READY glossary.p65
AFUE (Annualized Fuel Utilization Efficiency): A measure
of the efficiency of the heating unit (burner and boiler/
furnace) including standby losses during the off-cycles,
given on an annual basis. See also “Steady State Efficiency.”
Air: A mixture of nitrogen, oxygen and slight traces of
other gases. For purposes of combustion analysis, we say air
is 79% Nitrogen and 21% Oxygen.
Air Change: The number of times in an hour the air in a
room is changed either by mechanical means or by the
infiltration of outside air leaking into the room through
cracks around doors and windows, etc.
Air Cleaner: A device designed for the purpose of removing airborne impurities such as dust, fumes and smoke.
Air Conditioning: This is the process of simultaneously
controlling temperature, humidity, cleanliness and distribution of air to meet various requirements of the conditioned
Air Infiltration: The leakage of air into a house through
cracks and crevices, doors, windows, and other openings,
caused by wind, pressure, and/or temperature difference.
Alternating Current: In the case of alternating current,
electrons are made to move first in one directions and then
in the other. The direction of current flow reverses periodically in cycles.
Biofuel: A renewable, biodegradable combustible liquid
fuel. Manufactured by processing vegetable oils such as soy
and rapseed (canola). Also made from waste cooking oil and
trap grease, tallow, and animal fats such as fish oil.
Bioheat Fuel®: A blend of 95% or more #2 oil and 5% or
less B100 biofuel.
Boiler: A closed vessel in which steam is generated or in
which water is heated by fire.
Boiler Efficiency: The ratio of heat absorbed per pound of
fuel fired, to the heat of complete combustion of one pound
of fuel.
Boiler Heating Surface: The area of the heat transmitting
surfaces in contact with the water (or steam) in the boiler on
one side, and the fire or hot gases on the other.
Boiler Rating: The guaranteed output of a boiler in Btus
per hour, or in square feet of radiation, as determined in a
test laboratory such as the Institute of Boiler and Radiator
Manufacturers (IBR) or the American Society of Mechanical Engineers (ASME).
British Thermal Unit (BTU): The quantity of heat required
to raise the temperature of 1 lb. of water 1°F. This is somewhat approximate but sufficiently accurate for any work
discussed in this manual. Here is how the Btus of the
various fuels compare:
No. 2 Heating Oil = 138,690 Btus per gallon
Ammeter: An instrument for measuring the amount of
electron flow in amperes.
Natural Gas: Averages 1,027 Btus per cubic foot,
about 135 cubic feet equals one gallon of oil.
Ampere: A measure of current flowing through a conductor
having a resistance of 1 ohm and a difference of potential of
1 volt.
Kerosene: 131,890 Btus per gallon, 1.05 gallons of
kerosene equals the heat content of one gallon of 2
Aquastat: A term applied to a control which may be
inserted in, or attached to, a vessel for the purpose of
controlling the temperature of water within the vessel.
Atmospheric Pressure: The pressure of the atmosphere at a
given elevation, the atmospheric pressure at sea level is
14.7 pounds per square inch, allowing water to boil at
Propane: 91,330 Btus per gallon, 1.53 gallons of
propane equals one gallon of 2 oil.
Electricity: 3,412 Btus per kilowatt hour (kwh), 40.6
kwh equals one gallon of No. 2 oil.
Wood: one full cord of wood has the heat value of
between 95 and 140 gallons of oil.
Anthracite Coal: has 12,000 Btus per pound. About
12 pounds of coal equals the heat content of one
gallon of No. 2 oil.
Atomization: The reduction of a substance to minute
particles. In oil burning, atomization produces a fine mist of
Cad Cell Relay: See “Primary Control.”
Available Heat: The quantity of useful heat per unit of fuel
available from complete combustion, after deducting dry
flue gas and water vapor losses.
Carbon Dioxide (CO2): A gas which, in heating practice,
indicates the complete combustion of carbon in the fuel and
is found through analysis of the flue gas.
Oilheat Technicians Manual
Carbon Monoxide (CO): A gas which, in heating practice,
indicates incomplete combustion of the carbon in the fuel
and is found through analysis of the flue gas.
Centigrade: See “Celsius.”
Celsius: A thermometer scale at which the freezing point of
water is 0° and its boiling point is 100°. In the United States
it is only used in scientific and laboratory work.
Chimney Effect: The tendency of heated air or gas in a
vertical passage to rise due to lower density compared to
that of the surrounding air or gas. In buildings, the tendency
of the cold, denser outside air to replace the heated air
results in the “chimney effect.”
