Air Conditioner Terms

A guide to keeping your cool

Air conditioner:  Controls temperature, airflow, and humidity in a room.

Air conditioner filter:  Removes particulate matter from the air stream.

AFUE (Annual Fuel Utilization Efficiency):  A score measuring the efficiency of gas heating equipment based on tests devised by the Department of Energy; the amount of heat delivered for each dollar spent on fuel.  A higher rating indicates greater efficiency.

Ambient temperature:  The measured air temperature of the environment around the air conditioning equipment.

BTU (British Thermal Unit):  A measurement of heat; the amount of heat required to raise the temperature of one pound of water one degree Fahrenheit.

BTUH: BTUs per hour.

Central air:  A system that heats or cools air in a central location, then disperses the treated air to different areas through pipes and ducts.

CFM:  Cubic feet per minute; measures the rate of airflow in an air conditioning system.

Compressor:  A pump that circulates cooling medium through the system.

Condenser:  Transfers heat out of a refrigeration system to a medium (either air, water, or a combination of air and water) then disposes of the heated medium. Comes in three types: air-cooled, water-cooled, and evaporative condensers.  Most residential systems use an air-cooled condenser.

Computer room air conditioners:  Systems optimized to create a cool, dry environment for electronic equipment rather than for humans.

Ductless air conditioner:  A powerful unit designed to cool a given volume of space without the installation of permanent ducts or pipes.

EER: Energy Efficiency Rating; the ratio of the cooling capacity of the air conditioner (in BTU per hour) to the total electrical input in watts.

HVAC:  Heating, ventilation, and air conditioning.

Heat pump:  An air conditioning system in which outside air or water is used as a heat source or heat sink, depending upon whether the system is heating or cooling.

Insulation:  A material that hinders heat transfer.

Portable room air conditioners:  Freestanding units that can easily be moved to cool different rooms in a house.

SEER (Seasonal Energy Efficiency Ratio):  The ratio of cooling delivered by a system, measured in BTU) to the dollar cost of the electricity to run the system, as measured in watt-hours.

Single package:  A central air conditioning system that combines condenser and air handling capabilities in a single prepackaged unit.

Split system:  The most common central air conditioner consisting of two or more major components: a compressor unit and condenser, installed outside the building and an air handling unit installed within the building.

Year-round: A system that uses gas or oil for heating.

More information on air conditioners