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2017 Lennox Industries Inc.
Dallas, Texas, USA
INSTALLATION
INSTRUCTIONS
ML180UHE
MERIT ® SERIES GAS FURNACE
UPFLOW / HORIZONTAL AIR DISCHARGE
507103-02
10/2017
Supersedes 507103-01
Litho U.S.A.
THIS MANUAL MUST BE LEFT WITH THE
HOMEOWNER FOR FUTURE REFERENCE
This is a safety alert symbol and should never be ignored.
When you see this symbol on labels or in manuals, be alert to the potential for personal injury or death.
WARNING
Improper installation, adjustment, alteration, service or maintenance can cause property damage, person al injury or loss of life. Installation and service must be performed by a licensed professional installer (or equivalent), service agency or the gas supplier.
AIR FLOW
UPFLOW
HORIZONTAL LEFT HORIZONTAL RIGHT
CAUTION
As with any mechanical equipment, personal injury can result from contact with sharp sheet metal edges. Be careful when you handle this equipment.
Table of Contents
Unit Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ML180UHE Gas Furnace . . . . . . . . . . . . . . . . . . . . . . . . .
Shipping and Packing List
Safety Information
. . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Use of Furnace as a Construction Heater
General
. . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Combustion, Dilution & Ventilation Air
Setting Equipment
. . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11
Duct System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12
Venting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13
5
8
4
4
3
3
2
3
Gas Piping
Electrical
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20
22
Integrated Control
Unit Start-Up
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
25
26
Gas Pressure Adjustment
High Altitude
. . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
28
28
Proper Combustion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Other Unit Adjustments . . . . . . . . . . . . . . . . . . . . . . . . . .
28
29
Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Repair Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
30
32
Start Up Check List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
33
Page 1
Unit Dimensions - inches (mm)
1 NOTE - 60C and 60D units that require air volumes over 1800 cfm (850 L/s) must have one of the following:
1. Single side return air with transition to accommodate
20 x 25 x 1 in. (508 x 635 x 25 mm) cleanable air filter. (Required to maintain proper air velocity.)
2. Single side return with optional return air base.
3. Bottom return air.
4. Return air from both sides.
5. Bottom and one side return air.
See Blower Performance Tables for additional information.
2 Flue outlet may be horizontal but furnace must be vented vertically
3 Optional external side return air filter kit cannot be used with the optional RAB Return Air Base.
D
FLUE OUTLET
(Top)
3 OPTIONAL
EXTERNAL
SIDE RETURN
AIR FILTER KIT
(Either Side)
3/4(19)
Front Panel
A
B 9/16 (14)
3 (76) Right
6 − 3/4 (171) Left
3 OPTIONAL
EXTERNAL
SIDE RETURN
AIR FILTER KIT
(Either Side)
33
(838)
9 − 1/8 (232) Right
8 − 5/8 (219) Left
5 − 3/8 (137) Right
1 − 9/16 (40) Left
14 − 3/4
(375)
16
(406)
ELECTRICAL
INLET (Either Side)
(Either Side)
3 − 1/8 (79)
SUPPLY AIR
OPENING
23 − 3/4
(603)
25
(635)
TOP VIEW
27 − 3/4
(705)
3 − 1/4 (83)
19 − 7/16
(494)
2 FLUE OUTLET
(Either Side)
ELECTRICAL INLET
(Either Side)
GAS PIPING INLET
(Either Side)
3/4
(19)
1
C
Air Opening
FRONT VIEW
ML180UHE Model No.
045(X)E36A
070(X)E36B
090(X)E48B
090E60C
110(X)E60C
135E60D
3/4
(19) in.
14-1/2
17-1/2
21
24-1/2
A mm
368
446
533
622
3 − 1/4
(83) in.
13-3/8
16-3/8
19-7/8
23-3/8
B mm
340
416
504
546
9/16
(14)
23
(584)
1 Side Return
Air Opening
(Either Side)
14
(356)
1 − 15/16 (49)
23 − 1/2
1 Bottom Return
Air Opening
SIDE VIEW
1 − 1/2 in.
13
16
19-1/2
23
C mm
330
406
495
584 in.
4-3/4
6-1/4
8
9-3/4
D mm
121
159
203
248
Page 2
ML180UHE Gas Furnace
The ML180UHE unit is shipped ready for installation in the upflow or horizontal right position (for horizontal left posi tion the combustion air pressure switch must be moved) fueled by natural gas. A conversion kit (ordered separate ly) is required for use in LP/Propane gas applications. The furnace is shipped with the bottom panel in place. The bot tom panel must be removed if the unit is to be installed in a horizontal application. The panel may also be removed in upflow applications.
Shipping and Packing List
Package 1 of 1 contains
1 - Assembled ML180UHE unit
1 - Bag assembly containing the following:
2 - Screws
1 - Snap bushing
1 - Snap plug
1 - Wire tie
1 - Vent warning label
1 - Owner's manual and warranty card
The following items may be ordered separately:
1 - Thermostat
1 - Suspension kit (for horizontal installations)
1 - LP/Propane changeover kit
1 - Return air base
1 - High altitude kit
1 - Side filter kit
Check equipment for shipping damage. If you find any damage, immediately contact the last carrier.
Safety Information
DANGER
Danger of explosion.
There are circumstances in which odorant used with
LP/propane gas can lose its scent. In case of a leak,
LP/propane gas will settle close to the floor and may be difficult to smell. An LP/propane leak detector should be installed in all LP applications.
WARNING
Improper installation, adjustment, alteration, service or maintenance can cause property damage, person al injury or loss of life. Installation and service must be performed by a licensed professional installer (or equivalent), service agency or the gas supplier.
CAUTION
As with any mechanical equipment, personal injury can result from contact with sharp sheet metal edges. Be careful when you handle this equipment.
Certifications
ML180UHE units are CSA International certified to ANSI
Z21.47.
In the USA, installation of gas furnaces must conform with local building codes. In the absence of local codes, units must be installed according to the current National Fuel
Gas Code (ANSI‐Z223.1). The National Fuel Gas Code is available from the following address:
American National Standards Institute, Inc.
11 West 42nd Street
New York, NY 10036
Clearances
Adequate clearance must be made around the air open ings into the vestibule area. In order to ensure proper unit operation, combustion and ventilation air supply must be provided according to the current National Fuel Gas Code.
Vent installations must be consistent with the National Fuel
Gas Code venting tables (in this instruction) and applicable provisions of local building codes.
This furnace is CSA International certified for installation clearances to combustible material as listed on the unit
nameplate and in the tables in figures 7 and 11. Accessibility
and service clearances must take precedence over fire protection clearances.
NOTE - For installation on combustible floors, the furnace shall not be installed directly on carpeting, tile, or other combustible material other than wood flooring.
Installed Locations
For installation in a residential garage, the furnace must be installed so that the burner(s) and the ignition source are located no less than 18 inches (457 mm) above the floor. The furnace must be located or protected to avoid physical damage by vehicles. When a furnace is installed in a public garage, hangar, or other building that has a haz ardous atmosphere, the furnace must be installed accord ing to recommended good practice requirements and cur rent National Fuel Gas Code.
Temperature Rise
NOTE - Furnace must be adjusted to obtain a temperature rise within the range specified on the unit nameplate. Failure to do so may cause erratic limit operation and may result in premature heat exchanger failure.
This ML180UHE furnace must be installed so that its elec trical components are protected from water.
Page 3
Installed in Combination with a Cooling Coil
When this furnace is used with cooling units, it shall be installed in parallel with, or on the upstream side of, cooling units to avoid condensation in the heating compartment.
See figure 1. With a parallel flow arrangement, a damper (or
other means to control the flow of air) must adequately pre vent chilled air from entering the furnace. If the damper is manually operated, it must be equipped to prevent operation of either the heating or the cooling unit, unless it is in the full
HEAT or COOL
Heating Unit Installed Parallel to Cooling Coil
Dampers
(open during heating operation only)
Gas Unit
Cooling Coil
Dampers
(open during cooling operation only)
Heating Unit Installed Upstream of Cooling Coil
Gas Unit
Cooling Coil
FIGURE 1
When installed, this furnace must be electrically grounded according to local codes. In addition, in the United States, installation must conform with the current National Elec tric Code, ANSI/NFPA No. 70. The National Electric Code
(ANSI/NFPA No. 70) is available from the following ad dress:
National Fire Protection Association
1 Battery March Park
Quincy, MA 02269
NOTE - This furnace is designed for a minimum continu ous return air temperature of 60°F (16°C) or an intermit tent operation down to 55°F (13°C) dry bulb for cases where a night setback thermostat is used. Return air tem perature must not exceed 85°F (29°C) dry bulb.
The ML180UHE furnace may be installed in alcoves, clos ets, attics, basements, garages, crawl spaces and utility rooms in the upflow or horizontal position.
This furnace design has not been CSA International certified for installation in mobile homes, recreational vehicles, or outdoors.
Use of Furnace as Construction Heater
Lennox does not recommend the use of ML180UHE units as a construction heater during any phase of construction.
Very low return air temperatures, harmful vapors and op eration of the unit with clogged or misplaced filters will dam age the unit.
ML180UHE units may be used for heating of buildings or structures under construction, if the following conditions are met:
D The vent system must be permanently installed per these installation instructions.
D A room thermostat must control the furnace. The use of fixed jumpers that will provide continuous heating is not allowed.
D The return air duct must be provided and sealed to the furnace.
D Return air temperature range between 60°F (16°C) and
80°F (27°C) must be maintained.
D Air filters must be installed in the system and must be maintained during construction.
D Air filters must be replaced upon construction comple tion.
D The input rate and temperature rise must be set per the furnace rating plate.
D One hundred percent (100%) outdoor air must be pro vided for combustion air requirements during construc tion. Temporary ducting may supply outdoor air to the furnace. Do not connect duct directly to the furnace.
Size the temporary duct following these instructions in section for Combustion, Dilution and Ventilation Air in a confined space with air from outside.
D The furnace heat exchanger, components, duct system, air filters and evaporator coils must be thoroughly cleaned following final construction clean-up.
D All furnace operating conditions (including ignition, in put rate, temperature rise and venting) must be verified according to these installation instructions.
General
These instructions are intended as a general guide and do not supersede local codes in any way. Consult authorities having jurisdiction before installation.
In addition to the requirements outlined previously, the fol lowing general recommendations must be considered when installing a ML180UHE furnace:
Place the furnace as close to the center of the air dis tribution system as possible. The furnace should also be located close to the chimney or vent termination point.
Page 4
Do not install the furnace where drafts might blow direct ly into it. This could cause improper combustion and un safe operation.