Circuit (Electrical): The complete path of an electric
current from the source through a switch to a load and back
to the source.
Circuit Breaker: A thermal device which opens a circuit
when the current in the circuit exceeds a predetermined
Cloud Point: The temperature at which wax crystals begin
to form in fuel, typically 10 to 20 degrees above pour point.
Combustion: Defined as the rapid reaction of combustible
material with oxygen, with the resultant generation of heat.
For combustion to take place, the fuel must be heated to its
ignition temperature and brought into contact with oxygen.
Combustion Chamber: The refractory or metal lined area
within a boiler or furnace in which the combustion of fuel
takes place. When no chamber is present (as in wet base
boilers) the area is often referred to as “combustion space.”
Comfort Zone (Average): The range of effective temperatures over which the majority of adults feel comfortable.
Converter: A piece of equipment for heating water with
steam without mixing the two. It may be used for supplying
hot water for domestic purposes or for a hot water heating
Cycle (Electrical): One complete positive and one complete negative alternation of a current or voltage.
Degree-Day (Standard): A unit which is the difference
between 65°F and the daily average temperature, when the
latter is below 65°F. The degree days in any one day is
equal to the number of degrees F that the average temperature for that day is below 65°F.
Dew Point: The temperature below which water vapor
contained in flue gases turns to a liquid. This change is
referred to as condensation. To prevent condensation, stack
temperature should range from 270°F to 370°F above
ambient air temperature.
Dielectric: An insulator. The insulating material between
the plates of a capacitor. The insulating porcelain of an
ignition electrode.
Direct Current: An electric current that flows in one
direction only.
Direct Return System (Hot water): A two-pipe hot water
system in which the water, after it has passed through a
heating unit, is returned to the boiler along a direct path, so
that the total distance traveled by the water, from each
radiator, is the shortest feasible.
Direct Venting: The mechanical exhausting of the flue
gases of a heating unit in a structure that does not have a
suitable chimney.
Condensate: Liquid formed by the condensation of a
vapor,;in steam heating, water condensed from steam.
Down Feed System: A heating system in which the supply
mains are above the level of the heating units which they
Conduction: The process of diffusion or flow of heat energy
through a mass, or body of matter, by particle of molecular
contact from the warmer to the colder parts.
Draft: In heating systems, draft refers to the pressure
difference which causes a current of air or gases to flow
through a combustion chamber, flue, chimney or space.
Conductor (Thermal): A material capable of readily
transmitting heat by means of conduction.
Efficiency: In a heating unit, it is that percentage of the
heat energy input which is useful energy output. The ratio
of output power to input power is generally expressed as a
Conductor (Electrical): Any material suitable for carrying
electric current.
Convector: A concealed radiator. An enclosed heating unit
located (with enclosure) either within, adjacent to, or exterior
to, the room or space to be heated, but transferring heat to the
room or space mainly by the process of convection.
Electromagnet: A magnet made by passing an electrical
current through a wire wound on a soft iron core.
Electromotive Force (emf): The force that produces an
electric current in an electric circuit.
Oilheat Technicians Manual—IX
Electron: A negatively charged particle of matter.
temperature to a body of lower temperature.
Energy: The ability or capacity to do work.
Heat of Combustion: The heat evolved when the substance combines rapidly with oxygen.
Fahrenheit: A thermometer scale at which the freezing
point of water is 32°F and its boiling point is 212°F above
zero. It generally used in the United States for expressing
Flame Velocity (Rate of Flame Propagation): is the speed
with which a flame travels through a given fuel-air mixture.
It varies with the fuel, fuel-air mixture ratio and temperature of the mixture.
Flash Point: Maximum temperature at which fueloil can be
safely stored and handled without serious fire hazard.
ASTM minimum for No.1 and No.2 is 100°F).
Flue Gas: Includes all gases which leave the furnace
combustion chamber by way of a flue. Flue gas consists of
nitrogen, gaseous products of combustion, water vapor and
Frequency: The number of complete cycles per second
existing in any form of wave motion; such as the number of
cycles per second of an alternating current.
Fuel: May be defined as any substance, solid, liquid or
gaseous, which may be relatively easily ignited and burned
to produce heat. Practically all fuels consist of carbon and
Furnace: That part of a boiler or warm air heating plant in
which combustion takes place. Sometimes it is also the
complete heating unit of a warm air heating system.
Gauge Pressure: The pressure above that of the atmosphere. It is the pressure indicated on an ordinary pressure
gauge. It is expressed as a unit pressure such as pounds persquare inch (PSI) gauge.
