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The most important first step in the design of a ground source heat pump installation is the accurate calculation of the building's heat loss, its related energy consumption profile and the domestic hot water requirements. This will allow accurate sizing of the heat pump system, which is particularly important because the capital cost of a ground source heat pump system is generally higher than for conventional systems, and economies of scale are more limited.

Oversizing a ground source heat pump will significantly increase the installed cost for little operational saving, and will mean that the period of operation under part load is increased. Frequent cycling reduces equipment life and operating efficiency. If the system is undersized, design conditions may not be met and the use of top-up heating, usually direct acting electric heating, will reduce the overall system efficiency.

A ground source heat pump system can be designed to provide all the required heat (a monovalent system). However, because of the relatively high capital cost, it may be economic to consider a bivalent system where the heat pump is designed to cover the base heating load, while an auxiliary system covers the additional peak demand (e.g. if the savings in capital cost offset any increase in running costs).

Reducing the output temperature required from the heat pump will increase its performance. The majority of ground source heat pumps have an operating temperature limit of 50°C – 55°C in most applications. These are not suitable for monovalent operation in combination with traditionally sized, high temperature wet radiator distribution systems, or for providing all the domestic water heating as they will not be able to raise the water temperature to that required (60°C) to avoid the risk of Legionella. A few heat pumps, however, can provide output temperatures of up to 65°C.

The performance of the ground source heat pump depends on the performance of the ground loop and vice versa. It is therefore essential to design them together.

Closed-loop ground source heat pump systems will not normally require permissions/authorisations from the Environment Agency (see Useful contacts on page 22). However, the Agency can provide comment on proposed schemes with a view to reducing the risk of groundwater pollution or derogation that might result.

The main concerns for ground source heat pumps are:

  • The risk of the underground pipes/boreholes creating an undesirable pathway for water to flow between different water bearing strata.
  • Undesirable temperature changes in the aquifer that may result from the operation of a ground source heat pump.
  • Pollution of groundwater that might occur from leakage of additive chemicals used in the system.

Where there is a risk of, or actual, releases of polluting matter to groundwater the agency can serve statutory notices to protect groundwater. 


Before installing a ground source heat pump, it is important to explore ways of minimising space heating and hot water demand by incorporating energy efficiency measures. (For possible measures see 'Domestic energy efficiency primer' (GPG171/CE101)). 

Ground source heat pump systems

We offer a comprehensive range of Ground source heat pumps, air source heat pumps and water source heat pumps to suit all installations for domestic homes and commercial properties.



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