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

Do air source heat pumps work all year round?
According to air source heat pump manufacturers they are efficient down to air temperatures of -20°c, which means that they are more than suitable for installations within the UK. Heat pumps can produce water heated at 55C all year round in the UK without the aid of electrical immersions.
Where in my house should an air source heat pump be installed?
The bulkiest component of an air source heat pump is the air handling unit, which must be fitted outside. The unit can be fitted on an outside wall, but some designs allow this to be fitted some way away from the home, as far as 20-30 meters. The heat pump needs to be in or on the house and typically this is where the essential components are housed.
How much space do I need for my air source heat pump?
This will depend on the make and model of the heat pump. The air handling unit component of the pump will need to be fitted in a location where air can circulate freely, so typically on an outside wall. Typically the air handling unit will be similar in size to a kitchen appliance, such as a washing machine or dishwasher. You will also need space inside your house for the heat pump itself.
How many air source heat pumps would I need for a large building?
This depends on the model that you choose, however if you home is well insulated you will need fewer heat pumps to maintain the same temperature level. Your installer will be able to advise you on exactly how many you will need.
How much do they cost and how much will I save?
Complete our free home Energy Assessment to find out how much a typical air source heat pump would cost for your house, how much it would save you and how long the payback will be.
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