Generator: A machine that converts mechanical energy
into electrical energy.
Grille: A perforated covering for an air inlet or outlet
usually made of wire screen, cast iron or other material.
Heat Exchanger: Any device which is used for transferring
energy from one fluid or gas to another.
Heat Unit: In the foot-pound-second system: the British
Thermal Unit (BTU): in the centimetergram-second
system: the calorie (cal).
Heating Medium: A substance such as water, steam, or air
used to convey heat from the boiler, furnace, or other
source of heat to the heating units from which the heat is
Hot Water Heating System: A heating system in which
water is used as the medium by which heat is carried
through pipes from the boiler to the heating units.
Humidistat: An instrument which controls the relative
humidity of the air in a room.
Humidity: The amount of water vapor within a given
space, generally measured in pounds-per-cubic foot.
Hydronics: The science of heating and cooling with water.
Ignition: The act of starting combustion.
Ignition Point: Lowest temperature at which rapid combustion of a fuel will take place in air. For No.2 oil, the
ignition point is over 500°F.
Insulation: A material which is used to minimize the heat
losses from a given space.
Kilowatt Hour: It is 1000 Watts per hour of electrical
energy and is equivalent to 3,412 BTU.
Latent Heat: The energy involved to change the physical
state of a substance, (from a liquid to a gas) without
changing its temperature.
Magnetic Field: The space in which a magnetic force
Master Control: See “primary control.”
Gross Heating Value: Is the total amount of heat produced
by the complete combustion of the fuel at atmospheric
Milliammeter: An ammeter that measures current in
thousands of an ampere.
Ground: A metallic connection with the earth to establish
ground potential. Also a common return to a point of zero
Nitrogen (N2): Is present in air in a large quantity and does
not serve any purpose in the process of combustion.
Heat: That form of energy into which all other forms may
be changed. Heat always flows from a body of higher
Ohmmeter: An instrument for directly measuring resistance in ohms.
X—Oilheat Technicians Manual
Ohm: The unit of electrical resistance.
Oilheat Technicians Manual
One-Pipe System (Hot Water): A hot water heating system
in which one pipe serves both as a supply main and also as
a return main. The heating units have separate supply and
return connections to the same main.
Radiation, Equivalent Direct: The amount of heating
surface expressed in square feet which will deliver 240
Btu/HR for steam, and 150 BTU/HR for hot water systems
operating at design conditions.
One-Pipe System (Steam): A steam heating system
consisting of a main circuit in which the steam and
condensate flow in the same pipe. There is but one
connection to each heating unit, which must serve as both
the supply and return.
Radiator: Heated and exposed to view, radiator transfers
heat by radiation to objects “it can see” and by conduction
to the surrounding air, which in turn is circulated by
natural convection.
Over Head System: A heating system in which the supply
main is above the heating units.
Recirculation: A strong, swirling air pattern that recirculates combustion products for more complete mixing of
fuel and air.
Oxidizing Flame: A flame produced by the burning of a
fuel with more than the amount of oxygen required for
burning under stoichiometric conditions.
Register: In heating and air conditioning, it refers to a
grille for the distribution of air which most often contains a
built-in damper or shutter.
Oxygen (O2): The lesser quantity of air that is necessary in
the combustion of any fuel. When found in large quantity
in flue gases, it is an indication of excess air being
introduced to the unit.
Relative Humidity: The amount of moisture in a given
quantity of air compared with the maximum amount of
moisture the same quantity of air could hold at the same
temperature. It is expressed as a percentage.
Panel Heating: A method of heating involving the
installation of the heating units (pipe coils) within the
wall, floor or ceiling of a room.
Plenum Chamber: An air compartment maintained under
pressure and connected to one or more distributing ducts.
Pour Point: Lowest temperature at which fuel will flow.
The ASTM standard for untreated No. 2 oil is 17°F.
Primary Control: In an oil burner circuit, it is the control
responsible for the proper sequencing and safety of the
operation of the burner. It is often referred to as the cad cell
relay, protectorelay, stack switch or master control.
Pressure: The force-per-unit-area measured in pounds-persquare-inch, inches of water or millimeters of mercury.
Pressure Reducing Valve: A piece of equipment for
changing the pressure of a gas or liquid from a higher
pressure to a lower one.
Relay: An electromechanical switching device that can be
used as a remote control.
Return Mains: The pipes which return the heating medium
from the heating units to the source of heat supply.
Reverse Return System: (Hot Water) A two-pipe hot water
heating system in which the water from the several heating
units is returned along paths, arranged so that all radiator
circuits of the system are practically of equal length.
