BTUH:
The number of BTUs produced in one hour.

Closed-loop heat-pump system:
A heat-pump system that uses a loop of buried plastic pipe as a heat exchanger. Loops can be horizontal or vertical.

COP (Coefficient of Performance):
The ratio of heating or cooling provided by a heat pump (or other refrigeration machine) to the energy consumed by the system under designated operating conditions. The higher the COP, the more efficient the system.

Compressor:
The central part of a heat pump system. The compressor increases the pressure and temperature of the refrigerant and simultaneously reduces its volume while causing the refrigerant to move through the system.

Condenser:
A heat exchanger in which hot, pressurized (gaseous) refrigerant is condensed by transferring heat to cooler surrounding air, water or earth.

Cycling losses:
The actual efficiency of a heating or cooling system is reduced because of start-up and shut-down losses. Oversizing a heating or cooling system increases cycling losses.

Desuperheater:
A device for recovering superheat from the compressor discharge gas of a heat pump or central air conditioner for use in heating or preheating water.

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 that uses the earth as a heat source and heat sink.

Heat exchanger:
A device designed to transfer heat between two physically separated fluids or mediums of different temperatures.

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.

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.

Open-loop heat-pump system:
A heat-pump system that uses groundwater from a well or surface water from a lake, pond or river as a heat source. The water is returned to the environment.

Payback:
A method of calculating how long it will take to recover the difference in cost between two different heating and cooling systems by using the energy and maintenance-cost savings from the more efficient system.

Supplemental heating:
A heating system used during extremely cold weather, when additional heat is needed to moderate indoor temperatures. May be in the form of fossil fuel or electric resistance.

Conversion Table