The HVAC industry can be a maze of unfamiliar acronyms and
industry terms. This glossary will help you navigate the most common terms
you’ll come across during your buying decision.
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
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
ASHRAE – American Society of Heating,
Refrigeration and Air Conditioning Engineers.
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.
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
CFM – Cubic Feet per Minute. A measurement of
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.
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
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.
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.
Fahrenheit – A temperature scale in which
water freezes at 32 degrees and boils at 212 degrees at normal atmospheric
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.
GAMA – Gas Appliance Manufacturers
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
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
HVAC – Heating, Ventilation and Air
Ignition – Elevating the temperature of a
substance to the point of causing a combustion reaction.
Kilowatt (kW) – 1,000 watts.
Latent Heat – A type of heat that when added
to an area produces an effect other than an increase in temperature.
Media – The fine material of a filter that
traps dirt, dust, mildew or bacteria.
NEC – National Energy Council / National
NEMA – National Electrical Manufacturing
Orifice – An opening or hole.
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.
Reciprocating Compressor – A type of
compressor used in cooling systems to compress refrigerant by using a piston
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.
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
Split System – An outdoor unit combined with
an indoor unit.
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.
Upflow Furnace – A furnace that pulls in air
from the bottom and releases it through the top.
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.
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.
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.