When are Air Source Heat Pumps best used?

When are Air Source Heat Pumps best used?

- in Home Improvement

If you’re looking to increase the efficiency of a heating system, it may be worth you considering an Air Source Heat Pump (ASHP). However, ASHPs (or Air to Water Pumps as they are also known) are best used in certain circumstances to achieve maximum effectiveness.

Air Source Heat Pumps are an ideal alternative to a Ground Source Heat Pump where a ground array cannot be installed – such as limited external ground space.

ASHPs work with underfloor heating systems and radiator based systems, and in conjunction with electric or oil-fired boilers to dock to an existing heating/hot water system.

Air Source Heat Pumps extract heat from the surrounding air, rather than from the ground collection methods of a GSHP.

Considerations for best use of Air Source Heat Pumps

According to IsoEnergy a few key considerations will ensure the optimum efficiency and usage of an Air Source Heat Pump.

Power supply

Electricity in the form of three or single phase will be needed.

Groundworks/builders work

An ASHP requires a solid base – either concrete or similar hardstanding – to be positioned upon. A condensate soakaway will also need to be constructed.

Factors affecting the location of the ASHP

For optimum results, the pump should be located as close to the plant room as possible. This also minimizes cabling and ancillary works for distribution and connectivity.

A good flow of air is essential on both the input and exhaust sides, so physical obstructions such as trees or where the potential of falling debris may occur need to be avoided.

To maintain optimum airflow and avoid recycling of the cold exhaust air, minimum clearances need to be ensured.

Additional plant room sundries

Depending on the configuration of the renewables, high capacity hot water tanks or buffer tanks may also be required. Thus, it is essential when planning for an ASHP to consider the available space in a plant room and the sizes of any tanks.

Distribution system or heating emitters

For optimums results, it is often better to install Air Source Heat Pumps in conjunction with under-floor heating systems or warm air heating than with radiator-based systems due to the lower water temperatures required.

Of course, radiator based systems can still be incorporated, but it is essential that full consideration is given at planning and design stage.

Winter months – exposure to frosting/freezing

All Air Source Heat Pumps are not always optimized for the UK climate and can succumb to freezing up in the winter. Whilst this will not prevent the system from working, the ASHP will use electricity to defrost the evaporator heat exchange, resulting in increased running costs as the system is less efficient.

This can be easily avoided by dealing with experienced designers and consultants of Air Source Heat Pumps that will advise on the most effective ASHPs to include in a system.


Due to the potential complexity of installation and the many requirements considered, it is always advisable to seek professional design consultation when to consider an Air Source Heat Pump.

Consulting with experts such as Isoenergy will ensure factors such as plant room layout considerations and design of the ASHP system are optimized for peak results.

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