Do not block the furnace combustion air openings with clothing, boxes, doors, etc. Air is needed for proper combustion and safe unit operation.
When the furnace is installed in an attic or other insu lated space, keep insulation away from the furnace.
NOTE - The Commonwealth of Massachusetts stipu lates these additional requirements:
D Gas furnaces shall be installed by a licensed plumb er or fitter only.
D The gas cock must be “T handle” type.
D When a furnace is installed in an attic, the passage way to and service area surrounding the equipment shall be floored.
WARNING
This product contains a chemical known to the State of California to cause cancer, birth defects, or other reproductive harm.
Combustion, Dilution & Ventilation Air
In the past, there was no problem in bringing in sufficient out door air for combustion. Infiltration provided all the air that was needed. In today's homes, tight construction practices make it necessary to bring in air from outside for combus tion. Take into account that exhaust fans, appliance vents, chimneys, and fireplaces force additional air that could be used for combustion out of the house. Unless outside air is brought into the house for combustion, negative pressure
(outside pressure is greater than inside pressure) will build to the point that a downdraft can occur in the furnace vent pipe or chimney. As a result, combustion gases enter the liv ing space creating a potentially dangerous situation.
In the absence of local codes concerning air for combus tion and ventilation, use the guidelines and procedures in this section to install ML180UHE furnaces to ensure effi cient and safe operation. You must consider combustion air needs and requirements for exhaust vents. A portion of this information has been reprinted with permission from the
National Fuel Gas Code (ANSI‐Z223.1). This reprinted ma terial is not the complete and official position of the ANSI on the referenced subject, which is represented only by the standard in its entirety.
CAUTION
Do not install the furnace in a corrosive or contami nated atmosphere. Meet all combustion and ventila tion air requirements, as well as all local codes.
CAUTION
Insufficient combustion air can cause headaches, nausea, dizziness or asphyxiation. It will also cause excess water in the heat exchanger resulting in rust ing and premature heat exchanger failure. Excessive exposure to contaminated combustion air will result in safety and performance related problems. Avoid exposure to the following substances in the combus tion air supply:
Permanent wave solutions
Chlorinated waxes and cleaners
Chlorine base swimming pool chemicals
Water softening chemicals
De‐icing salts or chemicals
Carbon tetrachloride
Halogen type refrigerants
Cleaning solvents (such as perchloroethylene)
Printing inks, paint removers, varnishes, etc.
Hydrochloric acid
Cements and glues
Antistatic fabric softeners for clothes dryers
Masonry acid washing materials
All gas‐fired appliances require air for the combustion pro cess. If sufficient combustion air is not available, the fur nace or other appliances will operate inefficiently and un safely. Enough air must be provided to meet the needs of all fuel‐burning appliances and appliances such as exhaust fans which force air out of the house. When fireplaces, ex haust fans, or clothes dryers are used at the same time as the furnace, much more air is necessary to ensure proper combustion and to prevent a downdraft. Insufficient air causes incomplete combustion which can result in carbon monoxide.
In addition to providing combustion air, fresh outdoor air dilutes contaminants in the indoor air. These contami nants may include bleaches, adhesives, detergents, sol vents and other contaminants which can corrode furnace components.
The requirements for providing air for combustion and ven tilation depend largely on whether the furnace is installed in an unconfined or a confined space.
Unconfined Space
An unconfined space is an area such as a basement or large equipment room with a volume greater than 50 cubic feet (1.42 m 3 ) per 1,000 Btu (.29 kW) per hour of the com bined input rating of all appliances installed in that space.
This space also includes adjacent rooms which are not separated by a door. Though an area may appear to be un confined, it might be necessary to bring in outdoor air for combustion if the structure does not provide enough air by infiltration. If the furnace is located in a building of tight construction with weather stripping and caulking around the windows and doors, follow the procedures in the air from outside section.
Page 5
Confined Space
A confined space is an area with a volume less than 50 cu bic feet (1.42 m
3
) per 1,000 Btu (.29 kW) per hour of the combined input rating of all appliances installed in that space. This definition includes furnace closets or small equipment rooms.
When the furnace is installed so that supply ducts carry air circulated by the furnace to areas outside the space contain ing the furnace, the return air must be handled by ducts which are sealed to the furnace casing and which terminate outside the space containing the furnace. This is especially important when the furnace is mounted on a platform in a confined space such as a closet or small equipment room.
Even a small leak around the base of the unit at the platform or at the return air duct connection can cause a potentially dangerous negative pressure condition. Air for combustion and ventilation can be brought into the confined space either from inside the building or from outside.
EQUIPMENT IN CONFINED
SPACE ALL AIR FROM INSIDE
CHIMNEY
OR GAS
VENT
FURNACE
WATER
HEATER
NOTE - Each opening shall have a free area of at least one square inch (645 mm 2 ) per 1,000 Btu (.29 kW) per hour of the total input rat ing of all equipment in the enclosure, but not less than 100 square inches (64516 mm 2 ).
FIGURE 2
OPENINGS
(To Adjacent
Room)
Air from Inside
If the confined space that houses the furnace adjoins a space categorized as unconfined, air can be brought in by providing two permanent openings between the two spaces. Each opening must have a minimum free area of 1 square inch (645 mm
2
) per 1,000 Btu (.29 kW) per hour of total input rating of all gas-fired equipment in the confined space. Each opening must be at least 100 square inches
(64516 mm
2
). One opening shall be within 12 inches (305 mm) of the top of the enclosure and one opening within 12
inches (305 mm) of the bottom. See figure 2.
Air from Outside
If air from outside is brought in for combustion and ventila tion, the confined space must have two permanent open ings. One opening shall be within 12 inches (305 mm) of the top of the enclosure and one opening within 12 inches (305 mm) of the bottom. These openings must communicate di rectly or by ducts with the outdoors or spaces (crawl or at tic) that freely communicate with the outdoors or indirectly through vertical ducts. Each opening shall have a minimum free area of 1 square inch (645 mm 2 ) per 4,000 Btu (1.17
kW) per hour of total input rating of all equipment in the en closure. See
figures 3 and 4. When communicating with
the outdoors through horizontal ducts, each opening shall have a minimum free area of 1 square inch (645 mm
2
) per
2,000 Btu (.56 kW) per total input rating of all equipment in the enclosure. See
When ducts are used, they shall be of the same cross-sec tional area as the free area of the openings to which they connect. The minimum dimension of rectangular air ducts shall be no less than 3 inches (75 mm). In calculating free area, the blocking effect of louvers, grilles, or screens must be considered. If the design and free area of protective cov ering is not known for calculating the size opening required, it may be assumed that wood louvers will have 20 to 25 per cent free area and metal louvers and grilles will have 60 to
75 percent free area. Louvers and grilles must be fixed in the open position or interlocked with the equipment so that they are opened automatically during equipment operation.
Page 6
EQUIPMENT IN CONFINED SPACE
ALL AIR FROM OUTSIDE
(Inlet Air from Crawlspace and Outlet Air to Ventilated Attic)
CHIMNEY OR
GAS VENT
FURNACE
VENTILATION
LOUVERS
(For unheated crawl space)
VENTILATION LOUVERS
(Each end of attic)
OUTLET
AIR WATER
HEATER
INLET
AIR
CHIMNEY
OR GAS
VENT
NOTE-The inlet and outlet air openings shall each have a free area of at least one square inch (645 mm 2 ) per 4,000 Btu (1.17 kW) per hour of the total input rating of all equipment in the enclosure.
FIGURE 3
EQUIPMENT IN CONFINED SPACE
ALL AIR FROM OUTSIDE
(All Air Through Ventilated Attic)
VENTILATION LOUVERS
(Each end of attic)
OUTLET
AIR
CHIMNEY
OR GAS
VENT
FURNACE
FURNACE
INLET AIR
(Ends 12 in.
above bottom)
WATER
HEATER
EQUIPMENT IN
CONFINED SPACE
ALL AIR FROM
OUTSIDE
OUTLET AIR
INLET AIR
WATER
HEATER
NOTE-The inlet and outlet air openings shall each have a free area of at least one square inch (645 mm 2 ) per 4,000
Btu (1.17 kW) per hour of the total input rating of all equip ment in the enclosure.
FIGURE 4
NOTE - Each air duct opening shall have a free area of at least one square inch (645 mm 2 ) per 2,000 Btu (.59 kW) per hour of the total input rating of all equipment in the enclosure. If the equipment room is located against an outside wall and the air openings communi cate directly with the outdoors, each opening shall have a free area of at least one square inch (645 mm 2 ) per 4,000 Btu (1.17 kW) per hour of the total input rating of all other equipment in the enclosure.
FIGURE 5
Page 7
Setting Equipment
WARNING
Do not install the furnace on its front or its back. Do not connect the return air ducts to the back of the fur nace. Doing so will adversely affect the operation of the safety control devices, which could result in per sonal injury or death.
The ML180UHE gas furnace can be installed as shipped in either the upflow position or the horizontal position.
Select a location that allows for the required clearances that are listed on the unit nameplate. Also consider gas supply connections, electrical supply, vent connection, and installation and service clearances [24 inches (610 mm) at unit front]. The unit must be level.
NOTE Units with 1/2 or 3/4 hp blower motors are equipped
with three flexible legs and one rigid leg. See figure 6. The
rigid leg is equipped with a shipping bolt and a flat white plastic washer (rather than the rubber mounting grommet used with a flexible mounting leg). The bolt and washer must be removed before the furnace is placed into op eration.
After the bolt and washer have been removed, the rigid leg will not touch the blower housing.
Units with 1/2 or 3/4 HP Blower Motor
RIGID LEG remove shipping bolt and washer
FIGURE 6
Upflow Applications
Allow for clearances to combustible materials as indicated on the unit nameplate. Minimum clearances for closet or al
cove installations are shown in figure 7.
Upflow Application Installation Clearances
Top
Left Side Right Side
Bottom
Type of Vent
Connector
Type C Type B1
Top
*Front
Back
Sides
1 in. (25 mm)
2-1/4 in. (57 mm)**
0
0 †
1 in. (25 mm)
2-1/4 in. (57 mm)
0
0
Vent
Floor
6 in. (152 mm)
0 ‡
1 in. (25 mm)
0 ‡
*Front clearance in alcove installation must be 24 in. (610 mm).
Maintain a minimum of 24 in. (610 mm) for front service access.
** 4-1/2” if single wall vent pipe is used.
‡ For installation on a combustible floor, do not install the furnace directly on carpeting, tile or other combustible materials other than wood flooring.
† Left side requires 3 inches if a single wall vent is used on 14-1/2 inch cabinets, or 2 inches if a single wall vent pipe is used on
17-1/2 inch cabinets.
