Installation of ground source heat pumps
The installation of a ground source heat pump requires digging in your ground loop. This is often done when other building or landscaping work is being done.
With the right installer accredited by the Microgeneration Certification Scheme (MCS) you will be able to ensure that you qualify for the Renewable Heat Incentive, or in the short term the RHPP scheme.
Usually the loop is laid flat, or coiled inside trenches around two metres deep. A typical home needs about 600ft of piping. Usually a ground source installation for a two bed detached house needs a minimum of two trenches about a foot wide and 45m long. The trenches also need to be about 15 feet (5m) apart. Ideally the trenches will be level so as not to strain the pump and the wetter the ground is, the more heat will be conducted through it.
If the ground is very hard, the trench can be shallower (with a minimum depth of 4 feet or 1.2m) and the coils of the ground loop can be laid flat inside the trench rather than the normal upright loop. This, however, is not as efficient. If you do not have enough space in your garden the loop can be installed vertically down into the ground, typically to a depth of up to 100 metres for a domestic home.
There are other types of heat pump which draw heat from different sources and may be suitable:
- Air Source Heat Pumps: They draw heat from the outside air and are popular as they are cheaper and easier to install, particularly if you live in a city with limited outside space.
- 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.
- MVHR (Mechanical Ventilation and Heat Recovery): Exhaust air heat recovery is often called MVHR. These systems recover the heat from air leaving your home via vents. This is most effective in more air-tight homes.
You will need to consider the following:
- Installing a ground loop: Your garden doesn’t have to be particularly large, but you must be able to dig a trench or a borehole and, therefore, the ground must be accessible to digging machinery.
- Home insulation: To be really effective it’s essential that your home is insulated and draught proofed well. Ground source heat pumps produce a lower temperature heat than traditional boilers, therefore draughts make them much less effective.
- Existing heating fuel: When replacing an electric, oil, or solid fuel heating system, a ground source heating system will save you money on your heating bills. The savings are not so dramatic for homes on the gas network.
- Heating system: Under-floor heating systems, larger radiators or low temperature fan convectors (warm air heating) perform better than standard radiator-based systems when used with the pump because of the lower water temperatures required.
- Are you building? Combining the installation with other building work can reduce the cost of installing the system.
For every kilowatt of electricity used by a heat pump to heat water to 35 degrees centigrade, 4 kilowatts of energy are created. This means that GS systems are very efficient.
The term Coefficient of Performance (COP) is used to describe how efficient a heat pump is. The COP is the pump’s ratio of heat output to energy expenditure, so the larger the figure, the more efficient the pump is.
When choosing a system and considering everything including draughts, insulation etc, ideally you should look for a COP of at least 3.5 for a real energy advantage over modern day gas condensing boilers.
This will be very variable and dependent on the size of the system. It is a good idea to combine the pump installation with other building work and, as such, it will be dependent on this also.
Always use an MCS accredited installer: We will only put you in touch with installers that are MCS accredited. Only MCS accredited installers are able to sign off installations that will comply with the government’s Renewable Heat Incentive and RHPP scheme.
- How are the ground loops installed?
- The ground loop is either buried in trenches in the land outside your house at a depth of 1.5-2m or installed in boreholes that range from 25-150m deep. They can also be placed in lakes or ponds to capture the heat from the water - this is usually used on large estates.
- Where should I put my heat pump unit?
- Usual locations include your utility room, basement or even out in the garage.
- Are ground source heat pumps noisy?
- No, they make about the same level of noise as a fridge.
- Will a ground source heat pump be able to heat my home adequately in the winter?
- As long as you have enough space in your garden for a system that meets your needs, and your choice of system is suited to your heating needs, a ground source heat pump should be able to heat your home comfortably in the winter. They are often used very effectively in far colder countries than Britain.
- Can a ground source heat pump be installed in an old building?
- You can install ground source heat pumps in old buildings, and there are lots of examples of this being done. The design phase is very important as there are lots of issues to overcome in older buildings, especially if it is listed.
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