Air Source Heat Pumps

Air Source Heat Pumps

An Air Source Heat Pump (ASHP) is a system which absorbs heat from the outside air. That heat can then be used to heat radiators, underfloor heating systems, or warm air convectors and provide domestic hot water in your home.

ASHPs can get heat from the air even when the temperature is as low as -25°C.

In the outdoor unit there is an evaporator (grill with fins), a fan draws air across it, latent heat in the air crossing the evaporator is used to increase the temperature of the refrigerant within the evaporator, the refrigerant is now a gas.

Once it has absorbed the latent heat this gas is then passed through a compressor which in turn compresses (squeezes) the gas, this compression cycle of the refrigerant increases the temperature to between 25°C – 75°C. Now the higher temperature gas is passed through a plate heat exchanger this is where the high temperature from the gas is absorbed by the primary water within the heat pump system, this primary water, just like your boiler, is used to heat the house or produce domestic hot water.

There are two main types of air source heat pump systems:

  • An air to water system distributes heat via your wet central heating system. Heat pumps work much more efficiently at a lower temperature than a standard boiler system would. This makes them more suitable for underfloor heating systems or larger radiators, which give out heat at lower temperatures over longer periods of time.
  • An air-to-air system produces warm air which is circulated by fans to heat your home. (Please note, an air-to-air heat pump isn’t eligible for RHI)

An ASHP is installed outside your home, the unit can be fitted to a wall or placed on the ground. It will need plenty of space around it to get a good flow of air.

Image of an air source heat pump