FIGURE 7
Page 8
Return Air -- Upflow Applications
Return air can be brought in through the bottom or either side of the furnace installed in an upflow application. If the furnace is installed on a platform with bottom return, make an airtight seal between the bottom of the furnace and the platform to ensure that the furnace operates properly and safely. The furnace is equipped with a removable bottom panel to facilitate installation.
Markings are provided on both sides of the furnace cabinet for installations that require side return air. Cut the furnace cabinet at the maximum dimensions shown on page 2.
NOTE - 60C and 60D units that require air volumes over 1800 cfm (850 L/s) must have one of the following:
1 - Single side return air with transition to accommodate 20 x 25 x 1 in. (508 x 635 x 25 mm) cleanable air filter. (Re
quired to maintain proper air velocity.) See figure 8.
2 - Single side return air with optional return airbase. See fig
3 - Bottom return air.
4 - Return air from both sides.
5 - Bottom and one side return air.
Refer to Engineering Handbook for additional information.
Single Side Return Air
(with transition and filter)
AIR FLOW
20” X 25” X 1”
(508mm X 635mm X 25mm)
Cleanable Filter
Return Air
Transition
Plenum
FIGURE 8
Optional Return Air Base
(Upflow Applications Only -- For use with A, B, C and D cabinets)
FURNACE
FRONT
AIR FLOW
INDOOR AIR
QUALITY
CABINET
(PCO, Filter
Cabinet, etc.)
IF BASE
IS USED
WITHOUT
IAQ CABINET,
A SINGLE
RETURN AIR
PLENUM
MUST
COVER BOTH
UNIT AND
RETURN
AIR BASE
OPENINGS
3 − 1/4
(83)
1 23 (584)
Overall
(Maximum)
1 Unit side return air
Opening
1
Minimum
11 (279)
2 Maximum
14 (356)
1 22 − 7/16
(570)
Overall
(Maximum)
7 − 1/4
(184)
5 − 5/8
(143)
SIDE RETURN
AIR OPENINGS
(Either Side)
14 − 1/2 (368) A Width (65W75)
17 − 1/2 (446) B Width (50W98)
21 (533) C Width (50W99)
24 − 1/2 (622) D Width (51W00)
OPTIONAL
RETURN
AIR BASE
23
(584)
26 − 7/8
(683)
SIDE VIEW
3/4
(19)
NOTE- Optional Side Return Air Filter Kits are not for use with Optional Return Air Base.
1 Both the unit return air opening and the base return air opening must be covered by a single plenum or IAQ cabinet.
Minimum unit side return air opening dimensions for units requiring 1800 cfm or more of air (W x H): 23 x 11 in. (584 x 279 mm).
The opening can be cut as needed to accommodate plenum or IAQ cabinet while maintaining dimensions shown.
Side return air openings must be cut in the field. There are cutting guides stenciled on the cabinet for the side return air opening. The size of the opening must not extend beyond the markings on the furnace cabinet.
2 To minimize pressure drop, the largest opening height possible (up to 14 inches 356 mm) is preferred.
FIGURE 9
Page 9
Removing the Bottom Panel
Remove the two screws that secure the bottom cap to the furnace. Pivot the bottom cap down to release the bottom panel. Once the bottom panel has been removed, reinstall
the bottom cap. See figure 10.
Removing the Bottom Panel
Horizontal Applications
The ML180UHE furnace can be installed in horizontal ap plications. Order horizontal suspension kit (51W10) from
Lennox, or use equivalent suspension method.
Allow for clearances to combustible materials as indicated on the unit nameplate. Minimum clearances for closet or al cove installations are shown in
This furnace may be installed in either an attic or a crawl space. Either suspend the furnace from roof rafters or
floor joists, as shown in figure 12, or install the furnace on
a platform, as shown in figure 13.
Typical Horizontal Application
Unit Suspended in Attic or Crawlspace
Metal
Strap
Bracket
3/16”
Screw
Air
Flow
Bottom Panel
FIGURE 10
Horizontal Application
Installation Clearances
Top
Bottom Cap
Left
End
Right
End
Bottom
Vent Connector
Type
Type C Type B1
Top
*Front
Back
Ends
0
2-1/4 in. (57 mm)**
0
2 in. (51 mm)
0
2-1/4 in. (57 mm)
0
2 in. (51 mm)
Vent
Floor
6 in. (152 mm)
0 ‡
1 in. (25 mm)
0 ‡
*Front clearance in alcove installation must be 24 in. (610 mm).
Maintain a minimum of 24 in. (610 mm) for front service access.
** 4-1/2 in. if single wall vent pipe is used.
‡ For installations on a combustible floor, do not install the furnace directly on carpeting, tile or other combustible materials other than wood flooring.
FIGURE 11
FIGURE 12
NOTE - Heavy-gauge perforated sheet metal straps may be used to suspend the unit from roof rafters or ceiling joists. When straps are used to suspend the unit in this way, support must be provided for both the ends. The straps must not interfere with the plenum or exhaust pip ing installation. Cooling coils and supply and return air plenums must be supported separately.
NOTE - When the furnace is installed on a platform in a crawlspace, it must be elevated enough to avoid water damage and to allow the evaporator coil to drain.
Return Air -- Horizontal Applications
Return air must be brought in through the end of a furnace installed in a horizontal application. The furnace is equipped with a removable bottom panel to facilitate
Page 10
CAUTION
If this unit is being installed in a space serviced by an exhaust fan, power exhaust fan, or other device which may create a negative pressure in the space, take care when sizing the inlet air opening. The in let air opening must be sized to accommodate the maximum volume of exhausted air as well as the maximum volume of combustion air required for all gas appliances serviced by this space.
Horizontal Application
Unit Installed on Platform
Line contact is permissible but not preferred
See the unit nameplate for
GAS
ENTRY VENT
PIPE
SERVICE PLATFORM
FIGURE 13
WARNING
Improper installation of the furnace can result in per sonal injury or death. Combustion and flue products must never be allowed to enter the return air system or the living space. Use screws and joint tape to seal the return air system to the furnace.
In platform installations with bottom return air, the furnace should be sealed airtight to the return air ple num. A door must never be used as a portion of the return air duct system. The base must provide a stable support and an airtight seal to the furnace. Al low absolutely no sagging, cracks, gaps, etc.
The return and supply air duct systems must never be connected to or from other heating devices such as a fireplace or stove, etc. Fire, explosion, carbon monoxide poisoning, personal injury and/or proper ty damage could result.
WARNING
The blower access panel must be securely in place when the blower and burners are operating. Gas fumes, which could contain carbon monoxide, can be drawn into living space resulting in personal inju ry or death.
Filters
This unit is not equipped with a filter or rack. A field-pro vided high-velocity filter is required for the unit to operate
properly. Table 1 lists recommended filter sizes. A filter
must be in place any time the unit is operating.
TABLE 1
Furnace
Cabinet Width
A - 14-1/2”
B - 17-1/2”
C - 21”
D - 24-1/2”
Side Return
Filter Size
Bottom Return
16 X 25 X 1 (1)
16 X 25 X 1 (1)
16 X 25 X 1 (1)
16 X 25 X 1 (2)
14 X 25 X 1 (1)
16 X 25 X 1 (1)
20 X 25 X 1 (1)
24 X 25 X 1 (1)
IMPORTANT
If a highefficiency filter is being installed as part of this system to ensure better indoor air quality, the fil ter must be properly sized. Highefficiency filters have a higher static pressure drop than standardef ficiency glass/foam filters. If the pressure drop is too great, system capacity and performance may be re duced. The pressure drop may also cause the limit to trip more frequently during the winter and the indoor coil to freeze in the summer, resulting in an increase in the number of service calls.
Before using any filter with this system, check the specifications provided by the filter manufacturer against the data given in the appropriate Lennox
Product Specifications bulletin. Additional informa tion is provided in Service and Application Note
ACC002 (August 2000).
Page 11
Duct System
Use industry‐approved standards (such as those pub lished by Air Conditioning Contractors of America or Ameri can Society of Heating, Refrigerating and Air Conditioning
Engineers) to size and install the supply and return air duct system. This will result in a quiet and low‐static system that has uniform air distribution.
NOTE Do not operate the furnace in the heating mode with an external static pressure that exceeds 0.5 inches w.c. Higher external static pressures may cause erratic lim it operation.
Supply Air Plenum
If the furnace is installed without a cooling coil, a removable access panel must be installed in the supply air duct. The access panel should be large enough to permit inspection
(either by smoke or reflected light) of the heat exchanger for leaks after the furnace is installed. The furnace access panel must always be in place when the furnace is operat ing and it must not allow leaks into the supply air duct sys tem.
Return Air Plenum
NOTE - Return air must not be drawn from a room where this furnace, or any other gas-fueled appliance
(i.e., water heater), or carbon monoxide producing de vice (i.e., wood fireplace) is installed.
When return air is drawn from a room, a negative pres sure is created in the room. If a gas appliance is operating in a room with negative pressure, the flue products can be pulled back down the vent pipe and into the room. This reverse flow of the flue gas may result in incomplete com bustion and the formation of carbon monoxide gas. This toxic gas might then be distributed throughout the house by the furnace duct system.
In upflow applications, the return air can be brought in through the bottom or either side of the furnace. If a fur nace with bottom return air is installed on a platform, make an airtight seal between the bottom of the furnace and the platform to ensure that the unit operates properly and safely. Use fiberglass sealing strips, caulking, or equiva lent sealing method between the plenum and the furnace cabinet to ensure a tight seal. If a filter is installed, size the return air duct to fit the filter frame.
Page 12
Venting
A 4-inch diameter flue transition is factory‐installed on the combustion air inducer outlet of all models.
shows the combustion air inducer as shipped from the factory.
Flue Transition
Mounting Screws Location
Mounting Screws
1 - Remove the four mounting screws (figure 14) which
secure the combustion air inducer / pressure switch assembly to the orifice plate. Lift the assembly and ro tate it 90 degrees clockwise or counterclockwise to ei ther the 3 o'clock position or to 9 o'clock position. Resecure with four screws. Gasket should be left in place.
2 - Use tin snips to cut preferred opening on the cabinet for repositioning the flue outlet. Use the cut-out piece as a cover plate to patch unused opening on cabinet.
UPFLOW POSITION
Cover Plate
Left Side Vent Discharge
Collector Box
Pressure
Switch Make-Up
Box
Vent Pipe
FIGURE 14
Pressure
Switch
UPFLOW POSITION
Flue
Transition
Top Vent Discharge
Vent Pipe
Collector Box
Make-Up
Box
AIR FLOW
FIGURE 15
IMPORTANT
The unit will not vent properly with the flue transition pointed down in the 6 o'clock position.
