Description
Outside air, at any temperature above absolute zero, contains some heat. An air-source heat pump moves ('pumps') some of this heat to provide hot water or space heating. This can be done in either direction, to cool or heat the interior of a building.
The main components of an air-source heat pump are:
An outdoor heat exchanger coil, which extracts heat from ambient air
An indoor heat exchanger coil, which transfers the heat into a water tank or indoor heating system, such as radiators or under-floor circuits
Air source heat pumps can provide fairly low cost space heating. A high efficiency heat pump can provide up to four times as much heat as an electric heater using the same energy.[citation needed] In comparison to gas as a primary heat source, however, the lifetime cost of an air source heat pump may be affected by the high price of electricity versus gas (where available). Gas may cause higher carbon emissions, depending upon how the electricity is generated.
A "standard" air sourced heat pump found in most homes can extract useful heat down to about -5F or 0F (-15c).[citation needed] At colder outdoor temperatures the heat pump is inefficient; it could be switched off to run only on supplemental heat (or emergency heat) if the supplemental heat is sized large enough. There are specially designed heat pumps that, while giving up some performance in a/c mode, will provide useful heat extraction to even lower outdoor temperatures. An air source heat pump designed specifically for very cold climates can extract useful heat from ambient air as cold as -20F or even -25F (-30c), but these are uncommon in most homes.[citation needed]
Air source heat pumps can last for over 20 years with low maintenance requirements.[citation needed] There are numerous heat pumps from the 1970s and 1980s that are still in service as of 2011, even in places where winters are extremely cold. Few moving parts reduce maintenance requirements, however, the outdoor heat exchanger and fan must be kept free from leaves and debris. Heat pumps have significantly more moving parts than an equivalent electric resistance heater or fuel burning heater.[citation needed]
Usage
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