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AIR CONDITIONING - The process of controlling the temperature, humidity, cleanliness and distribution of air in a building.   


AIR HANDLER - Indoor unit (in ELECTRIC-HEAT applications) which contains the blower motor, evaporator coil and heat-strip device.  Also known as FAN COIL.   


BTU - British Thermal Unit.   Amount of heat necessary to change the temperature of 1 lb. of water 1 degree Fahrenheit. In air conditioning, we measure the size of an air conditioning system by BTU's (or tons of air conditioning).   Each TON of air conditioning equals 12,000 BTU's.  


CFM - cubic feet per minute.   Measurement of volume of air.  


COMPRESSOR - Mechanical device used to compress gas/refrigerant.   Located in the outdoor unit (condensing unit).


CONDENSER COILS - The component in an air conditioning circuit that releases heat into the air.  Usually referred to as the "outdoor coil" and is the hot side of an air conditioning system.  


CONDENSING UNIT - Outdoor unit which contains compressor, fan motor and condenser coils.   


EFFICIENCY - Rating on air conditioning equipment similar to MPG (miles per gallon) rating used on automobiles.  The higher the efficiency, the less electricity used by the equipment and cheaper to operate.  We use SEER rating to measure a system's efficiency. 




EVAPORATOR - The component in an air conditioning circuit that absorbs heat from the air.  Usually referred to as the "indoor coil" and is the cold side of an air conditioning system.    






FURNACE - Indoor unit (in GAS-HEAT applications) which contains the blower motor and heat exchanger.  The evaporator coil usually mounts next-to or on top of this unit on most air conditioning systems.  


HEAT EXCHANGER - Located inside the gas furnace, this component is where heat transfer takes place, bringing heat from a gas-fired source to the air.  


HEAT PUMP - An alternative air conditioning system, in which the outdoor unit reverses the flow of refrigerant and pumps heat INTO the house, rather than out of the house.   Where the outdoor unit is normally the condensing unit and the indoor coil is normally the evaporator, on a HEAT-PUMP system the opposite is true.   In HEAT-mode, the outdoor unit becomes the evaporator and the indoor unit becomes the condenser.   In COOL-mode, a heat-pump works exactly like a normal air conditioning unit.  


HVAC - stands for Heating, Ventilation & Air Conditioning.  


R-22 - Older refrigerant.   Being phased out of production.  


R-410A - Newer refrigerant.   Replacing R-22.  


REFRIGERANT - A substance/gas which produces a refrigerating (or "cooling") effect, when expanding or vaporizing. 


SEER - Seasonal Energy Efficiency Ratio.   Energy-efficiency rating system for air conditioners.   The higher the SEER rating, the more efficient the system and the lower the operating cost.  


SPLIT SYSTEM - Air Conditioning System, in which some components are located on inside (evaporator) and some components are located on outside (condensing unit). 


THERMOSTAT - Device used to turn system on / off and to display and regulate temperature. 


TWO STAGE OPERATION - High Speed and Low Speed operation of a device (usually outdoor unit), which allows for quieter operation and increased efficiency and comfort levels.  Usually requires variable-speed indoor blower.  


TXV - Thermostatic Expansion Valve.   Device found on indoor evaporator coil, which monitors and regulates when refrigerant is flashed from liquid to vapor.   This is where "cooling" takes place.   Alternatives to TXV's that are not as efficient are pistons and capillary tubes.   


VARIABLE SPEED - Describes a fan motor with multiple speeds, which allows for quieter operation and increased efficiency and comfort levels.  

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