The combustion air inducer may be rotated clock wise or counterclockwise by 90° to allow for top or side vent discharge in all applications. When the unit is installed, the flue transition must be in the 9 o'clock, 12 o'clock or 3 o'clock position.
If necessary, reposition the combustion air inducer, pres sure switch and/or make-up box as needed per the follow
ing steps. See figures 16 through 20.
Flue
Transition
AIR
FLOW
Gas supply piping must be brought into the unit from the right side in order to accommodate the flue pipe.
Cut Combustion air inducer tubing from 9” to 8” to avoid inter ference with inducer motor
Remove make-up box assembly (2 screws) and cut wire tie to free make-up box wires. Re-install make-up box on other side of cabinet.
Re-secure make-up box wires: Either pull excess wires through the blower compartment and secure using supplied wire tie, or coil excess wire and secure to the gas manifold.
FIGURE 16
Collector Box
UPFLOW POSITION
Right Side Vent Discharge
Cover Plate Flue Transition
Vent Pipe
Pressure
Switch
Make-Up
Box
AIR
FLOW
Cut combustion air inducer tubing from 9” to 5” to avoid interference with inducer motor
FIGURE 17
Page 13
Vent Pipe
Pressure
Switch
Flue
Transition
HORIZONTAL LEFT POSITION
Top Vent Discharge
AIR
FLOW
Vent Pipe
HORIZONTAL RIGHT POSITION
Top Vent Discharge
Pressure Switch
Flue
Transition
Cover Plate
AIR
FLOW Collector Box
Cover Plate
Make-Up Box Collector Box
Disconnect pressure switch hose from barbed fitting on the pressure switch assembly. Remove pressure switch assembly
(1 screw) and cut wire tie to free pressure switch wires. Reinstall pressure switch on the other side of orifice plate and reconnect pressure switch hose.
Re-secure pressure switch wires: Either pull excess wires through the blower compartment and secure using supplied wire tie, or coil excess wire and secure to the gas manifold.
FIGURE 18
HORIZONTAL LEFT POSITION
Side Vent Discharge
Pressure Switch
Gas supply piping must be brought into the unit from the bot tom in order to accommodate the flue pipe.
Cut combustion air inducer tubing from 9” to 8” to avoid inter ference with inducer motor
Remove make-up box assembly (2 screws) and cut wire tie to free make-up box wires. Re-install make-up box on other side of cabinet.
Re-secure make-up box wires: Either pull excess wires through the blower compartment and secure using supplied wire tie, or coil excess wire and secure to the gas manifold.
FIGURE 20
Make-Up Box
Vent Pipe
Make-Up Box
Collector Box
Cut combustion air inducer tubing from 9” to 7” to avoid inter ference with inducer motor
Disconnect pressure switch hose from barbed fitting on the pressure switch assembly. Remove pressure switch assembly
(1 screw) and cut wire tie to free pressure switch wires. Reinstall pressure switch on the other side of orifice plate and reconnect pressure switch hose.
Re-secure pressure switch wires: Either pull excess wires through the blower compartment and secure using supplied wire tie, or coil excess wire and secure to the gas manifold.
FIGURE 19
AIR
FLOW
HORIZONTAL RIGHT POSITION
Side Vent Discharge - no modifications necessary
Make-Up Box
Pressure Switch
Vent Pipe
AIR
FLOW
Flue Transition
FIGURE 21
Collector Box
Page 14
The ML180UHE series units are classified as fan-assisted
Category I furnaces when vertically vented according to the latest edition of National Fuel Gas Code (NFPA 54 /
ANSI Z223.1) in the USA. A fan-assisted Category I fur nace is an appliance equipped with an integral mechanical means to either draw or force combustion products through the combustion chamber and/or heat exchanger. The
ML180UHE is not approved for use with horizontal venting.
NOTE - Use these instructions as a guide. They do not su persede local codes. This furnace must be vented accord ing to all local codes these installation instructions, and the provided venting tables in these instructions
The venting tables in this manual were extracted from the
National Fuel Gas Code (NFPA 54 / ANSI Z223.1) and are provided as a guide for proper vent installation. Proper ap plication, termination, construction and location of vents must conform to local codes having jurisdiction. In the ab sence of local codes, the NFGC serves as the defining doc ument.
Use self-drilling sheet metal screws or a mechanical fas tener to firmly secure the vent pipe to the round collar of the flue transition. If self-drilling screws are used to attach the vent pipe, it is recommended that three be used. Drive one self-drilling screw through the front and one through each
side of the vent pipe and collar. See figure 22.
Install the first vent connector elbow at a minimum of six inches (152 mm) from the furnace vent outlet. See figure
Venting Using a Masonry Chimney
The following additional requirements apply when a lined masonry chimney is used to vent this furnace.
Masonry chimneys used to vent Category I central fur naces must be either tile‐lined or lined with a listed metal lining system or dedicated gas vent. Unlined masonry
chimneys are prohibited. See figures 23 and 24 for com
mon venting.
A chimney with one or more sides exposed to the outside of the structure is considered to be an exterior chimney.
An exterior masonry chimney that is not tile-lined must be lined with B1 vent or a listed insulated flexible metal vent.
An exterior tile-lined chimney that is sealed and capped may be lined with a listed uninsulated flexible metal vent.
If the existing chimney will not accommodate a listed metal liner, either the chimney must be rebuilt to accommodate one of these liners or an alternate approved venting meth od must be found.
Insulation for the flexible vent pipe must be an encapsu lated fiberglass sleeve recommended by the flexible vent
pipe manufacturer. See figure 23.
Refer to the tables and the venting information contained in these instructions to properly size and install the venting system.
IMPORTANT
Once the venting system is installed, attach the “Dis connected Vent” warning sticker to a visible area of
the plenum near the vent pipe. See figure 22. The
warning sticker is provided in the bag assembly. Or der kit 66W04 for additional stickers.
WARNING
Asphyxiation hazard. The exhaust vent for this fur nace must be securely connected to the furnace flue transition at all times.
VENT CONNECTION UPFLOW AND HORIZONTAL POSITION
“DISCONNECTED VENT”
WARNING
STICKER
VENT PIPE
(min. 6” length)
“DISCONNECTED VENT”
WARNING
STICKER
FLUE TRANSITION
COLLAR
VENT PIPE
(min. 6” length)
FLUE
TRANSITION
COLLAR
FIGURE 22
Page 15
Common Venting Using Metal-Lined Masonry Chimney
SEALED
5 ft. (1.5 m) minimum
MAX. LENGTH
-- SEE NOTE 1
BELOW.
MIN. LENGTH -- AS
SHORT AS PRACTICAL
EXTERIOR
CHIMNEY WITH
METAL
LINER
VENT CONNECTOR
4 in. (102 mm) minimum
FURNACE
OTHER
APPLIANCE
PERMANENTLY
SEALED FIREPLACE
OPENING
NOTE 1 - Refer to the provided venting tables for installations. Refer to the capacity requirements shown in the provided venting tables.
FIGURE 23
DO NOT insulate the space between the liner and the chimney wall with puffed mica or any other loose gran ular insulating material.
IMPORTANT
SINGLE appliance venting of a fan‐assisted furnace into a tile‐lined masonry chimney (interior or outside wall) is PROHIBITED. The chimney must first be lined with either type B1 vent or an insulated single wall flexible vent lining system which has been sized ac cording to the provided venting tables and the vent pipe manufacturer's instructions.
A fan-assisted furnace may be commonly vented into an existing lined masonry chimney if the following conditions are met:
The chimney is currently serving at least one drafthoodequipped appliance;
The vent connectors and chimney are sized according to the provided venting tables.
If type B1 double‐wall vent is used inside a chimney, no oth er appliance can be vented into the chimney. The outer wall of type B1 vent pipe must not be exposed to flue products.
A type B1 vent or masonry chimney liner shall terminate above the roof surface with a listed cap or a listed roof as sembly according to the terms of their respective listings and the vent manufacturer's instructions.
When inspection reveals that an existing chimney is not safe for the intended purpose, it shall be rebuilt to conform to nationally recognized standards, lined or relined with suitable materials, or replaced with a gas vent or chimney suitable for venting ML180UHE series units. The chimney passageway must be checked periodically to ensure that it is clear and free of obstructions.
Do not install a manual damper, barometric draft regulator, or flue restrictor between the furnace and the chimney.
Never connect a Category I appliance to a chimney that is servicing a solid-fuel appliance. If a fireplace chimney flue is used to vent this appliance, the fireplace opening must be permanently sealed.
A type B or listed chimney lining system that passes through an unused masonry chimney flue is not considered to be exposed to the outdoors.
General Venting Requirements
Vent all ML180UHE furnaces according to these instruc tions:
1 - Vent diameter recommendations and maximum allow able piping runs are found in the provided venting tables.
2 - In no case should the vent or vent connector diameter be less than the diameter specified in the provided venting tables.
3 - The minimum vent capacity determined by the sizing tables must be less than the low fire input rating and the maximum vent capacity must be greater than the high fire input rating.
4 Single appliance vents If the vertical vent or tile‐lined chimney has a larger diameter or flow area than the vent connector, use the vertical vent diameter to de termine the minimum vent capacity and the vent connector diameter to determine the maximum vent capacity . The flow area of the vertical vent, however, shall not exceed 7 times the flow area of the listed ap pliance categorized vent area, drafthood outlet area or flue collar area unless designed according to approved engineering methods.
5 Multiple appliance vents The flow area of the largest section of vertical vent or chimney shall not exceed 7 times the smallest listed appliance categorized vent area, drafthood outlet area or flue collar area unless de signed according to approved engineering methods.
Page 16
Common Venting Using Tile-Lined Interior Masonry Chimney and Combined Vent Connector
MINIMUM LENGTH = AS SHORT AS PRACTICAL.
FOR MAXIMUM LENGTH SEE NOTE TO LEFT
INTERIOR TILE-LINED
MASONRY CHIMNEY
NOTE- Refer to provided venting tables for installations.
NOTE - the chimney must be properly sized per provided venting tables or lined with listed metal lining system.
VENT
CONNECTOR
OTHER
APPLIANCE
PERMANENTLY
SEALED FIREPLACE
OPENING
FURNACE
FIGURE 24
6 - The entire length of single wall metal vent connector shall be readily accessible for inspection, cleaning, and replacement.
7 - Single appliance venting configurations with zero lat
eral lengths (tables 3 and 4 are assumed to have no el
bows in the vent system. For all other vent configura tions, the vent system is assumed to have two 90° elbows. For each additional 90° elbow or equivalent
(for example two 45° elbows equal one 90° elbow) be yond two, the maximum capacity listed in the venting
1‐1/2 feet (.46 m) for each inch (25 mm) of common vent diameter.
