A

AC
Abbreviation for alternating current, a type of electric current in which the polarity is constantly reversing, causing the electron flow to reverse.

ACCA
Air-Conditioning Contractors of America.

Accoustical
Of or pertaining to sound.

AC or DC
Abbreviation for equipment capable of operating on alternating or direct current.

A-Coil
A heat exchanger consisting of two diagonal coils that are joined together in a manner that looks like the letter "A".

AFUE
Annual Fuel Utilization Efficiency. A measure of a gas furnace's efficiency in converting fuel to energy—the higher the rating, the more efficient the unit.

AGA
Abbreviation for American Gas Association, Inc.

Air Conditioner
Any device that can change the temperature, humidity or general quality of the air. More specifically, an air conditioner makes your home cooler, by drawing heat energy out of the house and transferring that heat to the outdoors.

Air cleaner (also Air Filtration System)
Removes airborne allergens from your home.

Air Filtration System (also Air Cleaner)
Removes airborne allergens from your home.

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
An air moving and/or mixing unit. Residential air handlers include a blower, a coil, an expansion device, a heater rack and a filter. Heaters for air handlers are sold as accessories. In some models, heaters are factory installed.

AHRI
Conditioning, Heating & Refrigeration Institute

ASHRAE
American Society of Heating, Refrigeration and Air Conditioning Engineers