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 in residential
Heating and Cooling.
C D E
F G H
I K L
M N O
P R S
T U V
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
exchanger consisting of two diagonal coils that are joined
together and looks like the letter "A".
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 Balance Test -
A test used to measure airflow across a tower or air
Air Balancing Hood -
Measures airflow from grilles and diffusers.
Air Conditioner - A device that changes
humidity levels, temperature or quality of air.
Air Flow Volume
The amount of air the system circulates through your home,
expressed in cubic feet per minute (cfm). Proper air flow
depends on the outdoor unit, the indoor unit, the ductwork and
even whether the filters are clean.
Air Handler - Parts of a system including
the fan-blower, filter and housing.
portion of the central air conditioning or heat pump system that
moves heated or cooled air throughout a home’s ductwork. In some
systems a furnace handles this function.
Amp (Ampere) -
The practical meter-kilogram-second unit of electric current
that is equivalent to a flow of one coulomb per second or to the
steady current produced by one volt /web/20130605221219/http://en.wikipedia.org/wiki/Azeotrope">azeotropic
pentafluoroethane which is used
as a refrigerant in air conditioning /web/20130605221219/http://en.wikipedia.org/wiki/Haloalkane">
haloalkane refrigerants it does
not contribute to ozone depletion, and is therefore becoming
more widely used as ozone-depleting refrigerants like R-22 are
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.
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.
Variable Speed -
A "smart" motor that runs on DC current and can vary
it's operating speed using less electricity and providing
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