10 - The vent pipe should be as short as possible with the least number of elbows and angles required to com plete the job. Route the vent connector to the vent us ing the shortest possible route.
11 - A vent connector shall be supported without any dips or sags and shall slope a minimum of 1/4 inch (6.4 mm) per linear foot (305 mm) of connector, back toward the appliance.
table should be reduced by 10% (0.90 x maximum listed capacity).
8 - The common venting tables (4 and 5) were generated
using a maximum horizontal vent connector length of
1-1/2 feet (.46 m) for each inch (25 mm) of connector diameter as follows:
TABLE 2
12 - Vent connectors shall be firmly attached to the furnace flue collar by self-drilling screws or other approved means, except vent connectors of listed type B vent material which shall be assembled according to the manufacturer's instructions. Joints between sections of single wall connector piping shall be fastened by screws or other approved means.
Connector Diameter inches (mm)
Maximum Horizontal
Connector Length feet (m)
13 - When the vent connector used for Category I ap pliances must be located in or pass through a crawl
3 (76) 4-1/2 (1.37) space, attic or other areas which may be cold, that por tion of the vent connector shall be constructed of listed
4 (102) 6 (1.83)
5 (127) 7-1/2 (2.29) double‐wall type B vent material or material having equivalent insulation qualities.
6 (152)
7 (178)
9 (2.74)
10-1/2 (3.20)
14 - All venting pipe passing through floors, walls, and ceil ings must be installed with the listed clearance to com
9 - If the common vertical vent is offset, the maximum common vent capacity listed in the common venting tables should be reduced by 20%, the equivalent of two
90° elbows (0.80 x maximum common vent capacity).
The horizontal length of the offset shall not exceed bustible materials and be fire stopped according to lo cal codes. In absence of local codes, refer to NFGC
(Z223.1).
15 - No portion of the venting system can extend into, or pass through any circulation air duct or plenum.
Page 17
16 - Vent connectors serving Category I appliances shall not be connected to any portion of mechanical draft systems operating under positive pressure such as
Category III or IV venting systems.
two consecutive table size diameters over the size of the draft hood outlet or flue collar outlet.
20 - Do not install a manual damper, barometric draft regu lator or flue restrictor between the furnace and the chimney.
17 - If vent connectors are combined prior to entering the common vent, the maximum common vent capacity listed in the common venting tables must be reduced by
10%, the equivalent of one 90° elbow (0.90 x maximum common vent capacity).
18 - The common vent diameter must always be at least as large as the largest vent connector diameter.
21 - When connecting this appliance to an existing dedi cated or common venting system, you must inspect the venting system's general condition and look for signs of corrosion. The existing vent pipe size must conform to these instructions and the provided venting tables. If the existing venting system does not meet these re quirements, it must be resized.
19 - In no case, shall the vent connector be sized more than
TABLE 3
Capacity of Type B Double-Wall Vents with Type B Double-Wall Connectors
Serving a Single Category I Appliance
Height
H
(feet)
Lateral
L
(feet)
MIN
3 Inch
MAX
Vent and Connector Diameter - D (inches)
4 Inch 5 Inch
Appliance Input Rating in Thousands of Btu Per Hour
MIN MAX MIN MAX MIN
6 Inch
MAX
6
8
10
15
20
30
171
164
295
194
187
176
327
251
157
153
149
276
178
242
229
217
206
374
226
219
206
195
349
250
283
275
262
249
237
214
42
51
0
23
41
54
0
0
27
39
47
0
25
38
50
59
69
0
20
39
51
61
0
18
14
36
48
57
66
88
103
98
175
118
113
104
191
152
97
94
91
165
109
143
133
124
116
213
136
130
121
112
202
149
166
160
150
141
132
113
32
39
0
17
32
41
0
0
18
30
36
0
16
29
38
46
55
0
15
30
40
48
0
14
13
28
37
44
53
73
53
49
88
61
57
51
94
78
51
49
46
84
57
71
64
58
52
100
69
65
59
53
97
75
81
77
70
64
58
NA
23
28
0
12
23
30
0
0
13
21
25
0
12
21
28
34
48
0
11
22
29
35
0
10
9
21
27
33
56
NA
0
2
5
8
5
10
0
4
6
0
2
0
2
5
10
15
20
0
2
5
10
15
0
2
2
5
10
15
20
30
NOTE - Single appliance venting configurations with zero lateral lengths are assumed to have no elbows in the vent system. For all other vent configurations, the vent system is assumed to have two 90° elbows. For each additional 90° elbow or equivalent (for example two 45° elbows equal one 90° elbow) beyond two, the maximum capacity listed in the venting table should be reduced by 10 percent (0.90 x maxi mum listed capacity).
53
64
0
26
52
67
0
0
32
50
59
0
28
47
62
73
84
0
22
49
64
76
0
20
18
45
59
70
80
104
255
247
447
289
280
267
502
375
232
227
223
415
263
367
351
337
322
587
339
330
315
301
540
377
432
421
405
389
374
346
Page 18
Vent
Height
H
(feet)
6
8
10
15
20
30
Vent
Height
H
(feet)
6
8
10
15
20
30
Connector
Rise
R
(feet)
1
2
3
2
3
1
2
3
1
2
2
3
3
1
1
2
3
1
TABLE 4
Vent Connector Capacity
Type B Double-Wall Vents with Type B Double-Wall Connectors
Serving Two or More Category I Appliances
MIN
22
24
21
22
23
20
21
22
23
24
22
23
24
21
22
23
24
22
3 Inch
MAX
53
55
54
57
60
62
64
66
44
47
43
47
50
50
37
41
44
40
Vent and Connector Diameter - D (inches)
4 Inch 5 Inch
Appliance Input Rating in Thousands of Btu Per Hour
MIN MAX MIN MAX
35
36
33
34
35
31
33
34
36
37
34
36
37
33
35
37
38
35
66
75
81
72
80
87
78
86
92
89
96
102
99
105
110
113
118
123
46
48
49
49
51
53
49
51
52
47
49
51
46
48
50
45
47
48
153
163
157
167
176
181
190
198
128
139
123
136
146
142
106
121
132
114
MIN
66
68
62
64
66
60
62
64
66
67
65
67
69
64
58
60
62
64
6 Inch
FAN + FAN
92
101
110
125
136
152
TABLE 5
Common Vent Capacity
Type B Double-Wall Vents with Type B Double-Wall Connectors
Serving Two or More Category I Appliances
4 Inch
FAN + NAT
81
90
97
112
123
138
Common Vent Diameter - D (inches)
5 Inch 6 Inch
Appliance Input Rating in Thousands of Btu Per Hour
FAN + FAN FAN + NAT FAN + FAN FAN + NAT
140
155
169
195
215
244
116
129
141
164
183
210
204
224
243
283
314
361
161
178
194
228
255
297
FAN + FAN
309
339
367
427
475
547
7 Inch
FAN + NAT
248
275
299
352
394
459
MAX
235
248
246
259
271
288
299
309
195
210
189
206
220
220
164
183
199
176
Page 19
Removal of the Furnace from Common Vent
In the event that an existing furnace is removed from a venting system commonly run with separate gas ap pliances, the venting system is likely to be too large to properly vent the remaining attached appliances.
Conduct the following test while each appliance is operat ing and the other appliances (which are not operating) re main connected to the common venting system. If the venting system has been installed improperly, you must correct the system as indicated in the general venting re quirements section.
WARNING
CARBON MONOXIDE POISONING HAZARD
Failure to follow the steps outlined below for each appliance connected to the venting system being placed into operation could result in carbon mon oxide poisoning or death.
The following steps shall be followed for each ap pliance connected to the venting system being placed into operation, while all other appliances connected to the venting system are not in operation:
1 - Seal any unused openings in the common venting sys tem.
2 - Inspect the venting system for proper size and horizontal pitch. Determine that there is no blockage, restriction, leakage, corrosion, or other deficiencies which could cause an unsafe condition.
3 - Close all building doors and windows and all doors be tween the space in which the appliances remaining connected to the common venting system are located and other spaces of the building. Turn on clothes dry ers and any appliances not connected to the common venting system. Turn on any exhaust fans, such as range hoods and bathroom exhausts, so they will oper ate at maximum speed. Do not operate a summer ex haust fan. Close fireplace dampers.
4 - Follow the lighting instructions. Turn on the appliance that is being inspected. Adjust the thermostat so that the appliance operates continuously.
5 - After the burner have operated for 5 minutes, test for leaks of flue gases at the draft hood relief opening. Use the flame of a match or candle.
6 - After determining that each appliance connected to the common venting system is venting properly, (step 3) return all doors, widows, exhaust fans, fireplace damp ers, and any other gas-burning appliances to their pre vious mode of operation.
7 - If a venting problem is found during any of the preced ing tests, the common venting system must be modi fied to correct the problem.
Resize the common venting system to the minimum vent pipe size determined by using the appropriate tables in Appendix G. (These are in the current stan dards of the National Fuel Gas Code ANSI Z223.1.
Gas Piping
Gas supply piping should not allow more than 0.5”W.C. drop in pressure between gas meter and unit. Supply gas pipe must not be smaller than unit gas connection.
WARNING
Do not over torque (800 in-lbs) or under torque (350 in-lbs) when attaching the gas piping to the gas valve.
CAUTION
If a flexible gas connector is required or allowed by the authority that has jurisdiction, black iron pipe shall be installed at the gas valve and extend outside the furnace cabinet. The flexible connector can then be added between the black iron pipe and the gas supply line.
Gas Supply
1 - This unit is shipped standard for left or right side instal lation of gas piping (or top entry in horizontal applica tions). Connect the gas supply piping into the gas valve. The maximum torque is 800 in lbs and minimum torque is 350 in lbs when when attaching the gas piping to the gas valve.
2 - When connecting the gas supply piping, consider fac tors such as length of run, number of fittings, and fur
nace rating to avoid excessive pressure drop. Table 6
lists recommended pipe sizes for typical applications.
3 - The gas piping must not run in or through air ducts, clothes chutes, gas vents or chimneys, dumb waiters, or elevator shafts.
4 - The piping should be sloped 1/4 inch (6.4 mm) per 15 feet (4.57 m) upward toward the meter from the fur nace. The piping must be supported at proper intervals
[every 8 to 10 feet (2.44 to 3.01 m)] with suitable hang ers or straps. Install a drip leg in vertical pipe runs to the unit.
5 - A 1/8” N.P.T. plugged tap or pressure post is located on the gas valve to facilitate test gauge connection.
