© Envirotemp Refrigeration 2010
Air-source heat pumps draw heat from the outside air during the heating season and reject heat outside during the summer cooling season.
There are two types of air-source heat pumps:
More recently, ductless mini-split heat pumps have been introduced to the Canadian market. They are ideal for retrofit in homes with hydronic or electric resistance baseboard heating. They are wall-mounted, free-air delivery units that can be installed in individual rooms of a house. Up to eight separate indoor wall-mounted units can be served by one outdoor section.
Air-source heat pumps can be add-on, all-electric or bivalent. Add-on heat pumps are designed to be used with another source of supplementary heat, such as an oil, gas or electric furnace. All-electric air-source heat pumps come equipped with their own supplementary heating system in the form of electric-resistance heaters. Bivalent heat pumps are a special type, developed in Canada, that use a gas or propane fired burner to increase the temperature of the air entering the outdoor coil. This allows these units to operate at lower outdoor temperatures.
Air-source heat pumps have also been used in some home ventilation systems to recover heat from outgoing stale air and transfer it to incoming fresh air or to domestic hot water.