Glossary of Heating and Cooling Terms
AFUE – Annual Fuel Utilization Efficiency, a rating that reflects the efficiency of a gas furnace in converting fuel to energy. A rating of 80 means that approximately 80 percent of the fuel is utilized to provide warmth to your home, while the remaining 10 percent escapes as exhaust. A 96.7% afue furnace is the best available and it receives tax credit of $1500 from the federal government.
BTU – British Thermal Unit. A BTU represents the amount of energy required to raise one pound of water one degree Fahrenheit. One BTU is the equivalent to the amount of heat given off by a single wooden kitchen match. It is the measure of heat given off when natural gas or electricity is used for heating or the measure of heat extracted from your home for cooling. All furnaces and air conditioners have a BTU rating.
CFM – Cubic feet per minute, a standard of airflow measurement. A gas system produces 400 CFM per ton of air conditioning while a heat pump produces 450 CFM per ton.
Capacity – The output capability of a cooling or heating unit. Cooling and heating capacity are normally referred to and measure in BTUs.
Compressor – The internal heart of an air conditioning or heat pump system. It is the piece of the outdoor unit that pumps refrigerant to the indoor coil. The compressor pumps up and maintains the proper amount pressure needed to force refrigerant to flow in sufficient quantities in order to meet the cooling requirements of the system.
Condenser- This is the proper name for the outdoor unit most commonly called the air conditioner. The condenser contains the compressor, the outdoor coil, the contactor and many other components.
Condenser Coil or Outdoor Coil – Located in the outdoor air conditioner unit, the coil removes heat from the refrigerant, changing the refrigerant from gas vapor to a liquid. The outdoor fan pulls air through the coil and discharges the heat out the top or the side of the air conditioner or condenser.
Contactor–Electrical switch that is normally open and when closed, sends power to the compressor and outdoor fan motor to start the outdoor unit.
Damper – Installed indoor in ductwork, this movable plate opens and closes to control the amount of airflow to specific ducts and trunks. Motorized dampers are used effectively in zoning to regulate airflow to certain rooms or zones.
Downflow Furnace – A furnace that pulls in return air from the top and expels conditioned air at the bottom. Normally found in a closet or attic.
Ductwork – Metal or flexible pipes and channels that distribute air throughout your home or office.
Evaporator Coil/ Cooling Coil – The coil that is mounted on the top or the end of your furnace in a split system. In the evaporator, refrigerant evaporates and absorbs heat from air passed over the coil and moisture is removed from the air and collected in a pan to be drained outside.
Heat Exchanger – A containment vessel in the furnace in which gas is burned, heating the metal of the heat exchanger. Air is then passed over the hot metal, exchanging the heat to the air coming form the furnace blower.
Horizontal Furnace – A furnace that lies on its side, drawing in return air from one side and deliver conditioner air from the other. Normally found in crawl spaces or attics.
Humidifier – A device that evaporates water into vapor and sends it to the heated air of your furnace to keep from drying out you and your home.
Humidity – The amount of moisture suspended in the air. Air conditioners remove moisture for comfort in the summer and gas furnace dry out the air in the winter to the point you get static electricity and dry skin.
HSPF – Heating Seasonal Performance Factor. Measurement of the efficiency of the heating mode of heat pumps over an entire heating season. The higher the HSPF number, the more efficient the unit.
HVAC – Abbreviation for heating, ventilation and air conditioning.
ICM – Internally Commuted Motor. A D/C powered variable-speed motor used in furnaces and air handlers to provide greater comfort and dehumidification. ICM motors are more than 90 percent efficient versus 60 percent efficiency for conventional motors and only consume $30 a year in the typical home. Continuous comfort, quiet operation, and ultimate system efficiency are the benefits of the indoor products using the ICM motor.
Packaged System – An air conditioning and heating unit in which all components are located in one cabinet. Normally found in commercial applications and occasionally in residential applications, the packaged unit is installed on the rooftop or on the ground next to a home or business.
Refrigerant – A substance that removes heat as it is expanding or vaporizing.
Refrigerant Lines – Set of two copper lines connecting the outdoor unit and the indoor unit. One is covered in a black insulation and the other is a small round tube.
Reversing Valve- A valve in a heat pump that reverses the flow of refrigerant as the system is switched from cooling to heating.
SEER – Seasonal Energy Efficiency Ratio, a rating that measures the cooling efficiency of a heat pump or air conditioner. The higher the number, the more efficient the unit. The minimum SEER today is 13 and units are available up to 24 SEER.
Split System – Refers to a heating and cooling system configuration consisting of components in two locations. Common examples include an outside unit, such as an air conditioner, and an indoor unit, such as a furnace and coil. These pieces are connected by the line set.
Thermostat – A temperature control device, typically found on a wall inside the home. It consists of a series of sensors and relays that monitor and control the functions of a heating and cooling system. Programmable thermostats allow you to program different levels of comfort for different times of the day. Dehumidification thermostats allow you to control not only temperature but also humidity.
Ton – A unit of measurement used for determining cooling capacity of an air conditioner or heat pump. One ton is the equivalent of 12,000 BTUs per hour and it is called a ton because that is the amount of heat required to melt one solid block of ice weighing one ton.
Upflow Furnace – A furnace that pulls return air in from the bottom and expels warm air from the top. Most common furnace produced in America.
Zoning – A method of dividing a home into zones, each with it’s own thermostat or sensor which enables you to control the amount of comfort provided to each zone or area of your home or business.