6 - In some localities, codes may require the installation of a manual main shut‐off valve and union (furnished by the installer) external to the unit. The union must be of the ground joint type.
IMPORTANT
Compounds used on threaded joints of gas piping must be resistant to the actions of liquified petro leum gases.
Page 20
NOTE If emergency shutoff is necessary, shut off the main manual gas valve and disconnect main power to the fur nace. The installer should properly label these devices.
TABLE 6
Gas Pipe Capacity - ft 3 /hr (m 3 /hr)
1-1/4
(31.75)
1-1/2
(38.1)
2
(50.8)
2-1/2
(63.5)
3
(76.2)
Nominal
Iron Pipe
Size inches
(mm)
1/2
(12.7)
3/4
(19.05)
1
(25.4)
Internal
Diameter inches
(mm)
.622
(17.799)
.824
(20.930)
1.049
(26.645)
1.380
(35.052)
1.610
(40.894)
2.067
(52.502)
2.469
(67.713)
3.068
(77.927)
10
(3.048)
172
(4.87)
360
(10.19)
678
(19.19)
1350
(38.22)
2090
(59.18)
4020
(113.83)
6400
(181.22)
11300
(319.98)
20
(6.096)
118
(3.34)
247
(7.00)
466
(13.19)
957
(27.09)
1430
(40.49)
2760
(78.15)
4400
(124.59)
7780
(220.30)
30
(9.144)
95
(2.69)
199
(5.63)
374
(10.59)
768
(22.25)
1150
(32.56)
2220
(62.86)
3530
(99.95)
6250
(176.98)
40
(12.192)
81
(2.29)
170
(4.81)
320
(9.06)
657
(18.60)
985
(27.89)
1900
(53.80)
3020
(85.51)
5350
(151.49)
Length of Pipe - feet (m)
50
(15.240)
72
(2.03)
151
(4.28)
284
(8.04)
583
(16.50)
873
(24.72)
1680
(47.57)
2680
(75.88)
4740
(134.22)
NOTE - Capacity given in cubic feet (m
3
) of gas per hour and based on 0.60 specific gravity gas.
60
(18.288)
65
(1.84)
137
(3.87)
257
(7.27)
528
(14.95)
791
(22.39)
1520
(43.04)
2480
(70.22)
4290
(121.47)
70
(21.336)
60
(1.69)
126
(3.56)
237
(6.71)
486
(13.76)
728
(20.61)
1400
(39.64)
2230
(63.14)
3950
(111.85)
80
(24.384)
56
(1.58)
117
(3.31)
220
(6.23)
452
(12.79)
677
(19.17)
1300
(36.81)
2080
(58.89)
3670
(103.92)
90
(27.432)
52
(1.47)
110
(3.11)
207
(5.86)
424
(12.00)
635
(17.98)
1220
(34.55)
1950
(55.22)
3450
(97.69)
100
(30.480)
50
(1.42)
104
(2.94)
195
(5.52)
400
(11.33)
600
(17.00)
1160
(32.844)
1840
(52.10)
3260
(92.31)
Left Side Piping
(Standard)
MANUAL
MAIN SHUT-OFF
VALVE
(With 1/8 in. NPT
Plugged Tap Shown)
AUTOMATIC
GAS VALVE
AUTOMATIC
GAS VALVE
MANUAL
MAIN SHUT-OFF
VALVE
(With 1/8 in. NPT
Plugged Tap
Shown)
GROUND
JOINT
UNION
GROUND
JOINT
UNION
DRIP LEG
Right Side Piping
(Alternate)
DRIP LEG
FIELD
PROVIDED
AND INSTALLED
NOTE - BLACK IRON PIPE ONLY TO BE ROUTED INSIDE OF CABINET
FIGURE 25
Page 21
MANUAL
MAIN SHUT-OFF
VALVE
GROUND
JOINT
UNION
DRIP LEG
Horizontal Applications
Possible Gas Piping Configurations
MANUAL
MAIN SHUT-OFF
VALVE
Horizontal Application
Right-Side Air Discharge
GROUND
JOINT
UNION
DRIP LEG
Horizontal Application
Left-Side Air Discharge
MANUAL
MAIN SHUT-OFF
VALVE
GROUND
JOINT
UNION
FIELD
PROVIDED
AND INSTALLED
NOTE - BLACK IRON PIPE ONLY TO BE ROUTED INSIDE OF CABINET
FIGURE 26
DRIP LEG
Page 22
Leak Check
After gas piping is completed, carefully check all piping connections (factory- and field-installed) for gas leaks. Use a leak detecting solution or other preferred means.
NOTE - If emergency shutoff is necessary, shut off the main manual gas valve and disconnect the main power to the furnace. The installer should properly label these devices.
CAUTION
Some soaps used for leak detection are corrosive to certain metals. Carefully rinse piping thoroughly af ter leak test has been completed. Do not use matches, candles, flame or other sources of ignition to check for gas leaks.
The furnace must be isolated by closing its individual manual shut‐off valve and disconnecting from from the gas supply system during any pressure testing of the gas sup ply system at pressures greater than 1/2 psig (3.48 kPa, 14 inches w.c.).
WARNING
Fire Hazard. Use of aluminum wire with this product may result in a fire, causing property dam age, severe injury or death. Use copper wire only with this product.
CAUTION
Failure to use properly sized wiring and circuit breaker may result in property damage. Size wiring and circuit breaker(s) per Product Specifications bulletin (EHB) and unit rating plate.
The unit is equipped with a field make-up box on the left hand side of the cabinet. The make-up box may be moved to the right side of the furnace to facilitate installation. If the make-up box is moved to the right side, clip the wire ties that bundle the wires together. The excess wire must be pulled into the blower compartment. Secure the excess wire to the existing harness to protect it from damage.
INTERIOR MAKE-UP BOX INSTALLATION
Right Side
IMPORTANT
When testing pressure of gas lines, gas valve must
be disconnected and isolated. See figure 27. Gas
valves can be damaged if subjected to pressures greater than 1/2 psig (3.48 kPa, 14 inches w.c.).
BOX
MANUAL MAIN
SHUT-OFF VALVE
WILL NOT HOLD
NORMAL TEST
PRESSURE
1/8 NPT PLUG
ISOLATE
GAS VALVE
FURNACE
CAP
FIGURE 27
Electrical
ELECTROSTATIC DISCHARGE (ESD)
Precautions and Procedures
CAUTION
Electrostatic discharge can affect elec tronic components. Take precautions to neutralize electrostatic charge by touching your hand and tools to metal prior to handling the control.
FIGURE 28
Refer to figure 29 for schematic wiring diagram, field wiring
and trouble shooting.
The power supply wiring must meet Class I restrictions.
Protected by either a fuse or circuit breaker, select circuit protection and wire size according to unit nameplate.
NOTE Unit nameplate states maximum current draw.
Maximum over-current protection allowed is 15 AMP.
Holes are on both sides of the furnace cabinet to facilitate wiring.
Install a separate (properly sized) disconnect switch near the furnace so that power can be turned off for servicing.
Before connecting the thermostat, check to make sure the wires will be long enough for servicing at a later date. Make sure that thermostat wire is long enough to facilitate future removal of blower for service.
Page 23
Complete the wiring connections to the equipment. Use the provided unit wiring and field wiring diagram shown in fig
ure 29. Use 18-gauge wire or larger that is suitable for
Class II rating for thermostat connections.
WARNING
Electric Shock Hazard. Can cause injury or death. Unit must be properly grounded in accordance with national and local codes.
Electrically ground the unit according to local codes or, in the absence of local codes, according to the current Na tional Electric Code (ANSI/NFPA No. 70). A green ground wire is provided in the field make-up box.
NOTE - The ML180UHE furnace contains electronic components that are polarity sensitive. Make sure that the furnace is wired correctly and is properly grounded.
Accessory Terminals
One line voltage “EAC” 1/4” spade terminal is provided on
the furnace integrated control. See figure 30 for integrated
control configuration. This terminal is energized when the indoor blower is operating. Any accessory rated up to one amp can be connected to this terminal with the neutral leg of the circuit being connected to one of the provided neutral terminals. If an accessory rated at greater than one amp is connected to this terminal, it is necessary to use an exter nal relay.
One line voltage “HUM” 1/4” spade terminal is provided on
the furnace integrated control. See figure 30 for integrated
control configuration. This terminal is energized in the heating mode when the combustion air inducer is operat ing. Any humidifier rated up to one amp can be connected to this terminal with the neutral leg of the circuit being con nected to one of the provided neutral terminals. If a humidi fier rated at greater than one amp is connected to this termi nal, it is necessary to use an external relay relay.
One 24V ”H” 1/4” spade terminal is provided on the furnace
integrated control. See figure 30 for integrated control con
figuration. The terminal is energized in the heating mode when the combustion air inducer is operating and the pres sure switch is closed. Any humidifier rated up to 0.5 amp can be connected to this terminal with the ground leg of the circuit connected to ground or the ”C” terminal.
Generator Use - Voltage Requirements
The following requirements must be kept in mind when specifying a generator for use with this equipment:
The furnace requires 120 volts + 10% (Range: 108 volts to 132 volts).
The furnace operates at 60 Hz + 5% (Range: 57 Hz to
63 Hz).
The furnace integrated control requires both polarity and proper ground. Both polarity and proper grounding should be checked before attempting to operate the furnace on either permanent or temporary power.
Generator should have a wave form distortion of less than 5% total harmonic distortion.
Thermostat
Install the room thermostat according to the instructions
provided with the thermostat. See figure 29 for thermostat
designations. If the furnace is being matched with a heat pump, refer to the FM21 installation instruction or appropri ate dual fuel thermostat instructions.
Indoor Blower Speeds
1 - When the thermostat is set to “FAN ON,” the indoor blower will run continuously on the fan speed when there is no cooling or heating demand.
2 - When the ML180UHE is running in the heating mode, the indoor blower will run on the heating speed.
3 - When there is a cooling demand, the indoor blower will run on the cooling speed.
Page 24
ML180UHE Schematic Wiring Diagram
FIGURE 29
Page 25
Integrated Control
RED LED
Flash Code 2
Note
Diagnostic Codes / Status of Furnace
Off
Heartbeat 1
No power to control or board fault detected
Normal Operation - Idle, Continuous Fan, Cool
Continuous Rapid Flash Call For Heat / Burner Operation
1 Reverse Line Voltage Polarity
4
5
6
7
2
3
Improper Earth Ground
Burner failed to light, or lost flame during heat demand
Low Flame Signal - check flame sensor
Watchguard - burner failed to light, exceeded maximum number of retries or recycles.
