How Air Source heat pumps work

Air source heat pumps take ambient heat from the air and concentrate this for use as heating in your home. This significantly reduces the amount of energy from non-renewable sources that you need to use for heating, saving you money and reducing your carbon footprint.

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Technical information made simple

Unlike a ground source heat pump you do not need any outside space to bury piping. However you will need an exterior wall with a good air flow on which to mount the pump. They are generally the size of a small air conditioning unit.

  1. The Air Handling Unit takes energy from the outside air – this is the box that is situated outside. It contains a large fan that draws the external air into the unit.
  2. In the similar way as Ground Source Heat Pumps heat from the air is absorbed into a fluid which is pumped through a heat exchanger in the heat pump.
  3. Heat is extracted by the refrigeration system and then passed through the heat pump compressor, to concentrate it to a higher temperature that is capable of heating water for your heating and hot water systems.

Heat pumps can only deliver heat at lower temperatures, which means that they are most efficient if they are left on constantly during the winter. If you are using a heat pump to heat water for heating then you should use lower temperature radiators, as air source heat pumps do not produce water as hot as gas systems.

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There are two types of Air Source heat pump system, based on how they distribute the heat that they collect from the air into your home:

  • An air-to-water system – distributes heat via your water filled central heating system. For optimum efficiency they tend to use under-floor heating and large radiators as they operate at lower temperatures
  • An air-to-air system – creates warm air which is then circulated by fans to heat your home.

There are other types of heat pump, and they work on a very similar principle but tend to draw heat from different sources:

  1. Ground Source Heat Pumps: They draw heat from the ground and are typically more expensive but generate more heat.
  2. Water source heat pumps: This is very similar to a ground source system except that the ground loop is immersed in water, such as a lake or river.
  3. MVHR (Mechanical Ventilation and Heat Recovery): Exhaust-air-source systems, which are often called MVHR. These systems recover the heat from air leaving your home via vents. This is most effective in more air-tight homes.

Installation

In order to qualify for the Renewable Heat Incentive and RHPP the system must be fitted by a MCS accredited installer. Find out more about the Installation of Air Source Heat Pumps.

FAQs

How much noise do air source heat pumps generate?
Most modern air source heat pumps are fairly quiet. The noisy part is the air handling unit, which makes a similar level of noise as an air-conditioning unit. The heat pump itself, which is often installed inside, makes a noise too, but this is typically no more than the noise of a fridge.
Will an air source heat pump provide enough hot water for heating and hot water?
If you do not heat your water beyond 55°C and your system has been correctly scaled and fitted for your needs there is no reason why all your domestic hot water requirements shouldn't be provided by the air source heat pump throughout the year. It should be noted that heat pumps produce water at a lower temperature than boiler systems, meaning that you will need larger radiators or an underfloor heating system or the pump to heat your house effectively.
What properties are not suitable for an air source heat pump installation?
Air source heat pumps are not suitable for use in houses where the levels of insulation are not known and where the age and type of the heating distribution system (radiators and pipes) is unknown. Because they produce hot water at a lower temperature than conventional boilers they are particularly suited to house with under-floor heating.
Can I heat my swimming Pool with an air source heat pump?
Air source heat pumps are ideal for pools. Note that for existing swimming pools the current heat exchanger would need to be changed.
How much hot water is produced each day by an air source heat pump?
This will depend on the make and model of air source heat pump that you're planning to use, but a well chosen pump should be able to meet all of your heating needs. You should aim to get advice from at least one well accredited installer when choosing a model.
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