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 long should the ground loop be?
- That depends on the energy requirements of your house, the space that you have available and the type of ground you have. The larger the home that is to be heated, more energy that is required thus more loop needed in the ground. When planning and designing your system your installer will design your system so that it meets your needs.Typical systems are 6 to 12kW, and you'll usually need 10m of coiled pipe per kW for installation in horizontal trenches - you'll need less piping if you're installing it in a vertical borehole. If ground space is restricted, a vertical borehole (or several) is a good choice - these are now comparable in cost to installing the loops in horizontal trenches.
- Where should I put my heat pump unit?
- Usual locations include your utility room, basement or even out in the garage.
- Can a ground source heat pump be used with underfloor heating?
- Underfloor heating is a great choice for use with a ground source heat pump, but large radiators or a mix of both can be used for distributing heat around your home. Heat pumps produce a lower temperature heat than conventional boilers, therefore they are far more effective if used with a larger surface heating distribution system such as underfloor heating or large radiators. A good rule of thumb is that if used with heat pumps, the radiators should be around 30% larger compared to the size of radiator that would be used with a conventional boiler.
- 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 I heat a swimming pool using a ground source heat pump?
- Yes, a system can be designed purely for your pool, be it indoor or outdoor, and if required it can form a heating and hot water system for the whole of your property.
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