Not Used
Primary or Secondary Limit Open or Watchguard Mode - Limit Switch Open longer than 3 minutes
8
9
10
11
12
13
Note 1
Note 2
Rollout Switch Open
Pressure Switch failed to close or opened during heat demand
Watchguard - Pressure Switch opened 5 times during one heat demand
Pressure Switch stuck closed prior to activation of combustion air inducer
Flame Sensed without gas valve energized
Low Line Voltage
Notes
A ”Heartbeat” is indicated by a ”Slow Flash” - 1 sec on 1 sec off, repeating
Error codes are indicated by a ”Rapid Flash” - the LED flashes X times at 1/2 sec on 1/2 sec off, remains off for 3 sec, then repeats
Last 10 error codes are stored in memory including when power is shut off to the unit. - To recall, press and release button, most recent will be displayed first, LED off for 3 sec, then next error code is displayed, etc. To clear error codes, depress and hold button longer than 5 seconds.
TABLE 7
INTEGRATED CONTROL
(Automatic Hot Surface Ignition System)
120HUM
LINE
XFMR
CIRC
EAC
NEUTRALS
HUM24
COOL
HEAT
FAN
PARK (no power)
FLAME/FS
24 COM
1/4” QUICK CONNECT TERMINALS
Humidifier 120VAC
120VAC
Transformer 120VAC
Indoor blower 120VAC
Indoor air quality accessory 120VAC
Common 120VAC
Humidifier 24VAC
3/16” QUICK CONNECT TERMINALS
Cooling tap 24VAC
Heating tap 24VAC
Continuous blower 24 VAC
Park terminal for speed taps
Flame sense
Common 24VAC
RED LED
RECALL BUTTON
FIGURE 30
BLOWER OFF DELAY
Page 26
Unit Start-Up
FOR YOUR SAFETY READ BEFORE LIGHTING
WARNING
Do not use this furnace if any part has been under water. A flood-damaged furnace is extremely dan gerous. Attempts to use the furnace can result in fire or explosion. Immediately call a qualified ser vice technician to inspect the furnace and to replace all gas controls, control system parts, and electrical parts that have been wet or to replace the furnace, if deemed necessary.
4 - This furnace is equipped with an ignition device which automatically lights the burners. Do not try to light the burners by hand.
5 - Remove the upper access panel.
6 - Move switch on gas valve to OFF . Do not force. See
7 - Wait five minutes to clear out any gas. If you then smell gas, STOP! Immediately call your gas supplier from a neighbor's phone. Follow the gas supplier's instruc tions. If you do not smell gas go to next step.
MANIFOLD
PRESSURE
ADJUSTMENT
SCREW
MANIFOLD
PRESSURE
OUTLET
PORT
WARNING
If overheating occurs or if gas supply fails to shut off, shut off the manual gas valve to the appliance before shutting off electrical supply.
CAUTION
Before attempting to perform any service or mainte nance, turn the electrical power to unit OFF at dis connect switch.
BEFORE LIGHTING smell all around the appliance area for gas. Be sure to smell next to the floor because some gas is heavier than air and will settle on the floor.
The gas valve on the ML180UHE unit is equipped with a gas control switch. Use only your hand to move the switch.
Never use tools. If the switch will not turn or if the control switch will not move by hand, do not try to repair it.
Placing the furnace into operation:
ML180UHE units are equipped with an automatic ignition system. Do not attempt to manually light burners on these furnaces. Each time the thermostat calls for heat, the burners will automatically light. The ignitor does not get hot when there is no call for heat on units with an automatic ignition system.
WARNING
If you do not follow these instructions exactly, a fire or explosion may result causing property damage, personal injury or death.
Gas Valve Operation (Figure 31)
1 STOP ! Read the safety information at the beginning of this section.
2 - Set the thermostat to the lowest setting.
3 - Turn off all electrical power to the unit.
INLET
PRESSURE
PORT
GAS VALVE SHOWN IN ON POSITION
FIGURE 31
8 - Move switch on gas valve to ON . Do not force. See fig
9 - Replace the upper access panel.
10- Turn on all electrical power to to the unit.
11- Set the thermostat to desired setting.
NOTE - When unit is initially started, steps 1 through 11 may need to be repeated to purge air from gas line.
12- If the appliance will not operate, follow the instructions
“Turning Off Gas to Unit” and call your service techni cian or gas supplier.
Turning Off Gas to Unit
1 - Set the thermostat to the lowest setting.
2 - Turn off all electrical power to the unit if service is to be performed.
3 - Remove the upper access panel.
4 - Move switch on gas valve to OFF . Do not force.
5 - Replace the upper access panel.
Failure To Operate
If the unit fails to operate, check the following:
1 - Is the thermostat calling for heat?
2 - Are access panels securely in place?
3 - Is the main disconnect switch closed?
4 - Is there a blown fuse or tripped circuit breaker?
5 - Is the filter dirty or plugged? Dirty or plugged filters will cause the limit control to shut the unit off.
6 - Is gas turned on at the meter?
7 - Is the manual main shut‐off valve open?
8 - Is the internal manual shut‐off valve open?
9 - Is the unit ignition system in lock out? If the unit locks out again, call the service technician to inspect the unit for blockages.
10 - Is pressure switch closed? Obstructed flue will cause unit to shut off at pressure switch. Check flue and outlet for blockages.
Page 27
11 - Are flame rollout switches tripped? If flame rollout switches are tripped, call the service technician for in spection.
Heating Sequence Of Operation
(follow steps below or see Figure 29 for more detail)
1 - When thermostat calls for heat, combustion air blower starts.
2 - Combustion air pressure switch proves blower opera tion. Switch is factory-set and requires no adjustment.
3 - After a 15-second prepurge, the hot surface ignitor en ergizes.
4 - After a 20-second ignitor warm-up period, the gas valve solenoid opens. A 4-second trial for ignition peri od begins.
5 - Gas is ignited, flame sensor proves the flame, and the combustion process continues.
6 - If flame is not detected after first ignition trial, the igni tion control will repeat steps 3 and 4 four more times before locking out the gas valve (“WATCHGUARD” flame failure mode). The ignition control will then auto matically repeat steps 1 through 6 after 60 minutes.
7 - To interrupt the 60-minute “WATCHGUARD” period, move thermostat from “Heat” to “OFF” then back to
“Heat.” Heating sequence then restarts at step 1.
Gas Pressure Adjustment
Gas Flow (Approximate)
TABLE 8
GAS METER CLOCKING CHART
Seconds for One Revolution
ML180UHE Unit
Natural
1 cu ft
Dial
2 cu ft
Dial
1 cu ft
Dial
LP
2 cu ft
DIAL
-045
-070
-090
-110
80
55
41
33
160
110
82
66
200
136
102
82
-135 27 54 68
Natural-1000 btu/cu ft LP-2500 btu/cu ft
400
272
204
164
136
Furnace should operate at least 5 minutes before check ing gas flow. Determine time in seconds for two revolu tions of gas through the meter. (Two revolutions assures a more accurate time.) Divide by two and compare to time
in table 8. If manifold pressure matches table 10 and rate
is incorrect, check gas orifices for proper size and restric tion. Remove temporary gas meter if installed.
NOTE - To obtain accurate reading, shut off all other gas appliances connected to meter.
Supply Pressure Measurement
A threaded plug on the inlet side of the gas valve provides access to the supply pressure tap. Remove the threaded plug, install a field-provided barbed fitting and connect a
manometer to measure supply pressure. See table 10 for
proper line pressure. Replace the threaded plug after mea surements have been taken.
Manifold Pressure Measurement
1 - Remove the threaded plug from the outlet side of the gas valve and install a field-provided barbed fitting.
Connect to a manometer to measure manifold pres sure.
2 - Start unit and allow 5 minutes for unit to reach steady state.
3 - While waiting for the unit to stabilize, observe the flame. Flame should be stable and should not lift from burner. Natural gas should burn blue.
4 - After allowing unit to stabilize for 5 minutes, record manifold pressure and compare to value given in table
NOTE - Shut unit off and remove manometer as soon as an accurate reading has been obtained. Take care to remove barbed fitting and replace threaded plug.
Proper Combustion
Furnace should operate a minimum 15 minutes with cor rect manifold pressure and gas flow rate before checking combustion. Take combustion sample beyond the flue out let and compare to the tables below.
The maximum car bon monoxide reading should not exceed 50 ppm.
ML180UHE Unit
TABLE 9
CO
2
% For
Nat
CO
2
%
L.P.
For
-045
-070
-090
-110
-135
7.2 - 7.8
7.5 - 9.0
High Altitude
The manifold pressure may require adjustment and com bustion air pressure switch may need replacing to ensure
and gas conversion kits.
IMPORTANT
For safety, shut unit off and remove manometer as soon as an accurate reading has been obtained.
Take care to replace pressure tap plug.
Page 28
Model
Input Size
045
070
090
110
135
Gas
Nat
LP/propane
Nat
LP/propane
Nat
LP/propane
Nat
LP/propane
Nat
LP/propane
TABLE 10
Manifold Pressure Settings at all Altitudes
0-2000 ft
10.0
3.5
10.0
3.5
10.0
3.5
10.0
3.5
10.0
3.5
2001-4500 ft.
10
3.5
10.0
3.5
10.0
3.2
10.0
3.2
10.0
3.2
4501-7500 ft
9.6
3.0
9.6
2.9
9.6
3.0
10.0
2.8
10.0
2.7
7501 - 10,000 ft
10.0
3.5
10.0
3.5
10.0
3.5
10.0
3.5
10.0
3.5
Line Pressure in.wg.
Min
4.5
11.0
4.5
11.0
4.5
11.0
4.5
11.0
4.5
11.0
Max
13.0
13.0
13.0
13.0
13.0
13.0
13.0
13.0
13.0
13.0
Model
Input Size
045
070
090
110
135
0-4500 ft
No Change
TABLE 11
Pressure Switch and Gas Conversion Kits at all Altitudes
High Altitude Pressure Switch Kit
4501-7500 ft 7501 - 10,000 ft
80W52 80W51
80W52
80W52
80W51
80W51
80W57
80W52
80W52
80W51
High Altitude
Natural Gas Burner
Orifice Kit
7501 - 10,000 ft
73W37
Natural Gas to LP/Propane
Burner Orifice Kit
0 - 7500 ft 7501 - 10,000 ft
LP/Propane to
Natural Gas Burner
Orifice Kit
0 - 7500 ft
11K49 11K44 73W81
NOTE - A natural to L.P. propane gas changeover kit is necessary to convert this unit. Refer to the changeover kit installation instruction for the conversion procedure.
