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Air Source Heat Pumps

Air source heat pumps collect heat from the air, permitting a quicker and simpler installation compared to ground source heat pumps, which require installation of extensive ground heat collector loops. Depending on the particular project, air source units can be positioned inside, nearby or up to 50 metres from the building
Air source heat pumps are easy to install in new build or retrofit into existing properties. 
They can provide effective space heating and hot water for homes, commercial properties, and swimming pool water heating.

How Air Source Heat Pumps Work

Air source heat pumps have to work harder during the winter months, due to the large variation in air temperature between summer to winter. During the Summer there is more heat in the air, so it is easier for the air source heat pump to extract it. 
However, even though there is a limit to how cold the air can be before the heat pump stops working, they are designed to still be able to extract heat from the air on a cold winters day. even when the air temperature is below zero. 
Anything that is above absolute zero (-273 degrees celsius or 0 kelvin) contains heat. We are all so familiar with the Celsius temperature scale we are all conditioned to think that anything higher than zero degrees (the melting point of water) is warm and every thing below zero is cold.  

Correct design and installation of the air source system is essential to ensure that they work as efficiently as possible for each property, because
some of the key differences between heat pumps from different manufacturers come down to how efficiently they operate at low air temperatures. So for example an air source heat pump that is suitable for a property in the North of Scotland would be unlikely to be suitable for an identical property on the South Coast of England.
A heat pump uses the same principle to transfer heat that fridges use.  
Fridges keep cool by pumping heat away from food and drink to the grill on the back; a heat pump uses the same principle to transfer heat- extracting it from the renewable source and pumping it into buildings.  
A refrigeration cycle uses the renewable energy that is extracted from the air, ground or water to boil a special liquid refrigerant into a gas, these liquids have a boiling point that is much lower than that of water.  
The gas produced is then compressed, becoming hot and this heat is extracted, turning the gas back into a liquid again… and the cycle restarts. 
If you try pumping a bicycle pump with your thumb held on the end, as the air is compressed the pump will become hot. The is a simple experiment which shows how heat is generated when a gas is compressed.

How reliable are heat pumps and how much maintenance do they need?

In Europe and North America heat pumps have been used for decades. 

The refrigeration cycle on which they function is a tried and tested technology, so they tend to be extremely reliable.  However, in order to ensure they continue to run as reliably and as efficiently as possible, an annual service- just as with a conventional boiler- is recommended. 

Why are heat pumps becoming more commonly used?

Heat pumps are a very efficient way of indirectly using electricity to heat a home by extracting available heat from the ground or air. In doing so they can provide low running costs and low carbon heat. 


Traditionally the UK had fossil fuels aplenty, with oil and gas from the North Sea and extensive coal extraction processes. The two main issues with this, however are firstly the unsustainable burning of fossil fuels releasing climate changing carbon dioxide that had previously been locked away underground. The second issue is the cost, with rapidly rising energy prices whilst the UK imports oil and gas from abroad.

Temperature of the hot water produced

Heat pumps heat water to around 40 degrees celsius, which is the flow temperature at which underfloor heating systems work. Heat pumps will maintain a hot water cylinder at a temperature of around 55 degrees celsius - which is hotter than would be required for a bath or shower, though would less efficient at producing higher water temperatures than this. Heat pumps also automatically run periodic legionella cycles to ensure the eradication of any bacteria that might still survive at 55 degrees.

How much maintenance do Air Source Heat Pumps need?

Very little.

It is important to ensure that the external fan unit is clean and free of leaves or other such waste or vegetation that could impede the flow of air through it. This is particularly relevant in the Autumn months as leaves are falling and the system is starting to work harder with the approaching colder weather.  


The heat pump itself is a sealed system and so no waste gases, ash or moisture are produced.  

It is recommended that the heat pump be serviced annually by an accredited company to glycol refrigerant levels and system operating efficiency, but otherwise it should be maintenance free.

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