the crawl space. Doing so will eventually result in water damage
to the floor joists and other wood framing members.
During the heating cycle, heat is extracted from the outdoor air
and released by the indoor coil. The heat is blown into the interior
rooms and spaces by a fan, which is sometimes called an air handler
or blower. Both direct-drive and belt-drive motors are used.
Outdoor Coil and Fan
The outdoor coil is the part of a split-system heat pump located
outdoors in the same cabinet housing the compressor. The outdoor
fan is a direct-drive unit.
Refrigerant Lines
The refrigerant lines are divided into a liquid line containing the
refrigerant in a liquid state and a vapor or suction line containing
the refrigerant vapor. During the cooling cycle, cool refrigerant vapors
are moving through the line to the compressor section. During the
heating cycle, hot vapors are moving in the opposite direction.
The lines should be reasonably straight. Any excess lines that
need to be coiled should be coiled horizontally so that they don’t
form an oil trap. Vertical coils may prevent needed lubricant from
returning to the compressor.
Both refrigerant lines should be insulated. Reducing unwanted
heat loss and heat gain through the refrigerant lines saves energy.
Reversing Valve and Solenoid
A refrigerant reversing valve with an electromechanical solenoid
coil is used to reverse refrigerant flow during unit operation (see
Figure 10-14). It allows the heat pump to operate in either the heating
492 Chapter 10
OUTDOOR
FAN/MOTOR
CONTROL
BOX
DISCHARGE
MUFFLER
DEFROST
THERMOSTAT
REVERSING
VALVE
COMPRESSOR
CHECK/EXPANSION
VALVE
BI-FLOW
FILTER DRIER
Figure 10-14
Schematic of a four-way reversing valve.
(Courtesy Ranco Incorporated)
or cooling mode by changing the direction of the refrigerant between
the indoor and outdoor coils. The operation of a four-way reversing
valve is shown schematically in Figures 10-15 and 10-16.
Whenever the reversing valve changes the direction of refrigerant
flow, it also changes the functions of the indoor and outdoor coils.
During the heating mode, the indoor coil functions as an evaporator and is sometimes referred to as an evaporating coil. This is true
only as long as the system is in the heating mode. If the system is in
the cooling mode, the direction of the refrigerant reverses and the
indoor coil becomes a condenser (that is, a condenser coil). The
reversing valve also changes the function of the outdoor coil when
it changes the direction of refrigerant flow.
Conventional refrigerant reversing valves cause pressure drops and
undesired heat exchange that leads to a 5 to 10 percent degradation of
heat pump performance. A newly designed four-way reversing valve
has been developed to solve this problem.
As mentioned, the four-way reversing valve is operated by a
solenoid coil. When the room thermostat calls for heat, the solenoid
Heat Pumps 493
DISCHARGE
SUCTION
Figure 10-15
Heat cycle piping diagram. (Courtesy Bard Mfg. Co.)
coil is energized. This action causes a nylon slide in the vale cylinder
to move to the right and allow the high-pressure refrigerant to flow
through capillary tubes to the left piston side of the main valve. The
low-pressure refrigerant on the left side flows back to the compressor. When the system calls for cooling, the valve operation is
reversed.
Thermostatic Expansion Valve
The thermostatic expansion valve (TXV) was developed to provide more precise control of the refrigerant flow to the indoor
coil. The valve meters the exact amount of refrigerant required to
494 Chapter 10
DISCHARGE
PRESSURE
DISCHARGE
STATIONARY SCROLL
SUCTION
TIPS SEALED BY
DISCHARGE PRESSURE
Figure 10-16
ORBITING SCROLL
Cooling cycle piping diagram. (Courtesy Bard Mfg. Co.)
meet the indoor coil load demands. Using a thermostatic expansion valve increases the efficiency of the unit.
Note
A compressor in a system equipped with a thermostatic expansion valve may have difficulty starting. This may be caused by a
delay in system pressure equalizing for a short period of time
when the compressor is in the off cycle.The solution is to install a
start capacitor in the control box.
Desuperheater
Some heat pumps are equipped with a unit that recycles waste heat
from the interior of the structure during the cooling cycle. The recycled waste heat is used to produce domestic hot water.
Control Box
The control box contains various controls, connections, and wiring
important to the operation of the heat pump. The location of a control
box on a Lennox reciprocating heat pump is shown in Figure 10-17.
The controls may include contactors, capacitors, relays, circuit
boards, transformer, and various accessories. Not all control boxes
will contain the same controls, so it is important to consult the heat
pump manufacturer’s service and repair manuals when repairing or
replacing a control box. As shown in Figures 10-18, 10-19, and
10-20, control boxes may even differ among the makes and models
of the same manufacturer.
RIGHT PORT
LEFT PORT
PLUNGER NEEDLE
PLUNGER SPRING
STAINLESS STEEL PINS
SOLENOID COIL
LEFT NEEDLE
LOCK NUT
LEFT SPRING
PILOT VALVE BODY
LEFT CAPILLARY
PLUNGER
RIGHT CAPILLARY
SLIDE
COMMON (SUCTION)
CAPILLARY
DISCHARGE
TUBE
SLIDE
BRACKET
TEFLON PISTON
SEAL
BLEED HOLE
PISTON NEEDLE
SUCTION TUBES
MAIN BODY
INSIDE
COIL
495
Figure 10-17
RESTRICTOR
OUTSIDE
COIL
COMPRESSOR
Location of control box on a Lennox HP29 reciprocating compressor.
(Courtesy Lennox Industries Inc.)
496
HEATING CAPILLARY
STRAINER
STRAINER
COOLING
CAPILLARY
REFRIGERANT FLOW
SOLENOID
CHECK VALVE
OUTDOOR
COIL
CHECK VALVE
DE-ENERGIZED
FAN
MOTOR
INDOOR
COIL
BLOWER MOTOR
DISCHARGE
COMPRESSOR
UNIT PIPING
SUCTION
Figure 10-18
4-WAY REVERSING
VALVE
Lennox HP29 single-phase unit control box with reciprocating compressor.
(Courtesy Lennox Industries Inc.)
HEATING CAPILLARY
STRAINER
STRAINER
COOLING
CAPILLARY
REFRIGERANT FLOW
SOLENOID
CHECK VALVE
OUTDOOR
COIL
CHECK VALVE
DE-ENERGIZED
FAN
MOTOR
INDOOR
COIL
BLOWER MOTOR
DISCHARGE
COMPRESSOR
UNIT PIPING
SUCTION
Figure 10-19
4-WAY REVERSING
VALVE
Lennox HP29 single-phase unit control box with scroll compressor.
(Courtesy Lennox Industries Inc.)
497
498 Chapter 10
START
CAPACITOR
(C7)
DUAL CAPACITOR
(C12)
POTENTIAL
RELAY (K31)
COMPRESSOR
CONTACTOR
(K1)
DEFROST
CONTROL
(CMC1)
GROUNDING
LUG
Figure 10-20
Lennox HP29 three-phase unit control box.
(Courtesy Lennox Industries Inc.)
Start, Run, and Dual Capacitors
Every control box will contain capacitors. A capacitor is an electronic device that stores a charge (energy). A start capacitor (also
sometimes called a motor start capacitor) is used to provide the
torque required to start the compressor motor. It does this while
working in conjunction with a run capacitor (also called a motor
run capacitor) or a dual capacitor. A dual capacitor gives a phase
shift to single-phase motors in scroll-type or reciprocating-type compressor motors. It is called a dual capacitor because it contains one
capacitor for the compressor motor and another for the fan motor.
Compressor Contactor
A contactor is an electrically operated switching device in the heat
pump control circuit (commonly 24 volts AC circuits). It creates a
magnetic field to pull in a set of contacts controlling another device
that may or may not receive its electrical power from the same circuit.
Defrost Control
The defrost control (or defrost control board) is described later in
this chapter. See Heat Pump Defrost System.
Heat Pumps 499
Relays
The potential relay controls the starting function of the compressor
motor. The outdoor fan relay is used in some split-system heat
pumps to control the operation of the fan in the outdoor unit.
Fan/Blower Motors
Both the outdoor and indoor units of a split-system heat pump are
equipped with a fan. The indoor fan (or blower as it is also called) is
used to blow the warm air created by the indoor coil (evaporator)
through the ductwork into the rooms and spaces of the structure. The
most efficient type of indoor blower is a variable-speed one because
its operation enables it to compensate for potential airflow restrictions caused by dirty filters or coil or partially blocked air ducts.
Heat Pump Defrost System
A heat pump defrost system consists of a defrost thermostat and a
defrost control. The defrost thermostat is located on the liquid line
between the expansion/check valve and the distributor. The defrost
control board is located in the control box.
Defrost Thermostat
Its function is to signal the defrost control board to start the defrost
timing when the defrost thermostat senses a preset low temperature. It terminates the defrost mode when the liquid line warms up
to a higher preset temperature.
Defrost Control Board
The defrost control board is located in the control box. The type
and location of the various components on a defrost control board
will vary among different manufacturers. The two defrost control
boards shown in Figure 10-21 include a time-temperature defrost
control, defrost relay, time delay, two diagnostic LEDs, a 24-volt
terminal strip for field wiring connections, and provisions for pressure switch safety circuit connections. The control provides automatic switching from normal heating operation to defrost mode
and back depending on the defrost thermostat settings.
There are two principal types of defrost controls: demand-frost
controls and time-temperature defrost controls. The demand-frost
controls activate the defrost mode only when frost or ice forms on
the coil. The time-temperature defrost controls, on the other hand,
activate the defrost mode at regular timed intervals for set periods
of time whether frost or ice is present on the outdoor coils or not.
In both cases, activating the defrost mode causes the reversing valve
to divert warm refrigerant fluid to the outdoor coil to thaw the
frost or ice forming on the unit coils.
500 Chapter 10
DUAL CAPACITOR
(C12)
COMPRESSOR
CONTACTOR
(K1)
GROUNDING
LUG
DEFROST
CONTROL
(CMC1)
Defrost control board component
locations. (Courtesy Lennox Industries Inc.)
Figure 10-21
Two LEDs are installed on the defrost board for diagnostic
purposes. The LEDs flash a specific sequence according to the
condition.
The time delay protects the compressor from short-cycling in
case the power to the unit is interrupted or a pressure switch opens.
The time delay is electrically connected between a thermostat terminal and the compressor contactor.
Other relays, connections, and components forming a part of the
defrost control system and located on the defrost control board
include the following:
•
•
•
•
Defrost relay
Pressure switch safety circuit connections
24-volt terminal strip connections
Defrost interval timing pins
High-Pressure Switch
An auto-reset high-pressure switch (single pole, single throw) is
located on the liquid line. The switch shuts off the compressor if the
discharge pressure rises above the factory setting. The switch is
Heat Pumps 501
normally closed and is permanently adjusted to trip (open) at a
factory-preset maximum high-pressure point. The switch resets
(closes) when the pressure drops below a factory-preset minimum
low-pressure point.
Low-Pressure Switch
Some heat pumps may have a low-charge switch that functions if
there is a potentially damaging loss of refrigerant. The switch is an
N.C. pressure switch located on the discharge line of the compressor. The switch opens on low-pressure drop in the discharge line to
shut off the compressor. The switch opens and closes at preset pressure points.
Other Electric/Electronic Heat Pump Controls
and Connections
A lockout relay is used on many heat pumps to shut the unit off to
protect the compressor from damage if there is a problem in the
system. An anti-restart timer is required in scroll and rotary compressors to prevent them from running backwards when there is a
power failure. Every heat pump system requires a manually operated disconnect switch to turn off power and shut down the system
when there is a problem or when repairs have to be made.
A service light thermostat is a service light switch located on the
compressor discharge line and directly connected to the service light
in the indoor room thermostat. If the compressor stops running, the
service line thermostat senses the change in the discharge line and
turns on the service light on the room thermostat. The light is
turned off when the compressor is restored to operation and the
discharge line returns to normal. Some service light thermostats are
connected to terminals on the defrost control board.
Accumulator
Some compressors, such as the piston (reciprocating) types, can be
damaged by liquid refrigerant entering the compressor. These compressors are designed to compress the gas formed from the refrigerant. They have a problem compressing the refrigerant liquid. An
accumulator is installed in the return line to trap and store the
refrigerant liquid before it can enter the compressor. The operation
of a scroll compressor is such that an accumulator is not required.
It can handle small amounts of liquid refrigerant without damage.
Room Thermostat
The heat pump operation is controlled by a room thermostat.
Heat pump thermostats may vary in design among the various
502 Chapter 10
manufacturers, but their operation will be essentially the same.
Thermostat operation is controlled by the following:
•
•
•
•
Temperature selector levers or dial
Temperature indicator
Fan switch
System switch
The temperature selector levers (one for cooling and the other for
heating) or the temperature selector dial are used to manually select
the desired temperature setpoints for either heating or cooling.
The temperature indicator on the face of the thermostat is used
to indicate the actual room temperature. Most will also have an
amber (green) light that indicates when the heat pump is operating
in the emergency mode.
The fan switch will offer up to four settings. The ON or CONT
(continuous) setting provides continuous operation of the indoor
blower regardless of whether the compressor or an auxiliary heater
is operating. This setting is selected when continuous air circulation
or filtering is desired. The AUTO or INT (intermittent) setting
restricts blower operation only to those times when the thermostat
calls for heating or cooling. It is the recommended setting for
humidity control.
The system switch is used to set the heat pump for heating, cooling, or auto operation. The heating and cooling mode settings are
self-explanatory. The AUTO mode provides the heat pump with the
ability to automatically switch back and forth between the heating
and cooling modes in order to maintain a predetermined comfort
setting.
If the heat pump system is designed to provide supplementary
heat when there are excessively cold temperatures, the auxiliary
heater is controlled by the thermostat through an emergency heat
mode. The emergency heat mode locks out heat pump operation
while the auxiliary heater is operating.
If a programmable thermostat is used to control the heat pump,
then temperature setpoints can be selected (programmed) for different times of the day. For example, with 7-day programming, the
heat pump can be programmed for different temperature and
humidity settings at different times every day of the week.
Service Valves and Gauge Ports
As shown in Figure 10-22, service valves are installed in the liquid
and vapor lines of the heat pump. These valves are used to charge
Heat Pumps 503
RUN CAPACITOR
(C1)
TRANSFORMER (T5)
“J“ VOLTAGE
UNITS ONLY
OUTDOOR FAN
RELAY (K10) “G“
& “J” VOLTAGE
UNITS ONLY
COMPRESSOR
CONTACTOR
(K1)
DEFROST
CONTROL
L
(CMC1)
GROUNDING
LUG
Figure 10-22
Lennox HP29 refrigeration components.
(Courtesy Lennox Industries Inc.)
the system (and check the charge), to test for leaks, and to evacuate
the system. Each valve is equipped with a service port containing a
factory-installed Schrader valve covered by a protective cap. The
service port cap functions as the primary leak seal. Cutaway views
of the liquid line and vapor line service valves are illustrated in
Figures 10-23 and 10-24.
Gauge Manifold
The gauge manifold is a device equipped with two gauges (see Figure
10-25). One of the gauges measures suction (low) pressure, whereas
the other gauge measures head (high) pressure. These gauges indicate
how well the compressor is removing the heat collected by the evaporator coil, how well the condenser coil is expelling the heat, and the
amount of load placed on the heat pump. An efficient heat pump will
have a high suction pressure and a low head pressure.
Filter Dryer
The filter dryer (also called bi-flow filter dryer) is used to remove dirt,
other contaminants, and moisture from the refrigerant before it can
damage the compressor and other components in the heating system.
Crankcase Heater
When some heat pumps are shut down during the cold winter
months, the liquid refrigerant may enter the compressor crankcase
DIAGNOSTIC LEDs
PRESSURE SWITCH
SAFETY CIRCUIT
CONNECTIONS
FAN
CONNECTION FOR
ONE OPTIONAL
SWITCH
HIGH
PRESSURE
SWITCH
S4
PS2
COMMON
COMMON
Y1
OUT
Y1
OUT
FAN
FACTORY-INSTALLED
JUMPER
P
S
I
PS2
(REMOVE TO ADD
PRESSURE SWITCHES)
PS1
DIAGNOSTIC LEDs
P
S
I
PS2
DEFROST
INTERVAL
TIMING PINS
(REMOVE TO ADD
PRESSURE SWITCHES)
LED
2
PS1
90
1
60
LED
30
T
1 2
DF
60
30
OPTIONAL
SWITCH
PS2
S4
HIGH
PRESSURE
SWITCH
PS1
O
OUT
Figure 10-23
TEST
PS
DF
C
R
O
Y1
DEFROST INTERVAL
TIMING PINS
C
90
AMBIENT
DF THERMISTOR
CONNECTION
SERVICE LIGHT
CONNECTION
C
O
L
OUT
R
W1
O
Y1
Y1
24V TERMINAL STRIP
CONNECTIONS
Liquid line service valve. (Courtesy Lennox Industries Inc.)
TEST
CONNECTIONS FOR
TWO OPTIONAL
SWITCHES
TEST
PS1
FACTORY-INSTALLED
JUMPER
TEST
504
NOTE: Component locations will vary with board manufacturer.
PRESSURE SWITCH
SAFETY CIRCUIT
CONNECTIONS
PS DF C R
O
L
C
R
W
1
O
Y1
24V TERMINAL STRIP
CONNECTIONS
Heat Pumps 505
DISCHARGE
LINE
DISTRIBUTOR
DEFROST
THERMOSTAT
SUCTION LINE
DISCHARGE
LINE
REVERSING
VALVE
MUFFLER
PROCESS
COUPLING
CHECK/EXPANSION
VALVE
FILTER/DRIER
VAPOR LINE
SERVICE
LIQUID LINE VALVE
SERVICE VALVE
PRESSURE TAP
FITTING
SUCTION LINE
Figure 10-24
Vapor line service valve. (Courtesy Lennox Industries Inc.)
and mix with the lubricating oil. When the heat pump is turned on
again, the refrigerant in the crankcase evaporates rapidly and forms
a foam. This condition dilutes the oil, prevents adequate lubrication, and may shorten the service life of the compressor. A
crankcase heater will prevent the refrigerant from liquefying in the
lubricating oil. Some crankcase heaters are designed to operate all
the time; others only when required. Crankcase heaters are not
required on scroll compressors.
Muffler
As shown in Figure 10-13, a muffler is installed in the discharge line
to minimize noisy pulsations and vibrations. The muffler greatly
reduces the sound inside the house of compressor operation.
Sizing Heat Pumps
The recommended source of information for sizing heat pumps is
the latest edition of the Air-Conditioning Contractors of America’s
Manual H—Heat Pump Systems: Principles and Applications. It
covers basic principles, equipment, installation, operation, and system design.
The ability of the heat pump to extract heat from the outdoor
air decreases as the outdoor temperature drops. At the same time,
the heat required to maintain the desired indoor temperature
increases. If lines representing the outdoor and indoor conditions
506 Chapter 10
LIQUID SERVICE VALVE
(VALVE CLOSED)
STEM CAP
SERVICE
PORT
INSERT HEX
WRENCH HERE
TO OUTDOOR COIL
SERVICE
PORT CAP
TO INDOOR COIL
Schrader valve open
to line set when valve is
closed (front seated).
(VALVE FRONT SEATED)
LIQUID SERVICE VALVE
(VALVE OPEN)
INSERT HEX
WRENCH HERE
STEM CAP
SERVICE
PORT
TO OUTDOOR COIL
SERVICE PORT
CAP
SCHRADER
VALVE
TO INDOOR COIL
Lennox HP26 manifold gauge connections
(cooling cycle). (Courtesy Lennox Industries Inc.)
Figure 10-25
Heat Pumps 507
were drawn on a graph, the line representing the dropping outdoor
temperature would eventually cross the line representing the rising
indoor heat requirements. The point at which the two lines on the
graph cross is called the balance point. The capacity of a heat pump
must be sized to match the balance point for the house or building.
Most balance points will occur just below and above freezing
(Fahrenheit).
Heat Pump Installation Recommendations
All of the installation recommendations included here are provided
as a general guide. They do not supersede local, state, or national
codes. Always consult local authorities having jurisdiction before
installing the heat pump.
Note
Much more detailed installation instructions will be found in the
installation manual for the specific heat pump make and model.
Always read and carefully follow the manufacturer’s installation
instructions. Failure to do so could result in voiding the equipment
warranty.
To open: Rotate stem counter clockwise 90˚.
To close: Use adjustable wrench and
rotate stem clockwise 90˚.
SERVICE PORT
CAP
UNIT SIDE
SCHRADER
VALVE
SERVICE PORT
STEM
FIELD SIDE
BALL
(SHOWN OPEN)
STEM CAP
Figure 10-26
Vapor line service valve (valve open)
508
OUTDOOR UNIT
DEFROST THERMOSTAT
OUTDOOR COIL
REVERSING
VALVE
EXPANSION/CHECK VALVE
DISTRIBUTOR
BI-FLOW
FILTER/DRYER
LOW
HIGH
PRESSURE PRESSURE HIGH-PRESSURE
LIMIT
INDOOR UNIT
MUFFLER
THERMOMETER
WELL
TO
GAUGE HCFC-22
MANIFOLD DRUM
NOTE: Arrows indicate the direction
of refrigerant flow.
VAPOR
SERVICE
PORT
VAPOR
LINE
VALVE
COMPRESSOR
ACCUMULATOR
LIQUID LINE
SERVICE PORT
NOTE : Use gauge ports on vapor line valve and liquid valve for evacuating refrigerant lines
and indoor coil . Use vapor gauge port to measure vapor pressure during charging.
Figure 10-27
Manifold gauge connections (cooling cycle)
EXPANSION/CHECK
VALVE
INDOOR
COIL
Heat Pumps 509
The following recommendations are offered as a checklist for
installing a heat pump:
1. Install unit level or slightly slanted toward drain for proper
condensation drainage.
2. Check unit wiring for compliance with wiring diagram and
3.
4.
5.
6.
7.
8.
local codes and regulations.
Make sure all wiring connections are tight.
Ground unit by grounded waterproof conduit or with separate ground wire.
Check indoor and outdoor fan/blower for unobstructed and
quiet movement.
Check condensation drain line for proper slope and drainage.
Fasten and seal all ducts and fittings with a suitable duct tape.
Check the refrigeration system for leaks after installation.
Note
Heat pump manufacturers require that the outdoor unit be
matched with the indoor coils, line sets, and refrigerant control
devices. Failure to do so will result in loss of warranty. Check the
manufacturer’s specifications for the unit being installed.
Recommendations for installing the outdoor unit of the heat
pump are as follows:
1. Install the outdoor unit on a concrete pad separate from the
house foundation.
2. Do not locate the outdoor unit where its operation will dis3.
4.
5.
6.
7.
turb neighbors.
Do not locate the outdoor unit under a bedroom window.
Shelter the outdoor unit from prevailing cold winter winds.
Do not allow bushes or other obstructions to block the airflow
to the unit. Provide for free air travel to and from the condenser.
Locate the unit far enough from the roof eaves to avoid falling
snow and ice.
Locate the outdoor unit so that the lengths of copper refrigerant lines connecting to the indoor unit are minimized.
The following are recommendations for checking heat pump
operation after installation is completed and the system is running:
1. Check the compressor starting characteristics and capabilities
while the system is running.
510 Chapter 10
2. Measure high- and low-side system pressures.
3. Check to make sure the system is operating in accordance
4.
5.
6.
7.
8.
with the heat pump manufacturer’s specifications.
Check the system for correct line and load voltage/amperage.
Listen for abnormal noise or unusual odors.
Measure outdoor dry-bulb temperature.
Measure indoor dry- and wet-bulb temperature.
Check for correct refrigerant charge.
Read the heat pump manufacturer’s installation manual and add
any other recommendations to the preceding list. Not all heat
pumps have the same installation requirements.
Heat Pump Operating Instructions
The heat pump manufacturer should provide operating instructions
with the installation literature. If no copy is available, contact the
manufacturer’s local field representative for one.
If no operating instructions are available for the unit, follow
those contained in this section. These instructions are suitable for
most electric heat pumps used in residential installations.
The first step, of course, is to turn on the power supply at the disconnect switch. This is a very simple but important step that is often
overlooked. In remote heat pump installations, both the indoor and
outdoor sections may have a disconnect switch or a breaker or fuse
in the house box. Both switches must be in the on position to start
the system.
Move the thermostat setting as high as it will go, and switch the
fan selection switch to the on setting. This should start the blower.
The remainder of the operating instructions will depend on whether
heating or cooling is desired.
Heating
For the heating cycle, move the fan selector switch to the auto position and slowly raise the heating temperature setting on the thermostat. Stop moving the lever as soon as the first-stage (upper)
mercury bulb makes contact. The blower, compressor, and condenser fan should start at this point.
Under normal operating conditions, the unit may automatically
trip on its high-pressure cutout and stop the compressor and outdoor
fan if the outdoor ambient temperature exceeds approximately
80°F. If the outdoor ambient temperature is too low for automatic
Heat Pumps 511
cutout, block the return air until the unit trips. In a cold climate, it
may take 5 minutes or more to trip.
Check the thermostat heat anticipator setting to make sure it
matches the current draw of the heating relays (see Chapter 4 of
Volume 2, “Thermostats and Humidistats”), and make certain the
contactors and heaters are operating correctly.
The defrost timer can be checked in the winter when the outdoor
coil is cold enough to activate it. Observe at least one defrost cycle
to make sure the unit defrosts properly.
Turn the thermostat off. If the unit is set at the on position, only
the blower should operate. Turn the thermostat on again and proceed as follows:
1. Adjust discharge air grilles for suitable airflow.
2. Check the system for proper balance and correct if necessary.
3. Check for air leaks in the ductwork and correct if necessary.
Cooling
For the cooling cycle, move the fan selector switch to the auto position and lower the heating temperature setting on the thermostat to
below room temperature. This should start the blower, compressor,
and condenser fan. If these components are operating satisfactorily,
turn the thermostat off. The unit should stop with the exception of
the blower if the thermostat is set at the on position.
If a combination heating and cooling thermostat is used, switch
it to the heat position and check for correct heating operation.
Make certain the thermostat heat anticipator is set to match the
current draw of the heating relays (see Chapter 4 of Volume 2,
“Thermostats and Humidistats”).
After waiting approximately 5 minutes, turn the air conditioner
on and proceed as follows:
1. Adjust discharge air grilles.
2. Check the system for proper balancing.
3. Check for air leaks in the ductwork.
Heat Pump Service and Maintenance
The heat pump manufacturer will provide the necessary operation
and maintenance literature with the unit. This literature contains
nontechnical instructions that the average homeowner can understand and follow with little or no difficulty. By following these
instructions, the operational life span of the heat pump will be prolonged, and it will operate at maximum efficiency.
512 Chapter 10
Service and Maintenance Checklist
Warning
Turn off the electrical power to the heat pump at the disconnect
switch before performing any maintenance.The heat pump may have
multiple power supplies. Failure to disconnect the electrical power
may result in damage to the equipment and a severe shock hazard.
1. Periodically inspect and clean (or replace) the air filters.
2. Inspect and clean the blower wheel, housing, and motor as
required.
3. Annually lubricate blower motor on older heat pump models
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
according to the manufacturer’s instructions. If the motor
lacks lubricating oil, it will eventually burn out. Note: The
blower motors in newer heat pumps are sealed and do not
require lubrication.
Inspect fan motor and fan blades for wear or damage.
Inspect blower housing for lint and debris and clean as
necessary.
Check for excessive frost buildup on the coils. Contact your
local serviceperson if an excessive frost buildup is discovered.
Periodically clean the coils in the outdoor unit by washing
with water hose.
Check condensation drain line during cooling season for
free-flow condition. Water should flow freely.
Check the indoor coil drain pan and the primary and secondary
drain lines.
Check all refrigerant line connections to make sure they are
secure. Tighten loose connections. If the system is low on
refrigerant, find and repair the leak before adding any more.
Adding refrigerant to a leaking heat pump system will force
the equipment to work harder and less efficiently. Continuing
to operate a heat pump without refrigerant will eventually
overheat the compressor and cause it to fail.
Inspect and clean (if required) the auxiliary drain pan (if supplied with the heat pump) and line.
Check for damaged wiring and loose connections.
Inspect outdoor unit and pad for proper level and adjust if
necessary.
Heat Pumps 513
Monitor heat pump system for correct refrigerant charge.
Measure high- and low-side system pressures.
Remove dirt, leaves, and debris from inside the outdoor cabinet.
Inspect the base pan in the outdoor unit for restricted drain
openings and correct as necessary.
18. Inspect the control box for wear and damage and repair as
necessary. All control box and electrical parts should be
checked for wear or damage.
19. Check condition of control box components, connections,
and wiring.
20. Check the refrigeration system for leaks during each service call.
14.
15.
16.
17.
Adjusting Heat Pump Refrigerant Charge
Packaged heat pumps are charged with the refrigerant at the factory under controlled conditions and rarely need adjustment. Splitsystem heat pumps are charged in the field where there is a greater
chance of error. If the performance of a split-system heat pump
closely approximates the manufacturer’s listed SEER and HSPF ratings, then the system probably has the correct charge. If the performance fails to meet the listed ratings, then there is either too much
or too little refrigerant in the system.
Note
Section 608 of the Federal Clean Air Act mandates the requirements for handling HVAC refrigerants, including their reclaiming,
recovering, and recycling. All HVAC technicians who handle
refrigerants must be certified to do so. City, county, and state
governments may also have ordinances governing the handling of
refrigerants.
Measure the temperature and pressure readings on the heat
pump system and compare the results with those specified by the
manufacturer. If they do not match, refrigerant will have to be
added or withdrawn.
Note
Refrigerant measurements will not be accurate if the airflow is
incorrect.Therefore, the airflow must be measured first, checked
against the heat pump manufacturer’s specifications, and corrected if necessary before the refrigerant measurements can be
made.
514 Chapter 10
Troubleshooting Heat Pumps
Table 10-1 lists the most common problems associated with the
operation of a heat pump. For each symptom of a problem, a possible cause and remedy are suggested.
Make certain that the thermostat is set higher than the actual
room temperature and the selector switch is on heat if heat is
needed, or that the thermostat is set lower than the actual room temperature and the switch is on cool if air-conditioning is desired. If
the thermostat is programmable, be certain the batteries are fresh.
Test for power to the air handler by moving the fan switch from
auto to on. If the blower runs, the air handler is functional. If nothing happens, check the circuit breakers on the air handler cabinet
and the breakers or fuses in the main panel. If any breakers are
tripped, reset them at once.
Table 10-1 Troubleshooting Heat Pumps
Symptom and Possible Cause
Possible Remedy
Noisy operation.
(a) Loose parts.
(b) Loose belts.
(a) Check all setscrews on blower
and fan blade. Adjust and
tighten all thrust collars.
(b) Adjust all belts and check
drives.
Heat pump will not operate.
(a) Main power switch off.
(b) Incorrect thermostat setting.
(c) Tripped circuit breaker or
blown fuse.
(a) Turn switch on. Both
disconnect switches must be on
in remote system.
(b) Change to proper setting.
(c) Reset circuit breaker or
replace blown fuse.
Insufficient or no heating or cooling.
(a) Obstructed outdoor coil.
(b) Dirty or plugged air filter.
(c) Airflow blocked at supply
registers or return grilles.
(d) Blower not operating.
(a) Remove obstruction.
(b) Clean or change if necessary.
(c) Remove blockage.
(d) Make sure blower door is
secure. Close and secure door
to restore power to blower.
(continued)
Heat Pumps 515
Table 10-1 (continued )
Symptom and Possible Cause
Possible Remedy
Reversing valve will not shift from heat to cool.
(a) No voltage to coil.
(b) Defective coil.
(c) Low refrigerant charge.
(a) Repair electrical current.
(b) Replace coil.
(c) Repair leak and recharge
system.
(d) Pressure differential too high. (d) Reset differential.