Other Unit Adjustments
air temperatures have been allowed to stabilize, check the temperature rise. If necessary, adjust the blower speed to
Primary and Secondary Limits
The primary limit is located on the heating compartment maintain the temperature rise within the range shown on the unit nameplate. Increase the blower speed to decrease vestibule panel. The secondary limits (if equipped) are lo cated in the blower compartment, attached to the back side of the blower. These auto reset limits are factory-set and re quire no adjustment.
the temperature. Decrease the blower speed to increase the temperature rise. Failure to adjust the temperature rise may cause erratic limit operation.
Fan Control
Flame Rollout Switches
These manually reset switches are located on the burner box.
Pressure Switch
The pressure switch is located in the heating compartment adjacent to the combustion air inducer. The switch checks for proper combustion air inducer operation before allow ing ignition trial. The switch is factory-set and requires no adjustment.
Temperature Rise
After the furnace has been started, and supply and return
The heat fan-on time of 30 seconds is not adjustable. The heat fan-off delay (amount of time that the blower operates after the heat demand has been satisfied) may be adjusted by changing the jumper position across the five pins on the integrated control. The unit is shipped with a factory fan-off delay setting of 90 seconds. The fan-off delay affects com fort and is adjustable to satisfy individual applications. Ad just the fan-off delay to achieve a supply air temperature between 90° and 110°F at the moment that the blower is de-energized. Longer off delay settings provide lower re turn air temperatures; shorter settings provide higher re
turn air temperatures. See figure 32.
Page 29
HEAT FAN‐OFF TIME IN SECONDS
NO JUMPER
To adjust fan-off timing, reposition jumper across pins to achieve desired setting.
60 Second off Time
90 Second off Time
120 Second off Time
180 Second off Time
Electronic Ignition
The integrated control has an added feature of an internal
Watchguard control. The feature serves as an automatic re set device for integrated control lockout caused by ignition failure. This type of lockout is usually due to low gas line pressure. After one hour of continuous thermostat demand for heat, the Watchguard will re-set and remake thermostat demand to the furnace and automatically reset the inte grated control to begin the ignition sequence.
Service
FIGURE 32
Constant Torque Motor
ML180UHE units are equipped with a constant torque ECM motor. It has a DC motor coupled to an electronic control module both contained in the same motor housing. The mo tor is programmed to provide constant torque at each of the five selectable speeds. The motor has five speed taps.
Each tap requires 24 volts to energize.
Input Voltage Requirements
The circuit is designed to be operated with AC voltage. A voltage of 12 to 33VAC is required to energize the motor.
Expected current draw will be less than 20mA.
Blower Speeds
Follow the steps below to change the blower speeds.
1 - Turn off electrical power to furnace.
2 - Remove blower access panel.
3 - Disconnect existing speed tap at integrated control speed terminal.
NOTE - Termination of any unused motor leads must be insulated.
4 - Place unused blower speed tap on integrated control
“PARK” terminal or insulate.
5 - Refer to blower speed selection chart on unit wiring dia gram for desired heating or cooling speed. See Product
Specifications manual for blower performance data.
6 - Connect selected speed tap at integrated control speed terminal.
7 - Resecure blower access panel.
8 - Turn on electrical power to furnace.
9 - Recheck temperature rise.
WARNING
ELECTRICAL SHOCK, FIRE,
OR EXPLOSION HAZARD.
Failure to follow safety warnings exactly could result in dangerous operation, serious injury, death or property damage.
Improper servicing could result in dangerous opera tion, serious injury, death, or property damage.
Before servicing, disconnect all electrical power to furnace.
When servicing controls, label all wires prior to dis connecting. Take care to reconnect wires correctly.
Verify proper operation after servicing.
Annual Furnace Maintenance
At the beginning of each heating season, and to comply with the Lennox Limited Warranty , your system should be checked by a licensed professional technician (or equiva lent) as follows:
1- Check wiring for loose connections, voltage at indoor unit and amperage of indoor motor
.
2- Check the condition of the belt and shaft bearings if ap plicable.
3- Inspect all gas pipe and connections for leaks
.
4- Check the cleanliness of filters and change if necessary
(monthly).
5- Check the condition and cleanliness of burners and heat exchanger and clean if necessary.
6- Check the cleanliness of blower assembly and clean the housing, blower wheel and blower motor if neces sary
.
The blower motors are prelubricated for extended bearing life. No further lubrication is needed.
7- Inspect the combustion air inducer and clean if neces sary.
Page 30
8- Evaluate the heat exchanger integrity by inspecting the heat exchanger per the AHRI heat exchanger inspec tion procedure. This procedure can be viewed at www.ahrinet.org
9- Ensure sufficient combustion air is available to the fur nace. Fresh air grilles and louvers (on the unit and in the room where the furnace is installed) must be properly sized, open and unobstructed to provide combustion air
.
10 Inspect the furnace venting system to make sure it is in place, structurally sound, and without holes, corrosion, or blockage. Vent system must be free and clear of ob structions and must slope upward away from the fur nace
.
Vent system should be installed per the National
Fuel Gas Code
11 Inspect the furnace return air duct connection to ensure the duct is sealed to the furnace. Check for air leaks on supply and return ducts and seal where necessary
.
12 Check the condition of the furnace cabinet insulation and repair if necessary.
13 Perform a complete combustion analysis during the fur nace inspection to ensure proper combustion and oper ation. Consult Service Literature for proper combustion values.
14 Verify operation of CO detectors and replace batteries as required.
Perform a general system test. Turn on the furnace to check operating functions such as the start-up and shut-off operation.
1 - Check the operation of the ignition system, inspect and clean flame sensor. Check microamps before and after. Check controls and safety devices (gas valve, flame sensor, temperature limits). Consult Service
Manual for proper operating range. Thermal Limits should be checked by restricting airflow and not dis connecting the indoor blower. For additional details, please see Service and Application Note H049.
2 - Verify that system total static pressure and airflow set tings are within specific operating parameters.
3 - Clock gas meter to ensure that the unit is operating at the specified firing rate. Check the supply pressure and the manifold pressure. On two-stage gas furnaces check the manifold pressure on high fire and low fire. If manifold pressure adjustment is necessary, consult the Service Literature for unit specific information on adjusting gas pressure. Not all gas valves are ad justable . Verify correct temperature rise.
Blower
Check the blower wheel for debris and clean if necessary.
The blower motors are prelubricated for extended bearing life. No further lubrication is needed.
WARNING
The blower access panel must be securely in place when the blower and burners are operating. Gas fumes, which could contain carbon monoxide, can be drawn into living space resulting in personal inju ry or death.
Cleaning the Burners
NOTE - Use papers or protective covering in front of the fur nace during cleaning.
1 - Turn off both electrical and gas power supplies to fur nace.
2 - Label the wires from gas valve, rollout switches, prima ry limit switch and make-up box then disconnect them.
3 - Disconnect gas supply piping. Remove the screw se curing the burner box cover and remove cover. Re move the four screws securing the burner manifold as sembly to the vestibule panel and remove the assembly from the unit.
4 - To clean burners, run a vacuum cleaner with a soft brush attachment over the face of burners. Visually inspect in side the burners and crossovers for any blockage caused by foreign matter. Remove any blockage. Figure
5 - Reinstall burner box, manifold assembly and burner box cover.
6 - Re-install gas supply and turn on electrical pwer to fur nace.
Page 31
Rollout Switches
Ignitor
ML180UH BURNER ASSEMBLY & REMOVAL
Retention Rings
Cross Over
Sensor
Manifold And Gas Valve
FIGURE 33
Repair Parts List
The following repair parts are available through independent Lennox dealers. When ordering parts, include the complete furnace model number listed on the CSA International nameplate -- Example: ML180UHE045P24A-01. All service must be performed by a licensed professional installer (or equivalent), service agency, or gas supplier.
Cabinet Parts
Upper access panel
Blower panel
Top cap
Control Panel Parts
Transformer
Integrated control
Door interlock switch
Circuit breaker
Blower Parts
Blower wheel
Blower housing
Motor
Motor mounting frame
Motor power choke
Blower housing cutoff plate
Heating Parts
Flame sensor
Heat exchanger assembly
Gas manifold
Combustion air inducer
Gas valve
Main burner cluster
Main burner orifices
Pressure switch
Ignitor
Primary limit control
Flame rollout switch (s)
Secondary limit
Page 32
Start-Up & Performance Check List
UNIT SET UP
(typical)
Unit Model Number_______________
Serial Number___________________
2
Line Voltage
5
2
SUPPLY
AIR upflow furnace shown
1
1
Gas Supply Pressure
3
Filter
RETURN
AIR
4
1
GAS SUPPLY
Natural Gas LP/Propane Gas
Piping Connections Tight
Leak Tested
Supply Line Pressure “ W.C.________
2
VENT / EXHAUST PIPE
Secure to Unit
Elbows Secured to Pipe
Roof Flashing (water tight)
Vent Pipe Supported
3 DUCT SYSTEM
SUPPLY AIR DUCT
Sealed
Insulated (if necessary)
Registers Open and Unobstructed
RETURN DUCT
Sealed
Filter Installed and Clean
Grilles Unobstructed
4
INTEGRATED CONTROL
DIP Switches Set (if applicable)
Appropriate Links in Place (if applicable)
5 VOLTAGE CHECK
Supply Voltage _____
Electrical Connections Tight
Page 33
UNIT OPERATION
(typical)
Combustion CO
2
2
SUPPLY
AIR
Gas Manifold Pressure
1
7
Thermostat
6 upflow furnace shown
Temperatures
4
Filter
Blower Motor Amps
3
RETURN
AIR
Duct Static
5
1
2
3
HEATING MODE
GAS MANIFOLD PRESSURE “W.C._____
COMBUSTION SAMPLE CO
2
%
______
CO PPM_______
INDOOR BLOWER AMPS______
3
COOLING MODE
INDOOR BLOWER AMPS______
4
TEMPERATURE DROP
Return Duct Temperature _________
Supply Duct Temperature _ _______
Temperature Drop = _________
4
TEMPERATURE RISE
Supply Duct Temperature ________
Return Duct Temperature _ _____
Temperature Rise = ________
5
TOTAL EXTERNAL STATIC (dry coil)
Supply External Static _______
Return External Static + ______
Total External Static = _______
5
TOTAL EXTERNAL STATIC (dry coil)
Supply External Static _______
Return External Static + ______
Total External Static = _______
6 DRAIN LINE
Leak Free
7 THERMOSTAT
Adjusted and Programmed
Operation Explained to Owner
Contractor's: Name_________________________Telephone_____________Checklist Completed____________________
Job Address_____-________________________________Technician's Name___________________________________
Page 34
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