GROUND SOURCE HEAT – QUESTIONS AND ANSWERS
Ground source heat pumps use pipes buried in the garden to extract heat from the ground. This is usually used to heat radiators or underfloor heating systems and hot water.
How does a ground source heat pump work?
A ground source heat pump circulates a mixture of water and antifreeze around a loop of pipe – called a ground loop – which is buried in the garden. Heat from the ground is absorbed into this fluid and is pumped through a heat exchanger in the heat pump. Low grade heat passes through the heat pump compressor and is concentrated into a higher temperature useful heat capable of warming water for the heating and hot water circuits of the house. Ground loop fluid, now cooler, passes back into the ground where it absorbs further energy from the ground in a continuous process while heating is required.
The length of the ground loop depends on the size of your home and the amount of heat you need – longer loops can draw more heat from the ground, but need more space.
Normally, the loop is laid flat or coiled in trenches one to two metres deep, but if there is not enough space in your garden you can install a vertical loop down into a bore hole to a depth of up to 100 metres.
Heat pumps have some impact on the environment as they need electricity to run, but the heat they extract from the ground, air, or water is constantly being renewed naturally.
Unlike gas or oil boilers, heat pumps deliver heat at lower temperatures over much longer periods. This means that during the winter they may need to be left on 24/7 to heat your home efficiently. It also means that radiators should never feel as hot to the touch as they would do when using a gas or oil boiler.
Is your garden suitable for a ground loop?
It doesn't have to be particularly large, but the ground needs to be suitable for digging a trench or a borehole and accessible to digging machinery. The output from the pump varies from site to site because soil conditions can have a significant impact on performance.
Is your home well insulated?
Since ground source heat pumps produce a lower temperature heat than traditional boilers, it is essential that your home is insulated and draught proofed well for the heating system to be effective.
It could also make the system cheaper and smaller.
What fuel will you be replacing?
If you're replacing an electric, oil or coal heating system, ground source will save you more on your heating bills. Heat pumps are not usually recommended for homes on the gas network.
What type of heating system will you use?
Underfloor heating systems, larger radiators or low temperature fan convectors (warm air heating) can perform better than standard radiator-based systems because of the lower water temperatures required.
What are the costs of installing?
Costs of installing a typical system range from about £9,000 to £20,000 depending on the size of the house. Grants of about £750 may be available from April next year.