This term has two meanings: 1. A major part of a furnace that transfers heat created in the fuel combustion area to the surrounding air that is pumped into the rooms. This component can develop rust holes or other leaks and problems. To prevent carbon monoxide gas from entering the living areas and for other reasons, the heat exchanger and heating system should be professionally checked regularly. 2. A condenser or evaporator device in which heat is added or extracted to heat or cool indoor space.

The amount of heat lost, measured in BTU's from a space to be conditioned, at the local winter outdoor design temperature and a specified indoor design condition.

A type of mechanical compression cycle refrigeration system capable of heating. Heat pumps come in many varieties. Some can be reversed to either heat or cool indoor space, while others are for heating only. One main benefit of heat pumps is their ability to use naturally occurring temperature differentials in air, ground, or water as a heat source or sink to provide indoor comfort.

Heat Pumps have the ability to move heat energy from one environment to another, and in either direction. This allows the heat pump to bring heat into an occupied space, or to take it out. In cooling mode a heat pump works the same as an ordinary air conditioner (A/C).

A body of air or liquid from which heat is collected. With any heat pumps, the air outside the home is used as the heat source during the heating cycle.

The rate at which a specific device can add substantial heat to a substance, expressed in BTUh (British Thermal Units per hour).

A general term for a coil device that serves as a heat source. A coil unit is made of tubing or pipe.

A furnace that lies on its side, pulling in return air from one side and expelling warm air from the other.

Abbreviation for (Heating Seasonal Performance Factor). Means the total heating output of a heat pump in British Thermal Units during its normal usage period for heating divided by the total electrical energy input in watt-hours during the same period.

A device that adds water vapor to the indoor air to increase humidity. Contrast with dehumidifier.

A type of indoor comfort control device that senses humidity and cycles a humidifier on and off.

The amount of moisture in the air. Air conditioners remove moisture for added comfort.

Abbreviation for (Heating, Ventilation, and Air Conditioning). Control of the indoor environment (temperature, humidity, air flow, and air filtering) of a home or building.