The HVAC industry can be a maze of unfamiliar acronyms and
industry terms. This dictionary will help you navigate the
most common terms you’ll come across during your buying
decision.
A
AC Alternating Current - A type of current where the
polarity is perpetually reversing, causing the directional
flow in a circuit to reverse at regular intervals.
ACCA - Air Conditioning Contractors of America.
Acoustical - Relating to sound, the science of sound, or a
sense of hearing.
AFUE - Annual Fuel Utilization Efficiency. A measurement
used to rate furnace efficiencies by dividing the ratio of
heat output by heat input.
AGA - American Gas Association, Inc.
Air Conditioner - A device that changes humidity levels,
temperature or quality of air.
Air Flow Volume - Measured in cubic feet per minute (cfm),
this is the amount of air circulated in a space.
Air Handler - Parts of a system including the fan-blower,
filter and housing.
ARI - Air Conditioning and Refrigeration Institute.
ASHRAE - American Society of Heating, Refrigeration and Air
Conditioning Engineers.
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B
BTU - British Thermal Unit. Measures the amount of heat
required to raise or lower the temperature of one pound of
water one degree Fahrenheit.
BTUh - British Thermal Units per hour.
Burner - The device that facilitates the combustion of air
and gas.
Burner Orifice - The opening in the burner through which
the gas or fuel passes prior to combustion.
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C
Capacity - HVAC capacity is the output produced by the
heating or cooling unit and is measured in BTUs per hour.
Celsius - A temperature scale that registers the freezing
point of water as 0° and the boiling point as 100° under
normal atmospheric pressure.
CFM - Cubic Feet per Minute. A measurement of airflow
volume.
Charging a System - Adding coolant, or refrigerant, to an
HVAC system.
Compressor - A pump that increases the pressure of gas.
Condensate - Vapor that is turned into a liquid as its
temperature is lowered.
Condenser Coil - Also an outdoor coil. A device that
removes heat from the refrigerant, allowing the refrigerant
to be converted from vapor to liquid.
Condenser Fan - A fan that passes air over the condenser
coil to facilitate the removal of heat from the
refrigerant.
CSA - Canadian Standards Association.
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D
DC - Direct Current. A type of electrical current that only
flows in one direction.
Damper - Found at the exit point of ductwork, this plate
usually contains grates that can be opened or closed to
control the flow of air into a zone.
Degree-Day - Calculated by subtracting the average outdoor
temperature for an area from 65º Fahrenheit. This
measurement is used to estimate the amount of heating or
cooling a home or building will need.
Dehumidifier - A device that removes humidity, or moisture,
from the air.
Diffuser - A grille over an air supply duct with vanes that
distribute the discharging air in a specific pattern or
direction.
DOE - Department of Energy.
Downflow Furnace - A furnace with an intake on the top and
an air discharge at the bottom.
Drain Pan - Also a condensate pan. As the refrigerant vapor
is liquefied, the drain pan collects the condensate and
funnels it to the drain line.
Dry Bulb Temperature - The temperature as measured without
the consideration of humidity.
Ductwork - A network of metal, fiberboard or flexible
material flowing throughout a space which delivers air from
an HVAC unit to the respective zones of a home or office.
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E
EER - Energy Efficiency Ratio.
EPA - Environmental Protection Agency.
Expansion Valve - A valve that meters the levels of
refrigerant through a temperature or pressure control.
Evaporator Coil - Also an indoor coil. A device that is
designed to absorb heat in the air in order to change the
liquid refrigerant that flows through it into a vapor.
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F
Fahrenheit - A temperature scale in which water freezes at
32 degrees and boils at 212 degrees at normal atmospheric
pressure.
Fan - A device that creates air flow.
Filter - A device that acts like a strainer to remove dirt
or undesired particles.
Flue - A vent that removes the byproducts of combustion
from a furnace.
Furnace - The major component in heating a home. A device
that facilitates the combustion of fuel and air to create
heat.
Fuse - A delicate metal strip connecting two parts of an
electrical circuit. This strip breaks, or melts, in the
event of excess electrical charge, breaking the electrical
circuit.
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G
GAMA - Gas Appliance Manufacturers Association.
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H
Heat Exchanger - A device through which heat is transferred
to a cold area or surface.
Heat Gain - The amount of heat added or created in a
designated area.
Heating Coil - A coil that acts as a heat source for a
heating system.
Heat Loss - The amount of heat subtracted from a designated
area.
Heat Pump - A device used for either the heating or cooling
of a space by transferring heat between two reservoirs.
Heat Transfer - Moving heat from one location to another.
HSPF - Heating Seasonal Performance Factor. This factor
rates the efficiency of the heating portion of the heat
pump.
Humidifier - A device that adds humidity, or moisture, to
the air.
Humidistat - The device that measures humidity and turns
the humidifier on and off.
Humidity - Dampness in the air caused by water vapor.
HVAC - Heating, Ventilation and Air Conditioning.
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I
Ignition - Elevating the temperature of a substance to the
point of causing a combustion reaction.
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K
Kilowatt (kW) - 1,000 watts.
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L
Latent Heat - A type of heat that when added to an area
produces an effect other than an increase in temperature.
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M
Media - The fine material of a filter that traps dirt,
dust, mildew or bacteria.
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N
NEC - National Energy Council / National Electric Code.
NEMA - National Electrical Manufacturing Association.
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O
Orifice - An opening or hole.
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P
Package Unit - A heating and cooling system contained in
one outdoor unit.
PSI - Pounds per square inch.
PSIA - Pounds per square inch, absolute.
PSIG - Pounds per square inch gauge.
PVC - Polyvinyl chloride; a type of plastic.
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R
Reciprocating Compressor - A type of compressor used in
cooling systems to compress refrigerant by using a piston
action.
Refrigerant - A chemical that condenses from a vapor to
liquid and, in the process, decreases in temperature.
Refrigerant Charge - The amount of refrigerant in a system.
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S
SEER - Seasonal Energy Efficiency Ratio. A rating system
developed by the U.S. Government to indicate the efficiency
level of cooling equipment.
Self-contained System - A package unit.
Sensible Heat - Heat added or subtracted that causes a
change in temperature.
Sensor - A device that reacts to a change in conditions.
Split System - An outdoor unit combined with an indoor
unit.
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T
Thermostat - Sensors that monitor and control the output of
an HVAC system.
Thermostatic Expansion Valve - A device that creates a
constant evaporator temperature.
Ton - One ton is 12,000 BTUs per hour.
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U
Upflow Furnace - A furnace that pulls in air from the
bottom and releases it through the top.
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V
Vacuum - A space where the pressure is significantly below
that of standard atmospheric pressure.
Volt - A unit of electro-motive force.
Voltage - The force pushing electrical current along wires
and cables.
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W
Watt - The unit of electrical power equal to the flow of
one amp at a potential difference of one volt.
Wet Bulb Thermometer - A thermometer that measures the
relative humidity in the air.
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Z
Zoning - A system that divides a home, office or space into
different regions in order to better control the
temperature and effectiveness of a heating and cooling
system.
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