(e) Pilot valve operating correctly; (e) Deenergize solenoid, raise
dirt in one bleeder hole.
head pressure, and reenergize
solenoid to break dirt loose. If
unsuccessful, remove valve and
wash out. Check on air before
installing. If no movement,
replace reversing valve, add
strainer to discharge tube, and
mount valve horizontally.
(f) Piston cup leak.
(f) Stop unit. After pressure
equalizes, restart with valve
solenoid energized. If valve
shifts, reattempt with
compressor running. If still no
shift, replace reversing valve.
(g) Clogged pilot tubes.
(g) Raise head pressure and operate
solenoid to free tube of
obstruction. If still no shift,
replace reversing valve.
(h) Both ports of pilot open; back (h) Raise head pressure and operate
seat port did not close.
solenoid to free partially
clogged port. If still no shift,
replace reversing valve.
Reversing valve starts to shift but does not complete reversal.
(a) Not enough pressure
differential at start of stroke
or not enough flow to
maintain pressure differential.
(b) Body damage.
(c) Both ports of pilot open.
(a) Check unit for correct
operating pressures and charge.
Raise head pressure. If no shift,
use valve with smaller ports.
(b) Replace reversing valve.
(c) Raise head pressure and
operating solenoid. If no shift,
replace reversing valve.
(continued)
516 Chapter 10
Table 10-1 (continued )
Symptom and Possible Cause
Possible Remedy
(d) Valve hung up at mid-stroke;
pumping volume of
compressor not sufficient
to maintain reversal.
(d) Raise head pressure and operate
solenoid. If no shift, use a
reversing valve with smaller
ports.
Reversing valve has apparent leak in heating position.
(a) Piston needle on end of slide
leaking.
(b) Pilot needle and piston needle
leaking.
(a) Operate reversing valve several
times, then recheck. If excessive
leak, replace valve.
(b) Operate reversing valve several
times, then recheck. If excessive
leak, replace valve.
Reversing valve will not shift from heat to cool.
(a) Pressure differential too high.
(b) Clogged pilot tube.
(c) Dirt in bleeder.
(d) Piston cup leak.
(e) Defective pilot.
(a) Stop unit. Valve will reverse
during equalization period.
Recheck system.
(b) Raise head pressure. Operate
solenoid to free dirt. If still no
shift, replace reversing valve.
(c) Raise head pressure and operate
solenoid. Remove reversing
valve and wash it out. Check
on air before reinstalling. If no
movement, replace valve. Add
strainer to discharge tube.
Mount valve horizontally.
(d) Stop unit. After pressure
equalizes, restart with solenoid
deenergized. If valve shifts,
reattempt with compressor
running. If it still will not
reverse while running, replace
reversing valve.
(e) Replace valve.
Caution
Do not reset the circuit breakers if they trip a second time. Deadly
high-voltage conditions exist inside the air handler cabinet and
inside the access panel of the condenser. Let a qualified serviceperson open them.
Heat Pumps 517
If the air handler runs constantly but cannot satisfy the thermostat
setting, it is possible the backup heat is running but the condenser is
not. Some condensers have the high-pressure cutout switch externally accessible. Look for a button sticking out of the cabinet in the
vicinity of the refrigerant pipes. Press it in. If the machine starts up,
the head pressure got too high, possibly from turning on and off too
quickly, from too much or too little refrigerant, or from an electrical
interruption. As the unit ages, the switch can weaken and pop easily.
If the condition repeats itself often, have a service technician check it.
Warning
Because all the controls are internally mounted and high-voltage
wiring is exposed, only a qualified and experienced HVAC technician should open panels. High voltages can result in serious injury
and even death.
Troubleshooting Heat Pump Compressors
Residential heat pumps use hermetic compressors with the motor,
pump, and related components sealed inside a welded housing. A
failed hermetic compressor must be replaced. It cannot be repaired
on-site. The troubleshooting symptoms in Table 10-2 may be used
to identify some of the more common compressor problems.
Caution
Do not continue to operate a heat pump under the following conditions: fan motor not working, low refrigerant charge, or excessive frost/ice buildup. Continuing to run the heat pump under
these conditions can burn out the compressor motor.
Table 10-2
Troubleshooting Heat Pump Compressors
Symptom and Possible Cause
Possible Remedy
Compressor will not start.
(a) Loose wires and/or failed
components.
(b) Tripped circuit breaker or
blown fuse.
(a) Check wiring and components;
repair or replace as necessary. If
compressor still fails to start, it is
locked up and must be replaced.
(b) Reset circuit breaker or replace fuse.
If the problem continues and there
is a low ohm reading from one or
more of the compressor terminals
to ground, the compressor is
grounded and must be replaced.
(continued)
518 Chapter 10
Table 10-2 (continued)
Symptom and Possible Cause
Possible Remedy
(c) Defective run capacitor.
(d) Defective combination
(dual) run capacitor.
(c) Replace run capacitor.
(d) Replace.
Compressor will not start but fan runs.
(a) Failed run capacitor.
(b) Failed start capacitor.
(a) Replace run capacitor.
(b) Replace.
Compressor does not draw current but fan runs normally.
(a) Burned/broken common wire. (a) Repair.
(b) Open motor overload
(b) Wait for overload to reset.
protector.
Replace compressor if overload
protector fails to reset.
Noisy compressor.
(a) A hissing noise in a piston
(reciprocating) compressor.
(b) Sharp-pitched noise after
compressor is shut down
(piston compressor).
(a) Defective valves. Replace
compressor.
(b) Not a problem. Sound of
pressure equalizing in valves.
Chapter 11
Humidifiers and Dehumidifiers
The air around us has a capacity for holding a specific amount of
water at given temperatures. For example, 10,000 ft3 of air at 70°F
will hold 10.95 pints of water, no more. This means the air in a
home 25 ft by 50 ft with 8-ft ceilings (10,000 ft3) could hold nearly
11 pints of water when the temperature inside is 70°F. This would
represent 100 percent relative humidity conditions. If there were
only 2 pints of water in this same home at 70°F, the relative humidity would be 2⁄11 or 18 percent.
The amount of water air can hold depends on the temperature of
the air. For example, air at 70°F can hold 16 times as much water as
air at 0°F. This means that 10,000 ft3 of air at 0°F will hold 2⁄3 pint
of water. When that same air is heated to 70°F, it can hold nearly 11
pints of water, or 16 times as much water. Thus, if 0°F air that had a
relative humidity of 96 percent were brought into a house through a
door, window, or any other crack and warmed to the inside temperature of 70°F, this same air would then have a relative humidity of
96
⁄16, or 6 percent. This relationship between temperature and relative humidity can be illustrated by the data in Table 11-1.
As you can see, warming the fresh air will reduce the relative
humidity in the house until the air becomes extremely dry. In some
situations, the air in a house may be even drier than the Sahara Desert.
The Sahara has an average relative humidity of 20 percent. The average home in the winter months (that is, the heating season) without
humidity control or other means of adding moisture to the air
maintains a relative humidity of approximately 12 to 15 percent.
Table 11-1 Relationship Between Temperature
and Relative Humidity
Outside
Temperature
Outside Relative
Humidity (%)
20°F
0
20
40
60
80
Inside
Temperature
Inside Relative
Humidity (%)
70°F
0
3
6
8
11
519
520 Chapter 11
Air that has a low relative humidity will absorb water vapor
from any available source. Most important from a personal standpoint is the evaporation of moisture from the membranes of the nose,
mouth, and throat. These are our protective zones, and excessive
dryness of these membranes will cause discomfort.
Note
It is difficult to pinpoint the most desirable level of relative
humidity, but it is generally agreed that the range between 30 and
50 percent is the best from both health and comfort standpoints.
The upper part of this range (40 to 50 percent) is impractical
during many very cold days of the winter because of condensation on the windows.Therefore, it is recommended that a relative
humidity of between 30 and 40 percent be maintained during the
heating season.
Because dry air will pick up moisture from any available source,
the furnishings and other contents of the house are also affected by
low humidity. Furniture wood shrinks, and the joints may crack. If
plaster is used, it may also develop cracks. The wall paint will usually peel, and carpet materials may become dry and brittle.
If the air in the house is excessively dry, there is more evaporation from the skin as moisture from the body is absorbed by the
drier air. This evaporation generally makes the individual feel so
cool that temperature settings of 70°F (or even higher) are not
warm enough for comfort. Moving the temperature setting to a
higher point may obtain the desired comfort level, but the higher
temperature setting also increases the fuel cost. Each degree that the
thermostat setting is raised increases the fuel cost approximately 2
percent for the same period of time. Obviously it is impractical and
more costly to obtain comfort in this manner. It is far more economical to devise a means of reducing the rate of evaporation of
moisture from the body and thereby eliminate the chilling effect.
This can be done by increasing the relative humidity in the home
(see Humidifiers in this chapter).
Excessive moisture in a home can also be a problem. When there
is too much moisture in the indoor air, mold and mildew form on
surfaces, the indoor air has an unpleasant odor, and there is generally a feeling of stickiness or dampness. If the condition persists, the
excess moisture in the air can damage furniture, wood and metal
surfaces, leather shoes, and clothing. It can also cause peeling wallpaper, damp spots on ceilings and walls, and disintegrating plaster.
Finally, the allergens produced by mildew and mold are a definite
health problem. The solution, then, is to reduce the relative humidity
Humidifiers and Dehumidifiers 521
by removing moisture from the air. This can be accomplished by
installing a dehumidifier (see Dehumidifiers in this chapter).
Terminology
• Humidity. The amount of moisture in the air.
• Relative humidity. The amount of water vapor in the air compared with the amount it can hold at a given temperature
(expressed as a percentage).
• Humidifier. A device that adds moisture to the air.
• Dehumidifier. A device that removes moisture from the air.
• Output. A gallon-per-day measure for moisture put into the air.
• Humidistat. A control that automatically regulates humidity
comfort levels.
• Run time. The amount of time a humidifier runs before refilling
is required.
Humidifiers
A humidifier is a device used to add moisture to the air (see
Figure 11-1). This function is accomplished primarily either by
evaporation, by the use of steam, or by breaking water down into
fine particles and spraying them into the air.
Figure 11-1
Typical power humidifier. (Courtesy Amana Refrigeration, Inc.)
522 Chapter 11
The two types of humidifiers most widely used in residences and
small commercial buildings are the bypass humidifier and the
power humidifier. These and other types of humidifiers are briefly
described in this section. The service, maintenance, and troubleshooting sections of this chapter are primarily concerned with
the bypass and power humidifiers.
Spray Humidifiers
A spray humidifier (or air washer) can be used for either humidification or dehumidification. Essentially this type of humidifier consists of a chamber containing a spray nozzle system, a recirculating
water pump, and a collection tank (see Figure 11-2). As the air
passes through the chamber, it comes into contact with the water
spray from the nozzles, resulting in heat transfer between the air
and water. This, in turn, results in either humidification (adding
moisture) or dehumidification (removing moisture) depending on
the relative temperatures of the sprayed water and the air passing
through the chamber. Dehumidification occurs when the temperature
of the water is lower than the dew point of the air; humidification
occurs when it is higher.
SPRAY
NOZZLES
WATER
LEVEL
SUMP
MOTOR
PUMP STRAINER
Figure 11-2
DRAIN
Components of a spray humidifier.
In some spray humidifiers, the water is sprayed on a heating coil
through which steam or hot water is passed (see Figure 11-3). The
heat causes the water to evaporate and thereby increase the moisture content of the air.
An atomizing humidifier is a form of spray humidifier that uses
compressed air to reduce the water particles to a fine mist (see
Figure 11-4). The mist is converted to a vapor, which is absorbed by
the drier room air.
Humidifiers and Dehumidifiers 523
SPRAY NOZZLE
STEAM-HOT WATER
FROM HEAT SOURCE
HEATING COILS
Figure 11-3
Water sprayed on heating coil.
Figure 11-4
Atomizing humidifier.
(Courtesy American Moistening Co.)
The ultrasonic humidifier is also a spray-type humidifier. The principal components of an ultrasonic humidifier are a high-frequency
power oscillator that drives a piezo transducer, a small bower, a float
switch, and a water tank or reservoir. The piezo transducer creates
a wave on the surface of the water in the tank. The float switch is
used to sense and maintain the proper level of water in the tank.
These humidifiers use high-frequency vibrations to break the water
droplets down into a fine mist. The mist is blown into the room or
rooms by the small blower.
Caution
The piezo drive module operates with a line voltage as high as 100
volts or more on heat sinks. Do NOT attempt to repair or
replace the module unless you are a qualified HVAC technician.
Pan Humidifiers
A pan humidifier consists of a water tank (pan), heating coils, a fan,
and a fan motor (see Figure 11-5). The heating coils are installed in
524 Chapter 11
FAN
HUMIDIFIED AIR
DR
Y AI
R
PREWIRED
TRANSFORMER
RELAY
FILL
WATER
SUPPLY
WATER LEVEL
FLOAT CONTROL
HEATING COILS
TANK OF
HEATED WATER
STEAM OR HOT WATER
SUPPLY FROM BOILER OR
HOT WATER TANK
Figure 11-5
Pan humidifier.
the water tank. Heat is supplied to the pan heating coils either by
low-pressure steam or forced hot water where a water temperature
of 200°F or higher is maintained.
The pan humidifier is completely automatic; the water level in
the tank is controlled by means of a float control. When the relative
humidity drops below the setting on the humidistat, the fan blows
air over the surface of the heated water in the tank. The air picks up
moisture as it travels over the surface of the water and is blown into
the space to be humidified. When the humidistat is satisfied, the fan
is shut off.
Stationary-Pad Humidifiers
A stationary-pad humidifier contains a stationary evaporator pad
over which warm air from a supply duct is drawn by a motor-operated blower or fan. The air picks up moisture as it passes over the
pad. The humidified air is then returned to the room or space.
Steam Humidifiers
A steam humidifier (also sometimes called a vaporizer) is used with
an electric warm-air furnace or an electric heat pump because neither generates warm air at sufficiently high temperatures to evaporate water. These humidifiers are either gas-fired (natural gas or
Humidifiers and Dehumidifiers 525
propane) or operated by electricity. They boil the water and send
the steam into the room or rooms.
A typical steam humidifier consists of a metal reservoir to hold
the water, a heating element submerged in the reservoir, a float
valve, and the control wiring. Water is supplied to the reservoir
from the domestic water supply. A float valve regulates the amount
of water in the reservoir.
Some steam humidifiers are installed in the return duct (or
plenum) or the supply duct (or plenum) of a forced warm-air furnace. When line voltage current is passed through the heating element submerged in the reservoir, it produces steam, which releases
its moisture into the warm air passing over it. Other steam humidifiers are independent stand-alone units. Some steam humidifiers
boil the water and then cool it before it leaves the unit. Instead of
steam, a mist of warm water droplets is sent into the room or
rooms.
Bypass Humidifiers
A bypass humidifier (also sometimes called a rotary humidifier, a
wet-pad humidifier, or a drum humidifier) consists basically of an
evaporator pad (made of sponge or foam fabric) attached to a
rotating device such as a drum, disc, wheel, or belt; a float valve;
and a small motor. The evaporator pad is first rotated by the motor
through a pan of water where it absorbs moisture. Warm air from
the supply plenum passes over the rotating pad, causing the moisture to evaporate and humidify the air. The humidified air then
mixes with supply air and is ducted into the rooms of the house.
Water is supplied to the humidifier from the domestic water supply
and is regulated by a float valve. The float valve controls the level
of the water in the reservoir.
The principal components of a bypass humidifier are the following:
1.
2.
3.
4.
5.
6.
7.
8.
9.
Motor
Water tank or reservoir
Rotating disc, wheel, drum, or belt
Automatic drain valve
Float-operated fill valve
Overflow line
Fill-water connection
Drain connection
Metal or plastic cabinet
526 Chapter 11
Some of these components are illustrated by the humidifier in
Figures 11-6 and 11-7. This humidifier uses bronze wire-mesh discs
that rotate at an angle in the reservoir water. The water-level float is
isolated in a separate compartment.
Figure 11-6
Bypass power humidifier. (Courtesy Mueller Climatrol Corp.)
A bypass humidifier is commonly located on the furnace supply
plenum in a residential heating system where it makes use of the
pressure difference between the supply and return air plenums to
move the air.
Power Humidifiers
A power humidifier is similar in design to a bypass humidifier
except that a fan is added to the unit, the cabinet is larger, and there
is no duct connection to the return plenum of the furnace. The fan
is used to blow the air across the wet drum, pick up the moisture,
and then blow it back into the supply plenum.
Automatic Controls
The operation of a humidifier is controlled by a room or furnacemounted humidistat (see Figure 11-8). The sensing element of the
furnace-mounted humidistat should be installed in the return air
Humidifiers and Dehumidifiers 527
Figure 11-7 Components of a bypass humidifier. (Courtesy Mueller Climatrol Corp.)
duct with the open side down (see Figure 11-9). If the humidifier is
installed with a plenum adapter, the sensing element of the humidistat
should be mounted above the bypass duct. Never use a furnacemounted humidistat with a horizontal furnace.
528 Chapter 11
CALIBRATING
MARK
STOP PIN
HIGH LIMIT
STOP
LOW LIMIT
STOP
Typical humidistat used to control both
humidifying and dehumidifying equipment. (Courtesy Penn Controls, Inc.)
Figure 11-8
SUPPLY AIR
DUCT
Figure 11-9
RETURN AIR
DUCT
HUMIDITY
SENSING
ELEMENT
Location of furnace-mounted humidistat sensing element.
A room humidistat should be mounted on a wall 4 to 5 ft above
the floor in a location that has free air circulation of average temperature and humidity for the entire space to be controlled. Avoid
spots near air ducts or supply air grilles.
Humidifiers and Dehumidifiers 529
Modern programmable humidistats have displays that give the
exact humidity level plus the temperature in Fahrenheit or Celsius.
The humidity level on the humidistat can be manually set.
Depending on the type of installation, either a low-voltage or
line voltage humidistat may be used. Wiring diagrams for both
types of control circuits are illustrated in Figures 11-10 and 11-11.
120 V FROM FAN
OR FAN CONTROLENERGIZE ON HEATING ONLY
(R) RELAY
24 V CONTROL
TRANSFORMER
R
HUMIDISTAT
RED
LIGHT ON
HUMA-299
ONLY
HUMIDIFIER
MOTOR
Figure 11-10
NOTE:
1. Min wire size
#18 AWG.
2. All components
& wiring shown
dotted are to be
supplied by customer.
Wiring diagram of a low-voltage humidistat.
Installation Instructions
A common location for a bypass humidifier is on the underside of a
horizontal warm-air supply duct as close to the furnace as convenient
working conditions will permit. The duct should be at least 12 inches
wide (see Figure 11-12). As shown in Figure 11-12, a deflector should
be installed in the duct to guide the airflow into the humidifier. The
deflector should be about 4 to 5 inches wide. It can be cut from sheet
metal and screwed to the duct wall with sheet-metal screws.
If the humidifier is to be installed in a furnace plenum that also
contains a fan and limit control, care must be taken to keep the
sensing element of the fan and limit control a suitable distance from
the inlet of the humidifier (see Figure 11-13); otherwise, the return
air may be drawn through the humidifier and over the element and
cause improper operation of the fan control.
530 Chapter 11
120 V FROM FAN
OR FAN CONTROLENERGIZE ON HEATING ONLY
Wiring
diagram of a line voltage
humidistat.
Figure 11-11
HUMIDISTAT
RED
LIGHT ON
HUMA-299
ONLY
HUMIDIFIER
MOTOR
Deflector installed
to guide airflow.
Figure 11-12
DEFLECTOR
AIR FLOW
DEFLECTOR
AIR FLOW
Humidifiers are also installed on the sides of furnace plenums.
The manufacturer usually supplies a plenum adapter kit to mount
the humidifier. As shown in Figure 11-14, a typical kit consists of a
plenum adapter hood, closing panel adapter collar, and round coldair collar. A length of flexible or galvanized ductwork is installed
between the adapter hood and the cold-air collar (see Figure 11-15).
Humidifiers and Dehumidifiers 531
HUMIDIFIER
FAN & LIMIT
FAN & LIMIT
CORRECT
INCORRECT
Furnace plenum location of humidifier, fan, and limit
controls. (Courtesy Thermo-Products, Inc.)
Figure 11-13
CLOSING
PANEL
ADAPTOR
COLLAR
COLD AIR COLLAR
(ROUND)
PLENUM ADAPTOR
HOOD
Figure 11-14
Plenum adapter kit. (Courtesy Trane Co.)
The most desirable location for a humidifier is the warm-air
plenum. Some special installations are illustrated in Figures 11-16,
11-17, and 11-18.
If the adapter is installed on the cold-air return plenum, the distance that the hot air is ducted must be as short as possible. In an
air-conditioning system, a damper must be installed to close off the
532 Chapter 11
HOT-AIR PLENUM
COLD-AIR RETURN
51/2"
CUTOUT
X-RAY VIEW
OF PLENUM ADAPTER
MOUNTING FRAME
TYPICAL INSTALLATION
Figure 11-15
Use of flexible ductwork. (Courtesy Trane Co.)
Figure 11-16
Horizontal furnace installation. (Courtesy Trane Co.)
cold-air return opening during the cooling season. If the opening is
not closed, sufficient air can circulate through the shutdown
humidifier to frost the evaporator coil.
The following recommendations should be followed when
installing a bypass humidifier:
1. Carefully read the manufacturer’s installation instructions
and any local codes and regulations that would apply to the
installation of a humidifier.
Humidifiers and Dehumidifiers 533
Counterflow
installation slab mounted.
Figure 11-17
(Courtesy Trane Co.)
Plenum
installation. (Courtesy Trane Co.)
Figure 11-18
2. Unpack the humidifier and examine it for any shipping dam-
age. Check the equipment and parts against the inventory list.
3. Place the humidifier base or template against the duct or
plenum wall, and mark the position where it will be mounted.
534 Chapter 11
4. Cut out the opening for the humidifier, and mount it accord-
ing to the manufacturer’s instructions.
5. Connect the saddle valve to a convenient water line. Never
connect to a water line supplying chemically softened water.
6. Install the required drain fittings and connections in the
reservoir.
7. Turn on the water supply, and fill the reservoir. The float
valve arm should be adjusted to maintain a 2-inch water level
in the reservoir.
8. Place the drum or wheel in the reservoir so that the axles are
properly seated on the sloped supports. The gears will mesh
automatically. Do not attempt to rotate the drum by hand
because you may damage the gears inside the motor.
Service and Maintenance Suggestions
Many service and maintenance instructions will be model specific.
Whenever possible, read and follow the manufacturer’s instructions
when servicing these units. If none is available, the instructions in
this section will provide some guidance.
A humidifier equipped with a reservoir containing standing
water should be regularly drained to remove lime and other
residue. The first draining of the reservoir is recommended for 2
weeks after the unit has been installed or 2 weeks after the seasonal
startup. Subsequent drainings should follow the schedule suggested
by the manufacturer. A major problem with any humidifier is the
buildup of lime or other mineral deposits in the water reservoir and
on the evaporator pad. Manufacturers have attempted to minimize
this problem by constructing the reservoir out of an extremely
smooth material, such as an acrylic, so that these mineral deposits
can be easily flushed loose during maintenance.
Some humidifiers are equipped with an automatic flush system
to clean the mineral deposits from the unit. The components of a
Thermo-Pride automatic flush system are illustrated by the
schematic of a humidifier in Figure 11-19. The drum is the rotating
pad with the flush wheel attached. As the drum rotates, water in the
reservoir pan is scooped up into the flush wheel. The float assembly
then permits fresh water to enter the pan to replace that which was
scooped out (and which evaporated from the pad). As the flush
wheel continues to rotate, the mineral-laden water scooped out is
conveyed into the drain cavity of the pan and out the drain hose.
Humidifiers and Dehumidifiers 535
Operating principles of an automatic
flush system. (Courtesy Thermo-Products, Inc.)
Figure 11-19
The mineral content of the water in the reservoir pan will be
maintained at the lowest possible level with the operation of the
automatic flush system.
A commonly used method for removing lime and other mineral
deposits from the inside surface of the reservoir and the rotating
evaporator pad is by cleaning these parts with muriatic acid (never
with a detergent). Muriatic acid is an extremely efficient cleaning
agent for this purpose, but it generates toxic fumes as it works on
the deposits. For this reason, it is absolutely mandatory that the
cleaning take place outdoors.
Note
A safer method of dissolving recently formed mineral deposits
(although not as effective as muriatic acid or some of the specialpurpose chemical cleaners) is by wiping them with a solution of
50 percent water and 50 percent vinegar. This is not effective on
older deposits.
Troubleshooting Humidifiers
Table 11-2 lists the most common problems associated with the
operation of a humidifier. For each operating problem, a possible
cause is suggested and a remedy proposed.
536 Chapter 11
Table 11-2
Troubleshooting Humidifiers
Symptom and Possible Cause
Possible Remedy
Humidifier fails to maintain proper humidification.
(a) Humidistat set too low.
(b) Humidistat broken.
(c) Water valve closed.
(d) Water valve clogged.
(e) Limed unit.
(a) Raise setting.
(b) Repair or replace.
(c) Open valve.
(d) Clean valve.
(e) Clean lime from discs
or replace.
Humidifier fails to operate.
(a) Drum motor not receiving
current.
(b) Inoperative motor due to
lack of lubrication.
(a) Check wiring to motor.
(b) Lubricate or replace motor.
No water flow.
(a) Plugged orifice or strainer.
(b) No electric power to
humidifier.
(c) Furnace fan not running.
(Note: A humidistat will not
operate if the furnace fan is
not running.)
(d) Solenoid valve not opening.
(e) Closed or plugged saddle
valve.
(a) Clean orifice on inlet side
of solenoid valve.
(b) Reset circuit breaker or
replace blown fuse.
(c) Check humidistat wiring
and correct as necessary.
(d) Check circuit for loose
connections. Check continuity
through solenoid valve.
Make corrections as
necessary.
(e) Open saddle valve and check
for water flow to solenoid
valve. Correct as necessary.
Excessive humidification (humidistat installed).
(a) Continuous water flow.
(b) Short in humidistat wiring.
(c) Humidistat not turning off.
(a) See Continuous Water Flow.
(b) Check wiring and repair as
required.
(c) Check wiring and repair
as required.
(continued)
Humidifiers and Dehumidifiers 537
Table 11-2 (continued)
Symptom and Possible Cause
Possible Remedy
Excessive humidification (without humidistat)
(a) Defective humidistat.
(b) Manual air control
incorrectly set.
(a) Replace humidistat.
(b) Reset to reduce airflow.
Continuous water flow.
(a) Worn valve seat.
(b) Valve installed incorrectly.
(c) Valve plunger stuck in
open position.
(a) Replace valve if leaking at seat.
(b) Reinstall correctly (arrow on
valve should be pointed in
direction of water flow).
(c) Clean valve sleeve and plunger
assembly.
Excessive water flow.
(a) Orifice too large.
(a) Replace orifice fitting.
Insufficient or slow water flow.
(a) Low water pressure.
(b) Partially plugged orifice
or strainer.
(a) Install low-pressure orifice.
(b) Disassemble orifice and
strainer. Clean thoroughly and
reinstall.
Overflowing drain pan.
(a) Plugged pan outlets or
drain hose.
(b) Incorrect drain hose slope
from humidifier to drain.
(c) Kink in drain line.
(a) Clean drain pan outlets.
Flush drain hose.
(b) Correct slope.
(c) Remove kink.
Excess condensation on windows.
(a) Humidistat setting too high.
(a) Lower the humidistat setting.
Dehumidifiers
Dehumidification is the name given to the process of removing
moisture from the air. The device used for this purpose is called a
dehumidifier (see Figure 11-20). Dehumidifiers can be classified on
the basis of how they remove moisture from the air into the following
three categories:
538 Chapter 11
DEHUMIDIFIER
1. Absorption dehumidifiers
2. Spray dehumidifiers
3. Refrigeration dehumidifiers
Both spray and refrigeration dehumidifiers remove moisture from the air by cooling it. The cooled air condenses and the
condensation falls into the dehumidifier
tank. Dehumidifiers operating on the refrigeration principle are the type most commonly used in residential heating and
cooling
systems
(see
Refrigeration
Dehumidifiers in this chapter).
Figure 11-20
model electric
dehumidifier.
Cabinet-
Absorption Dehumidifiers
An absorption dehumidifier extracts moisture from the air by means of a sorbent
(Courtesy Westinghouse Electric
material. This type of dehumidifier is very
Corp.)
common in commercial and industrial
installations but is rarely found in residences except in very large houses.
A sorbent material is one that contains a vast number of microscopic pores. These pores afford great internal surface to which
water adheres or is absorbed. Moisture is removed from the air as a
result of the low vapor pressure of the sorbent material.
Figure 11-21 illustrates the operating principle of a rotating-bed
dehumidifier. The unit consists of a cylinder or drum filled with a
dehumidifying or drying agent. In operation, airflow through the
drum is directed by baffles, which form three independent
airstreams to flow through the adsorbing material. One airstream
consists of the wet air to be dehumidified. The second airstream is
heated drying air used to dry that part of the dehumidifying material that has become saturated. The third airstream precools the bed
to permit an immediate pickup of moisture when that part of the
bed returns to the dehydration cycle. In the rotating-bed dehumidifier, the baffle sheets are stationary and the screened bed rotates at
a definite speed to permit the proper time of contact in the drying,
cooling, and dehumidifying cycles.
The operating principles of a stationary-bed solid-adsorbent
dehumidifier are illustrated in Figure 11-22. It has two sets of stationary adsorbing beds arranged so that one set is dehumidifying
the air while the other set is drying. With dampers in position as
ACTIVATION AND
COOLING AIR EXHAUST
ACTIVATION
AIR HEATER
ACTIVATION
AIR INLET
ACTIVATION
AIR FAN
DRUM
COOLING
AIR INLET
DRY AIR OUTLET
WET AIR
INLET
Figure 11-21
Rotating-bed solid-adsorbent dehumidifier.
ACTIVATION
AIR INLET
ACTIVATION
AIR HEATER
UPPER DAMPER
DRY AIR
OUTLET
DAMPER
SHAFT TO
TIMING
DEVICE
ADSORBER BEDS
ACTIVATION
EXHAUST
LOWER DAMPER
PUMP
WET AIR INLET
Figure 11-22
Stationary-bed solid-adsorbent dehumidifier.
539
540 Chapter 11
shown, air to be dried flows through one set of beds and is
dehumidified while the drying air is heated and circulated through
the other set. After completion of drying, the beds are cooled by
shutting off the drying air heaters and allowing unheated air to circulate through them. An automatic timer controller is provided to
cause the dampers to rotate to the opposite side when the beds have
adsorbed moisture to a degree that begins to impair performance.
The liquid adsorbents most frequently used in dehumidifiers are
chloride brines or bromides of various inorganic elements, such as
lithium chloride and calcium chloride.
A typical liquid-adsorbent dehumidifier is shown in Figure 11-23.
It includes an external interchamber having essential parts consisting
of a liquid contactor, a solution heater, and a cooling coil, as shown.
In operation, the air to be conditioned is brought into contact with an
aqueous brine solution having a vapor pressure below that of the
entering air. This results in a conversion of latent heat to sensible heat,
which raises the solution temperature and consequently the air temperature. The temperature change of the air being processed is determined by the cooling water temperature and the amount of moisture
removed in the equipment.
COOLING COIL AND
CONTACT SURFACE
ELIMINATORS
WET AIR
INLET
DRY AIR
OUTLET
CONCENTRATED LIQUID
ACTIVATION
AIR EXHAUST
PUMP
ELIMINATORS
SUMP
STEAM SUPPLY
SOLUTION HEATER
FAN
CONDENSATE
ACTIVATION AIR
INLET
Figure 11-23
Liquid-adsorbent dehumidifier.
PUMP
CONCENTRATOR
Humidifiers and Dehumidifiers 541
Spray Dehumidifiers
Dehumidification can be accomplished by means of an air washer
as long as the temperature of the spray is lower than the dew point
of the air passing through the unit. This is an important fact to
remember because condensation will not take place if the temperature of the spray is higher than the dew point. Sensible heat is
removed from the air during the time it is in contact with the water
spray. Latent heat removal occurs during condensation.
Spray dehumidifiers, or air washers, usually have their own recirculating pumps. These pumps deliver a mixture of water from the
washer sump (which has not been cooled) and refrigerated water.
The mixture of sump water and refrigerated water is proportioned
by a three-way or mixing valve actuated by a dew-point thermostat
located in the washer air outlet or by humidity controllers located
in the conditioned space.
A spray dehumidifier results in greater odor absorption and
cleaner air than is possible with those using a cooling coil. A
principal disadvantage of this type of dehumidifier is that it
sometimes experiences problems with the water-level control and
may flood.
Refrigeration Dehumidifiers
A refrigeration dehumidifier removes moisture from the air by passing it over a cooling coil. The cool surfaces of the coil cause the
moisture in the air to condense. This moisture then collects on the
coils and eventually runs into a collection tray or pan located below
the unit, or through a hose into a nearby drain. Portable electrically
operated refrigeration dehumidifiers are the type of units most
commonly found in residences.
The amount of moisture removed from the air by a refrigeration
dehumidifier will depend on the volume of air and its relative
humidity. The initial amount of moisture removed will be relatively
large in comparison to the amount removed at later stages in the
operation of the dehumidifier. This reduction in the amount of
moisture removal is not an indication that the dehumidifier is not
operating properly. This is a normal operating characteristic. As the
relative humidity approaches the desired level, the amount of moisture being removed from the air will be considerably less.
Dehumidifying coils depend on the dew point of the air entering
and leaving the coil for removal of moisture from the air. To accomplish moisture removal, the dew point of the air entering the coil
must be higher than the dew point of the air leaving the coil.
542 Chapter 11
Automatic Controls
A refrigeration dehumidifier consists of a motor-driven compressor,
a condenser or cooling coil, and a receiver. A refrigerant circulates
through the cooling coil of the unit, the refrigerant flow being controlled by a capillary tube circuit.
The room air is drawn over the cooling coil by means of a
motor-operated fan or blower. When the moisture-laden air comes
in contact with the cool surfaces of the cooling coil, it condenses
and runs off the coil into a collection tray or pan, or through a hose
into a drain.
Dehumidifier operation is controlled by a humidistat, which
starts and stops the unit to maintain a selected humidity level. The
humidistat accomplishes this function by switching the compressor
and unit fan on and off in response to changes in the moisture content of the air.
Humidistat control settings will generally range from dry to
extra dry to continuous to off. During the initial period of operation (usually 3 to 4 weeks), the humidistat should be set at extra
dry. If the moisture content of the air has been noticeably reduced,
the humidistat setting can be moved to dry. Minor adjustments may
be required from time to time.
Never purchase a dehumidifier that does not have a humidistat.
Without a humidistat, a dehumidifier will run long after the humidity of the air has dropped to a satisfactory level. Operating such a
dehumidifier can prove to be very costly and wasteful of energy.
Dehumidifiers that empty the condensate into a container are
equipped with an integral cutoff (float) switch to turn the unit off
when the condensate container is full. This action avoids overflow
conditions. Most of these dehumidifiers will also have a signal light
that indicates when the condensate container needs emptying.
Installation Suggestions
A dehumidifier is most effective in an enclosed area where good air
circulation is found. For maximum effectiveness, the unit should be
located as close to the center of room, space, or structure as possible.
Operating and Maintenance Suggestions
A dehumidifier generally will not operate very satisfactorily at temperatures below 60°F. The reason for this is obvious. When the
ambient temperature is below 60°F, the cooling coil must operate at
below-freezing temperatures in order to cause the moisture in the
air to condense. Unfortunately, operating at these temperatures also
causes ice to form on the coils, and this ice formation may eventually
Humidifiers and Dehumidifiers 543
damage the dehumidifier. The ice is removed by running the dehumidifier through a defrost cycle. When a defrost sensor in the dehumidifier detects frost on the coils, it turns off the compressor but
allows the fan to continue running. The fan draws the warmer surrounding air across the coils and melts the frost. After the frost has
melted, the compressor restarts and the appliance resumes reducing
the moisture in the indoor air.
Note
The dehumidifier cannot remove moisture from the air while it is
in the defrost cycle.
Fungus will sometimes collect on the cooling coil. This accumulation of fungus can be removed by loosening it with a soft brush
and washing away the residue with water.
The principal components of a refrigeration dehumidifier are
hermetically sealed at the factory. These components are permanently lubricated and should not require any further servicing. On
the other hand, both the condensate collector and the dehumidifier
filter can be inspected and cleaned.
As an alternative to manually emptying the condensate container, a unit located in the basement can be connected by a hose to
a floor drain, or it can be positioned directly over the drain. In any
event, the dehumidifier should be equipped with a cutoff (float)
switch to turn off the unit when the condensate container is full.
Troubleshooting Dehumidifiers
Running a dehumidifier will sometimes produce results that are misdiagnosed as problems when, in fact, they are perfectly normal for
these appliances. The most frequent complaints include the following:
• The dehumidifier switches on and off several times during the
day. The dehumidifier simply is responding to a signal from
the humidistat. When the humidity in the surrounding air
falls to the setpoint on the humidistat, the dehumidifier shuts
off. It turns on again when the humidity rises above the
humidistat setpoint.
• The condensate container fills up and must be emptied often.
This is normal operation in areas of high humidity, such as
Florida and the other Gulf states.
Table 11-3 lists the most common problems associated with the
operation of a refrigeration dehumidifier.
544 Chapter 11
Table 11-3
Troubleshooting Dehumidifiers
Symptom and Possible Cause
Possible Remedy
Condensation container fills to brim or flows over.
(a) Overflow prevention control
malfunctioning.
(b) Shutoff level too high.
(a) Replace cutoff float switch.
(b) Lower shutoff level.
Dehumidifier runs continuously.
(a) Humidity too high for unit.
(b) Defective humidistat.
(a) Use dehumidifier with higher
capacity.
(b) Replace humidistat.
Rattling noise when dehumidifier is running.
(a) Dehumidifier not level.
(b) Condensation container not
positioned properly.
(a) Check level and correct if
necessary.
(b) Check and correct as necessary
Dehumidifier will not start.
(a) Full condensate container
(the red indicator light on the
unit should be on).
(b) Faulty wiring.
(c) Defective humidistat.
(d) Faulty compressor or
compressor starter relay.
(e) Low line voltage.
(a) Empty container and restart
dehumidifier.
(b) Check to make sure the dehumidifier is plugged in and then
rotate the control. If a click is
heard when the control is rotated
past its setting (and the unit does
not start), there is probably a
problem with the wiring. Inspect
and repair as necessary.
(c) Check to make sure the dehumidifier is plugged in and then
rotate the control. If no click is
heard when the control is
rotated past its setting (and the
unit does not start), the humidistat needs to be repaired (dirty
or worn contacts) or replaced.
(d) Fan runs but compressor
won’t start after the internal
pressure has equalized. Replace
compressor or compressor
starter relay.
(e) Correct as necessary.
(continued)
Humidifiers and Dehumidifiers 545
Table 11-3 (continued)
Symptom and Possible Cause
Possible Remedy
Compressor overheats and short-cycles.
(a) Low line voltage.
(b) Seized fan.
(c) Slow fan rotation.
(d) Excessive dirt buildup on
fan, fan shaft, or coils.
(a) Correct as necessary.
(b) Correct as necessary.
(c) Correct as necessary.
(d) Clean.
Excessive ice buildup on coils
(a) Defective defrost sensor. Unit
cannot run defrost cycle.
(b) Defective low-temperature
shutoff sensor. Dehumidifier
continues to run when room
temperatures are too cold.
(a) Replace defrost sensor.
(b) Replace low-temperature
shutoff sensor.
Condensate container does not fill.
(a) Dehumidifier does not run
often enough to reduce
humidity and fill condensate
container.
(b) Dehumidifier runs constantly
but sends little or no
condensate to container.
(a) Set humidistat to drier setting.
(b) Dirty coils. Clean and restart
dehumidifier or defective
refrigeration system. Should be
repaired only by a qualified and
experienced technician.
No air blows out of front of dehumidifier.
(a) Defective fan motor.
(b) Seized fan or broken fan
blade.
(a) Replace fan motor.
(b) Replace fan.
Chapter 12
Air Cleaners and Filters
All indoor air contains a certain amount of microscopic airborne
dust and dirt particles. Cooking and tobacco smoke also contribute
to the pollution of the indoor air, and pollen is a factor during some
months of the year.
Excessive air pollution stains furniture and fabrics and causes a
dust film to form on glass surfaces such as windows or mirrors. It
can also be a health problem, especially to those with dust or pollen
allergies.
A number of devices are used to remove dust, dirt, smoke,
pollen, and other contaminants from the indoor air. They are not
all equally effective. For example, an ordinary air filter in a furnace
removes only approximately 10 percent of all airborne contaminants. An electronic air cleaner, on the other hand, can remove as
much as nine times that amount.
The air-cleaning devices described in this chapter are: (1) electronic air cleaners, (2) air washers, and (3) conventional air filters.
Electronic Air Cleaners
Electronic air cleaners are devices designed to remove airborne particles from the air electrically. The best electronic air cleaners remove
70 to 90 percent of all air contaminants. These standards are met in
testing methods devised by the National Bureau of Standards and the
Air-Conditioning and Refrigeration Institute. Claims by manufacturers for higher rates of airborne particle removal should be attributed
to enthusiasm for their product. In any event, an electronic air cleaner
is vastly more effective than the conventional filter used in a warmair furnace. They are available as permanently mounted units for
use in central heating and/or cooling systems or as independent
cabinet units.
Permanently mounted electronic air cleaners are installed at the
furnace, air handler, or air-conditioning unit or in wall or ceiling
return air grilles. Some typical installations are shown in Figure 12-1.
An electronic air cleaner installed at the furnace, air handler, or
air-conditioning unit is either mounted against the surface of the
unit or a short distance from it on the return air duct. These electronic air cleaners are sometimes referred to as multiposition models
because they can be installed in a number of locations with equal
547
548 Chapter 12
HORIZONTAL
UPFLOW — SIDE RETURN
UPFLOW — BOTTOM RETURN
COUNTERFLOW
WALL MOUNTED
Figure 12-1
CEILING MOUNTED
Some typical electronic air cleaner installations.
(Courtesy Mueller Climatrol Corp.)
effectiveness. Some typical examples of multiposition electronic air
cleaners are shown in Figures 12-2, 12-3, and 12-4.
A design feature of some return grille electronic air cleaners is a
hinged cell carrier, which swings out to allow the cells to be
removed (see Figure 12-5). Return grille electronic air cleaners can
be installed in the wall or ceiling openings of return air ducts, but
Air Cleaners and Filters 549
CONTROL PANEL
PERFORMANCE INDICATOR
POWER SWITCH
IONIZING
SECTION
PRE-FILTER FOR
LARGE PARTICLES
Figure 12-2
COLLECTING CELLS
Multiposition electronic air cleaner.
(Courtesy Lennox Air Conditioning and Heating)
not in a floor return. These units are also referred to as wall (or
ceiling) electronic air cleaners or as through-the-wall electronic
air cleaners. Typical installations are shown in Figures 12-6, 12-7,
and 12-8.
The independent cabinet units (see Figures 12-9 and 12-10) are
designed for use in installations where a permanently mounted unit
is impractical or where selective air cleaning is desired. These units
can be installed anywhere in the structure.
Based on their operating principle, electronic air cleaners can be
divided into the following two principal types:
1. Charged-media air cleaners
2. Two-stage air cleaners
Charged-Media Air Cleaners
The basic working components of a charged-media electronic air
cleaner are an electrically charged grid operating in conjunction
with a media pad or mat. Media pads are commonly made of fiberglass, cellulose, or a similar material.
550 Chapter 12
Climatrol multiposition electronic
air cleaner. (Courtesy Mueller Climatrol Corp.)
Figure 12-3
The charged-media air cleaner operates on the electrostatic principle. When voltage is applied to the grid, an intense electrostatic
field is created. Dust particles passing through this field are polarized and caught by the media pads in much the same way that metal
filings adhere to a magnet. When these media pads are filled, they
must be removed and replaced with clean ones.
Air Cleaners and Filters 551
ELECTRONIC CONTROL
COMPONENTS
AIR FILTER
EFFICIENCY
INDICATOR
SERVICE
SWITCH
COLLECTION
CELL
Figure 12-4
LINT SCREEN
FILTER
Utica International multiposition electronic air cleaner.
(Courtesy International Heating and Air Conditioning)
552 Chapter 12
COLLECTING CELLS
PERFORMANCE INDICATOR
POWER SWITCH
PRE-FILTER FOR
LARGE PARTICLES
Figure 12-5
CONTROL PANEL
Wall-mounted electronic air cleaner. (Courtesy Trane Co.)
AIR
FLOW
UPFLOW
FURNACE
ELECTRONIC AIR CLEANER
AIR
FLOW
Typical application on a platform-mounted
upflow furnace. (Courtesy Trane Co.)
Figure 12-6
Air Cleaners and Filters 553
Typical installation on an upflow (highboy)
furnace. (Courtesy Trane Co.)
Figure 12-7
Two-Stage Air Cleaners
The two-stage (or ionizing) electronic air cleaner also operates on
the electrostatic principle, but the airborne particles pass through
two electrical fields rather than the single field used in chargedmedia air cleaners. The effectiveness of this type of air cleaner is
indicated in test results from the National Bureau of Standards (see
Figure 12-11).
Air entering a two-stage air cleaner must first pass through a
permanent screen or prefilter, which catches the larger airborne
particles. After passing through the prefilter, the air enters the socalled ionizer, or first stage, where the airborne particles receive an
intense positive electrical charge. The positively charged airborne
particles subsequently enter the collection, or second stage, which
consists of a series of collector plates. These collector plates are metal
554 Chapter 12
ELECTRONIC
AIR
CLEANER
ELECTRONIC AIR CLEANER
COUNTERFLOW
FURNACE
AIR
FLOW
Typical application on a high-capacity counterflow
(downflow) furnace. (Courtesy Trane Co.)
Figure 12-8
plates or screens alternately charged with positive and negative high
voltages. Because the airborne dust and dirt particles received a
positive charge when they passed through the first stage of the electronic air cleaner, they are repelled by the positively charged plates
in the second stage and propelled against the negatively charged
collector plates where they adhere until washed away. The airborne
particles are removed from the negative collector plates by periodic
vacuuming or washing. Some electronic air cleaners are equipped
with washing systems that flush the particles off the plates.
The first stage (ionizing section) and second stage (collector section) are referred to collectively as the electronic cell, or the electronic air-cleaning cell.
Automatic Controls
A built-in electronic air cleaner can be connected electrically to the
system blower motor or directly through a disconnect switch to the
120-volt line voltage power source. If the unit is connected to the system blower motor, the electronic cell will energize each time the blower
motor operates.
Because the electronic air cleaner can be wired to operate either
automatically or continuously in conjunction with fan operation,
there is no need for a special wall-mounted air cleaner control. Thus,
the fan control on a room thermostat, or combination thermostat
Air Cleaners and Filters 555
POWER SWITCH
PERFORMANCE
INDICATOR
WASH
MANIFOLDS
CONTROL PANEL
IONIZING
SECTION
COLLECTING
CELLS
WATERPROOF
AF TER-FILTER
DRAIN PAN
DRAIN
CONNECTION
Figure 12-9
Cabinet-model electronic air cleaner.
(Courtesy Lennox Air Conditioning and Heating)
and humidistat, is used to control both the system fan and the electronic air cleaner. A typical unit combining all heating and/or cooling system controls under a single cover is shown in Figure 12-12.
When the fan control switch is set on auto, the air is cleaned automatically whenever the heating and/or cooling system is operating.
Continuous air cleaning (when extra air cleaning is required) is
obtained by setting the fan control switch at on.
556 Chapter 12
Cabinet-model
electronic air cleaner with builtin automatic water-wash system.
Figure 12-10
Percent efficiency as determined by the
National Bureau of Standards dust
spot test using atmospheric air only.
10
20
30
40
50
60
70
80
90
TRUE ELECTRONIC AIR CLEANERS = 90%
"CHARGED MEDIA" FILTERS = 30 – 60%
MECHANICAL FILTERS = 0 – 7%
Figure 12-11
National Bureau of Standards test results.
Clogged-Filter Indicator
The clogged-filter indicator shown in Figures 12-13 and 12-14 is
used with Trane electronic air cleaners to sense pressure conditions
in the blower chamber between the unit and the blower. An increase
in pressure indicates a clogged filter, and this condition will be indicated by the light on the room thermostat control (see Figure 12-12)
or when the clogged-filter indicator on the furnace shows red.
Air Cleaners and Filters 557
SELECTOR
SWITCH
CLOGGED-FILTER
LIGHT
HUMIDITY
CONTROL
FAN
CONTROL
SWITCH
TEMPERATURE
CONTROL
Combination thermostat and humidistat
used to control electronic air cleaner. (Courtesy Trane Co.)
Figure 12-12
Furnacemounted clogged-filter
indicator. (Courtesy Trane Co.)
Figure 12-13
RESET
KNOB
CLOGGED
FILTER
FLAG
The clogged-filter indicator should be located on a rigid sheetmetal mounting surface to prevent bumps or other vibrations from
tripping the indicator. It should also be located where it can properly sense the pressure conditions.
Performance Lights
Most electronic air cleaners are equipped with performance lights
to indicate how the unit is operating. How these lights will be used
will depend on the individual manufacturer. Read the manufacturer’s
558 Chapter 12
MOUNTING SURFACE
WIRE CHANNELS
MOUNTING HOLES (2)
(FOR SCREW MOUNTING)
SUCTION PORT
DIFFERENTIAL
PRESSURE PORT
TINNERMAN
FASTENER
Figure 12-14
TEMPLATE
STEADYING LUG
Clogged-filter indicator details. (Courtesy Trane Co.)
operating instructions concerning the use of these lights. As the following paragraphs make clear, they are not always used in the same
way.
The built-in performance indicator light on the Trane electronic
air cleaner shown in Figure 12-15 operates in conjunction with the
on-off switch. If the electronic air cleaner is operating correctly, the
performance indicator light will be on whenever the system fan is
running and the on-off switch is in the on position.
The performance indicator light on the Lennox electronic air
cleaner shown in Figure 12-16 glows red when the unit is operating
correctly. This light also operates in conjunction with the on-off
switch, which must be on. An optional performance light is available
with a Lennox electronic air cleaner for installation in the living
spaces (see Figure 12-17). It remains off when the unit is operating
correctly.
Thermo-Pride electronic air cleaners use both an amber-colored
operating light and a red performance light with their units. The
Air Cleaners and Filters 559
POWER SUPPLY
ENCLOSURE
QUARTER
TURN
FASTENER
INTERLOCK
SWITCH
ON-OFF
SWITCH
WITH
INDICATOR
LIGHT
SNAP
CLIP
CELL
CARRIER
HINGE
ELECTRONIC
CELL
POLYSTYRENE
GRILLE
METAL
MESH
PREFILTER
Trane multiposition electronic air cleaner. (Courtesy Trane Co.)
Figure 12-15
INDICATOR LIGHT
ON/OFF SWITCH
SAFETY SWITCH
Figure 12-16
Lennox performance indicator light.
(Courtesy Lennox Air Conditioning and Heating)
operating light indicates that line voltage is on. The red performance light indicates that the electronic cell is operating properly.
Both lights must be on during normal operation.
Sail Switch
A sail switch (see Figure 12-18) is designed to complete circuit
power to auxiliary equipment in a forced warm-air system when
the duct air velocity is increased. Consequently, it provides on-off
560 Chapter 12
control of electronic air cleaners,
humidifiers, odor-control systems, and
other equipment that is energized when
the fan is operating.
In operation, the air movement pushing against the sail actuates the switching
device, which then energizes the power
supply. Using a sail switch allows the
Figure 12-17 Optional
auxiliary equipment to be wired indepenperformance light.
dently of the system blower motor.
(Courtesy Lennox Air Conditioning and
The manufacturer’s installation instrucHeating)
tions should be carefully read and followed because the sail is installed at the site.
The switch mechanism or sail switch body is mounted on the back of
the electronic air cleaner usually before it is installed in the return air
duct opening (see Figure 12-18). The sail is mounted on the switch
body after installation of the air cleaner to prevent damage of the
sail. A typical wiring diagram is shown in Figure 12-19.
CONNECT BLACK
AND BLUE WIRES
HERE
AND HERE
Sail switch mounted on back of electronic
air cleaner. (Courtesy Trane Co.)
Figure 12-18
Air Cleaners and Filters 561
JUNCTION BOX
SAIL SWITCH
L1
2
BLACK
ELECTRONIC
AIR
CLEANER
N.O.
N.C.
C
1
BLACK
L2
1
Power supply; provide disconnect means
and overload protection as required.
2
Sail switch mounted in return duct energizes
electronic air cleaner when fan is running.
Wiring diagram of an electronic air cleaner controlled
by a sail switch. (Courtesy Honeywell Tradeline Controls)
Figure 12-19
In-Place Water-Wash Controls
Some electronic air cleaners are equipped with a water-wash system
for in-place cleaning of the electronic cells. Operation of the waterwash system is governed by a control unit that includes a sequencing
timer, water valve, detergent aspirator and valve, and a fan interlock
switch to control the system fan during the wash cycle (see Figure
12-20). The timer controls the internal water and detergent valves
TM
1
MM
L1
4
5
16
5
6
16 A
13
10 A
12
DETERGENT
VALVE
4
TM
2
WATER
VALVE
TIMER
MOTOR
10
1
1
Figure 12-20
11
11 A
220–240 V, 50⁄60 Hz models provide switching on both sides of line to system.
Water-wash control wiring diagram.
(Courtesy Honeywell Tradeline Controls)
3
562 Chapter 12
W922B WASH
CONTROL CENTER
TM
1
L1 (HOT)
1
4
2
L2
5
FAN
SWITCH
SYSTEM
FAN
F51
ELECTRONIC
AIR
CLEANER
1
3
6
FURNACE
PRIMARY
120 V, 60 Hz power supply. Provide disconnect means and overload protection as required.
Typical hookup of wash control and electronic air cleaner
for in-place washing of the electronic cell. (Courtesy Honeywell Tradeline Controls)
Figure 12-21
W922A
WASH CONTROL CENTER
FAN
SWITCH
L1 (HOT)
2
1
SYSTEM
FAN
FURNACE
PRIMARY
F51
ELECTRONIC
AIR
CLEANER
L2
1
120 V, 60 Hz power supply. Provide disconnect means and overload protection as required.
2
The normally closed contacts open when cover is opened.
Typical hookup of wash control and electronic air
cleaner for automatic wash and rinse of electronic cells.
Figure 12-22
(Courtesy Honeywell Tradeline Controls)
Air Cleaners and Filters 563
to provide automatic wash and rinse of the electronic cells. Typical
hookups for a Honeywell W922 wash control are shown in Figures
12-21 and 12-22.
Cabinet-Model Control Panels
The cabinet-model electronic air cleaner shown in Figure 12-9 is
equipped with a control panel that contains a meter, operating controls, and water-wash controls.
The meter is used to check the performance of the electronic air
cleaner (see Figure 12-23). The meter is divided into three sections. If the unit is operating properly, the indicator needle will be
steady and remain in the center section (the normal operating
range on the meter). Fluctuations of the needle outside the normal
operating range indicate that the unit is not operating properly.
The specific problem is determined by the position of the needle.
FUSE
BLOWER BUTTON
VOLTAGE CONTROL KNOB
METER
Figure 12-23
Cabinet-model control panel.
(Courtesy Lennox Air Conditioning and Heating)
The system/blower controls are located to the right of the meter;
the washer/cleaner controls to the left. The voltage-control knob
operates in conjunction with the meter and is used to adjust the unit
for line voltage variations. The basic procedure for operating the
electronic air cleaner shown in Figure 12-9 is as follows:
1. Turn cleaner time switch to on position.
2. Push the off wash button.
564 Chapter 12
3. Push the on cleaner button.
4. Push the cont blower button for continuous operation or the
auto blower button for intermittent operation.
5. Push the on system button.
6. Adjust the voltage-control knob so that the needle remains in
the normal operating range section on the meter.
Installation Instructions
When installing a built-in electronic air cleaner, make certain there
is enough clearance to allow easy access to the filters and collector
cells. These components must be cleaned periodically and should
not be obstructed. Most manufacturers recommend at least 30
inches of clearance for servicing.
Pay particular attention to the airflow arrow printed on the side
of the electronic cell. This arrow is used to indicate the correct
direction of the airflow through the unit. If the electronic cell is
installed so that the airflow arrow is facing the wrong direction,
excessive arcing will occur and the unit will not operate efficiently.
The conventional air filter should be removed after the electronic
air cleaner has been installed in order to help reduce pressure drop
through the furnace.
Air volume adjustment is another factor that must be taken into
consideration when installing one of these units. These adjustments
should be made in accordance with the manufacturer’s instructions.
They will involve determining the required temperature rise through
the heat exchanger, making the necessary fan speed adjustments,
and calibrating the filter flag setting (when used).
Some existing installations may require transitions or duct turns.
If the ductwork makes an abrupt turn at the air cleaner, turning
vanes should be installed in the duct to help provide an equal distribution of air across the entire surface of the filters. Do not install an
atomizing humidifier upstream from an electronic air cleaner.
Electrical Wiring
Read and carefully follow the manufacturer’s installation instructions before attempting to make any wiring connections. All wiring
should be done in accordance with local codes and regulations.
Always disconnect the power source before beginning any work in
order to prevent electric shock or damage to the equipment.
Electronic air cleaners operate on regular 120-volt current and
use less electricity than a 60-watt light bulb. Typical wiring connections for a Trane Model EAP-12A Electrostatic Air Cleaner are
shown in Figure 12-24. A ground wire for this unit is required. No
Air Cleaners and Filters 565
120 V POWER SUPPLY
GROUNDING
LUG
INDICATOR
LIGHT
L1
HOT
G
L2
NEUTRAL
POWER DOOR
INTERLOCK
CABINET
INTERLOCK
POWER
PACK
FURNACE FAN
CONTROL
FAN MOTOR
Wiring diagram for Trane Model EAP-12A electronic
air cleaner. (Courtesy Trane Co.)
Figure 12-24
ground wire is required for the return grille electronic air cleaner
shown in Figure 12-25. Other than installing the ground wire
(where required), wiring an electronic air cleaner generally consists
of simply hooking the unit up to the power source.
When making external circuit connections to the line voltage
lead wires of an electronic air cleaner, only connectors listed by
Underwriters Laboratories should be used.
An electronic air cleaner can be connected electrically to the system blower motor or directly through a disconnect switch to the 120volt power source. If the unit is connected to the system blower
motor, the electronic cell will energize each time the blower operates.
As shown in Figure 12-25, resistors are installed in the circuit to
bleed off the electrical charges that the collector plates, acting as
capacitors, are capable of storing. As a result, the serviceperson and
homeowner are protected against shock. On a unit that does not
include bleed-off resistors in its circuit, the cell must be grounded
out before it is touched.
Maintenance Instructions
The function of the filter in an electronic air cleaner is to eliminate
the need for frequent cleaning of the electronic cell. Particles build
up on the collecting plates until they reach a size large enough to be
affected by the air velocity. When this point is reached, the particles
are blown off the plates onto the after filter.
YELLOW
566
YELLOW
SAFETY
INTERLOCK
SWITCH
SAIL
SWITCH
BLACK
BLACK
BLACK
WHITE
L1
120 V
60 HZ
POWER SUPPLY
L2
WHITE
RED
DIODE 1
DIODE 2
CONTACT
BOARD
22.6 MEG. Ω
C2
1
WHITE
2
C1
RED
Figure 12-25
1
LEFT CELL AND CONTACT BOARD
2
22.6 MEG. Ω RESISTOR
Wiring diagram for Trane return grille electronic air cleaner. (Courtesy Trane Co.)
Air Cleaners and Filters 567
The prefilter (lint filter) and the after filter (so named because it
follows the collecting plates in the unit) should be cleaned every 4
to 6 weeks. The required frequency of cell washing varies from one
installation to the next and will depend largely on the level of air
pollution each unit is expected to handle. In any event, the normal
period will range from 1 to 6 months. Homes with large families,
heavy and frequent cooking and laundering, and several tobacco
smokers usually require monthly cleaning of the cell.
An automatic dishwasher can be used to wash an electronic cell
without any fear of damaging the cell itself. Place the cells on the
lower rack of the dishwasher with the airflow arrows facing up. If
the cells are too large for the dishwasher, they will have to be
washed by hand.
The procedure for manually cleaning the filters is as follows:
1. Turn off the current to the unit. Wait a few minutes to allow
2.
3.
4.
5.
6.
7.
the grids to lose their static charge.
Note direction in which airflow arrows are pointing on the cell.
Remove the cell and both filters.
Soak cell and filters in a tub of water and electric dishwater
detergent for about 30 minutes.
Rinse both sides of cell and filters with clear, clean water until
all traces of dirt and detergent have been removed.
Shake excess water from cell and filters.
Replace cell and filters in the same order as before.
Caution
Do not turn the power back on if the reinstalled filters are not completely dry. Moisture can short out the grids and damage the power
pack. Keep the power switch off and allow air to flow through the
grids for 2 or 3 days until any remaining moisture is gone.
This last step is very important. If the cell and filters are not
replaced so that the air flows in the direction of the arrow, the unit
will not function properly.
Excess arcing or flickering of the red performance light immediately after washing the cell and filters is normal and is caused by
water droplets on the surface. If these conditions continue, check to
make certain the cell and filters were replaced in the correct order.
If there is no problem with the direction of airflow, the unit is shorting (see Electrical Wiring and Troubleshooting Electronic Air
Cleaners in this chapter).
568 Chapter 12
Replacing Tungsten Ionizing Wires
From time to time, the tungsten ionizing wires in the charging section of the electronic cell may break or become damaged. A broken
or damaged wire generally causes a short to ground, which may or
may not be accompanied by visible arcing or sparking. All parts of
these broken or damaged wires should be removed from the unit
immediately to prevent further shorting of the circuit. The unit will
be able to operate on a temporary basis with one wire missing, but
a new wire should be installed as soon as possible.
Some electronic air cleaners require the disassembly of the electronic cell in order to replace a broken or damaged ionizing wire.
The procedure is as follows:
1. Place the cell on a flat surface and remove the screws from
2.
3.
4.
5.
6.
7.
the terminal end of the cell (see Figure 12-26). Pull off the
terminal end.
Remove the screws from the rear end and then pull off the end
and the two sides.
Remove the top screen and carefully lift off the ionizer section.
Turn the ionizer section upside down as shown in Figure 12-27.
Remove all parts of the broken or damaged wire.
Compress both tension members and string the new ionizing
wire.
Slowly and carefully release the compression force first on
one tension member and then on the other (sudden release
may snap the wire).
Reassemble the cell.
TOP SCREEN OF
CELL ASSEMBLY
SIDES (4)
Figure 12-26
Cell placed on a flat surface. (Courtesy Trane Co.)
Air Cleaners and Filters 569
IONIZER SECTION
COLLECTOR SECTION
Figure 12-27
Ionizer section turned upside down. (Courtesy Trane Co.)
The complete disassembly of the cell in order to replace an ionizing wire is not necessary on all electronic air cleaners. On the return
grille electronic air cleaner, shown in Figure 12-15, the replacement
wires are cut to length and installed as follows:
1. Remove all parts of the broken or damaged ionizing wire.
2. Hook one eyelet of the ionizing wire over the spring connec-
tor at one end of the cell (see Figure 12-28).
3. Hold the opposite eyelet of the ionizing wire with needle-nose
pliers and stretch the wire the length of the cell.
4. Depress the opposite spring connector and hook the eyelet
over it.
Troubleshooting Electronic Air Cleaners
Most electronic air cleaners are equipped with a performance indicator light, which is usually mounted in the control panel with the
other controls. If the unit performance indicator light is off and the
unit switch is on when the furnace is running, the air cleaner power
pack may be burned out or disconnected from its power source, or
the pressure switch used to sense airflow and charge the grids is
defective. Each of these problems requires opening up the power
pack and exposing dangerous high voltages. These repairs should
be done only by a qualified electrician or HVAC technician.
570 Chapter 12
SPRING CONNECTOR
EYELET
DEPRESS SPRING CONNECTOR
IONIZING
WIRE
IONIZER GROUND PLATE
Figure 12-28
Installation of new ionizing wires. (Courtesy Trane Co.)
A flickering performance indicator light is not necessarily an indication that the air cleaner is malfunctioning. It is not unusual for the
light to flicker when the unit needs cleaning. Another indication that
grid cleaning is required is loud snapping sounds caused by electrical
shorts when dirt or other debris becomes stuck on the wire grid.
Table 12-1 lists the most common problems associated with
operating an electronic air cleaner. For each operating problem, a
possible cause and its remedy have been suggested.
Table 12-1
Troubleshooting Electronic Air Cleaners
Symptom and Possible Cause
Possible Remedy
Air cleaner will not operate.
(a) Unit power switch off.
(b) System fuse blown.
(c) Blower unit or furnace
power (disconnect) switch off.
(d) Unit rectifier malfunctioning.
(e) Unit transformer
malfunctioning.
(a) Turn switch on.
(b) Check and replace with
same-size fuse.
(c) Turn switch on.
(d) Replace rectifier.
(e) Replace transformer.
Air Cleaners and Filters 571
Table 12-1 (continued)
Symptom and Possible Cause
Possible Remedy
Unit performance indicator light flickers.
(a) Dirty electronic cells.
(b) Air flowing through cell
in wrong direction.
(a) Remove and clean cells.
(b) Rearrange components
in proper order (airflow
in direction of arrow
on cell).
Excess arcing.
(a) Broken ionizing wires.
(b) Bent collecting plates.
(c) Foreign object wedged
between plates or ionizers.
(a) Replace wires.
(b) Repair or replace plates.
(c) Inspect and remove.
Air Washers
Air washers operate by first passing the air through fine sprays of
water and then past baffle plates, on the wetted surface of which is
deposited whatever dust and dirt were not caught by the sprays.
An air washer functions as a filter, humidifier, and dehumidifier.
Using it to regulate the moisture in the air decreases its efficiency as
a filter for removing airborne dust and dirt particles.
Air washers are classified as either two-unit or three-unit types.
The two-unit air washer consists simply of sprays and eliminators
as shown in Figure 12-29. A three-unit air washer includes a filter
located between the sprays and eliminators (see Figure 12-30).
Excluding the air filter, the basic components of a typical air washer
are the following:
1.
2.
3.
4.
5.
6.
Cabinet
Spray nozzles
Eliminators or baffles
Sump
Pump
Blower
The major advantage of using an air washer instead of a conventional air filter or an electronic air cleaner is that it does not become
clogged with dust and dirt and is therefore not subject to loss of
572 Chapter 12
PLAN
ELIMINATORS
FLOODING
HEADER
WASH
SPRAY
SPRAY MANIFOLD
MOTOR
PUMP
ELEVATION
STRAINER
SPRAY NOZZLES
WATER
LEVEL
SUMP
WATER
DRAIN
Elevation and plan of a two-unit (sprayer and
eliminator) washer.
Figure 12-29
efficiency; however, air washers are no longer used in air-cleaning
installations because of the following disadvantages:
1.
2.
3.
4.
Equipment bulk.
Higher operating expense.
Inefficiency in removing fine particles.
Tendency to add moisture to the air when the water is not cool.
Air Filters
Conventional air filters are commonly used in forced warm-air furnaces to trap and remove airborne particles and other contaminants
from the air (see Figure 12-31). These filters are generally placed in
the return air duct at a point just before the air supply enters the furnace or in the outdoor air intake ducts. In air conditioners, filters
are properly placed ahead of heating or cooling coils and other airconditioning equipment in the system to protect them from dust and
dirt. Air filters are not used in gravity warm-air furnaces because they
Air Cleaners and Filters 573
SPRAYS
ELIMINATORS
FILTER
TANK
Three-unit air washer consisting of sprays, filter, and
eliminator plates.
Figure 12-30
obstruct the flow of air. Conventional air filters will effectively clean
the air that is being circulated through the structure, but they will not
prevent dirt from leaking into the house. On the average, a conventional air filter installed in the furnace can be expected to remove
approximately 10 percent of all airborne particles from the air.
Filters should be inspected at least twice a year. Throwaway filters
must be replaced with new ones, and washable filters should be
Figure 12-31
Conventional permanent washable air filter.
(Courtesy Dornback Furnace & Foundry Co.)
574 Chapter 12
cleaned when they become loaded with foreign matter. If this action
is not taken, the efficiency of the furnace or air conditioner will be
greatly reduced. As the dirt builds up on the filter, it increases the
resistance of the passage of the air.
In a new house, the first set of filters may become clogged after a
short time due to the presence of dust and dirt in the air created by
the building operation. Check the filters after the first month of
operation.
In an older house in which a winter air-conditioning system has
been installed, the dust and dirt that accompanies the dismantling
of the old heating system may also clog the first set of filters in a
short time. The new filters should also be checked after about a
month of furnace operation.
If new rugs or carpets have been installed in the house, considerable lint will be given off at first. Under such conditions, replacement or cleaning of the filters will be necessary.
Dry Air Filters
A dry air filter consists of a dry filtering medium such as cloth,
porous paper, pads of loosely held cellulose fiber, wool felt, or
some similar material held together in a lightweight metal or wire
frame.
Both washable and disposable (throwaway) dry air filters are
used in forced warm-air furnaces. Disposable filters are constructed
of inexpensive materials and are designed to be discarded after one
use. The frame is frequently a combination of cardboard and wire.
Washable filters usually have metal frames. Various cleaning methods have been recommended, such as air jet, water jet, steam jet, or
washing in kerosene and dipping in oil. The latter method may
serve both to clean the filter and to add the necessary adhesive.
Viscous Air Filters
A viscous air filter (or viscous-impingement air filter) contains a filtering material consisting of coarse fibers coated with a sticky substance. This sticky substance catches the dust and dirt as the air
passes through the mat. Viscous air filters can be reconditioned by
washing them and recoating their surface with fresh liquid.
An oil or grease, sometimes referred to as the adhesive or saturant, is used as the viscous substance in these filters. The arrangement of the filter mat is such that the airstream is broken up into
many small airstreams, and these are caused to abruptly change
direction a number of times in order to throw the dust and dirt particles by centrifugal force against the adhesive.
Air Cleaners and Filters 575
The method used for cleaning a viscous filter will depend on the
filter and the dust and dirt particles trapped by it. Most dry dust
and dirt particles, as well as lint, can often be removed by rapping
the filter frame.
Filter Installation and Maintenance
Access to filters must be provided through a service panel in the furnace. Inspection and replacement of the filter by the user must be
made possible without the use of special tools. When a new furnace is
installed, care must be taken to provide sufficient clearance to the
filter service panel. The furnace manufacturer will usually specify the
minimum clearance in the installation instructions. An additional set
of filter instructions should be attached to the filter service panel.
Always replace a disposable filter with one having the same
dimensional size. The filter dimensions are printed on the filter
frame. Always replace a filter with one of the same size.
The mat-type filter is commonly used in a gas-fired downflow
furnace. It consists of a removable metal cage located in the blower
cabinet of the furnace. The metal cage contains the filter material,
which is either cut to size and prepackaged or available in rolls for
measuring and cutting on-site. When installing a mat-type filter,
make sure the side that collects the dust and other airborne contaminants (that is, the oily side) is facing upward into the cold-air duct.
Box-type filters are commonly installed in the top of the blower
or in a slot in the cold-air return. Some of these filters have an
arrow on the top of the frame. The arrow points to the direction of
the airflow and the filter should always be installed with the arrow
facing the blower. Most box-type filters have one side that is covered with wire mesh. The wire mesh should face the blower (see
Figure 12-31).
Appendix A
Professional and Trade Associations
Many professional and trade associations have been formed to
develop and provide research materials, services, and support for
those working in the heating, ventilating, and air conditioning
trades. The materials, services, and support include:
1. Formulating and establishing specifications and professional
2.
3.
4.
5.
6.
7.
8.
standards.
Certifying that equipment and materials meet or exceed minimum standards.
Certifying that technicians have met education and training
standards.
Conducting product research.
Promoting interest in the product.
Providing education and training.
Publishing books, newsletters, articles, and technical papers.
Conducting seminars and workshops.
A great deal of useful information can be obtained by contacting
these associations. With that in mind the names and addresses of
the principal organizations have been included in this Appendix.
They are listed in alphabetical order.
Air-Conditioning and Refrigeration Wholesalers
International (ARWI)
(See Heating, Air Conditioning & Refrigeration Distributors International)
Air-Conditioning and Refrigeration Institute (ARI)
4100 North Fairfax Drive, Suite 200
Arlington, Virginia
Phone: (703) 524-8800
Fax: (703) 528-3816
Email: [email protected]
Web site: www.ari.org
577
578 Appendix A
A national trade association of manufacturers of central air conditioning, warm-air heating, and commercial and industrial refrigeration equipment, ARI publishes ARI standards and guidelines, which
can be downloaded free from its web site. ARI is an approved certifying organization for the EPA Technician Certification Exam. ARI also
provides a study manual for those taking the EPA Technician
Certification Exam. ARI developed the Curriculum Guide in collaboration with HVACR instructors, manufacturing training experts, and
other industry professionals for use in all school programs that
educate and train students to become competent, entry-level HVACR
technicians.
Air Conditioning Contractors of America (ACCA)
2800 Shirlington Road
Suite 300
Arlington, Virginia 22206
Phone: (703) 575-4477
Fax: (703) 575-4449
Email: [email protected]
Web site: www.acca.org
A national trade association of heating, air conditioning, and
refrigeration systems contractors, ACCA (until 1978, the National
Environmental Systems Contractors Association) publishes a variety of different manuals useful for those working in the HVAC
trades, including residential and commercial equipment load calculations, residential duct system design, and system installation.
ACCA also publishes training and certification manuals. The
ACCA publications can be purchased by both members and nonmembers. Check the web site for a list of the ACCA publications,
because it is very extensive.
Air Diffusion Council (ADC)
1000 E. Woodfield Road
Suite 102
Schaumburg, Illinois 60173
Phone: (847) 706-6750
Fax: (847) 706-6751
Email: [email protected]
Web site: www.flexibleduct.org
Professional and Trade Associations 579
The Air Diffusion Council (ADC) was formed to promote the
interests of the manufacturers of flexible air ducts and related air
distribution equipment. The ADC supports the maintenance and
development of uniform industry standards for the installation, use,
and performance of flexible duct products. It encourages the use of
those standards by various code writing groups, government
agencies, architects, engineers, and heating and air conditioning
contractors.
Air Filter Institute
(See Air-Conditioning and Refrigeration Institute)
Air Movement and Control Association International,
Inc. (AMCA)
30 West University Drive
Arlington Heights, Illinois 60004
Phone: (847) 394-0150
Fax: (847) 253-0088
Email: [email protected]
Web site: www.amca.org
The Air Movement and Control Association International, Inc.
(AMCA) is a trade association of the manufacturers, wholesalers,
and retailers of air movement and control equipment (fans, louvers,
dampers, and related air systems equipment). The AMCA Certified
Ratings Programs are an important function of the association.
Their purpose is to give the buyer, specification writer, and user of
air movement and control equipment assurance that published ratings are reliable and accurate. The AMCA publishes current test
standards for fans, louvers, dampers, and shutters. It also issues a
variety of AMCA certified rating seals for different types of air
movement and control equipment. It publishes a newsletter various
technical specifications for members and those who work with air
movement and control systems.
American Boiler Manufacturers Association (ABMA)
4001 North 9th Street
Suite 226
Arlington, Virginia 22203
Phone: (703) 522-7350
Fax: (703) 522-2665
580 Appendix A
Email: [email protected]
Web Site: www.abma.com
The American Boiler Manufacturers Association (ABMA) is a
national association representing the manufacturers of commercial,
industrial, and utility steam generating and fuel burning equipment,
as well as suppliers to the industry. The primary goal of ABMA is
topromote the common business interests of the boiler manufacturing industry and to promote the safe, environmentally friendly use
of the products and services of its members. Publishes technical
guides and manuals.
American Gas Association (AGA)
151400 North Capitol Street, N.W.
Washington, DC 20001
Phone: (202) 824-7000
Fax: (202) 824-7115
Email: Fax: [email protected]
Web site: www.aga.org
The AGA develops residential gas operating and performance
standards for distributors and transporters of natural, manufactured, and mixed gas.
American Society of Heating, Refrigeration, and
Air-Conditioning Engineers (ASHRAE)
1791 Tullie Circle NE
Atlanta, GA 30329
Phone: (800) 527-4723 (toll free)
Phone: (404) 636-8400
Fax: (404) 321-5478
Email: [email protected]
Web site: www.ashrae.org
The American Society of Heating, Refrigeration, and AirConditioning Engineers (ASHRAE) is an international professional
association concerned with the advancement of the science and technology of heating, ventilation, air conditioning, and refrigeration
through research, standards writing, continuing education, and publications. Membership in ASHRAE is open to any person associated
Professional and Trade Associations 581
with heating, ventilation, air conditioning, or refrigeration. There
are several different types of membership depending on the individual’s background and experience in the different HVAC and refrigeration fields. An important benefit of belonging to ASHRAE is
access to numerous technical publications.
American Society of Mechanical Engineers (ASME)
Three Park Avenue
New York, New York 10016
Phone: (800) 843-2763 or (973) 882-1167
Fax: (973) 882-1717
Email: [email protected]
Web site: www.asme.org
A nonprofit technical and education association, ASME develops safety codes and standards and has an extensive list of technical
publications covering pressure vessels, piping, and boilers. ASME
offers educational and training services and conducts technology
seminars and on-site training programs.
Better Heating-Cooling Council
(See Hydronics Institute)
Fireplace Institute
(Merged with Wood Energy Institute in 1980 to form the
Wood Heating Alliance. See Wood Heating Alliance) Gas
Appliance Manufacturers Association (GAMA)
2701 Wilson Boulevard, Suite 600
Arlington, Virginia 22201
Phone: (703) 525-7060
Fax: (703) 525-6790
Email: [email protected]
Web Site: www.gamanet.org
GAMA is a national trade association of manufacturers of gasfired appliances, and certain types of oil-fired and electrical appliances, used in residential, commercial, and industrial applications.
An important service provided by GAMA to its members is a
testing and certification program. GAMA will test the rated efficiency and capacity of a manufacturer’s product and, if it passes the
582 Appendix A
testing criteria, certify it. The manufacturer can then market the
product with the appropriate certification label. Program participants and their products are listed in the ratings directories.
Heating and Piping Contractors National Association
(See Mechanical Contractors Association of America)
Heating, Airconditioning & Refrigeration Distributors
International (HARDI)
1389 Dublin Road
Columbus, Ohio 43215
Phone: (888) 253-2128 (toll free)
Phone: (614) 488-1835
Fax: (614) 488-0482
Email: [email protected]
Web site: www.hardinet.org
Heating, Airconditioning & Refrigeration Distributors International (HARDI) is national trade association of wholesalers and
distributors of air conditioning and refrigeration equipment. It was
formed by merging the Northamerican Heating, Refrigeration &
Airconditioning Wholesalers (NHRAW) and the Air-conditioning
& Refrigeration Wholesalers International (ARWI). Among products and services provided to its members are self-study training
materials, statistical studies, as well as training and reference materials. See Appendix B (Education, Training, and Certification) for a
description of the HARDI Home Study Institute. The HARDI publications are available to both members and nonmembers.
Home Ventilating Institute (HVI)
30 West University Drive
Arlington Heights, Illinois 60004
Phone: (847) 394-0150
Fax: (847) 253-0088
Email: [email protected]
Web site: www.hvi.org
The Home Ventilating Institute (HVI) is a nonprofit trade association representing national and international manufacturers of
Professional and Trade Associations 583
residential ventilation products. HVI is primarily concerned with
developing performance standards for residential ventilating equipment. It has created a number of certified ratings programs that
provide a fair and credible method of comparing ventilation performance of similar products. HVI publishes a number of interesting
and informative articles on ventilation that can be downloaded
from its Web site.
The Hydronics Foundation, Inc. (THFI)
The Hydronics Foundation, Inc. (THFI) was chartered in 1997 as a
nonprofit organization to disseminate knowledge about hydronic
equipment and technology. Manufacturers of HVAC equipment
also contribute material from installation manuals, specification
sheets, and product reviews.
119 East King Street
P.O. Box 1671
Johnson City, TN 37606
Phone: (800) 929-8548
Fax: (800) 929-9506
Email: [email protected]
Web site: www.hydronics.com or www.hydronics.org
Hydronic Heating Association (HHA)
P.O. Box 388
Dedham, MA 02026
Phone: (781) 320-9910
Fax: (781) 320-9906
Email: [email protected]
Web site: www.comfortableheat.net
The Hydronic Heating Association is an organization of independent contractors, wholesalers, and manufacturers established to
promote the latest hydronic technology, set uniform industrial standards, educate HVAC contractors, and inform the public of the benefits of having a quality hot-water system installed. Their Web site
contains useful articles and essays on hydronic equipment and systems. It also offers many useful links to manufacturers of hydronic
system products.
584 Appendix A
The Hydronics Institute Division of GAMA
P.O. Box 218
Berkley Heights, New Jersey 07922
Phone: (908) 464-8200
Fax: (908) 464-7818
Email: [email protected]
Web site: www.gamanet.org
The Hydronics Institute was originally formed by a merger
of the Better Heating-Cooling Council and the Institute of
Boiler and Radiator Manufacturers. It represents manufacturers,
suppliers, and installers of hot-water and steam heating and
cooling equipment. It is now a division of the Gas Appliance
Manufacturers Association. The Hydronics Institute represents
and promotes the interests of the manufacturers of hydronic
heating equipment. It also provides training materials for
hydronic heating courses in schools and technical publications
for technicians in the field.
Institute of Boiler and Radiator Manufacturers
(See Hydronics Institute)
Mechanical Contractors Association of America,
Inc. (MCAA)
1385 Piccard Drive
Rockville, MD 20850
Phone: 301-869-5800
Fax: 301-990-9690
Web site: www.mcaa.org
The Mechanical Contractors Association of America, Inc.
(MCAA) is a national trade association for contractors of piping
and related equipment used in heating, cooling, refrigeration, ventilating, and air conditioning.
National Association of Plumbing Heating Cooling
Contractors (PHCC)
180 S. Washington Street
P.O. Box 6808
Falls Church, VA 22040
Professional and Trade Associations 585
Phone: (800) 533-7694 (toll free) or (703) 237-8100
Fax: (703) 237-7442
Email: [email protected]
Web site: www.phccweb.org
The National Association of Plumbing Heating Cooling Contractors (PHCC) is a trade association of local plumbing, heating,
and cooling contractors. There are 12 regional chapters.
National Environmental Systems
Contractors Association
(See Air Conditioning Contractors of America)
National Warm Air Heating and Air
Conditioning Association
(See Air Conditioning Contractors of America)
North American Heating Refrigerating Air conditioning
Wholesalers (NHRAW)
(See Heating, Airconditioning & Refrigeration Distributors
International)
Radiant Panel Association (RPA)
P.O. Box 717
1399 South Garfield Avenue
Loveland, CO 80537
Phone: (800) 660-7187 (toll free) or (970) 613-0100
Fax: (970) 613-0098
Email: [email protected]
Web site: www.radiantpanelassociation.org
The Radiant Panel Association provides downloadable technical papers and notes on a variety of different topics concerning
radiant panel heating and cooling systems. Links to several manufacturers of radiant heating equipment are also available at their
Web site.
Refrigeration and Air Conditioning
Contractors Association
(See Air Conditioning Contractors of America)
586 Appendix A
Refrigeration Service Engineers Society (RSES)
1666 Rand Road
Des Plaines, Illinois 60016
Phone: (800) 297-5660 (toll free) or (847) 297-6464
Email: [email protected]
Web site: www.rses.org
The Refrigeration Services Engineers Society (RSES) is an international association of refrigeration, air conditioning, and heating
equipment installers, service persons, and sales persons. The Society
conducts educational meetings, seminars, workshops, technical
qualification and examination programs, instructor-led and selfstudy training courses. It offers a variety of certification program
for technicians.
Sheet Metal and Air Conditioning Contractors National
Association (SMACNA)
4201 Lafayette Center Dr.
Chantilly, Virginia 20151
Phone: (703) 803-2980
Fax: (703) 803-3732
Email: [email protected]
Web site: www.smacna.org
The SMACNA is an international trade association of union contractors who install ventilating, warm-air heating, and air-handling
equipment and systems. SMACNA publishes technical papers,
answers technical question, and provides distance learning courses
for its members. American National Standards Institute has accredited SMACNA as a standards-setting organization matter.
Steam Heating Equipment Manufacturers Association
(defunct)
Steel Boiler Institute
(defunct)
Underwriters Laboratories, Inc. (UL)
Northbrook Division
Corporate Headquarters
333 Pfingsten Road
Professional and Trade Associations 587
Northbrook, Illinois 60062
Phone: (847) 272-8800
Fax: (847) 272-8129
Email: [email protected]
Web site: www.ul.com
The Underwriters Laboratories is an independent, nonprofit
product safety testing and certification organization. It promotes
safety standards for equipment through independent testing.
Wood Energy Institute
(Merged with Fireplace Institute in 1980 to form Wood Heating
Alliance.)
Other National and International Professional
and Trade Associations
The following associations also provide support, services, technical
publications, and/or training to its members who are involved in
the manufacture, sale, or installation and repair of heating, ventilating, and air conditioning systems and equipment. Because space
is limited, only their names are listed. Contact information can be
obtained by accessing the Internet and entering the association
name or by visiting the reference room of your local library and
using the Encyclopedia of Associations.
Air Distribution Institute (ADI)
American National Standards Institute (ANSI)
American Society for Testing and Materials (ASTM)
Australian Home Heating Association (AHHA)
Australian Institute of Refrigeration, Air Conditioning and
Heating (AIRAH)
Heating Alternatives, Inc
Heating, Refrigeration and Air Conditioning Contractors of
Canada (HRAC)
Heating, Refrigeration and Air Conditioning Institute of
Canada (HRAE)
Institute of Heating & Air Conditioning, Inc (IHACI).
Insulation Contractors of America (ICA)
International Energy Association (IEA)—Solar Heating and
Cooling Programme
588 Appendix A
National LP-Gas Association (NLPGA)
National Oil Fuel Institute
National Oilheat Research Alliance
Plumbing-Heating-Cooling Contractors—National Association
(PHCC)
Plumbing-Heating-Cooling Information Bureau (PHCIB)
Wood Heating Alliance (WHA)
Appendix B
Manufacturers
Adams Manufacturing Company
9790 Midwest Avenue
Cleveland, OH 44125
(216) 587-6801
(216) 587-6807 (Fax)
www.gamanet.org
Amana Refrigeration, Inc.
1810 Wilson Parkway
Fayetteville, TN 37334
(800) 843-0304
(931) 433-6101
(931) 433-1312
www.amana.com
American Standard Companies Inc.
One Centennial Ave.
Piscataway, NJ 08855
(732) 980-6000
(732) 980-3340 (Fax)
www.americanstandard.com
A.O. Smith Water Products Company
600 E. John Carpenter Freeway #200
Irving, TX 75062-3990
(972) 719-5900
(972) 719-5960 (Fax)
www.hotwater.com
Bacharach Inc.
621 Hunt Valley
New Kensington, PA 15068
(724) 334-5000
589
590 Appendix B
(724) 334-5001 (Fax)
www.bacharach-inc.com
Bard Manufacturing Co
P.O. Box 607
Bryan, OH 43506
(419) 636-1194
(419) 636-2640 (Fax)
www.bardhvac.com
R.W. Beckett Corporation
P.O. Box 1289
Elyria, OH 44036
(800) 645-2876
(440) 327-1060
(440) 327-1064 (Fax)
www. beckett.com
Bell & Gossett
(See ITT Bell & Gossett)
Bryan Boilers/Bryan Steam Corporation
P.O. Box 27
783 N. Chili Avenue
Peru, IN 46970
(765) 473-6651
(765) 473-3074 (Fax)
www.bryanboilers.com
Burnham Hydronics
U.S. Boiler Co., Inc.
P.O. Box 3079
Lancaster, PA 17604
(717) 397-4701
(717) 293-5827 (Fax)
www.burnham.com
Manufacturers 591
Carrier Corporation
World Headquarters
One Carrier Place
Farmington, CT 06034
(860) 674-3000
www.carrier.com
Cash Acme
2400 7th Avenue S.W.
Cullman, Alabama 35055
(256) 775-8200
(256) 775-8238 (Fax)
www.cashacme.com
Coleman Corporation
Unitary Products Group
5005 York Dr.
Norman, OK 73069
(405) 364-4040
www.colemanac.com
Columbia Boiler Company
P.O. Box 1070
Pottstown, PA 19464
(610) 323-2700
(610) 323-7292 (Fax)
www.columbiaboiler.com
Danfoss A/S
DK-6430 Nordborg
Denmark
⫹45 7488 2222
⫹45 7449 0949 (Fax)
www.danfoss.com
Domestic Pump
(See ITT Domestic Pump)
592 Appendix B
Dornback Furnace
9545 Granger Road
Garfield Heights, OH 44125
(216) 662-1600
(216) 587-6807
www.gamanet.org
Ernst Gage Co.
250 S. Livingston Ave.
Livingston, NJ 07039 4089
973-992-1400
888-229-4243
973-992-0036 (Fax)
General Filters Inc.
43800 Grand River Ave.
Novi, MI
(248) 476-5100
(248) 349-2366 (Fax)
www.generalfilters.com
Goodman Manufacturing Corp
2550 North Loop West #400
Houston, TX 77092
(713) 861-2500
(888) 593-9988
www.goodmanmfg.com
Heat Controller, Inc.
1900 Wellworth Avenue
Jackson, MI 49203
(517) 787-2100
(517) 787-9341
www.heatcontroller.com
Hoffman Specialty
(See ITT Hoffman Specialty)
Manufacturers 593
Honeywell, Inc.
101 Columbia Road
Morristown, NJ 07962
(973) 455-2000
(800) 328-5111
(983) 455-4807 (Fax)
www.honeywell.com
Hydro Therm, A Division of Mastek, Inc.
260 North Elm Street
Westfield, MA 01085
(413) 564-5515
www.hydrotherm.com
Invensys Building Systems, Inc.
1354 Clifford Ave.
P.O. Box 2940
Loves Park, IL 61132-2940
(815) 637-3000
(815) 637-5350 (Fax)
www.invensys.com
ITT Bell & Gossett
8200 North Austin Avenue
Morton Grove, IL 60053
(847) 966-3700
(847) 966-9052
www.bellgossett.com
ITT Domestic Pump
8200 N. Austin Ave.
Morton Grove, IL 60053
(847) 966-3700
(847) 966-9052
www.domesticpump.com
594 Appendix B
ITT Hoffman Specialty
3500 N. Spaulding Avenue
Chicago, IL 60618
(773) 267-1600
(773) 267-0991
www.hoffmanspecialty.com
ITT McDonnell & Miller
3500 N. Spaulding Avenue
Chicago, IL 60618
(723) 267-1600
(773) 267-0991
www.mcdonnellmiller.com
Janitrol Air Conditioning and Heating
www.janitrol.com
(See Goodman Manufacturing Company)
S.T. Johnson Company
Innovative Combustion Technologies, Inc.
925 Stanford Avenue
Oakland, CA 94608
(510) 652-6000
(510) 652-4302 (Fax)
www.johnsonburners.com
Johnson Controls, Inc.
5757 North Green Bay Avenue
Milwaukee, WI 53209
(262) 524-3285
www.johnsoncontrols.com
www.jci.com
Lennox Industries Inc.
2100 Lake Park Boulevard
Richardson, TX 75080
(972) 497-5000
Manufacturers 595
(972) 497-5392 (Fax)
www.davelennox.com
Marathon Electric, Inc.
P.O. Box 8003
Wausau, WI 54402
(715) 675-3359
(715) 675-8050 (Fax)
McDonnell & Miller
(See ITT McDonnell & Miller)
Midco International Inc.
4140 West Victoria Street
Chicago, IL 60646-6790
(773) 604-8700
(773) 604-4070 (Fax)
www.midco-intl.com
Nordyne
P.O. Box 8809
O’Fallon, MO 63366
(636) 561-7300
(800) 222-4328
(636) 561-7365 (Fax)
www.nordyne.com
Raypak
2151 Eastman Ave.
Oxnard, CA 93030
(805) 278-5300
(805) 278-5468 (Fax)
www.raypak.com
RBI, Mestek Canada, Inc.
1300 Midway Blvd.
Mississauga Ontario L5T 2G8
(905) 670-5888
www.rbimestek.com
596 Appendix B
Rheem Manufacturing
5600 Old Greenwood Road
Fort Smith, AR 72908
(479) 646-4311
(479) 648-4812 (Fax)
www.rheemac.com
Robertshaw
(See Invensys)
Smith Cast Iron Boilers
260 North Elm Street
Westfield, MA 01085
(413) 562-9631
www.smithboiler.com
SpacePak
125 North Elm Street
Westfield, MA 01085
(413) 564-5530
www.spacepak.com
Spirax Sarco Inc.
Northpoint Business Park
1150 Northpoint Blvd
Blythewood, SC 29016
(803) 714-2000
(803) 714-2222
www.spiraxsarco.com
Sterling Hydronics
260 North Elm Street
Westfield, MA 01085
(413) 564-5535
www.sterlingheat.com
Sterling HVAC
125 North Elm Street
Westfield, MA 01085
Manufacturers 597
(413) 564-5540
www.sterlinghvac.com
Suntec Industries Incorporated
2210 Harrison Ave
P.O. Box 7010
Rockford IL 61125-7010
(815) 226-3700
(815) 226-3848 (Fax)
www.suntecpumps.com
Thermo Pride
P.O. Box 217
North Judson, IN 46366
(574) 896-2133
(574) 896-5301
www.thermopride.com
Trane
P.O. Box 9010
Tyler, TX 75711-9010
(903) 581-3200
www.trane.com
Triangle Tube/Phase III Company, Inc.
Blackwood, NJ
(856) 228-1881
(856) 228-3584 (Fax)
www.triangletube.com
Vulcan Radiator (Mastec)
515 John Fitch Blvd
South Windsor, CT 06074
(413) 568-9571
www.mestec.com
Water Heater Innovations, Inc.
3107 Sibley Memorial Highway
Eagan, MN 55121
598 Appendix B
(800) 321-6718
www.marathonheaters.com
Watts Regulator Company
815 Chestnut Street
North Andover, MA 01845
(976) 688-1811
(978) 794-848 (Fax)
www.wattsreg.com
Wayne Combustion Systems
801 Glasgow Ave.
Fort Wayne, IN 46803
(800) 443-4625
www.waynecombustion.com
Weil-McLain
500 Blaine St.
Michigan City, IN 46360
(219) 879-6561
(219) 879-4025
www.weil-mclain.com
White-Rodgers, Div. of Emerson Electric Co.
9797 Reavis Rd.
St. Louis, MO 63123
(314) 577-1300
(314) 577-1517
www.white-rodgers.com
Wm. Powell Company
2503 Spring Grove Avenue
Cincinnati, OH 45214
(513) 852-2000
(513) 852-2997 (Fax)
www.powellvalves.com
York International Corporation
P.O. Box 1592-232F
York, PA 17405
Manufacturers 599
(717) 771-7890
(717) 771-7381 (Fax)
www.york.com
Yukon-Eagle Wood & Multifuel Furnaces
10 Industrial Blvd.
P.O. Box 20
Palisade, MN 56469
(800) 358-0060
(800) 440-1994 (Fax)
www.yukon-eagle.com
John Zink Company
Gordon-Piatt Group
11920 East Apache
Tulsa, OK 74116
(800) 638-6940
www.johnzink.com
Appendix C
HVAC/R Education,Training,
Certification, and Licensing
A career in the heating, ventilating, air-conditioning, and refrigeration (HVAC/R) trades requires special education and training.
Formal education and training in the HVAC/R trades is available in
many local public colleges and proprietary schools. Certification
requires passing a standardized test indicating a thorough knowledge of the subject matter. The states also require HVAC/R technicians and contractors to take and pass licensing examinations.
HVAC/R Education and Training Programs
HVAC/R education and training programs are offered by four-year
colleges, community colleges, proprietary schools, professional and
trade associations, and manufacturers of HVAC/R appliances and
system components.
One way to find a local school offering courses in HVAC/R education and training is to go online to the Cool Careers Web site at
www.coolcareers.org. On their “Schools with HVACR Programs”
page, you will find a list of all fifty states. Each state has the names
of all the schools in that state offering programs in HVAC/R
training. According to Cool Careers, their database contains the
names of over 1300 training schools. You will have to contact the
schools to enquire about entrance requirements, course content,
class schedules, and financial aid.
Note
If you don’t have a computer, or know how to use one, go to
the reference section in your local public library and ask the
reference librarian to download the information from the
internet and provide a printout. They will be willing to do this
for you. It’s part of the many services offered by the local
public library.
Some of these schools offer only courses; others offer both
courses and degrees. The least expensive courses are found at community colleges. The level of instruction will vary, depending on the
school and the instructors. Your best source of information in this
601
602 Appendix C
regard is local word of mouth. If you are already working as an
entrance level trainee with a local HVAC firm, they should be able
to help you find the best school and courses. After all, they often
hire the graduates.
Cool Careers-Hot Jobs
The Cool Careers-Hot Jobs web site was created in 2000 by a
coalition of organizations representing the heating, air conditioning, refrigeration, and plumbing industry. Its purpose is to
provide information about education, training, jobs, and
careers in the HVAC/R trades.
HVAC/R Certification
Certification means that the individual has taken and passed a standardized examination that certifies the individual’s knowledge
level. After the basic certification has been obtained, the technician
can then study for and take certification exams at more advanced
levels.
The following four organizations provide guidance and/or testing for the certification of HVAC/R technicians. Their addresses,
telephone numbers, and web site addresses are listed in Appendix A
(Professional and Trade Associations).
1. Air-Conditioning and Refrigeration Institute (ARI). ARI is a
national trade association whose members represent most of
the manufacturers of central air conditioning and refrigeration equipment. ARI administers the Industry Competencies
Exam (ICE), which is given primarily to students from vocational school HVAC/R programs. The ARI also provides textbooks and training materials for preparing for both the ICE
and EPA certification exams.
2. North American Technician Excellence, Inc. (NATE). NATE
is a nonprofit organization established in 1997 by members of
the HVAC/RE industry to test and certify technicians working
in the heating ventilation, air-conditioning, and refrigeration
trades. The tests are intended for experienced technicians.
3. Refrigeration Service Engineers Society (RSES). The RSES
Educational Foundation was established in 1983 as a separate
nonprofit organization to develop a comprehensive voluntary
technician certification program (NTC). The program guides,
tests, and certifies members through each of five levels of
HVAC/R technician competency ranging from Level I
(Technician) to Level V (Mastertech specialist).
HVAC/R Education,Training, Certification, and Licensing 603
4. Air Conditioning Contractors of America (ACCA). ACCA
works in conjunction with RSES and NATE to provide a
national certification program for HVAC/R technicians.
HVAC/R State Licensing
HVAC/R work is regulated at the state level by law. The law
requires that a licensing exam must be taken and passed before
working in an HVAC/R trade. It is the responsibility of the individual to contact the appropriate state office and obtain the necessary
information about the state licensing examination. An easy way to
locate the state office charged with licensing HVAC/R technicians
and contractors is to ask the reference librarian at your local public
library. You could also phone the state government and ask the
operator to connect you to the office.
Appendix D
Data Tables
605
606
Table D-1 Equivalent Length of New Straight Pipe for Valves and Fittings for Turbulent Flow
Pipe Size
Fittings
1
⁄4
2.3
—
—
—
1.5
—
—
—
0.34
—
—
—
0.79
—
—
—
2.4
—
—
—
3
⁄8
3.1
—
—
—
2
—
—
—
0.52
—
—
—
1.2
—
—
—
3.5
—
—
—
1
⁄2
3.6
—
0.92
—
2.2
—
1.1
—
0.71
—
0.45
—
1.7
—
0.69
—
4.2
—
2
—
3
⁄4
1
4.4
—
1.2
—
2.3
—
1.3
—
0.92
—
0.59
—
2.4
—
0.82
—
5.3
—
2.6
—
5.2
—
1.6
—
2.7
—
1.6
—
1.3
—
0.81
—
3.2
—
1
—
6.6
—
3.3
—
11⁄4 11⁄2
6.6
—
2.1
—
3.2
—
2
—
1.7
—
1.1
—
4.6
—
1.3
—
8.7
—
4.4
—
7.4
—
2.4
—
3.4
—
2.3
—
2.1
—
1.3
—
5.6
—
1.5
—
9.9
—
5.2
—
2
21⁄2
3
8.5
—
3.1
—
3.6
—
2.7
—
2.7
—
1.7
—
7.7
—
1.8
—
12
—
6.6
—
9.3
—
3.6
—
3.6
—
2.9
—
3.2
—
2
—
9.3
—
1.9
—
13
—
7.5
—
11
9
4.4
3.6
4
3.3
3.4
2.8
4
3.3
2.6
2.1
12
9.9
2.2
1.9
17
14
9.4
7.7
4
5
6
8
10 12 14 16 18 20 24
13 — — — — — — — — — —
11 — — — — — — — — — —
5.9 7.3 8.9 12 14 17 18 21 23 25 30
4.8 — 7.2 9.8 12 15 17 19 22 24 28
4.6 — — — — — — — — — —
3.7 — — — — — — — — — —
4.2 5 5.7 7 8 9 9.4 10 11 12 14
3.4 — 4.7 5.7 6.8 7.8 8.6 9.6 11 11 13
5.5 — — — — — — — — — —
4.5 — — — — — — — — — —
3.5 4.5 5.6 7.7 9 11 13 15 16 18 22
2.9 — 4.5 6.3 8.1 9.7 12 13 15 17 20
17 — — — — — — — — — —
14 — — — — — — — — — —
2.8 3.3 3.8 4.7 5.2 6 6.4 7.2 7.6 8.2 9.6
2.2 — 3.1 3.9 4.6 5.2 5.9 6.5 7.2 7.7 8.8
21 — — — — — — — — — —
17 — — — — — — — — — —
12 15 18 24 30 34 37 43 47 52 62
10 — 15 20 25 30 35 39 44 49 57
2.3
—
—
—
—
—
21
—
—
—
0.32
—
—
—
12.8
—
—
—
7.2
—
—
—
0.14
3.1
—
—
—
—
—
22
—
—
—
0.45
—
—
—
15
—
—
—
7.3
—
—
—
0.18
3.6
—
0.92
—
1.1
—
22
—
38
—
0.56
—
—
—
15
—
15
—
8
—
3.8
—
0.21
4.4
—
1.2
—
1.3
—
24
—
40
—
0.67
—
—
—
15
—
15
—
8.8
—
5.3
—
0.24
5.2
—
1.6
—
1.6
—
29
—
45
—
0.84
—
—
—
17
—
17
—
11
—
7.2
—
0.29
6.6
—
2.1
—
2
—
37
—
54
—
1.1
—
—
—
18
—
18
—
13
—
10
—
0.36
7.4
—
2.4
—
2.3
—
42
—
59
—
1.2
—
—
—
18
—
18
—
15
—
12
—
0.39
8.5
—
3.1
—
2.7
—
54
—
70
—
1.5
—
2.6
—
18
—
21
—
19
—
17
—
0.45
9.3
—
3.6
—
2.9
—
62
—
77
—
1.7
—
2.7
—
18
—
22
—
22
—
21
—
0.47
11
9
4.4
3.6
3.4
2.8
79
65
94
77
1.9
1.6
2.8
2.3
18
15
28
23
27
22
27
22
0.53
13
11
5.9
4.8
4.2
3.4
110
86
120
99
2.5
2
2.9
2.4
18
15
38
31
38
31
38
31
0.65
—
—
7.3
—
5
—
—
—
150
—
—
—
3.1
—
—
—
50
—
—
—
50
—
—
—
—
8.9
7.2
5.7
4.7
—
—
190
150
—
—
3.2
2.6
—
—
63
52
—
—
63
52
—
—
—
12
9.8
7
5.7
—
—
260
210
—
—
3.2
2.7
—
—
90
74
—
—
90
74
—
—
—
14
12
8
6.8
—
—
310
270
—
—
3.2
2.8
—
—
120
98
—
—
120
98
—
—
—
17
15
9
7.8
—
—
390
330
—
—
3.2
2.9
—
—
140
120
—
—
140
120
—
—
—
18
17
9.4
8.6
—
—
—
—
—
—
3.2
3
—
—
160
150
—
—
—
—
—
—
—
21
19
10
9.6
—
—
—
—
—
—
3.2
3
—
—
190
170
—
—
—
—
—
607
— — —
— — —
23 25 30
22 24 28
11 12 14
11 11 13
— — —
— — —
— — —
— — —
— — —
— — —
3.2 3.2 3.2
3 3 3
— — —
— — —
210 240 300
200 230 280
— — —
— — —
— — —
— — —
— — —
(continued)
608
Table D-1 (continued)
Pipe Size
Fittings
1
⁄4
3
⁄8
1
⁄2
—
0.1
—
0.96
—
1.9
—
5
3
⁄4
1
—
0.13
—
1.3
—
2.6
—
6.6
—
0.18
—
1.8
—
3.6
—
7.7
11⁄4 11⁄2
—
0.26
—
2.6
—
5.1
—
18
—
0.31
—
3.1
—
6.2
—
20
2
21⁄2
3
4
5
6
8
—
0.43
—
4.3
—
8.5
—
27
—
0.52
—
5.2
—
10
—
29
0.44
0.67
0.55
6.7
5.5
13
11
34
0.62
0.95
0.77
9.5
7.7
19
15
42
—
1.3
—
13
—
25
—
53
—
1.6
1.3
16
13
32
26
61
—
2.3
1.9
23
19
45
37
10 12 14 16 18 20 24
—
0.04
—
0.44
—
0.88
—
—
—
0.07
—
0.68
—
1.4
—
4.6
h
(V1 V2)2
V2
Feet of Liquid; If V2 0 h Feet of Liquid
(2g)
(2g)
Courtesy The Hydraulic Institute (reprinted from the Standards of the Hydraulic Institute, Eleventh Edition, Copyright 1965)
—
2.9
2.4
29
24
58
49
—
3.5
3
35
30
70
61
—
4
3.6
40
36
80
73
—
4.7
4.3
47
43
95
86
—
5.3
5
53
50
110
100
—
6.1
5.7
61
57
120
110
—
7.6
7
76
70
150
140
Table D-2 Schedule 80 Pipe Dimensions
Length of Pipe
Per Square Foot of
Diameters
Transverse Areas
Nominal
Size External Internal Thickness External Internal Metal
in in
in
in
in2
in2
in2
1
⁄8
⁄4
3
⁄8
1
⁄2
3
⁄4
1
11⁄4
11⁄2
2
21⁄2
3
31⁄2
4
5
6
8
1
0.405
0.54
0.675
0.84
1.05
1.315
1.66
1.9
2.375
2.875
3.5
4
4.5
5.563
6.625
8.625
0.215
0.302
0.423
0.546
0.742
0.957
1.278
1.5
1.939
2.323
2.9
3.364
3.826
4.813
5.761
7.625
0.095
0.119
0.126
0.147
0.154
0.179
0.191
0.2
0.218
0.276
0.3
0.318
0.337
0.375
0.432
0.5
0.129
0.229
0.358
0.554
0.866
1.358
2.164
2.835
4.43
6.492
9.621
12.56
15.9
24.3
34.47
58.42
0.036
0.072
0.141
0.234
0.433
0.719
1.283
1.767
2.953
4.238
6.605
8.888
11.497
18.194
26.067
46.663
0.093
0.157
0.217
0.32
0.433
0.639
0.881
1.068
1.477
2.254
3.016
3.678
4.407
6.112
8.3
12.76
External Internal Cubic Feet Weight
Surface Surface per ft
per ft
ft
ft
of Pipe
Pounds
Number
Threads
per in
of Screw
9.431
7.073
5.658
4.547
3.637
2.904
2.301
2.01
1.608
1.328
1.091
0.954
0.848
0.686
0.576
0.442
27
18
18
14
14
111⁄2
111⁄2
111⁄2
111⁄2
8
8
8
8
8
8
8
17.75
12.65
9.03
7
5.15
3.995
2.99
2.542
1.97
1.645
1.317
1.135
0.995
0.792
0.673
0.501
0.00025
0.0005
0.00098
0.00163
0.003
0.005
0.00891
0.01227
0.02051
0.02943
0.04587
0.06172
0.0798
0.1263
0.181
0.3171
0.314
0.535
0.738
1
1.47
2.17
3
3.65
5.02
7.66
10.3
12.5
14.9
20.8
28.6
43.4
609
(continued)
610
Table D-2 (continued)
Length of Pipe
Per Square Foot of
Diameters
Transverse Areas
Nominal
Size External Internal Thickness External Internal Metal
in
in
in
in
in2
in2
in2
10
12
14
16
18
20
24
10.75
12.75
14
16
18
20
24
9.564
11.376
12.5
14.314
16.126
17.938
21.564
Courtesy Sarco Company, Inc.
0.593
0.687
0.75
0.843
0.937
1.031
1.218
90.76
127.64
153.94
201.05
254.85
314.15
452.4
71.84
101.64
122.72
160.92
204.24
252.72
365.22
18.92
26
31.22
40.13
50.61
61.43
87.18
External Internal Cubic Feet Weight
Surface Surface per ft
per ft
ft
ft
of Pipe
Pounds
0.355
0.299
0.272
0.238
0.212
0.191
0.159
0.4
0.336
0.306
0.263
0.237
0.208
0.177
0.4989
0.7058
0.8522
1.112
1.418
1.755
2.536
64.4
88.6
107
137
171
209
297
Number
Threads
per in
of Screw
8
Table D-3 Schedule 40 Pipe Dimensions
Length of Pipe
Per ft2 of
Diameters
Transverse Areas
Nominal
Size External Internal Thickness External Internal Metal
in
in
in
in
in2
in2
in2
1
⁄8
⁄4
3
⁄8
1
⁄2
3
⁄4
1
11⁄4
11⁄2
2
21⁄2
3
31⁄2
4
5
6
8
1
0.405
0.54
0.675
0.84
1.05
1.315
1.66
1.9
2.375
2.875
3.5
4
4.5
5.563
6.625
8.625
0.269
0.364
0.493
0.622
0.824
1.049
1.38
1.61
2.067
2.469
3.068
3.548
4.026
5.047
6.065
7.981
0.068
0.088
0.091
0.109
0.113
0.133
0.14
0.145
0.154
0.203
0.216
0.226
0.237
0.258
0.28
0.322
0.129
0.229
0.358
0.554
0.866
1.358
2.164
2.835
4.43
6.492
9.621
12.56
15.9
24.3
34.47
58.42
0.057
0.104
0.191
0.304
0.533
0.864
1.495
2.036
3.355
4.788
7.393
9.886
12.73
20
28.9
50.02
0.072
0.125
0.167
0.25
0.333
0.494
0.669
0.799
1.075
1.704
2.228
2.68
3.174
4.3
5.581
8.399
External Internal Cubic Feet Weight
Surface Surface per ft
per ft
ft
ft
of Pipe
Pounds
Number
Threads
per in
of Screw
9.431
7.073
5.658
4.547
3.637
2.904
2.301
2.01
1.608
1.328
1.091
0.954
0.848
0.686
0.576
0.442
27
18
18
14
14
111⁄2
111⁄2
111⁄2
111⁄2
8
8
8
8
8
8
8
14.199
10.493
7.747
6.141
4.635
3.641
2.767
2.372
1.847
1.547
1.245
1.076
0.948
0.756
0.629
0.478
0.00039
0.00072
0.00133
0.00211
0.0037
0.006
0.01039
0.01414
0.0233
0.03325
0.05134
0.06866
0.0884
0.1389
0.2006
0.3552
0.244
0.424
0.567
0.85
1.13
1.678
2.272
2.717
3.652
5.793
7.575
9.109
10.79
14.61
18.97
28.55
611
(continued)
612
Table D-3 (continued)
Length of Pipe
Per ft2 of
Diameters
Transverse Areas
Nominal
Size External Internal Thickness External Internal Metal
in
in
in
in
in2
in2
in2
External Internal Cubic Feet Weight
Surface Surface per ft
per ft
ft
ft
of Pipe
Pounds
10
12
14
16
18
20
24
0.355
0.299
0.272
0.238
0.212
0.191
0.159
10.75
12.75
14
16
18
20
24
10.02
11.938
13.125
15
16.874
18.814
22.626
Courtesy Sarco Company, Inc.
0.365
0.406
0.437
0.5
0.563
0.593
0.687
90.76
127.64
153.94
201.05
254.85
314.15
452.4
78.85
111.9
135.3
176.7
224
278
402.1
11.9
15.74
18.64
24.35
30.85
36.15
50.3
0.381
0.318
0.28
0.254
0.226
0.203
0.169
0.5476
0.7763
0.9354
1.223
1.555
1.926
2.793
40.48
53.6
63
78
105
123
171
Number
Threads
per in
of Screw
8
Table D-4 Properties of Saturated Steam
In Vac.
Gauge
Pressure
psig
TemperHeat in Btu/lb
ature
ⴗF
Sensible Latent Total
613
25
20
15
10
5
0
1
2
3
4
5
6
7
8
9
10
12
14
134
162
179
192
203
212
215
219
222
224
227
230
232
233
237
239
244
248
102
129
147
160
171
180
183
187
190
192
195
198
200
201
205
207
212
216
1017
1001
990
982
976
970
968
966
964
962
960
959
957
956
954
953
949
947
Specific Gauge
TemperHeat in Btu/lb
Volume Pressure ature
3
ft /lb
psig
ⴗF
Sensible Latent Total
1119 142
1130 73.9
1137 51.3
1142 39.4
1147 31.8
1150 26.8
1151 25.2
1153 23.5
1154 22.3
1154 21.4
1155 20.1
1157 19.4
1157 18.7
1157 18.4
1159 17.1
1160 16.5
1161 15.3
1163 14.3
150
155
160
165
170
175
180
185
190
195
200
205
210
215
220
225
230
235
366
368
371
373
375
377
380
382
384
386
388
390
392
394
396
397
399
401
339
341
344
346
348
351
353
355
358
360
362
364
366
368
370
372
374
376
857
885
853
851
849
847
845
843
841
839
837
836
834
832
830
828
827
825
1196
1196
1197
1197
1197
1198
1198
1198
1199
1199
1199
1200
1200
1200
1200
1200
1201
1201
Specific
Volume
ft3
per lb
2.74
2.68
2.6
2.54
2.47
2.41
2.34
2.29
2.24
2.19
2.14
2.09
2.05
2
1.96
1.92
1.89
1.85
(continued)
614
Table D-4 (continued)
Gauge
Pressure
psig
16
18
20
22
24
26
28
30
32
34
36
38
40
42
44
46
48
50
55
TemperHeat in Btu/lb
ature
ⴗF
Sensible Latent Total
Specific Gauge
TemperHeat in Btu/lb
Volume Pressure ature
3
ft /lb
psig
ⴗF
Sensible Latent Total
Specific
Volume
ft3
per lb
252
256
259
262
265
268
271
274
277
279
282
284
286
289
291
293
295
298
300
13.4
12.6
11.9
11.3
10.8
10.3
9.85
9.46
9.1
8.75
8.42
8.08
7.82
7.57
7.31
7.14
6.94
6.68
6.27
1.81
1.78
1.75
1.72
1.69
1.66
1.63
1.6
1.57
1.55
1.53
1.49
1.47
1.45
1.43
1.41
1.38
1.36
1.34
220
224
227
230
233
236
239
243
246
248
251
253
256
258
260
262
264
267
271
944
941
939
937
934
933
930
929
927
925
923
922
920
918
917
915
914
912
909
1164
1165
1166
1167
1167
1169
1169
1172
1173
1173
1174
1175
1176
1176
1177
1177
1178
1179
1180
240
245
250
255
260
265
270
275
280
285
290
295
300
305
310
315
320
325
330
403
404
406
408
409
411
413
414
416
417
418
420
421
423
425
426
427
429
430
378
380
382
383
385
387
389
391
392
394
395
397
398
400
402
404
405
407
408
823
822
820
819
817
815
814
812
811
809
808
806
805
803
802
800
799
797
796
1201
1202
1202
1202
1202
1202
1203
1203
1203
1203
1203
1203
1203
1203
1204
1204
1204
1204
1204
Table D-4 (continued)
Gauge
Pressure
psig
60
65
70
75
80
85
90
95
100
105
110
115
120
125
130
140
145
615
Courtesy Sarco Company, Inc.
TemperHeat in Btu/lb
ature
ⴗF
Sensible Latent Total
307
312
316
320
324
328
331
335
338
341
344
347
350
353
356
361
363
277
282
286
290
294
298
302
305
309
312
316
319
322
325
328
333
336
906
901
898
895
891
889
886
883
880
878
875
873
871
868
866
861
859
1183
1183
1184
1185
1185
1187
1188
1188
1189
1190
1191
1192
1193
1193
1194
1194
1195
Specific Gauge
TemperHeat in Btu/lb
Volume Pressure ature
3
ft /lb
psig
ⴗF
Sensible Latent Total
5.84
5.49
5.18
4.91
4.67
4.44
4.24
4.05
3.89
3.74
3.59
3.46
3.34
3.23
3.12
2.92
2.84
335
340
345
350
355
360
365
370
375
380
385
390
395
400
450
500
550
600
432
433
434
435
437
438
440
441
442
443
445
446
447
448
460
470
479
489
410
411
413
414
416
417
419
420
421
422
424
425
427
428
439
453
464
475
794
793
791
790
789
788
786
785
784
783
781
780
778
777
766
751
740
728
1204
1204
1204
1204
1205
1205
1205
1205
1205
1205
1205
1205
1205
1205
1205
1204
1204
1203
Specific
Volume
ft3
per lb
1.33
1.31
1.29
1.28
1.26
1.24
1.22
1.2
1.19
1.18
1.16
1.14
1.13
1.12
1
0.89
0.82
0.74
616 Appendix D
Table D-5
U.S.
gal/min
Friction Loss for Water in Feet per 100 Feet
of Schedule 40 Steel Pipe
Velocity
ft/sc
hf Friction
U.S.
gal/min
3
2.25
2.68
3.02
3.36
4.2
5.04
5.88
6.72
8.4
10.08
11.8
13.4
15.1
16.8
⁄2" Pipe
9.03
11.6
14.3
17.3
26
36.6
49
63.2
96.1
136
182
236
297
364
2
2.5
3
3.5
4
5
6
7
8
9
10
12
14
16
3
⁄4" Pipe
4
5
6
7
8
9
10
12
14
16
18
20
22
24
26
28
2.41
3.01
3.61
4.21
4.81
5.42
6.02
7.22
8.42
9.63
10.8
12
13.2
14.4
15.6
16.8
hf Friction
1
⁄8" Pipe
1.4
1.6
1.8
2
2.5
3
3.5
4
5
6
7
8
9
10
Vel. ft/sec
2.11
2.64
3.17
3.7
4.22
5.28
6.34
7.39
8.45
9.5
10.56
12.7
14.8
16.9
5.5
8.24
11.5
15.3
19.7
29.7
42
56
72.1
90.1
110.6
156
211
270
1" Pipe
4.85
7.27
10.2
13.6
17.3
21.6
26.5
37.5
50
64.8
80.9
99
120
141
165
189
6
8
10
12
14
16
18
20
22
24
26
28
30
35
40
45
50
2.23
2.97
3.71
4.45
5.2
5.94
6.68
7.42
8.17
8.91
9.65
10.39
11.1
13
14.8
16.7
18.6
3.16
5.2
7.9
11.1
14.7
19
23.7
28.9
34.8
41
47.8
55.1
62.9
84.4
109
137
168
(continued)
Data Tables 617
Table D-5 (continued)
U.S.
gal/min
Velocity
ft/sc
hf Friction
U.S.
gal/min
11⁄4" Pipe
12
14
16
18
20
22
24
26
28
30
35
40
45
50
55
60
65
70
75
2.57
3
3.43
3.86
4.29
4.72
5.15
5.58
6.01
6.44
7.51
8.58
9.65
10.7
11.8
12.9
13.9
15
16.1
2.39
2.87
3.35
3.82
4.3
4.78
5.74
6.69
7.65
8.6
hf Friction
11⁄2" Pipe
2.85
3.77
4.83
6
7.3
8.72
10.27
11.94
13.7
15.6
21.9
27.1
33.8
41.4
49.7
58.6
68.6
79.2
90.6
16
18
20
22
24
26
28
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
2.52
2.84
3.15
3.47
3.78
4.1
4.41
4.73
5.51
6.3
7.04
7.88
8.67
9.46
10.24
11.03
11.8
12.6
13.4
14.2
15
15.8
2.26
2.79
3.38
4.05
4.76
5.54
6.34
7.2
9.63
12.41
15.49
18.9
22.7
26.7
31.2
36
41.2
46.6
52.4
58.7
65
71.6
21⁄2" Pipe
2" Pipe
25
30
35
40
45
50
60
70
80
90
Vel. ft/sec
1.48
2.1
2.79
3.57
4.4
5.37
7.58
10.2
13.1
16.3
35
40
45
50
60
70
80
90
100
120
2.35
2.68
3.02
3.35
4.02
4.69
5.36
6.03
6.7
8.04
1.15
1.47
1.84
2.23
3.13
4.18
5.36
6.69
8.18
11.5
(continued)
618 Appendix D
Table D-5 (continued)
U.S.
gal/min
Velocity
ft/sc
hf Friction
U.S.
gal/min
4.34
11.5
13.4
15.3
2.72
28.5
38.2
49.5
200
160
180
200
220
240
3" Pipe
50
60
70
80
90
100
120
140
160
180
200
220
240
260
280
300
350
2.17
2.6
3.04
3.47
3.91
3.34
5.21
6.08
6.94
7.81
8.68
9.55
10.4
11.3
12.2
13
15.2
2.57
2.89
3.21
3.53
3.85
4.17
4.81
5.04
10.7
12.1
13.4
14.7
16.1
12.61
20
25.2
30.7
37.1
43.8
4" Pipe
0.762
1.06
1.4
1.81
2.26
2.75
3.88
5.19
6.68
8.38
10.2
12.3
14.5
16.9
19.5
22.1
30
100
120
140
160
180
200
220
240
260
280
300
350
400
450
500
550
600
5" Pipe
160
180
200
220
240
260
300
hf Friction
21⁄2" Pipe
2" Pipe
100
120
140
160
Vel. ft/sec
2.52
3.02
3.53
4.03
4.54
5.04
5.54
6.05
6.55
7.06
7.56
8.82
10.1
11.4
12.6
13.9
15.1
0.718
1.01
1.35
1.71
2.14
2.61
3.13
3.7
4.3
4.95
5.63
7.54
9.75
12.3
14.4
18.1
21.4
6" Pipe
0.557
0.698
0.847
1.01
1.19
1.38
1.82
220
240
260
300
350
400
450
2.44
2.66
2.89
3.33
3.89
4.44
5
0.411
0.482
0.56
0.733
0.98
1.25
1.56
(continued)
Data Tables 619
Table D-5 (continued)
U.S.
gal/min
Velocity
ft/sc
hf Friction
350
400
450
500
600
700
800
900
1000
5.61
6.41
7.22
8.02
9.62
11.2
12.8
14.4
16
2.43
3.13
3.92
4.79
6.77
9.13
11.8
14.8
18.2
Courtesy Sarco Company, Inc.
U.S.
gal/min
Vel. ft/sec
hf Friction
500
600
700
800
900
1000
1100
1200
1300
1400
5.55
6.66
7.77
8.88
9.99
11.1
12.2
13.3
14.4
15.5
1.91
2.69
3.6
4.64
5.81
7.1
8.52
10.1
11.7
13.6
620
Table D-6 Flow of Water through Schedule 40 Steel Pipe
Pressure Drop 1000 Feet of Schedule 40 Steel Pipe, in Pounds per Square Inch
DisVeloc- Prescharge ity
sure
gal/min ft/sec Drop
1
2
3
4
5
6
8
10
15
20
25
30
35
40
45
50
60
70
1"
0.37
0.49
0.74
1.7
1.12
3.53
1.49
5.94
1.86
9.02
2.24 12.25
2.98 21.1
3.72 30.8
5.6
64.6
7.44 110.5
Veloc- Pres- Veloc- Pres- Veloc- Pres- Veloc- Pres- Veloc- Pres- Veloc- Pres- Veloc- Pres- Veloc- Presity
sure ity
sure ity
sure ity
sure ity
sure ity
sure ity
sure ity
sure
ft/sec Drop ft/sec Drop ft/sec Drop ft/sec Drop ft/sec Drop ft/sec Drop ft/sec Drop ft/sec Drop
11⁄4"
0.43 0.45
0.64 0.94
0.86 1.55
1.07 2.36
1.28 3.3
1.72 5.52
2.14 8.34
3.21 17.6
4.29 29.1
5.36 43.7
6.43 62.9
7.51 82.5
11⁄2"
0.47 0.44
0.63 0.74
0.79 1.12
0.95 1.53
1.26 2.63
1.57 3.86
2.36 8.13
3.15 13.5
3.94 20.2
4.72 29.1
5.51 38.2
6.3 47.8
7.08 60.6
7.87 74.7
2"
0.57
0.76
0.96
1.43
1.91
2.39
2.87
3.35
3.82
4.3
4.78
5.74
6.69
0.46
0.75
1.14
2.33
3.86
5.81
8.04
10.95
13.7
17.4
20.6
29.6
38.6
21⁄2"
0.67 0.48
1
0.99
1.34 1.64
1.68 2.48
2.01 3.43
2.35 4.49
2.68 5.88
3
7.14
3.35 8.82
4.02 12.2
4.69 15.3
3"
0.87 0.59
1.08 0.67
1.3 1.21
1.52 1.58
1.74 2.06
1.95 2.51
2.17 3.1
2.6 4.29
3.04 5.84
31⁄2"
0.81 0.42
0.97 0.6
1.14 0.79
1.3 1
1.46 1.21
1.62 1.44
1.95 2.07
2.27 2.71
4"
0.88 0.42
1.01 0.53
1.13 0.67
1.26 0.8
1.51 1.1
5"
1.76 1.5 1.12 0.48
Table D-6 (continued)
Pressure Drop 1000 Feet of Schedule 40 Steel Pipe, in Pounds per Square Inch
DisVeloc- Pres- Veloc- Pres- Veloc- Pres- Veloc- Pres- Veloc- Pres- Veloc- Pres- Veloc- Pres- Veloc- Pres- Veloc- Prescharge ity
sure ity
sure ity
sure ity
sure ity
sure ity
sure ity
sure ity
sure ity
sure
gal/min ft/sec Drop ft/sec Drop ft/sec Drop ft/sec Drop ft/sec Drop ft/sec Drop ft/sec Drop ft/sec Drop ft/sec Drop
621
80
90
100
125
150
175
200
225
250
275
300
325
350
375
400
425
450
475
6"
1.11
1.39
1.67
1.94
2.22
2.5
2.78
3.06
3.33
3.61
3.89
4.16
4.44
4.72
5
5.27
0.39
0.56
0.78
1.06
1.32
1.66
2.05
2.36
2.8
3.29
3.62
4.16
4.72
5.34
5.96
6.66
7.65 50.3
8.6 63.6
9.56 75.1
8"
1.44
1.6
1.76
1.92
2.08
2.24
2.4
2.56
2.27
2.88
3.04
0.44
0.55
0.63
0.75
0.88
0.97
1.11
1.27
1.43
1.6
10"
1.69 1.93 0.3
5.37
6.04
6.71
8.38
10.06
11.73
21.7
26.1
32.3
48.2
60.4
90
3.48
3.91
4.34
5.45
6.51
7.59
8.68
9.77
10.85
11.94
13.02
7.62
9.22
11.4
17.1
23.3
32
39.7
50.2
61.9
75
84.7
2.59
2.92
3.24
4.05
4.86
5.67
6.48
7.29
8.1
8.91
9.72
10.53
11.35
12.17
13.78
12.97
14.59
3.53 2.01
4.46 2.26
5.27 2.52
7.86 3.15
11.3 3.78
14.7 4.41
19.2 5.04
23.1 5.67
28.5 6.3
34.4 6.93
40.9 7.56
45.5 8.18
52.7 8.82
60.7 9.45
77.8 10.7
68.9 10.08
87.3 11.33
11.96
1.87
2.37
2.81
4.38
6.02
8.2
10.2
12.9
15.9
18.3
21.8
25.5
29.7
32.3
41.5
39.7
46.5
51.7
1.28 0.63
1.44 0.8
1.6 0.95
2
1.48
2.41 2.04
2.81 2.78
3.21 3.46
3.61 4.37
4.01 5.14
4.41 6.22
4.81 7.41
5.21 8.25
5.61 9.57
6.01 11
6.82 14.1
6.41 12.9
7.22 15
7.62 16.7
(continued)
622
Table D-6 (continued)
Pressure Drop 1000 Feet of Schedule 40 Steel Pipe, in Pounds per Square Inch
DisVeloc- Pres- Veloc- Pres- Veloc- Pres- Veloc- Pres- Veloc- Pres- Veloc- Pres- Veloc- Pres- Veloc- Pres- Veloc- Prescharge ity
sure ity
sure ity
sure ity
sure ity
sure ity
sure ity
sure ity
sure ity
sure
gal/min ft/sec Drop ft/sec Drop ft/sec Drop ft/sec Drop ft/sec Drop ft/sec Drop ft/sec Drop ft/sec Drop ft/sec Drop
500
550
600
650
700
750
800
850
900
950
1,000
1,100
1,200
1,300
1,400
1,500
1,600
1,800
5.55
6.11
6.66
7.21
7.77
8.32
8.88
9.44
10
10.55
11.1
12.22
13.32
14.43
15.54
16.65
17.76
19.98
7.39 3.2
8.94 3.53
10.6 3.85
11.8 4.17
13.7 4.49
15.7 4.81
17.8 5.13
20.2 5.45
22.6 5.77
23.7 6.09
26.3 6.41
31.8 7.05
37.8 7.69
44.4 8.33
51.5 8.97
55.5 9.62
68.1 10.26
79.8 11.54
1.87
2.26
2.7
3.16
3.69
4.21
4.79
5.11
5.73
6.38
7.08
8.56
10.2
11.3
13
15
17
21.6
2.04
2.24
2.44
2.65
2.85
3.05
3.26
3.46
3.66
3.87
4.07
4.48
4.88
5.29
5.7
6.1
6.51
7.32
0.63
0.7
0.8612"
1.01
1.18 2.01
1.35 2.15
1.54 2.29
1.74 2.44
1.94 2.58
2.23 2.72
2.4 2.87
2.74 3.16
3.27 3.45
3.86 3.73
4.44 4.02
5.11 4.3
5.46 4.59
6.91 5.16
12.59 57.3
13.84 69.3
15.1 82.5
0.48
0.55
0.62
0.7
0.79
0.88
0.98
1.18
1.4
1.56
1.8
2.07
2.36
2.98
14"
2.02 0.43
2.14 0.48
2.25 0.53
2.38 0.59
2.61 0.68
2.85 0.81
3.09 0.95
3.32 1.1
3.55 1.19
3.8 1.35
4.27 1.71
16"
2.18 0.4
2.36 0.47
2.54 0.54
2.73 0.62
2.91 0.71
18"
3.27 0.85 2.58 0.48
8.02
8.82
9.62
10.42
11.22
12.02
12.82
13.62
14.42
15.22
16.02
17.63
18.5
22.4
26.7
31.3
36.3
41.6
44.7
50.5
56.6
63.1
70
84.6
Table D-6 (continued)
Pressure Drop 1000 Feet of Schedule 40 Steel Pipe, in Pounds per Square Inch
DisVeloc- Pres- Veloc- Pres- Veloc- Pres- Veloc- Pres- Veloc- Pres- Veloc- Pres- Veloc- Pres- Veloc- Pres- Veloc- Prescharge ity
sure ity
sure ity
sure ity
sure ity
sure ity
sure ity
sure ity
sure ity
sure
gal/min ft/sec Drop ft/sec Drop ft/sec Drop ft/sec Drop ft/sec Drop ft/sec Drop ft/sec Drop ft/sec Drop ft/sec Drop
2,000 22.2 98.5 12.83 25
8.13 8.54 5.73 3.47 4.74 2.11
2,500
16.03 39
10.18 12.5 7.17 5.41 5.92 3.09
3,000
19.24 52.4 12.21 18
8.6 7.31 7.12 4.45
3,500
22.43 71.4 14.25 22.9 10.03 9.95 8.32 6.18
4,000
25.65 93.3 16.28 29.9 11.48 13
9.49 7.92
4,500
18.31 37.8 12.9 15.4 10.67 9.36
5,000
20.35 46.7 14.34 18.9 11.84 11.6
6,000
24.42 67.2 17.21 27.3 14.32 15.4
7,000
28.5 85.1 20.08 37.2 16.6 21
8,000
22.95 45.1 18.98 27.4
9,000
25.8 57
21.35 34.7
10,000
28.63 70.4 23.75 42.9
12,000
34.38 93.6 28.5 61.8
14,000
33.2 84
16,000
Courtesy Sarco Company, Inc.
3.63
4.54
5.45
6.35
7.25
8.17
9.08
10.88
12.69
14.52
16.32
18.16
21.8
25.42
29.05
1.05
1.63
2.21
3
3.92
4.97
5.72
8.24
12.2
13.6
17.2
21.2
30.9
41.6
54.4
2.88
3.59
4.31
5.03
5.74
6.47
7.17
8.62
10.04
11.48
12.92
14.37
17.23
20.1
22.96
0.56
0.88
1.27
1.52
2.12
2.5
3.08
4.45
6.06
7.34
9.2
11.5
16.5
20.7
27.1
20"
3.45 0.73
4.03 0.94
4.61 1.22
5.19 1.55
5.76 1.78
6.92 2.57
8.06 3.5
9.23 4.57
10.37 5.36
11.53 6.63
13.83 9.54
16.14 12
18.43 15.7
24"
3.19 0.51
3.59 0.6
3.99 0.74
4.8 1
5.68 1.36
6.38 1.78
7.19 2.25
7.96 2.78
9.57 3.71
11.18 5.05
12.77 6.6
623
624
Table D-7 Warmup Load in Pounds of Steam per 100 Feet of Steam Main
(Ambient Temperature 70ⴗF)a*
Steam
Pressure
(psig)
2"
21⁄2"
3"
4"
5"
6"
8"
10"
12"
14"
16"
0
5
10
20
40
60
80
100
125
150
175
200
250
300
400
500
600
6.2
6.9
7.5
8.4
3.9
11
12
12.8
13.7
14.5
15.3
16
17.2
25
27.8
30.2
32.7
9.7
11
11.8
13.4
15.8
17.5
19
20.3
21.7
23
24.2
25.3
27.3
38.3
42.6
46.3
50.1
12.8
14.4
15.5
17.5
20.6
22.9
24.9
26.6
28.4
30
31.7
33.1
35.8
51.3
57.1
62.1
67.1
18.2
20.4
22
24.9
29.3
32.6
35.3
37.8
40.4
42.8
45.1
47.1
50.8
74.8
83.2
90.5
97.9
24.6
27.7
29.9
33.8
39.7
44.2
47.9
51.2
54.8
58
61.2
63.8
68.9
104
115.7
125.7
136
31.9
35.9
38.8
43.9
51.6
57.3
62.1
66.5
71.1
75.2
79.4
82.8
89.4
142.7
158.7
172.6
186.6
48
48
58
66
78
86
93
100
107
113
119
125
134
217
241
262
284
68
77
83
93
110
122
132
142
152
160
169
177
191
322
358
389
421
90
101
109
124
145
162
175
188
200
212
224
234
252
443
493
535
579
107
120
130
146
172
192
208
222
238
251
265
277
299
531
590
642
694
140
176
207
157
198
233
169
213
251
191
241
284
225
284
334
250
316
372
271
342
403
290
366
431
310
391
461
328
414
487
347
437
514
362
456
537
390
492
579
682
854 1045
759
971 1163
825 1033 1263
893 1118 1367
24"
0ⴗF
Correction
Factor †
208
324
350
396
465
518
561
600
642
679
716
748
807
1182
1650
1793
1939
1.5
1.44
1.41
1.37
1.32
1.29
1.27
1.26
1.25
1.24
1.23
1.22
1.21
1.2
1.18
1.17
1.16
Main Size
18"
*Loads based on Schedule 40 pipe for pressures up to and including 250 psig and on Schedule 80 pipe for pressures above 250 psig.
†
For outdoor temperature of 0⬚F, multiply load value in table for each main size by correction factor corresponding to steam pressure.
Courtesy Sarco Company, Inc.
20"
Table D-8
Condensation Load in Pounds per Hour per 100 Feet of Insulated Steam Main
(Ambient Temperature 70ⴗF; Insulation 80% Efficient)a*
Steam
Pressure
(psig)
2"
21⁄2"
3"
4"
5"
6"
8"
10"
12"
14"
16"
18"
20"
24"
0ⴗF
Correction
Factor †
10
30
60
100
125
175
250
300
400
500
600
6
8
10
12
13
16
18
20
23
27
30
7
9
12
15
16
19
22
25
28
33
37
9
11
14
18
20
23
27
30
34
39
44
11
14
18
22
24
26
34
37
43
49
55
13
17
24
28
30
33
42
46
53
61
68
16
20
27
33
36
38
50
54
63
73
82
20
26
33
41
45
53
62
68
80
91
103
24
32
41
51
56
66
77
85
99
114
128
29
38
49
61
66
78
92
101
118
135
152
32
42
54
67
73
86
101
111
130
148
167
36
48
62
77
84
98
116
126
148
170
191
39
51
67
83
90
107
126
138
162
185
208
44
57
74
93
101
119
140
154
180
206
232
53
68
89
111
121
142
168
184
216
246
277
1.58
1.5
1.45
1.41
1.39
1.38
1.36
1.35
1.33
1.32
1.31
Main Size
*Chart loads represent losses due to radiation and convection for saturated steam.
†
For outdoor temperature of 0⬚F, multiply load value in table for each main size by correction factor corresponding to steam pressure.
Courtesy Sarco Company, Inc.
625
626
Table D-9 Flange Standards (All dimensions are in inches)
125-lb Cast Iron
Pipe Size
Diameter of
Flange
Thickness of
Flange (min)1
Diameter of
Bolt Circle
Number of
Bolts
Diameter of
Bolts
1
⁄2
3
⁄4
ASA B16.1
1
11⁄4
11⁄2
41⁄4
45⁄8
5
7
⁄16
1
⁄2
9
⁄16
21⁄2
2
6
5
⁄8
7
11
⁄16
3
31⁄2
71⁄2
81⁄2
3
⁄4
13
⁄16
4
5
9
15
⁄16
6
10
12
11
131⁄2
16
19
⁄16
1
11⁄8
13⁄16
11⁄4
10
15
8
31⁄8
31⁄2
37⁄8
43⁄4
51⁄2
6
7
71⁄2
81⁄2
91⁄2
113⁄4
141⁄4
17
4
4
4
4
4
4
8
8
8
8
8
12
12
⁄4
7
7
1
⁄2
1
⁄2
1
⁄2
5
⁄8
5
⁄8
5
⁄8
5
⁄8
5
⁄8
3
⁄4
3
⁄4
3
⁄8
⁄8
250-lb Cast Iron
Pipe Size
Diameter of
Flange
Thickness of
Flange (min)2
Diameter of
Raised Face
Diameter of
Bolt Circle
Number of
Bolts
Diameter of
Bolts
1
⁄2
3
⁄4
ASA B16.2
11⁄4
1
47⁄8
11
⁄16
51⁄4
3
⁄4
11⁄2
61⁄8
13
⁄16
21⁄2
2
61⁄2
31⁄2
3
71⁄2
7
⁄8
1
81⁄4
4
5
9
10
11⁄8 13⁄16
11⁄4
6
8
11 121⁄2
13⁄8
17⁄16
10
12
15
171⁄2
201⁄2
15⁄8
17⁄8
2
211⁄16 31⁄16 39⁄16 43⁄16 415⁄16 65⁄16 65⁄16 615⁄16 85⁄16 911⁄16 1115⁄16 141⁄16 167⁄16
31⁄2
37⁄8
41⁄2
5
57⁄8
65⁄8
71⁄4
77⁄8
4
4
4
8
8
8
8
8
5
⁄8
5
⁄8
3
⁄4
5
⁄8
3
⁄4
3
⁄4
3
⁄4
3
⁄4
91⁄4 105⁄8
13
151⁄4
173⁄4
16
16
1
11⁄8
8
12
12
⁄4
3
7
3
⁄4
⁄8
(continued)
627
628
Table D-9 (continued)
150-lb Bronze
Pipe Size
Diameter of
Flange
Thickness of
Flange (min)3
Diameter of
Bolt Circle
Number of
Bolts
Diameter of
Bolts
1
⁄4
1
11⁄4
37⁄8
41⁄4
45⁄8
3
⁄2
31⁄2
5
⁄16
ASA B16.24
11
⁄32
3
⁄8
13
⁄32
11⁄2
21⁄2
2
5
7
⁄16
6
1
⁄2
7
9
⁄16
3
31⁄2
71⁄2
81⁄2
5
⁄8
11
⁄16
4
5
9
11
⁄16
6
10
3
⁄4
8
11
13
⁄16
10
131⁄2
15
12
16
19
⁄16
1
11⁄16
23⁄8
23⁄4
31⁄8
31⁄2
37⁄8
43⁄4
51⁄2
6
7
71⁄2
81⁄2
91⁄2
113⁄4
141⁄4
17
4
4
4
4
4
4
4
4
8
8
8
8
8
12
12
⁄4
7
7
1
⁄2
1
⁄2
1
⁄2
1
⁄2
1
⁄2
5
⁄8
5
⁄8
5
⁄8
5
⁄8
5
⁄8
3
⁄4
3
⁄4
3
⁄8
⁄8
300-lb Bronze
Pipe Size
Diameter of
Flange
Thickness of
Flange (min)4
Diameter of
Bolt Circle
Number of
Bolts
Diameter of
Bolts
1
⁄4
1
11⁄4
11⁄2
2
21⁄2
3
45⁄8
47⁄8
51⁄4
61⁄8
61⁄2
71⁄2
81⁄4
3
⁄2
33⁄4
1
⁄2
ASA B16.24
17
⁄32
19
⁄32
5
⁄8
11
⁄16
3
⁄4
13
⁄16
31⁄2
29
⁄32
31
4
5
6
8
10
9
10
11
121⁄2
15
⁄32
11⁄16
11⁄8
13⁄16
13⁄8
25⁄8
31⁄4
31⁄2
37⁄8
41⁄2
5
57⁄8
65⁄8
71⁄4
77⁄8
91⁄4
105⁄8
13
4
4
4
4
4
8
8
8
8
8
8
12
12
⁄4
3
7
1
⁄2
5
⁄8
5
⁄8
5
⁄8
3
⁄4
5
⁄8
3
⁄4
3
⁄4
3
⁄4
3
⁄4
3
⁄4
12
⁄8
(continued)
629
630
Table D-9 (continued)
150-lb Steel
Pipe Size
Thickness of
Flange (min)5
Diameter of
Raised Face
Diameter of
Bolt Circle
Number of
Bolts
Diameter of
Bolts
1
⁄2
3
⁄4
ASA B16.5
1
11⁄4
11⁄2
41⁄4
45⁄8
5
71⁄6
1
⁄2
9
⁄16
21⁄2
2
6
5
⁄8
7
13
⁄16
3
31⁄2
71⁄2
81⁄2
3
⁄4
13
⁄16
4
5
9
15
⁄16
6
10
12
11
131⁄2
16
19
⁄16
1
11⁄8
13⁄16
11⁄4
10
15
8
2
21⁄2
27⁄8
35⁄8
41⁄8
5
51⁄2
63⁄16
75⁄16
81⁄2
105⁄8
123⁄4
15
31⁄8
31⁄2
37⁄8
43⁄4
51⁄2
6
7
71⁄2
81⁄2
91⁄2
113⁄4
141⁄4
17
4
4
4
4
4
4
8
8
8
8
8
12
12
⁄4
7
7
1
⁄2
1
⁄2
1
⁄2
5
⁄8
5
⁄8
5
⁄8
5
⁄8
5
⁄8
3
⁄4
3
⁄4
3
⁄8
⁄8
300-lb Steel
Pipe Size
Diameter of
Flange
Thickness of
Flange (min)6
Diameter of
Raised Face
Diameter of
Bolt Circle
Number of
Bolts
Diameter of
Bolts
1
ASA B16.5
⁄2
3
1
11⁄4
11⁄2
2
47⁄8
51⁄4
61⁄8
61⁄2
71⁄2
81⁄4
9
10
11
121⁄2
7
⁄8
1
11⁄8
13⁄16
11⁄4
11
⁄4
⁄16
3
13
⁄4
⁄16
21⁄2
31⁄2
3
4
5
6
8
10
15
171⁄2
201⁄2
13⁄8
17⁄16
15⁄8
17⁄8
2
21⁄2
27⁄8
35⁄8
41⁄8
5
51⁄2
63⁄16
75⁄16
81⁄2
105⁄8
123⁄4
15
31⁄2
37⁄8
41⁄2
5
57⁄8
65⁄8
71⁄4
77⁄8
91⁄4
105⁄8
13
151⁄4
173⁄4
4
4
4
8
8
8
8
8
8
12
12
16
16
⁄4
3
7
1
11⁄8
5
⁄8
5
⁄8
3
⁄4
5
⁄8
3
⁄4
3
⁄4
3
⁄4
3
⁄4
3
⁄4
⁄8
12
2
(continued)
631
632
Table D-9 (continued)
400-lb Steel
Pipe Size
Diameter of
Flange
Thickness of
Flange (min)7
Diameter of
Raised
Diameter of
Bolt Circle
Number of
Bolts
Diameter of
Bolts
3
1
⁄2
⁄4
33⁄4
9
⁄16
45⁄8
5
⁄8
ASA B16.5
1
11⁄4
11⁄2
2
21⁄2
3
47⁄8
51⁄4
61⁄8
61⁄2
71⁄2
81⁄4
9
10
11
121⁄2
⁄8
1
11⁄8
11⁄4
13⁄8
13⁄8
11⁄2
15⁄8
11
⁄16
13
⁄16
7
31⁄2
4
5
6
8
10
12
171⁄2
201⁄2
⁄8
21⁄8
21⁄4
15
7
13⁄8
111⁄16
2
21⁄2
27⁄8
35⁄8
41⁄8
5
51⁄2
63⁄16
75⁄16
81⁄2
105⁄8
123⁄4
15
25⁄8
31⁄4
31⁄2
37⁄8
41⁄2
5
57⁄8
65⁄8
71⁄4
77⁄8
91⁄4
105⁄8
13
151⁄4
173⁄4
4
4
4
4
4
8
8
8
8
8
8
12
12
16
16
⁄8
1
11⁄8
11⁄4
1
⁄2
5
⁄8
5
⁄8
5
⁄8
3
⁄4
3
⁄4
7
⁄8
7
⁄8
7
⁄8
7
600-lb Steel
Pipe Size
Diameter of
Flange
Thickness of
Flange (min)8
Diameter of
Raised
Diameter of
Bolt Circle
Number of
Bolts
Diameter of
Bolts
1
1
3
⁄2
⁄4
33⁄4
9
⁄16
45⁄8
5
⁄8
ASA B16.5
1
11⁄4
11⁄2
2
21⁄2
3
47⁄8
51⁄4
61⁄8
61⁄2
71⁄2
81⁄4
9
103⁄4
13
14
161⁄2
10
12
⁄8
1
11⁄8
11⁄4
13⁄8
11⁄2
13⁄4
17⁄8
23⁄16
21⁄2
25⁄8
11
⁄16
13
⁄16
7
31⁄2
4
5
8
10
12
13⁄8
111⁄16
2
21⁄2
27⁄8
35⁄8
41⁄8
5
51⁄2
63⁄16
75⁄16
81⁄2
105⁄8
123⁄4
15
25⁄8
31⁄4
31⁄2
37⁄8
41⁄2
5
57⁄8
65⁄8
71⁄4
81⁄2
101⁄2
111⁄2
131⁄4
17
191⁄2
4
4
4
4
4
8
8
8
8
8
8
12
12
16
20
⁄8
1
1
11⁄8
11⁄4
11⁄4
1
⁄2
5
⁄8
5
⁄8
5
⁄8
3
⁄4
5
⁄8
3
⁄4
3
⁄4
7
⁄8
7
125-lb. flanges have plain faces.
250-lb. flanges have a 1⁄16" raised face, which is included in the flange thickness dimensions.
3
150-lb. bronze flanges have plain faces with two concentric gasket-retaining grooves between the port and the bolt holes.
4
300-lb. bronze flanges have plain faces with two concentric gasket-retaining grooves between the port and the bolt holes.
5
150-lb. steel flanges have a 1⁄16" raised face, which is included in the flange thickness dimensions.
6
300-lb. steel flanges have a 1⁄16" raised face, which is included in the flange thickness dimensions.
7
400-lb. steel flanges have a 1⁄4" raised face, which is NOT included in the flange dimensions.
8
600-lb. steel flanges have a 1⁄4" raised face, which is NOT included in the flange dimensions.
2
6
633
634
Table D-10 Pressure Drop in Schedule 40 Pipe
Data Tables 635
Table D-11
Steam Velocity Chart
636
Table D-12 Pressure Drop in Schedule 80 Pipe
Data Tables 637
Table D-13 Chimney Connector and Vent Connector
Clearance from Combustible Materials
Description
of
Appliance
Residential Appliances
Single-Wall, Metal Pipe Connector
Electric, gas, and oil incinerators
Oil and solid-fuel appliances
Oil appliances listed as suitable
for use with Type L venting
system, but only when
connected to chimneys
Type L Venting-System
Piping Connectors
Electric, gas, and oil incinerators
Oil and solid-fuel appliances
Oil appliances listed as suitable
for use with Type L venting systems
Commercial and Industrial
Appliances
Low-Heat Appliances
Single-Wall, Metal Pipe
Connectors
Gas, oil, and solid-fuel boilers,
furnaces, and water heaters
Ranges, restaurant type
Oil unit heaters
Other low-heat industrial
appliances
Medium-Heat Appliances
Single-Wall, Metal Pipe Connectors
All gas, oil, and solid-fuel appliances
Minimum
Clearance,
Inches*
18
18
9
9
9
†
18
18
18
18
36
*These clearances apply except if the listing of an appliance specifies different clearances, in which case the
listed clearance takes precedence.
†
If listed Type L venting-system piping is used, the clearance may be in accordance with the venting-system
listing.
If listed Type B or Type L venting-system piping is used, the clearance may be in accordance with the ventingsystem listing.
The clearances from connectors to combustible materials may be reduced if the combustible material is
protected in accordance with Table 1C.
Courtesy National Oil Fuel Institute
638
Table D-14 Standard Clearances for Heat-Producing Appliances in Residential Installations
Appliance
Above Top
of Casing
or
Appliance
From Top
and Sides
of WarmAir Bonnet
or Plenum
From
Front†
From
Back
From
Sides
Automatic oil
or combination
gas-oil
6
—
24
6
6
Automatic oil
or combination
gas-oil
6†
6c
24
6
6
Residential-Type Appliances for
Installation in Rooms That Are Large*
Boilers and Water Heaters
Steam boilers—
15 psi; water
boilers—250⬚F;
water heaters—
200⬚F; all water
walled or jacketed
Furnaces—Central
gravity, upflow,
downflow,
horizontal and
duct. warm-air—
250⬚F max.
Table D-14 (continued)
Appliance
Residential-Type Appliances for
Installation in Rooms That Are Large*
Furnaces—Floor
For mounting in
combustible floors
Automatic oil
or combination
gas-oil
Above Top
of Casing
or
Appliance
From Top
and Sides
of WarmAir Bonnet
or Plenum
From
Front†
From
Back
From
Sides
36
—
12
12
12
*Rooms that are large in comparison to the size of the appliance are those having a volume equal to at least 12 times the total volume of a furnace and at least 16 times the
total volume of a boiler. If the actual ceiling height of a room is greater than 8 ft, the volume of a room shall be figured on the basis of a ceiling height of 8 ft.
†
The minimum dimension should be that necessary for servicing the appliance including access for cleaning and normal care, tube removal, etc.
‡
For a listed oil, combination gas-oil, gas, or electric furnace, this dimension may be 2 in if the furnace limit control cannot be set higher than 250⬚F or 1 in if the limit control cannot
be set higher than 200⬚F.
Courtesy National Oil Fuel Institute
639
640
Table D-15 Standard Clearances for Heat-Producing Appliances
in Commercial and Industrial Installations
Appliance
Above Top
of Casing
or
Appliance*
From Top
and Sides
of WarmAir Bonnet
or Plenum
From
Front
From
Back*
From
Sides*
All fuels
18
—
48
18
18
All fuels
18
—
48
18
18
1
—
—
1
1
6
18
18
—
—
—
24
48
48
18
18
18
18
18
18
Commercial-Industrial Type Low
Heat Appliance (Any and All
Physical Sizes Expect As Noted)
Boiler and Water Heaters
100 ft3 or less,
any psi, steam
50 psi or less,
any size
Unit Heaters
Floor mounted
or suspended—
Suspended—100 ft3
or less
Steam or
hot water
Oil or
combination
gas-oil
Suspended —over 100 ft3 All fuels
Floor mounted any
All fuels
*If the appliance is encased in brick, the 18 in clearance above and at sides and rear may be reduced to not less than 12 in
Courtesy National Oil Fuel Institute
Table D-16
Clearance (in Inches) with Specified Forms of Protection
Available Hot-Water Storage Plus Recovery
Input
heat units
Electricity, kW
1.5
2.5
4.5
4.5
6
7
Gas, Btu/h
34,000
42,000
50,000
60,000
Oil, gph
0.5
0.75
0.85
1
1.2
1.35
1.5
1.65
Efficiency
%
Usable
Btu/h
gph 100ⴗF
rise
Tank size,
gal
100ⴗF Rise
15 min
30 min
45 min
60 min
25.7
39.5
57.1
67.1
88.8
106.5
Continuous
Draw, gph
92.5
92.5
92.5
92.5
92.5
92.5
4,750
7,900
14,200
14,200
19,000
22,100
5.7*
9.5*
17.1*
17.1*
22.8*
26.5
20
20
30
50
66
80
21.4
32.4
44.3
54.3
71.6
86.6
22.8
34.8
48.6
58.6
77.2
93.2
24.3
37.1
52.9
62.9
82.8
99.8
75
75
75
75
25,500
31,600
37,400
45,000
30.6
38
45
54
30
30
40
50
37.7
39.5
51.3
63.5
45.3
49
62.6
77
53
58.8
73.9
90.5
55.6†
61.7†
77.6†
95.0†
25.6†
31.7†
37.6†
45.0†
75
75
75
75
75
75
75
75
52,500
78,700
89,100
105,000
126,000
145,000
157,000
174,000
63
94.6
107
126
151.5
174
188.5
204.5
30
30
30
50
50
50
85
85
45.8
53.6
57.7
81.5
87.9
93.5
132.1
136.1
61.6
77.2
83.4
13
125.8
137
179.2
187.2
77.4
100.8
110.1
144.5
163.7
180.5
226.3
238.4
82.5†
109.0†
119.1†
155.0†
176.0†
195.0†
242.0†
259.0†
52.5†
79.0†
89.0†
105.0†
126.0†
145.0†
157.0†
174.0†
641
*Assumes simultaneous operation of upper and lower elements.
†
Based on 50 minute-per-hour operation.
Courtesy National Oil Fuel Institute
5.7
9.5
17.1
17.1
22.8
26.5
Appendix E
Psychrometric Charts
The atmosphere around us is made up essentially of dry air and
water vapor in various percentages, each with its own characteristics. The water vapor is not dissolved in the air in the sense that it
loses its own individuality, but merely serves to moisten the air.
Psychrometry is that branch of physics concerned with the measurement or determination of atmospheric conditions, particularly
the moisture content of air. These measurements are obtained with
a psychrometer and are graphically represented on a psychrometric
chart. Insofar as air-conditioning is concerned, psychrometry is
specifically concerned with the thermodynamic properties of moist
air. The technical application of thermodynamics to air-conditioning
is called psychrometrics.
The typical sling psychrometer consists of a handle and an
attached unit containing the wet-bulb and dry-bulb thermometers.
The thermometer unit fits inside the handle when not in use. The
wet-bulb, dry-bulb, and relative humidity scales are read from the
handle. Temperature readings are obtained by twirling the thermometer unit around the handle and then allowing the thermometers time to stabilize.
The readings given on a psychrometric chart are represented by
the relative positions of a number of different lines running vertically, horizontally, and diagonally. These lines are simplified for
purposes of explanation in Figures E-1, E-2, E-3, and E-4.
In Figure E-1, the horizontal distances on the chart are a measure of sensible heat as obtained from dry-bulb temperatures. The
vertical distances are a measure of latent heat as obtained from the
dew-point temperatures. The inclined (solid) lines are a measure of
the total heat (not including the heat of the liquid) and are constant
for a given wet-bulb temperature.
The curved lines indicate the relative humidity between the limiting conditions of dry and saturated air. As shown in Figure E-2, the
grains in water vapor per pound of dry air in the mixture can be
obtained by proceeding to the left through the dew-point temperature to the scale of grains at the left of the chart.
The cubic feet of mixture per pound of dry air in the mixture can
be obtained by proceeding from the intersection of dry-bulb, wetbulb, and dew-point temperature upward and parallel with the
643
LATENT HEAT
SA
TU
R
AT
IO
N
LIN
E
644 Appendix E
WE
TB
ULB
TY
IDI
TOT
AL
M
HU
DEW POINT
HEA
T
E
TIV
ELA
R
SENSIBLE HEAT
Horizontal distances as measure of sensible heat;
vertical distances of latent heat.
GR. PER LB. DRY AIR
Figure E-1
WE
TB
ULB
DEW POINT
IVE
LAT
DRY BULB
RE
Figure E-2
Curved lines indicate relative humidity.
Y
DIT
MI
HU
Psychrometric Charts 645
WE
TB
ULB
Y
DIT
MI
HU
E
IV
LAT
NE
E LI
UM
Figure E-3
VOL
DRY BULB
RE
Obtaining cubic feet of mixture per pound of dry air.
TOTAL HEAT B. T. U. PER LB. DRY AIR
WE
TB
ULB
TY
IDI
M
HU
IVE
LAT
DRY BULB
RE
Figure E-4
Obtaining total heat per pound of dry air.
646 Appendix E
inclined volume lines (shown dotted) to the saturation curve and
then directly to the volume scale at the right of the chart (see Figure
E-3). The grains of water vapor per cubic feet of mixture is
obtained by dividing the reading obtained through Figure E-2 by
that obtained through Figure E-3.
The total heat per pound of dry air in the mixture can be
obtained by following up along the inclined wet-bulb temperature
line to the saturation curve and then vertically upward to the total
heat scale at the top of the chart (see Figure E-4).
Index
A
absolute humidity, 363
absolute pressure, 370
absorption dehumidifiers, 538–540
absorption refrigeration, 398
adiabatic compression, 372
adjustable air valves, 98
after filter, 567
air
atmospheric pressure of, 368–370
calculating rate of change in, 386
cleaning and filtering, 374–376
components of, 362
compression of, 370–372
dehumidification of, 365
(see also dehumidifiers)
dew point of, 364
drying effect of, 363–364
humidification of, 364 (see also
humidifiers)
humidity of, 362–365
latent heat in, 368
measuring physical properties of,
372–374
properties of, 362–370
relative humidity of, 519–520
saturation of, 362, 363
sensible heat in, 368
temperature of, 365–368
water vapor in, 362
air change method, 323–325
air circulation. See circulation
air cleaners. See electronic air
cleaners
air compressor, 46
air conditioners. See airconditioning equipment;
air-conditioning systems
Air-Conditioning Contractors of
America (ACCA), 396–397
air-conditioning equipment
adding refrigerant to, 465–467
choosing correct size of,
394–395
cleaning and filtering aspects of,
374–376
compression in, 370–372
compressors (see compressors)
condensers, 439–446
cooling load estimate form for,
379–383
defined, 361
dryers for, 457, 458
electrical components in,
438–439
estimating required British
thermal units (Btus) for, 395
evaporative coolers, 398–400
evaporators for, 446–448
filters for, 457, 458
float valves, 452–454
maintenance of, 460, 463–470
mechanical refrigeration (see
mechanical refrigeration
equipment)
motors and engines for,
435–437
pressure-limiting controls in,
457–458
processes of, 361
rate of air change for, 386
receivers for, 443, 447
refrigerants for, 448–449
(see also refrigerants)
repairing, 467–470
room units, 421, 424
silver-brazing repairs for,
467–470
water-regulating valves in,
458–459
647
648 Index
air-conditioning systems
ACCA design manuals for sizing,
396–397
atmospheric air in, 368
automatic controls for, 459
capillary tubes in, 454
central (see central airconditioning systems)
and the comfort chart,
377–379
cooling methods for (see cooling
methods)
for cooling structures, 386–393
dampers for, 531–532
efficiency ratings of, 423–424
estimating heat gain for,
379–383
and indoor-outdoor design
conditions, 383
recommended relative humidity
for, 378
refrigerant piping in, 454–457
and standards of comfort,
376–377
troubleshooting problems in,
459, 462–463
and ventilation requirements,
384–386
year-round, 412, 413
air-cooled condensers, 414,
415–416, 439, 443
air filters
box-type, 575
common placement of,
572–573
dry, 574
functions of, 572–573
inspection of, 573–574
installation of, 575
maintenance of, 575
mat-type, 575
symptoms of problems with, 433
viscous, 574–575
air horsepower (AHP), 315
air intake, 326–327
air leakage, 309–310
Airmaster fans, 336–337
air-restricting device, 407
air scoop, 19
air separator, 26–27
air-source heat pumps, 476–480,
486
air stratification, preventing, 139
air valves
adjustable, 98
automatic, 87–92, 100
identifying clogs in, 100
manual, 86–87
nonadjustable, 98
for radiators, 86–92
air velocity, 317
air ventilation. See ventilation
air venting, 18, 32, 33, 96
air volume control, 347
air washers, 376, 522–523, 541,
571–572, 573
ambient temperature, 77
American Society of Heating and
Ventilating Engineers,
312–313
American Society of Heating,
Refrigeration, and AirConditioning Engineers
(ASHRAE), 376
research of solar radiation, 388
ventilation standards of,
384–385
anodes, 197, 232, 244
anti-restart timer, 501
antisiphon hole, 195–196
aquastats
for circulating pumps, 230
for gas-fired pool heater, 258
in hydronic heating system, 19,
21
symptoms of problem in, 106
temperature-control, 263,
265
ash dump, 152
ashpit, 152
Atlantic box stove, 174
atmospheric air, 368–370
atmospheric pressure, 368–370
atomizing humidifiers, 522–523
Index 649
attic fans, 348
boxed-in, 349, 350
centrifugal, 349–350, 351
cleaning, 354
control of, 349
exhaust outlets for, 353, 354
fly screening for, 352, 354
importance of, 348
location of, 354
louvers for, 352
lubrication of, 354
outlet area for, 350
attics, fresh air requirements for,
288, 384
auditoriums, fresh air
requirements for, 384
automatic air valves, 87–92
automatic air vent valve, 18
automatic cooling control circuits,
459, 460, 461
automatic expansion valves,
449–450
automatic float vent valve, 19
automatic gas shutoff device, 216,
220
automatic gas valves, 257
automatic pilot valve, 212–217
automatic spark ignition systems,
256
automatic storage water heaters,
180–182, 183, 204, 206
available line voltage, 342
axial-flow fans, 318
B
backdraft diverter, 229
backdrafts
causes of, 356
in chimneys, 168–169
preventing, 358
remedy for, 170
backflow preventer, 19, 21
baffles, 129, 133, 237
balancing valves, 25
ball valves, 19, 21
barometers, 369
baseboard heaters
around corners, 114, 115
electric (see electric baseboard
heaters)
fin-and-tube, 108, 110–113
hydronic, 109–110, 119
installing, 113–119
location of, 107
maintenance of, 119
operating efficiency of,
115–116
and plaster walls, 116
rating output of, 108
types of, 108
basic fan laws, 319–321
bathroom exhaust fans, 356
belt-driven fans, 341, 343, 358
bleeders, 515, 516
blower coils, 447
blowers, 491, 499
boiler drain valve, 19, 21
boiler energy saver, 19
boiler fill valve, 19
boiler rooms, fresh air
requirements for, 288, 384
boilers
coal-fired, 6
drain valve for, 19, 21
electric, 7
gas-fired, 6
for heating pools, 250–251
in hydronic heating systems,
6–7
minimum temperature of, 107
oil-fired, 6
in piping diagram, 20–21
symptoms of problems with, 50
booster heaters, 183–184
boxed-in fans, 349, 350
box-type filters, 575
Boyle’s law, 370–372
brake horsepower (BHP), 316,
338–339
brass adapter, 9
brass coupling, 9
British thermal units (Btu)
given off by cast-iron radiators,
105
650 Index
for heat-exchanger pool heaters,
264
for measuring heat gain, 368
for measuring output of heatemitting units, 71
needed for air-conditioning
equipment, 395
bucket traps, 138
building codes, for water heaters,
230–231
built-in electronic air cleaners, 564
burners. See gas burners
butterfly dampers, 306–307
bypass humidifiers, 525–526, 527
common location for, 529
installation of, 532–534
bypass piping, 261
bypass valves, 257, 276
C
cabinet-model electronic air
cleaners, 563–564
capacitor motor, 333
capacitors, 431, 432, 498, 518
capillary tubes, 454
capture velocities, 329
carbon monoxide, 310–311
cast-iron radiators. See radiators
ceiling panel heating systems, 2–5
central air-conditioning systems
applications of, 410–421
cooling methods of, 397–410
energy efficiency of, 424
internal workings of, 423
central cooling packages, 414–417
centrifugal compressors, 429–430
centrifugal fans, 318, 349–350,
351, 407
cfm. See cubic feet per minute
(cfm)
charged-media electronic air
cleaners, 549–550
charging, 465–467
Charles’s law, 370–372
check valves, 19–23, 230
chimney effect, 284–285,
309–310
chimneys
cap for, 164
cleanout traps in, 168
connecting water heater flues to,
239
construction details for,
164–165
downdraft in, 168–169
and fireplaces, 145
flues in, 165–167
foundation for, 164
for gas-fired water heaters, 227
induced draft in, 285, 286
liners in, 165–167
metal, 169, 171, 173
providing good draft in, 162,
164
smoke pipe in, 167–168
troubleshooting problems in,
170
circuit breakers, symptoms of
tripped, 106, 242, 278, 340,
514, 517
circuits
defined, 7
signs of defect in, 277
circulating fans, 348
circulating pumps, 230
control of water flow by, 31
for heat-exchanger pool heaters,
264
for hydronic radiant heating
system, 26
in piping diagram, 21
symptoms of problems with,
50–51
circulating tank, 245
circulation, 281, 296, 315
cleanout door, 152
cleanout traps, 168
clogged-filter indicators, 556–557,
558
closed-loop ground coupling
system, 482–483
coal-fired boilers, 6
Coefficiency of Performance
(COP), 267, 488
Index 651
coils
condenser, 403
dehumidifying, 541
evaporator, 402, 404
for heat pumps, 491
for manual water heaters, 245
patterns of, 41–43
symptoms of problems with,
514, 515
testing of, 46–48
used in hydronic radiant floor
heating systems, 41–43
water-cooled, 401
cold-water coil cooling, 401, 420
cold-water supply lines, 194–195,
246
collector plates, 553–554
combination gas valves, 221–225,
257
combination water heaters,
191–192
comfort chart, 377–379
comfort cooling, 325
comfort levels, 520
commercial water heaters, 179
compound gauge, 373–374, 376
compressed-air test, 46
compression, 370–372
compression fittings, 13
compression tanks, 20–21,
26, 27
compressors
centrifugal, 429–430
contactor for, 498
control box on, 495–497
defined, 424
disconnecting, 435
dual, 486
and evacuated refrigerant, 465
function of, 424
for heat pumps, 490
hermetic, 429–430, 490
internal devices for, 434–435
knocking in, 465
open-type, 429
protection from short-cycling,
500
and pumping down refrigerant,
464
reciprocating, 424–425,
495–496
for refrigeration dehumidifiers,
542
replacement of, 435
rotary, 427–428
scroll, 426, 497
semihermetic, 430
symptoms of freezing in, 431
symptoms of improper wiring of,
431, 432
symptoms of overheating in, 432
symptoms of problems with
valves in, 462
symptoms of tightness in, 432,
433
troubleshooting problems with,
430–434, 517–518, 544
types of, 424–430
concrete work, 34–35, 36
condensation
and heat sink, 473
latent heat of, 362, 363
in roof ventilators, 299–300
condensation drain line, 509
condensation gutters, 299–300
condenser coils, 403
condensers
air-cooled, 439, 443
in central cooling package, 414,
417
common operating problems in,
445
defined, 439
evaporative, 441–442, 445
maintenance of, 442–443
shell-and-coil construction for,
441, 444
in steam cooling systems,
409–410
symptoms of problems with,
433, 445, 462, 517
types of, 439, 440, 441, 442,
443
water-cooled, 441, 444
652 Index
contactor, 498
control box
capacitors in, 498
compressor contactor for, 498
defrost control board in,
499–500
for heat pumps, 494–499
on reciprocating compressor,
495–496
relays in, 499
on scroll compressor, 497
three-phase unit, 498
control circuit, 257, 529
convection, 71
convection loss, 1
convector capacities, 104–105
convector coils, 412
convectors
access door for, 101, 102
basic description of, 100
checking wiring in, 107
cleaning heating element of, 101,
102
determining capacities of,
104–105
heating element in, 101, 102
hydronic fan, 106–107
picture of, 101
piping connections for, 101,
103–105
rating of, 101
types of, 100
converter-type heater applications,
207
cooling coils, 447
in central cooling packages, 414
in gas absorption refrigeration
cooling, 404–405
for refrigeration dehumidifiers,
541, 542
symptoms of problems with, 462
in warm-air heating systems,
417–418, 419
cooling control circuits, 459, 460,
461
cooling cycle, in heat pumps, 473,
474, 491–493, 494, 511
cooling loads, 379–383, 395–397
cooling methods
absorption refrigeration, 398
cold-water coil, 401
evaporative, 398–400
gas absorption refrigeration,
403–408
gas compression refrigeration,
401
list of, 397
mechanical refrigeration cycle,
401–403
with steam, 398, 408–410
thermoelectric refrigeration,
397–398, 408
cooling systems
for hydronic radiant floor
heating systems, 68–69
working with heating system,
418–419
cooling tower fans, 348
cooling with steam, 398,
408–410
copper heating elements, 111–112,
114
copper tubing
bending, 9
cause of leaks in, 9
coil lengths of, 9–10
determining proper size of, 9
fittings for, 10–11
for indirect water heaters,
185–188
inside diameters (ID) of, 8, 9
in radiant floor heating systems,
8–10
spacing between, 10
straightening, 9
Type L, 8–9
corrosion, in water heater storage
tanks, 193
counterflow spiral tube coil
pattern, 41, 42
coupling systems, 482–484
crack method, 392
crankcase heaters, 503, 505
crimping fittings, 13
Index 653
cross-linked polyethylene (PEX)
tubing, 11–14, 44–48
cubic feet per minute (cfm), 320,
322, 323–326
D
dampers, 153–155
in air-conditioning systems,
531–532
butterfly, 306–307
controlling, 304
in dehumidifier, 540
for fans, 333
in gas absorption refrigeration
units, 407–408
louver, 305
in modified fireplace, 156
in roof ventilators, 296
sliding cone, 306
sliding sleeve, 306
and stiffener angles, 303
symptoms of problems with,
170
types of, 305
for ventilators, 304–307
decoiler bending device, 9
defrost cycle
for dehumidifiers, 543
in heat pumps, 473, 475–476
defrost systems, 499–500
defrost thermostat, 499
defrost timer, 511
dehumidification, 365, 537
dehumidifiers
absorption, 538–540
air washers as, 571–572,
573
defined, 521
defrost cycle for, 542–543
and ice formation, 542–543
liquid-absorbent, 540
locating, 542
maintenance of, 542–543
refrigeration, 541–543
rotating-bed, 538, 539
spray, 541
stationary-bed, 538–540
troubleshooting problems in,
543–545
types of, 537–538
dehydrators, 457, 458
demand-frost controls, 499
depressurization, 281
desuperheat, 486
desuperheaters, 494
dew point, 364
dew-point thermostats, 541
dimmer switches, 57
dining rooms, fresh air
requirements for, 288, 384
dip tubes, 194–196, 230–231,
234, 243
direct-connected fans, 333
direct-driven fans, 344, 358
direct-expansion coils, 447
direct-fired water heaters, 180
direct-type pool heaters, 251,
255
discharge valves, 433, 436
disconnect switch, 23, 501
distribution manifold, 17
domestic water heaters, 179
double delta burner, 211
double-pipe condensers, 441, 444
double serpentine coil pattern, 41,
42
double-venting, 98
downdrafts, 168–169, 170,
237–238
downward ventilation, 311
draft hoods, 228–229, 272
dry air filters, 574
dry-bulb temperature, 365–367,
373, 398, 400
dryers, 457, 458, 503
dry installations, 6, 34, 39–40
dual capacitor, 498
dual compressors, 486
dual-fuel heat pumps, 486
dual-source heat pumps, 486
ductless heat pumps, 487
ductless split system, 420
ducts, figuring proper length for,
327–328
654 Index
E
effective temperature, 377
ejectors, 409–410
electrical shock
from electric baseboard heaters,
124
and electric cable installations,
65
from heat pumps, 512, 517
from pool heaters, 273, 278
risk during electrical
installations, 58
electric baseboard heaters,
119–120
continuity of grounding in,
126–127
heating element in, 120–121
installing, 124–127, 128, 129,
130
preventing electrical shock from,
124
supply voltage of, 124, 125
temperature-limit switch in, 121,
124
thermostats for, 121, 123
time-delay relay in, 121
electric boilers, 7
electric cable, 65, 68
electric furnace cabinet, 67
electric motors, for mechanical
refrigeration equipment,
435–437
electric pool heaters, 260–263
electric radiant floor heating
systems
automatic controls of, 54–57
eliminating potential health risks
from, 52
floor sensors for, 56
ground fault circuit interrupter
for, 57
installation of electric cable for,
65
installation of heating mats for,
58–65
servicing and maintaining, 67
system components of, 52–57
troubleshooting problems in,
67–68
electric water heaters, 227,
240–244
electromagnetic fields, eliminating
potential health risks from,
52
electronic air cleaners
airflow through, 564
air volume adjustment for, 564
automatic controls for, 554–555
cabinet-model, 563–564
charged-media, 549–550
checking performance of, 563
clogged-filter indicator for,
556–557, 558
control panels for, 563–564
filters for, 565, 567
function of, 547
independent cabinet units, 549,
555–556
in-place water-wash controls for,
561–563
installation of, 564
locations of, 547–548
maintenance of, 565, 567
multiposition, 549, 550, 551
on-off control of, 559–561
operating, 563–564
performance lights for, 557–559,
560, 569–570
replacing ionizing wires in,
568–569, 570
return grille, 548–549, 552–553,
554, 565, 566, 569, 570
sail switch for, 559–561
system/blower controls for, 563
troubleshooting problems in,
569–571
two-stage, 553–554, 556
wiring of, 564–565
electronic cells, 567, 568–569,
571
Energy Efficiency Ratio (EER),
424, 488
energy recovery ventilators
(ERVs), 358
Index 655
Energy Star Rating, 488
engine rooms, fresh air
requirements for, 288
Environmental Protection Agency
(EPA), 483
equivalent square feet of direction
radiation (EDR), 104
evacuating the system, 464–465
evaporation, latent heat of, 363
evaporation loss, 1
evaporative condensers, 441–442,
445
evaporative cooling, 398–400, 419
evaporator coils, 402, 404, 446
controlling flow of refrigerant to,
450–452
in warm-air heating systems,
417–418, 419
evaporator pads, 525
evaporators, 446–448, 452, 455,
456
exhaust fans, 344, 345, 348,
355–356
exhaust hoods, 332, 355
expansion devices, 449–454
expansion joints, 114, 115
expansion tank, 19, 26, 27
expansion valves
automatic, 449–450
and evaporators, 452
symptoms of problems with,
433, 434, 456
thermostatic (TXV), 450–453,
493–494
exposed radiators, 72
F
factory buildings, fresh air
requirements for, 288, 384
fan coils, 420–421
fans
air intakes for, 344, 346
ampere ratings for, 334–337
applications of, 347–348
for attic ventilation, 348–354
available line voltage of, 342
axial-flow, 318
basic laws of, 319–321
belt-drive arrangement in, 333
belt-driven, 341, 343
centrifugal, 318
circulating, 348
codes and standards for, 315
controlling air volume of, 347
covering air intake of, 326–327
decreasing noise of, 347
determining air intake of, 326
determining cubic feet per
minute (cfm) of, 320,
323–326
direct-connected, 333
direct-driven, 344
and duct systems, 344
exhaust, 348, 355–356
friction losses in, 327
furnace blowers, 319
general ventilation from, 322
for heat pumps, 499
horsepower input of, 316
inlet area of, 316
inspection of, 346–347
installation of, 344–347
kitchen, 348
for local ventilation systems,
328–331
maximum tolerable noise level
of, 342
mechanical efficiency (ME) of,
319
minimum fan capacity (cfm) of,
343
motors for, 333–341
mounting arrangement of, 342
outlet area of, 316
overload relay heaters for, 337
parallel operation of, 321
performance curves for, 322
propeller, 318, 341
quantifying qualities of, 316–317
screen efficiency of, 326–327
selection of, 333, 341–344
series operation of, 321
static pressure of, 327–328,
341–342
656 Index
fans (continued)
symptoms of problems with,
514, 545
temperature of ambient air in, 342
terms and definitions dealing
with, 315–317
troubleshooting problems with,
337–341
tubeaxial, 318
types of, 317–318
unitary system, 348
in unit heaters, 139–140
vaneaxial, 318
for ventilating kitchens, 355
for ventilation systems, 287
for water heater venting systems,
227–228
for whole-house ventilation,
356–359
fan ventilators, 294–295
Federal Clean Air Act, 513
feed water pressure regulator, 22, 23
felt sleeves, 114, 115, 116
fill valves, 20–21
filter dryers, 503
filters
in air-conditioning equipment,
375–376
air washers as, 571–572, 573
for electronic air cleaners, 565,
567
See also air filters
fin-and-tube baseboard heaters, 101
design features of, 108, 110
expansion of heating elements in,
113–114
heating element in, 108, 111
integral, 112–113
keeping enclosure surface
temperature down in, 119
metals used for, 111–112
separate, 108, 110–112
fireboxes, 150–151, 156, 160, 162
fireman switch, 257
fireplaces
ash dump in, 152
ashpit in, 152
chimneys for (see chimneys)
cleanout door in, 152
components of, 146, 149–150
construction details of, 149–150
dampers for, 153–155
dimensions of, 146–149
elevation of, 146
firebox in, 150–151
freestanding, 157–158, 160, 161
hearth of, 148, 149, 151
importance of well-designed
chimney to, 162
lintel in, 151
location of, 145
mantel in, 151
modified, 156–157, 158
Rumford, 158, 160, 162, 163
smoke chamber of, 150, 152
troubleshooting problems in,
170
fittings
for copper tubing, 10
for cross-linked polyethylene
(PEX) tubing, 13
used in hydronic radiant heating
systems, 9
for water storage tanks, 194,
195
flexible ducts, 420–421
float valves, 453–454, 525
float vent, 19
floor covering materials, 40–41
floor panel heating systems, 2, 3.
See also hydronic radiant
floor heating systems
floor sensors, 56–57
flow check valves, 19
flow-control valves, 19, 20–21, 22
flow rate, 9
flow switch, 257
flue effect, 284–285
flue gases, 227, 229
flue liner, 165, 166
flues
backdraft diverter in, 229
connecting to chimney, 239
construction of, 167
Index 657
function of, 165
for gas-fired water heaters,
228–229
induced draft in, 285, 286
placement in automatic storage
heaters, 181, 182, 183
for pool heater ventilation, 272
serving two fireplaces, 166, 167
and smoke pipes, 178
symptoms of clogging in, 170,
233, 234, 235, 236
in water heaters, 183–184
fluid dynamics, 319–321
fly screening, 352, 354
forced-air cooling, 68–69
forced-air unit heaters, 135
formulas
for air change rate, 386
for air supplied per minute, 385
for calculating heat gain, 394
for calculating heat leakage, 387
for change in watt output, 125
for compression of air, 371–372
for determining air intake, 326
for determining cubic feet per
minute (cfm) of fans, 320,
323, 325
for determining heat gain from
solar radiation, 387, 388,
389–391
for determining rate of flow, 285
for equivalent square feet of
direct radiation (EDR), 104
for fan air velocity, 317
for fan tip speed, 317
for fan velocity pressure (VP), 317
for measuring fan power,
320–321
for mechanical efficiency (ME),
316
for relative humidity, 363
for relative radiating surface, 77
rpm ratio, 320
for static pressure, 330–331
for theoretical draft of chimneys,
164
for total heating load, 26
Franklin stoves, 175, 176, 177
freestanding fireplaces, 157–158,
160, 161
Freon. See refrigerants
fresh air, requirements for,
287–289, 384–385
friction loss, 9
fuel pumps, 277
furnace plenums, 530, 531
furnaces
air filters in, 572, 573, 574, 575
capture velocities for, 329
humidistat in, 526–527, 528
steam humidifiers in, 525
used for heat pump, 486
fuses, blown, 242, 278, 340, 514,
517
G
galvanizing plants, fresh air
requirements for, 288, 384
garages
fresh air requirements for, 288,
384
placement of ventilators for,
308–309
ventilation of, 310–311
gas absorption refrigeration,
403–408
gas burners
automatic pilot valves on, 212,
213–214, 215, 216, 217
gas cocks for, 214, 217
for gas-fired pool heater, 258
in gas-fired water heaters, 210,
211
lighting pilot of, 223, 224–225
shutoff device for, 216, 220
symptoms of problems with,
233, 234, 235, 274, 276
types of, 211
gas cocks, 214, 217
for lighting pilot, 223, 224–225
symptoms of problems with,
235, 274
gas compression refrigeration,
401
658 Index
gas engines, 437
gases, compression of, 370–371
gas-fired boilers, 6
gas-fired heat pumps, 485–486
gas-fired pool heaters, 255–259,
272, 274–276
gas-fired unit heaters, 140–141,
142–143
gas-fired water heaters
automatic controls on, 210–220
automatic gas shutoff device for,
216, 220
automatic pilot valve on, 212,
213–214, 215, 216, 217
burners for, 210, 211
combination gas valves for,
221–225, 226
draft hoods for, 228–229
gas cocks for, 214
gas supply line to, 229
general description of, 209
installation and operation of,
225–229
location of, 226
placement of flues in, 181, 182,
183
pressure regulators for, 214–215,
217–219
pressure relief valve for, 220
safety controls for, 215–220
slow-recovery, 189
storage capacity of, 209
temperature relief valve for, 216,
219
thermostatic valves for, 212, 213
troubleshooting problems in,
233–237
venting regulations for, 226–227
venting systems for, 227–229
gaskets, 80–84, 229
gas meters, 229
gas-pressure regulators, 257
gas ranges, 172
gas shutoff valves, 258
gas supply lines, 229, 232, 236,
275
gas valve regulators, 276
gate valves, 19, 21
gauge manifold, 503, 506
gauge pressure, 370
general ventilation, 322
geothermal heat pump, 7,
481–483
globe valves, 19, 21
gravity air convectors, 101, 103,
104–105
gravity ventilators, 306, 307
ground fault circuit interrupter
(GFCI), 56, 57
ground-source coupling system,
482–483
ground-source heat pumps, 477,
481–483, 486
H
headers, 258
hearths, 148, 149, 151
heat
external sources of, 386–392
internal sources of, 392–393
heat-emitting units
convectors, 100–107
list of, 71
output of, 71
radiators (see radiators)
selection of, 71
heat-exchanger pool heaters,
263–264, 265
heat exchangers
air-to-air, 356, 358
in central cooling package, 414
in gas absorption refrigeration
units, 405
for gas-fired pool heater, 258
for ground-source coupling
systems, 482
liquid-to-air, 418
maintaining constant flow of
water through, 257
piping connections for, 207
in pool heaters, 255
in radiant heating systems, 27
temperature-control aquastats
for, 263, 265
Index 659
heat gain
estimating, 379–383
from infiltration and ventilation,
388, 392, 394
from occupants of conditioned
spaces, 393
from solar radiation, 387–388,
389–391
total instantaneous, 388
heating coils
for manual water heaters, 245
patterns of, 41–43
testing of, 46–48
used in hydronic radiant floor
heating systems, 41–43
in wall panel, 5
heating cycle, in heat pumps,
471–473, 510–511
heating elements
aluminum, 111–112
copper, 111–112
in electric baseboard heaters,
120–121
in electric water heaters, 240,
242
expansion of, 113–114
in fin-and-tube baseboard
heaters, 108, 111
for indirect water heaters,
185–188
for unit heaters, 130–131
in steam humidifier, 525
steel, 111–112
symptoms of problems with,
243
heating loads
calculating, 26
sizing, 396–397
heating mats
checking ohm resistance of, 58
detecting break in cable in, 67
for electric radiation floor
heating systems, 53–54
installing in joist cavities under
subfloors, 61–65
installing over subfloors, 58–61
insulation of, 65, 66
insulation test for, 58
manufacturers of, 53–54
ordering, 53
repair kits for, 67
wiring of, 62
Heating Season Performance
Factor (HSPF), 488
heating systems
in ceiling panels, 2–5
electric radiant floor (see electric
radiant floor heating
systems)
in floor panels (see floor panel
heating systems; hydronic
radiant floor heating
systems)
heat-emitting units used in (see
heat-emitting units)
hydronic (see hydronic radiant
heating systems)
most popular installation
method for, 2
radiator efficiency of, 74, 76–77
steam (see steam heating
systems)
supplementary radiant, 476–477
for swimming pools (see pool
heaters)
temperature drop in, 44–45
values of materials that insulate,
41
wall panel, 5
warm-air, 417–418, 419
heat leakage, 386–387
heat loss, 1
heat output, 77–78
heat pump pool heaters, 267
heat pumps
accumulators for, 501
adjusting refrigerant charge in,
513
air handler in, 517
air-handler section of, 490, 491
air-source, 476–480
anti-restart timer for, 501
capacitors for, 498
checking operation of, 509–510
660 Index
heat pumps (continued)
coding cycle of, 511
compressor contactor for, 498
compressor section of, 490
compressors in, 430
control box on, 495
controls for, 490
cooling cycle in, 473, 474
crankcase heater for, 503, 505
defrost cycle in, 473, 475–476
defrost system for, 499–500
desuperheaters for, 494
disconnect switch for, 501
dual-fuel, 486
dual-source, 486
ductless, 487
efficiency ratings for, 487–488
fan motors for, 499
filter dryer for, 503
function of, 471
gas-fired, 485–486
gauge manifold for, 503, 506
ground-source, 481–483
heat exchanger for, 482
heating cycle of, 471–473,
510–511
and heat sink, 473
and heat transfer, 473
high-pressure switches for,
500–501
for hydronic radiant floor
heating systems, 7
identifying problems with
compressors in, 517–518
indoor coil and blower for, 491
installation of, 507, 509–510
lockout relay for, 501
low-pressure switches for, 501
muffler for, 505
operating instructions for,
510–511
operating principles of, 471–476
outdoor, 489
packaged, 478, 480
performance ratings for,
487–488
refrigerant lines of, 490, 491
relays for, 499
for residential heating and cooling
systems, 477–478, 479
reverse-cycle conditioning, 471
reversing valve and solenoid in,
491–493, 494
room thermostats for, 501–502
service valves for, 502–503,
504–505
sizing, 505, 507
split-system, 477–478, 479, 513
for supplementary heat, 502
supplementary radiant heating
systems for, 476–477
system components of, 488–490
troubleshooting problems in,
514–517
types of, 476
water-source, 483–485
heat pump water heaters, 190–191
heat recovery ventilators (HRVs),
356, 358
heat removal method, 325–326
heat sink, 473, 483
heat transfer, 1
from heat pumps, 473
of heat pump water heaters,
190–191
heat transfer coils, 185
heat transference, 481
heat-transfer plates, 38, 40
heat transfer surface, 183–184
heat transmission, coefficient of,
387
hermetic compressors, 429–430,
435, 490
troubleshooting problems with,
517–518
high-limit switches, 257, 277
high-pressure gauge, 373, 376
high-pressure switches, for heat
pumps, 500–501
horizontal draft hood, 228
horizontal slot port cast burner,
211
hospitals, fresh air requirements
for, 288, 385
Index 661
hot-water baseboard heaters
figures of, 109–110
temperature types of, 119
hot-water heating systems. See
hydronic radiant heating
systems
hot-water radiators, 73
locating vents for, 96
water temperature in, 77
hot water safety relief valve, 19
hot-water space-heating boilers,
186
hot-water supply lines
circulation in, 230
for manual water heaters, 246
vacuum relief valve for, 206, 208
for water heaters, 196
humidification, 364
humidifiers, 364
air washers as, 571–572, 573
atomizing, 522–523
automatic controls for, 526–529
automatic flush system for,
534–535
best location for, 531, 532,
533
bypass, 525–526
defined, 521
draining reservoir of, 534
in gas absorption refrigeration
units, 407
guiding airflow to, 529, 530
humidistats for, 526–529
installation of, 529–534
maintenance of, 534–535
pan, 523–524
placing base of, 533
power, 526
spray, 522–523
stationary-pad, 524
steam, 524–525
troubleshooting problems with,
535–537
types of, 522
ultrasonic, 523
and wet-bulb depression, 367
humidistats, 349
combined with thermostat,
554–555, 557
control circuits for, 529, 530
defined, 521
for electronic air cleaners,
554–555, 557
figure of, 528
furnace-mounted, 526–527, 528
in pan humidifiers, 524
programmable, 529
for refrigeration dehumidifiers,
542
settings on, 542
symptoms of problems with,
536, 537, 544
wall-mounted, 528
humidity
absolute, 363
controlling, 364–365
defined, 521
description of, 362
dew point, 364
and drying effect of air, 363–364
measuring, 373
problems of excessive levels of,
520
relative, 363, 519–520
specific, 363
and wet-bulb readings, 366
hybrid heating and cooling
systems, 418–421
hydraulic knock, 434
hydraulic pressure test, 46
hydronic fan convectors, 106–107
hydronic forced-air systems, 418
hydronic radiant floor heating
systems
air venting requirements for, 32,
33
basic description of, 6
boilers used in, 6–7
coils and coil patterns for, 41–43
components of, 6
constant water circulation in,
30–32
construction details for, 33–40
control system for, 25
662 Index
hydronic radiant floor heating
systems (continued)
cooling for, 68–69
designing, 28–41
design procedures for, 32–33
floor coverings for, 40–41
heat pumps used in, 7
installing, 44–48
manifolds for, 14–17
for melting ice and snow, 51–52
servicing and maintaining, 49
sizing calculations for, 32–33
testing of heating panels in, 46–48
troubleshooting problems in,
49–52
tubing used in, 7–14
typical size of tubing in, 45
valves in, 17–25
water heaters used in, 7
hydronic radiant heating systems
air separator for, 26–27
applying central air-conditioning
to, 411–412, 413
automatic controls for, 27–28
baseboard heaters, 109–110, 119
circulator pump for, 26
convector piping connections in,
103
and ductless split systems, 420
and evaporative coolers, 419
expansion tank for, 26, 27
with fan coil and flexible ducts,
420–421
fittings used in, 10–11
heat exchanger for, 27
kickspace heaters, 127–129, 131
for melting ice and snow, 51–52
piping diagram of, 20–21
recessed radiation in, 129,
132–133
and residential chillers with
ceiling-mounted panels, 421
thermostat for, 27–28, 29, 30
in unit heaters, 137, 138
water chiller for, 410–411, 412
working with cooling systems,
418–419
I
ice-melting systems, 51–52
ignition systems, for pool heaters,
256
impellers
function of, 317–318
symptoms of problems with, 278
indirect-type pool heaters, 251,
255
electric-fired, 261, 262–263
gas-fired, 255–256
oil-fired, 259–260, 261
indirect water heaters
advantages of, 188–189
with built-in coils, 188
heat source for, 185–186
versus hot-water space-heating
boilers, 186
piping connections for, 207
storage capacity of, 188
water circulation in, 188
indoor design conditions, 383
induced draft, 285, 286
induction
caused by wind, 297
defined, 282
in revolving ventilators, 290–291
in siphonage ventilators, 294
from wind, 282–285
induction motors, 435–436
industrial buildings, ventilation
for, 313
infiltration, 309–310
calculating heat gain from, 394
defined, 392
inlet air openings
for attic fans, 350
in gas absorption refrigeration
units, 406–407
general rules for, 312
for ventilators, 298–299
inline thermometers, 23
inspections
of air filters, 573–574
of cross-linked polyethylene
(PEX) tubing, 44
of fans, 346–347
Index 663
installations
of air filters, 575
of baseboard heaters, 113–119
of bypass humidifiers, 532–534
dry, 6, 34, 39–40
of electric baseboard heaters,
124–127, 128, 129, 130
of electric cable, 65
of electronic air cleaners, 564
of fans, 344–347
of gas-fired water heaters,
225–229
of heating mats, 58–65
of heat pumps, 507, 509–510
of humidifiers, 529–534
of hydronic radiant floor heating
systems, 44–48
of pool heaters, 271–273
of pressure relief valves,
201–202
of radiators, 79–86
of relief valves, 201–202
of stoves, 177–178
of temperature relief valves,
201–202, 203–204
of wall panel heating systems, 5
of water heaters, 232–233
wet, 6, 33–35, 36
instantaneous water heaters,
184–185
insulating values, for materials
covering radiant heating
systems, 41
insulation, of heating mats, 58,
65, 66
intermittent ignition systems, 256
ionizing wires, 568–569
isolation valve, 22–23
K
J
M
jig, 9
joining key, 82, 83, 84
joist cavities
codes regulating notching of, 62
installing electric heating mats
in, 61–65
sealing ends of, 65
magnet valves, symptoms of
problems in, 236
main gas–pressure regulator,
214–215, 217–219
maintenance
of air-conditioning equipment,
460, 463–470
kickspace heaters, 127–129, 131
kitchen fans, 348, 355–356
kitchens
capture velocities for ranges in,
329
fresh air requirements for, 288,
385
ventilation of, 311–312
L
large-volume water heaters,
182–183
latent heat, 368
gain of, 379
removal of, 541
leaks
air, 309–310
in copper tubing, 9
locating source of, 46
testing for in heating coils, 46
lintels, 151
liquid-absorbent dehumidifiers,
540
liquid heat exchanger, 405
liquid line, 455
local ventilation, 322, 328–331
exhaust hoods for, 332
lockout relay, 501
loop continuity, 45
loops, 7
loose fill insulation, 40
louver dampers, 305
louvers
for attic fans, 352–353
on evaporative coolers, 398
low-pressure switches, 501
664 Index
maintenance (continued)
of air filters, 575
of baseboard heaters, 119
of condensers, 442–443
of dehumidifiers, 542–543
of electronic air cleaners, 565, 567
of humidifiers, 534–535
of hydronic radiant floor heating
systems, 49
of mechanical refrigeration
equipment, 460, 463–470
of pool heaters, 273–274
of thermostats, 511–513
of water heaters, 232–233
manifold balancing valves, 17
manifolds
combinations of, 15
diagrams of, 14–15
function of, 14
for gas-fired pool heater, 258
gauge, 503, 506
in hydronic radiant floor heating
system installations, 47–48
measuring temperature of water
in, 17
preassembled, 16
return,
supply, 16–17
types of, 14
valves for, 16–17
manifold station, 16
mantels, 151
manual gas valves, 214, 217, 223,
224–225
manual water heaters, 245–246
masonry filler, 40
masonry fireplaces, 149–150
mat-type filters, 575
mean temperature difference, 296
mechanical efficiency (ME), 316,
319
mechanical refrigeration cycle,
401–403
mechanical refrigeration
equipment
adding refrigerant to, 465–467
automatic controls for, 459
capillary tubes in, 454
components of, 423
compressors in (see compressors)
condensers for, 439–446
electric motors for, 435–437
evacuating, 464–465
evaporators for, 446–448
float valves, 452–454
gas engines for, 437
maintenance of, 460, 463–470
operating pressure in, 449
pressure-limiting controls in,
457–458
pumping down, 464
purging of, 464
receivers for, 443, 447
refrigerant for, 448–449
refrigerant piping in, 454–457
water-regulating valves in,
458–459
mechanical ventilation, 282, 287
media pads, 549–550
metal chimneys, 169, 171, 173
metal tubing, bending, 9
milled slot port cast burner, 211
millivolt ignition systems, 256,
257
mills, fresh air requirements for,
385
mixing valves
automatic, 24
locations of, 19, 20–21
manual, 24
in piping diagram, 20–21
in radiant heating systems, 23–24
symptoms of problems with, 50
thermostatic, 23
modified fireplaces, 156–157,
158
motorized zone valve, 24–25
motor overload protector,
symptoms of problems with,
518
motors, for fans, 333–341
motor shafts, symptoms of
problems with, 278
mufflers, 505
multicoil water heaters, 182–183
multiflue water heaters, 183–184
Index 665
multimeters, testing heating mats
with, 58
multiple stamped ribbon ports, 211
multiple-story buildings, use of
ceiling panel heating system
in, 3–4
N
National Electrical Manufacturer’s
Association (NEMA), 333
natural ventilation, 282, 289
nipples
for radiator sections, 80–84
smooth beveled, 85–86
nonadjustable air valves, 98
nonbarrier tubing, 11
nonprogrammable thermostats, 56
O
office buildings
ceiling panel heating system in, 5
fresh air requirements for, 288,
385
ohm resistance, checking, 58
oil burners, symptoms of problems
with, 277–278
oil-fired boilers
hydronic, 186, 187
use of, 6
oil-fired pool heaters, 259–260,
261, 277
oil-fired unit heaters, 141, 144
oil-fired water heaters, 182, 183,
238–240, 241
open-type compressors, 429
outdoor design conditions, 383
outlet velocity (OV), 316
overflow prevention control,
symptoms of problems with,
544
overload relay heaters, 337
oxygen barrier tubing (BPEX), 11
oxygen-induced damage, 191–192
P
packaged heat pumps, 478, 480
packed-type radiator valve, 86, 87
packless radiator valve, 86, 88
pan humidifiers, 523–524
passive ventilation, 282
performance curves, 322
PEX tubing, 11–14, 44–48
pilot gas–pressure regulator,
214–215, 217–219
pilot generators, for gas-fired pool
heater, 257
pilot lights
in millivolt ignition systems,
256
symptoms of problems with,
233, 234, 235, 236, 274,
275
pilot valves, symptoms of
problems with, 236, 515, 516
pipe bend support, 47
pipes
for air-conditioning refrigerant,
454–457
wrapping with felt sleeve, 114,
115, 116
See also tubing
piping connections
for convectors, 101, 103–105
for heat exchangers, 207
for indirect water heaters, 207
in mechanical refrigeration
equipment, 454–457
for radiators, 92–93, 95–97
for refrigerants, 454–457
for unit heaters, 135–138, 139,
140, 141
piston compressor, 424–425
plastic pipe. See cross-linked
polyethylene (PEX) tubing
plenum adapter kit, 531
point-of-use water heaters,
184–185
pool filters, 278
pool heaters
aquastat in, 258
basic systems of, 249–251
classifying, 251, 255
diagrams of system of, 252–254
direct-type, 251, 255
electric, 260–263
666 Index
pool heaters (continued)
and electrical shock, 278–279
finding required energy rating
for, 270–271
gas burner assembly in, 258
gas-fired, 255–259, 274–276
header for, 258
heat-exchanger, 263–264, 265
heat exchanger for, 258
heat pump, 267
ignition systems for, 256
indirect-type, 251, 255
installing, 271–273
manifold for, 258
oil-fired, 259–260, 261
operating principles of, 251
repair and maintenance of,
273–274
sizing, 267–271
solar, 264, 266–267
standard set of clearances for,
272
troubleshooting problems in,
274–279
wiring diagram for, 259
pool pumps, 278
port cast burners, 211
power humidifiers, 526
power venting, 227–228
prefabricated roof curbs, 303–304
prefilter, 567
pressure gauges, 373–374, 376,
377
for heating coils, 46
location in hydronic heating
system, 19
pressure-limiting controls,
457–458
pressure-reducing valves, 25
pressure regulators
for gas-fired water heaters,
214–215, 217–219
symptoms of problems with, 234
pressure relief valves
components of, 199–200, 203,
204
figures of, 200, 201
functions of, 25, 198–199
for gas-fired water heaters, 220
importance of, 198
installation of, 201–202
location in hydronic heating
system, 19
for manual water heater, 245
rated capacity of, 204, 205
safety requirements for, 199
symptom of problems with, 244
temperature-sensing element in,
199–200, 201–202
pressure switches, 257
symptoms of problems with,
274, 275, 276
programmable thermostat, 55–56
propeller fans, 318, 341, 342
psychrometers, 373
pumping down, 464
pump rooms, 288, 385
pumps
air-source heat, 476–480, 486
aquastats for, 230
circulating (see circulating
pumps)
dual-fuel, 486
ductless, 487
fuel, 277
gas-fired, 485–486
heat (see heat pumps)
heat transfer from, 473
for pools, 278
recirculating, 541
for spray dehumidifiers, 541
water, 190
purge valves, 19, 25
purging, 464
push nipples, 85–86
Q
quick-recovery heaters, 189
quick vents, 98
R
radiant heat, from fireplaces, 158
radiant panel heating systems
Index 667
ceiling panel systems, 2–5
electric floor systems (see electric
radiant floor heating
systems)
floor panel systems (see floor
panel heating systems)
heat transfer in, 1
hydronic floor heating (see
hydronic radiant floor
heating systems)
principles of, 1–2
typical control system for, 25
wall panel systems, 5
radiation
defined, 71
from fireplaces, 158
recessed, 129, 132–133
radiation heat loss, 1
radiators
automatic air valves in, 100
cast-iron, 72
column-type, 72, 74
effect of paint on efficiency of,
100
exposed, 72
finding square-foot equivalent
direct radiation (EDR) of,
79
heat output from, 77–78
hot-water, 73
installing, 79–86
joining sections of, 79–86
leveling, 76
location of air vents for, 96
manual air valves in, 100
operating efficiency of, 74,
76–77
piping connections for, 92–93,
95–97
ratings for, 74–76
relative radiating surface of, 77
removing air from, 86–92
sizing, 78–79
steam, 72–73
steam traps in, 99
supply and return connections
for, 95
surface area of, 77
test pressure of, 84
troubleshooting problems with,
99–100
tubular, 73, 75–76
two-pipe connections to, 97
types of, 72, 73–74
valves for, 86–92
venting in, 76–77, 93–94, 96,
98–99
venting trapped air in, 98–99
waterways in, 72
radiator sections
checking alignment of, 83, 85
joining, 79
joining of threaded, 80–85
joining with smooth beveled
nipples, 85–86
radiator valves
air valves, 86–92
functions of, 86
packed-type, 86, 87
packless, 86, 88
thermostatic expulsion, 89–90,
92
ranges
capture velocities for, 329
categories of, 171–172
defined, 171
figures of, 176, 178
solid fuels used in, 172
wood-burning, 176
rate of flow, 285
receivers, 443, 447
recessed heaters, 129, 132–134
reciprocating compressors,
424–425
recirculating pumps, 541
recycling heating, 250–251
refrigerant cylinder, 465–467
refrigerants
adding to air-conditioning
equipment, 465–467
adjusting charge in heat pumps,
513
and air-conditioning efficiency,
449
668 Index
refrigerants (continued)
automatic expansion valves for,
449–450
charging, 465–467
control devices for, 449
in cooling cycle of heat pumps,
473, 474
in crankcase heater, 503, 505
defined, 448
evaporation of, 447
in evaporative condensers, 442
and float valves, 453–454
Freon, 448
in gas absorption refrigeration
cooling, 403–404, 405–406
and heat pumps, 471–473, 491
maintaining line connections of,
512
measuring, 513
operating pressure in, 449
piping for, 454–457
properties of, 448
pumping down, 464
in refrigeration dehumidifiers,
542
removing, 464–465
reversing valve for, 491–493,
494
in scroll compressor, 426
symptoms of overcharged, 463
symptoms of problems with,
433, 434, 456, 457, 462,
515
symptoms of shortage of, 462
thermostatic expansion valves
for, 450–453
in water-cooled condensers, 441
refrigeration dehumidifiers,
541–543
relative humidity, 363, 519
defined, 521
desirable levels of, 520
measuring, 373
recommended for airconditioning systems, 378
reducing, 520–521
relative radiating surface, 77
relay contactor, 57
relays, 499, 501
relief valves
components of, 199–200, 203,
204
in domestic hot-water heaters,
197–206
functions of, 198–199
in hot-water discharge line, 202
importance of, 198
installation of, 201–202
in piping diagram, 20–21
safety requirements for, 199
symptoms of problems with, 237
temperature-sensing element in,
199–200, 201–202
vacuum, 206, 208
See also pressure relief valves;
temperature relief valves
repair coupling, 9
repair kits, for heating mats, 67
resistance tests, 58
resistors, 120, 121
restaurants, fresh air requirements
for, 288, 385
return grille electronic air cleaners,
548–549, 552–553, 554, 565,
566, 569, 570
return line, in radiant heating
systems, 7
return manifold, 16
reverse-cycle conditioning, 471
reversing valve, 473
four-way, 492–493
in heat pumps, 491–493
revolving ventilators, 290–291
ridge ventilators, 293–294
roof curbs, 303–304
roof ventilators
angle rings for, 302
base of, 289, 299–301
components of, 295–296
connection to roof, 299–301
dampers for, 304–307
fan, 294–295
function of, 289
inlet air openings in, 298–299
Index 669
prefabricated roof curbs for,
303–304
purpose of, 298
revolving, 290–291
ridge, 293–294
siphonage, 294
stationary-head, 290
stiffener angles for, 303
turbine, 291–293
types of, 289–290
room air conditioners, 421, 424
rotary compressors, 427–428
rotating-bed dehumidifiers, 538,
539
rpm ratio, 320
Rumford fireplaces, 158
distinguishing features of, 162
invention of, 160
reducing turbulence in, 162
vertical path of flue in, 163
run capacitor, 498, 518
S
sacrificial anode rod, 193
saddle valves, symptoms of
problems with, 536
safety codes, for water heaters,
230–231
safety controls, for gas-fired water
heaters, 215–220
safety relief valves
components of, 199–200, 203,
204
in domestic hot-water heaters,
197–206
functions of, 198–199
in hot-water discharge line, 202
safety requirements for, 199
temperature-sensing element in,
199–200, 201–202
See also pressure relief valves;
temperature relief valves
safety switches, for gas-fired pool
heater, 257
sail switches, 559–561
sandwich floor construction,
35–36, 37
scale buildup, 191
schools, fresh air requirements for,
288, 385
scroll compressor, 426
Seasonable Energy Efficiency
Ratio (SEER), 424, 488
semihermetic compressors, 430
sensible heat, 368
gains of, 379
removal of, 541
sensor bulbs, 452–453
serpentine coil patterns, 41–43
service check valve, 19
service valves, for heat pumps,
502–503, 504–505
shade factors, 391
sheathed cable, 126
shops, fresh air requirements for,
288–289, 385
shutoff valve
in piping diagram, 21
for testing heating coils, 46
sidearm heaters, 209, 245
silver brazing, 467–470
single-phase motors, ampere
ratings for, 334
single serpentine coil pattern, 41, 43
single-stage wiring diagrams, 122
siphonage ventilators, 294
slab manifold, 17
slab-on-grade construction, 34, 35
sliding cone dampers, 306
sliding sleeve dampers, 306
sling psychrometer, 373
slow-recovery heaters, 189
smoke chambers, 149, 150, 152,
170
smoke pipes, 167–168, 178
smoke shelf, 148, 149, 170
snap-action thermostat, 189
snow-melting systems, 51–52
solar collectors, 267
solar pool heaters, 264, 266–267
solar radiation
heat gain from, 387–388,
389–391
and shade factors, 391
670 Index
solar sensors, 266
solar water heaters, 246–247
solenoids, 491–493
solenoid valve, symptoms of
problems with, 431, 536
sorbent material, 538
space heaters. See unit heaters
specific humidity, 363
split-system cooling, 411–412,
413
split-system heat pumps, 477–478,
479, 513
spray dehumidifiers, 541
spray humidifiers, 522–523
square-foot equivalent direct
radiation (EDR), 79
stack effect, 284–285, 309–310
stack height, 297
stamped horizontal port burner, 211
stamped mono-port burner, 211
standard air, 316
standard atmosphere, 368
standards of comfort, 376–377
standing pilot light, 256
staple-up method, 36, 38–39
start capacitors, 494, 498, 518
static efficiency (SE), 316
static pressure (SP), 316, 327–328
calculation of, 330
and fan selection, 341–342
stationary-bed dehumidifiers,
538–540
stationary-head ventilators,
290
stationary-pad humidifiers, 524
steam
cooling with, 398, 408–410
in gas absorption refrigeration
units, 407
heating with (see steam heating
systems)
steam cooling systems, 408–410
steam diverter valve, 407
steam generator, 407
steam heating systems
applying central air-conditioning
to, 411–412, 413
convector connections in, 104,
105
in unit heaters, 136–138, 139,
140, 141
water chiller for, 410–411, 412
steam humidifiers, 524–525
steam radiators, 72–73
locating vents for, 96
steam traps
in radiators, 99
for unit heaters, 136
steel heating elements, 111–112,
113
stiffener angles, 303
storage tanks. See water storage
tanks
stoves
Atlantic box, 174
defined, 169
eighteenth-century, 175
figures of, 174–176, 177
Franklin, 175, 176, 177
history of, 170–171, 175
installing, 177–178
operating instructions for,
178
primary function of, 170
wood-burning, 174
strainers, 457, 458
suction line, 455
superheat, 452
removing, 486
superheated water, 198
supply manifold, 16–17
supply voltage, in electric
baseboard heaters, 124,
125
surface-area method, 268–269,
270–271
swimming pools
diagrams of water-heating
system for, 252–254
heating systems for (see pool
heaters)
heating through recycling,
250–251
heat sources for, 249–250
Index 671
maintaining proper temperature
in, 251
protection from wind, 270
radiant heating systems for,
249–250
solar heating of, 249
swing-check valve, 22, 230
T
tankless water heater. See indirect
water heaters
temperature
comfort chart index, 377–379
daily range of, 367
defined, 365
dry-bulb, 373
dry-bulb versus wet-bulb,
365–367
effective, 377
and latent heat, 368
measuring, 372–373, 374
relationship to relative humidity,
519
and sensible heat, 368
wet-bulb, 373
and wet-bulb depression,
367–368
temperature-control valves, 251
temperature difference, effect on
ventilation, 312–313
temperature drip, 44
temperature gauge, 19
temperature-humidity index, 365
temperature lag, 203, 205
temperature-limit switches, 121,
124
temperature relief valves
components of, 199–200, 203,
204
figures of, 201
function of, 199
for gas-fired water heaters, 216,
219
importance of, 198
installation of, 201–202,
203–204
rated capacity of, 204, 205
safety requirements for, 199
symptoms of problems with,
237, 244
temperature-sensing element in,
199–200, 201–202
temperature rise, in fan motors,
339
test plugs, 19
theaters, fresh air requirements
for, 288, 385
theoretical draft, 164
thermal cutouts, 121, 124
thermal effect, 282
and wind effect, 285–287
thermocouple connections
for gas-fired pool heater,
257
symptoms of problems in, 236,
275
in thermoelectric refrigeration
units, 408
thermocouple valves, symptoms of
problems with, 235
thermoelectric refrigeration,
397–398, 408
thermomagnets, 223
thermometers
for air temperature, 372–373,
374
inline, 23
in piping diagram, 20–21
thermostatic expansion valves
(TXV), 450–453, 493–494
thermostatic expulsion valves,
89–90, 92
illustration of, 93, 94
thermostatic valves, 212, 213
thermostats
for attic fans, 349
combined with humidistat,
554–555, 557
for controlling heat pump
operation, 501–502
defrost, 499
for defrost cycle in heat pumps,
475
dew-point, 541
672 Index
thermostats (continued)
for electric baseboard heaters,
121, 123
for electric radiant floor heating
systems, 55–56
for electric water heaters,
240–241
for electronic air cleaners,
554–555, 557
for gas-fired pool heater, 258
heat anticipator setting, 511
for hydronic radiant heating
systems, 27–28, 29, 30
for instantaneous water heaters,
185
maintenance of, 511–513
nonprogrammable, 56
in piping diagram, 20–21
programmable, 55
for quick-recovery heaters, 189
and refrigeration systems, 437
service-light, 501
for slow-recovery heaters, 189
snap-action, 189
for solar water heaters, 247
symptoms of problems with, 50,
68, 233, 234, 235,
242–243, 274, 514
throttling, 189
on wood-burning stoves, 177
zone, 26
thin-slab construction, 34–35, 36
30-minute cams, 476
threaded radiator sections, joining,
80–85
three-phase motors
ampere ratings for, 335
connection diagram for, 338
three-way valves, for solar pool
heaters, 266–267
throttling thermostat, 189
time delay, 500
time-rise method, 268–269, 271
timers, 57
time-temperature defrost controls,
499
tip speed (TS), 316–317
ton of refrigeration, 395
total heating load, 26
total pressure (TP), 317
traps
bucket, 138
cleanout, 168
for radiator steam, 99
versus thermostatic expulsion
valves, 90
for unit heaters, 136
triple-venting, 98, 99
tubeaxial fans, 318
tubing
copper (see copper tubing)
cross-linked polyethylene (see
cross-linked polyethylene
(PEX) tubing
installing above subfloor, 39–40
loop continuity in, 45
measuring temperature of water
in, 17
nonbarrier, 11
oxygen barrier (BPEX), 11
in radiant heating systems, 7–14
return line of, 7
spacing of, 45
staple-up method for installing,
36, 38–39
supply line of, 7
symptoms of break in, 51
tungsten ionizing wires, 568–569
turbine rooms, fresh air
requirements for, 288, 385
turbine ventilators, 291–293
two-stage air cleaners, 553–554,
556
two-stage wiring diagram, 123
Type L copper tubing, 8–9
U
U-factor, 387
ultrasonic humidifiers, 523
unitary system fans, 348
unit heaters
air stream of, 131, 134
components of, 130
continuous circulation in, 139
Index 673
controls for, 138–140
defined, 130
fan operation in, 139–140
forced-air, 135
gas-fired, 140–141, 142–143
heat supply from, 130–131
horizontal, 131, 135
oil-fired, 141, 144
piping connections for, 135–138,
139, 140, 141
steam supply to, 137, 139
vapor steam system in, 136
upward ventilation, 311
V
vacuum
greatest area of, 313
and inductive action, 283–284
vacuum relief valves, 206, 208
valves
air (see air valves)
in air conditioners, 458–459
automatic air vent, 18
automatic pilot, 212, 213–214,
215, 216, 217
backflow preventer, 21
balancing, 25
ball, 19, 21
for boilers, 19, 21
bypass, 257, 276
check, 19–23, 230
combination gas, 221–225,
226
discharge, 433, 436
in domestic hot-water heaters,
197
expansion (see expansion valves)
fill, 20–21
float, 452–454, 525
float vent, 19
flow-control, 19–22
functions of, 17–18
gas, 257, 258
gate, 19, 21
globe, 19, 21
for heat pumps, 502–503,
504–505
for hydronic radiant floor heating
systems, 17–25, 47–48
isolation, 22–23
magnet, 236
for manifolds, 16–17
manual gas, 214, 217, 223,
224–225
in mechanical refrigeration
equipment, 458–459
mixing (see mixing valves)
motorized zone, 24–25
pilot, 212–217, 236, 515, 516
pressure-reducing, 25
pressure relief (see pressure relief
valves)
purge, 19, 25
for radiators, 86–92
for refrigerants, 449–454,
491–493, 494
relief (see relief valves)
reversing, 473, 491–493, 494
saddle, 536
safety relief (see safety relief
valves)
service, 19, 502–503, 504–505
shutoff, 21, 46
solenoid, 431, 536
steam diverter, 407
swing-check, 22, 230
temperature-control, 251
temperature relief (see
temperature relief valves)
thermocouple, 235
thermostatic, 212, 213
thermostatic expansion,
450–453, 493–494
thermostatic expulsion, 89–90,
92, 93, 94
three-way, 266–267
vacuum relief, 206, 208
water pressure reducing, 19
water-regulating, 458–459
water-tempering, 206, 208
zone, 16–17
vaneaxial fans, 318
vapor barrier, 46, 47
vaporizers, 524–525
674 Index
velocity pressure (VP), 317
ventilating systems
considerations for, 298
localized, 328–332
for whole houses, 356–359
ventilation
air changes required for,
324–325
and air leakage, 309–310
of attics, 348–354
of bathrooms, 356
calculating heat gain from, 394
versus circulation, 315
defined, 281
and forces of temperature
difference, 312–313
of garages, 310–311
general, 322
general rules for, 312–313
importance of, 281
and induced draft, 285, 286
and inductive action of the wind,
282–285
for industrial buildings, 313
of kitchens, 311–312, 355–356
local, 322, 328–332
mean temperature difference in,
296
mechanical, 287
natural, 282
requirements for, 287–289,
384–386
thermal effect in, 285–287
types of, 282
upward versus downward, 311
wind effect in, 285–287
See also ventilators
ventilation fans, 344, 346
for attics, 348–354
See also fans
ventilation heat gain, 380
ventilators
base of, 299–301
calculating required number and
size of, 307–309
capacity of, 296–297
dampers for, 304–307
energy recovery (ERVs), 356
exhaustive capacity of, 307
factors for selection of, 296
fan, 294–295
gravity, 306, 307
heat recovery (HRV), 356, 358
inlet air openings in, 298–299
proper operating conditions of,
308
revolving, 290–291
ridge, 293–294
in roof (see roof ventilators)
siphonage, 294
spacing of, 307, 308–309
stack height of, 297
stationary-head, 290
turbine, 291–293
venting systems
for gas-fired water heaters,
227–229
in hydronic radiant floor heating
systems, 32, 33
for indoor pool heaters, 272
for radiators, 93–94, 96, 98–99
regulations for gas-fired water
heaters, 226–227
vents
in radiators, 76–77, 93–94, 96,
98–99 (see also radiator
valves)
symptoms of problems with, 275
vertical draft hood, 228
vertical drilled port cast burners,
211
viscous air filters, 574–575
volume of air required, 341
W
wall panel heating systems, 5
wall radiators, 73–74
warehouses, fresh air requirements
for, 288, 385
warm-air heating systems, cooling
coils in, 417–418, 419
water
circulating at fixed temperature,
27, 28
Index 675
converting from liquid to vapor,
363
determining circulation rate of,
26
superheated, 198, 199
water chillers, 417–418
cooling with, 410–411, 412
evaporator coil and, 446
water-cooled condensers, 414,
415–417, 441, 444
water heaters
automatic storage, 180–182,
183, 204, 206
Btu output of, 7
causes of explosions in, 197–198
code requirements for, 230–231
combination, 191–192
commercial versus domestic, 179
direct-fired, 180
draft hoods for, 228–229
electric, 240–244
fuels for, 180
function of, 179
gas-fired (see gas-fired water
heaters)
heat-control method in, 180
heat pump, 190–191
hot-water circulating methods in,
230
for hydronic radiant floor
heating systems, 7
indirect, 185–189
installation and maintenance
checklist for, 232–233
instantaneous, 184–185
lighting and operating
instructions for, 231–232
manual, 245–246
minimum temperature of, 107
most common, 179, 192
multicoil, 182–183
multiflue, 183–184
oil-fired, 182, 183, 238–240, 241
placement of flues in, 181, 182,
183
power-vent, 227–228
quick-recovery, 189
recovery rate of, 180
requirements for gas supply to,
231
safety relief valves in, 197–206
service guide for, 232
signs of sediment accumulation
in, 237
slow-recovery, 189
solar, 246–247
storage tanks for (see water
storage tanks)
for swimming pools (see pool
heaters)
temperature of water in, 195
types of, 179–180
venting systems for, 227–229
water temperature control in,
232
water pressure
reducing valve for, 19
regulators for, 23
water pumps, 190
water-regulating valves, 458–459
water sensors, 266
water-source heat pumps, 483–485
water storage tanks
anodes in, 197
antisiphon hole in, 195–196
causes of explosions in,
197–198, 199
in combination water heaters,
191–192
construction details for, 193
corrosion in, 193
dip tubes in, 194–196, 230–231
in electric water heaters, 242
fittings for, 194, 195
in gas-fired water heaters, 209
glass-lined, 193
for heat pump water heaters, 190
for oil-fired water heaters,
238–239
operating life of, 193
safety relief valves in, 197–206
scale buildup in, 191
symptoms of problems with,
243–244
676 Index
water temperature
control for, 232
in oil-fired water heaters, 238
water-tempering valves, 206, 208
water valves, symptoms of
problems with, 536
water vapor
latent heat of, 368
saturated, 364
water-wash controls, 561–563
waterways, threaded, 80–85
watt output, calculating change in,
125
Weil-McLain ratings, 77–78
wet-bulb depression, 367–368
wet-bulb temperature, 365–367,
373
wet installations
defined, 6
for hydronic radiant floor
heating systems, 33–34
thin-slab construction, 34–35, 36
whole-house ventilation,
356–359
windbands, 296
wind effect, 285–287
window radiators, 73–74
window-ventilated buildings,
312
wood-burning ranges, 176
wood-burning stoves, 174
wood heaters, 177
Y
year-round air-conditioning, 412,
413
Z
zone manifold, 17
zone thermostat, 26
zone valves, 16–17
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