Sensible Heat: Heat which only increases the temperature
of objects as opposed to latent heat.
Series Loop System: A hot water heating system in which
a single pipe connects from the heating unit to the first
distributing unit then on to the next distributing unit,
continuing this way until it returns to the heating unit. All
distributing units would then be connected in series.
Solenoid: An electromagnetic coil that contains a movable
Pressuretrol: A pressure controller often used to identify
the control used to limit the pressure in a steam system.
Square Foot of Heating Surface: See “Radiation, equivalent direct.”
Proportioning: Can be applied to the maintenance of the
ratio between fuel and air supply throughout the operating
range of the burner.
Stack Switch: See “Primary control.”
Protectorelay: See “primary control.”
Radiant Heating: A heating system in which the heating
is by radiation only. Sometimes applied to a panel heating
Stack Temperature: The stack (flue gas) temperature is the
temperature of combustion gases leaving the appliance,
and reflects the energy that did not transfer from the fuel to
the heat exchanger.
Static Pressure: The pressure necessary to overcome the
frictional resistance to flow. In an oil burner, it will refer to
Oilheat Technicians Manual—XI
Oilheat Technicians Manual
the pressure within the burner tube as developed by the
fan. In an air distribution system, it refers to the pressure
necessary to overcome the total resistance created by the
duct work.
Vacuum Heating System (Steam): A two-pipe heating
system equipped with the necessary accessory apparatus to
permit the pressure in the system to go below atmospheric
Steady State Efficiency: A measure of the carbon dioxide
in the flue gases, expressed as a percentage, to determine
the level of completion of the chemical reaction during
combustion taken at “steady state” conditions, meaning
there is no further change in the reaction process.
Vapor Heating System (Steam): A two-pipe heating
system which operates at pressures at or near atmospheric
and which returns the condensate to the boiler or receiver
by gravity.
Steam: Water vapor found when water has been heated to a
boiling point, corresponding to the pressure it is under.
Stoichiometric: Describes a condition in which the
reactants of a chemical reaction are present in the exact
quantities, as predetermined for the chemical equation of
the reaction. It describes perfect combustion when the
reactants are fuel and oxygen.
Sulfur Dioxide (SO2): It is present in small quantities in
fuel oil. It is the product of the combustion of sulfur.
Supply Mains: The pipes through which the heating
medium flows from the boiler, or source of supply, to the
run-outs and risers leading to the heating units.
Therm: A quantity of heat equal to 100,000 Btus.
Thermistor: A resistor that is used to compensate for
temperature variations in a circuit.
Thermocouple: A junction of two dissimilar metals that
produces a voltage when heated.
Thermostat: An instrument which responds to changes in
temperature and which directly or indirectly controls the
room temperature.
Transformer: A device composed of two or more coils,
linked by magnetic lines of force. In transferring energy
from one source to another, it can increase or decrease
Two-Pipe System (Steam or water): A heating system in
which one pipe is used for the supply main and another for
the return main. The essential feature of a two-pipe system
is that each heating unit receives a direct supply of the
heating medium which cannot have served a preceding
heating unit.
Up-Feed System (Hot Water or Steam): A heating system
in which the supply mains are below the level of the
heating units which they serve.
XII—Oilheat Technicians Manual
Ventilation: Air circulated through a room for ventilating
purposes. It may be mechanically circulated with a blower
system or it may be natural circulation through an open
window, etc.
Vent Valve (Steam): A device for permitting air to be
forced out of a heating unit or pipe and which closes
against steam.
Vent Valve (Water): A device permitting air to be forced
out of a pipe or heating unit, but which closes against
Viscosity: The measure of a liquid’s resistance to flow,
generally measured in terms of Saybolt Universal or
Saybolt Furol Seconds.
Volt: The unit of electrical potential.
Voltmeter: An instrument designed to measure a difference
in electrical potential, in volts.
Warm Air Heating System: A warm air heating plant
consists of a heating unit (fuel burning furnace) enclosed
in a casing, from which the heated air is distributed to the
various rooms of building through ducts. If the motive heat
producing flow depends on the difference in weight
between the heated air leaving the casing and the cooler air
entering the bottom of the casing, it is termed a gravity
system. If a fan is used to produce circulation and the
system is designed especially for fan circulation, it is
termed a forced warm air system.
Watt: The unit of electrical power.
Wattmeter: An instrument for measuring electrical power
in watts.
Wet Return (Steam): That part of a return main of a steam
heating system which is completely filled with water or
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF