How Air Source Heat Pumps Work

An air source heat pump system is comprised of a heat pump unit which can be located inside or outside your home, as well as an evaporator and a condenser to transfer the captured heat from the air to either heating or hot water production. The technology functions very similarly to a refrigeration process by moving energy from one place to another.

The air handling unit is typically situated outside the building, and draws air into the heat exchange unit, where a transfer fluid draws low temperature energy from the air. The energy in the transfer fluid is then passed via the evaporator into a liquid refrigerant to convert it into a gas.

This gas is transported to a compressor, where the pressure is increased, which causes the temperature of the compressed gas to rise dramatically. In the condenser the heat in the refrigerant is transferred to the buildings heating system through a second heat exchanger. The temperature and pressure of the refrigerant is then decreased, turning the gas back into a liquid. The refrigerant is then forwarded to the evaporator where it is once again reheated into a gas.

Air source heat pumps can perform down to air temperatures of -20°c which means that they are more than suitable for installations within the UK. Hot water and heating can be provided 365 days a year. The hot water is produced without the aid of electrical immersions and at 55°c is more than hot enough for baths and showers.

The main components of an air source heat pump are:

• A heat exchanger, over which air is blown, to extract the heat from the air
• A compressor, which acts like a refrigerator but in reverse and raises the temperature from the outside air
• A way to transfer the heat into a hot water tank or heating system, such as radiators or under-floor heating tubes