Glossary of Terms

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EPA: The Environmental Protection Agency develops and enforces federal environmental regulations.

Evaporator Coil: Part of a split-system air conditioner or heat pump typically located inside a building in an air handler or on a furnace. The evaporator coil cools and dehumidifies the air by converting liquid refrigerant into a gas (or vice versa). A blower motor (from the air handler or furnace) then moves the air over the coil to either heat or cool your home.

Fan Coil: An indoor component of an air conditioner or heat pump system, used in place of a furnace and evaporator coil, to provide a change in the refrigerant from a gas to a liquid (or vice versa) and blow air over the coil to either heat or cool your home. Sometimes called Air Handler.

Fossil Fuel: Any of several types of combustible fuels formed from the decomposition of organic matter. Examples are natural gas, propane, fuel oil, oil, and coal.

Geothermal Heat Pump: A heat pump system that uses the earth as a heat source or heat sink.

Heat Exchanger: Located in a fossil fuel furnace or boiler, the heat exchanger transfers heat from the combustion process to the surrounding air or liquid medium. It is then pumped throughout the home for heating.

Heat pump: A mechanical device used for heating and cooling, which operates by pumping heat from a cooler to a warmer location. Heat pumps can extract heat from air, water, or the earth. They are classified as either air-source or geothermal units. During the winter, a heat pump draws heat from the exterior and circulates it through your home’s heating system. In the summer, it reverses the process and removes heat from your house and releases it to the exterior.

Heat Sink: The medium- air, water, or earth- which receives heat rejected from a heat pump.

Heat Source: The medium- air, water, or earth- from which heat is extracted by a heat pump.

HSPF: Heating Seasonal Performance Factor is a measure of the heating efficiency of an air source heat pump. HSPF is a ratio of BTU heat output over the heating season to Watt-hours of electricity used. The higher the HSPF number, the more efficient the heat pump heats your home. The DOE’s established minimum HSPF rating is 7.7.