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FAQs – Ground Source Heat Pumps
The heat in the ground comes from the sun rather than the common misconception it is geothermal heat coming from the Earth’s core. Depending on where you are in the UK the temperature of the earth is around 8 – 10°c throughout the year.
An “array” of pipes filled with an environmentally friendly anti-freeze and water solution is buried 1m below the ground surface, keeping pipes apart by a similar amount. The ground source heat pump circulates the “brine” through the array which absorbs heat from the ground, increasing its temperature by 2 – 3°c. The ground source heat pump, through the refrigeration cycle, intensifies the small increase in brine temperature to a level whereby it can be used for space and hot water heating.
As heat is extracted through the winter it is important that the ground is allowed to recover this energy in the summer months to prevent it cooling over time.
The rule of thumb for a horizontal collector loop for a house meeting current building regulations is that a minimum an area of land twice that of the floor area of the property will be required to bury the collector loops. The exact amount will depend on a number of factors including soil type, heating requirements of the home and how wet the ground is.
Sizing the ground loop is just as critical as calculating the heat load of the house. If there is insufficient ground collector, or too much heat is extracted from the ground there is danger of a vicious circle being created with the ground source heat pump working harder to extract heat from the cooling earth making it less efficient, and increasing running costs. The ultimate result is the ground will freeze and the ground source heat pump fail.
Where there is not enough ground for a horizontal collector it is possible to collect heat from boreholes. These are slightly more efficient than horizontal collectors but drilling can be expensive.
Other options for collecting heat exist from water source collectors or “open-loop” collectors from subterranean aquifers, lakes or rivers.
No, the collectors should be buried more than 1m below the surface and will leave no trace
The wetter the ground conditions the better! Water is the conductor to moving heat through the ground and is an excellent medium to have around the collector array. Well drained sandy soils that do not retain water require more collector loop than wet loamy soils.
This will depend on how well your property is insulated. Most heat pumps produce low grade heat so cannot produce high flow temperatures and therefore your property will not heat up quickly from cold. For this reason, they run most efficiently by maintaining the property at a constant temperature with heat emitters such as under floor heating or fan-convectors designed for low flow temperature systems. Traditional radiators can be used however to work at low flow tempertures may require to be oversized.
For some older properties that are poorly insulated and where an air source heat pump alone may not cope at the coldest times of the year, they can be docked with a fossil fuel boiler to provide supplemental heat. Such systems allow the property owner to enjoy all the efficiencies and benefits of a heat pump whilst ensuring they remain warm all year.
The efficiency of a ground source heat pumps is often referred to as its Coefficient of Performance (CoP) or as a Seasonal Performance Factor (SPF). The CoP is the performance of the heat pump at a stated ground temperature and flow temperature, whereas the SPF reflects the performance of the GSHP over a year.
A correctly sized ground source heat pump and collector array for a well-insulated home will be around 400 – 500% (SPF of 4 to 5) efficient, this means that for every 1kW of energy put into the ground source heat pump, between 4 to 5kWh of energy is delivered.
As part of the system design, Fervo will advise you what the SPF of your ground source heat pump will be and what it will provide an estimate as to what it will cost to run.
A ground source heat pump has greatest efficiencies when connected to an under floor heating system or fan convectors designed for use with a heat pump. Traditional radiators can also be used provided they are correctly sized. Several radiator manufacturers now have ranges designed for use with heat pumps.
Yes, the ground source heat pump will meet all your heating needs and hot water requirements. Heat pumps, whilst still a relatively new technology to the UK have been a primary heat source to homes across Scandinavia for over 40 years.
Fervo, as an accredited MCS installer are required to ensure that our recommendations meet all your heating and hot water needs.
Yes. As with many renewable energy systems a ground source heat pump can be docked with fossil fuel systems and can form part of an integrated energy system with the likes of MVHR, solar thermal and solar PV.
Most ground source heat pump systems comprise three indoor elements being the heat pump itself, a hot water tank and a buffer tank which improves the efficiency of the ground source heat pump by levelling out peak heat demands. The capacity of the two tanks will be dependent on the size of the property whilst most ground source heat pumps are comparable in size to a fridge freezer. Many ground source heat pump systems combine individual elements such as the heat pump/hot water tank or the hot water tank/buffer tank into a single unit thereby saving space.
Typically, a ground source heat pump will be located in a plant room, utility room or garage. If planning a new build property, it is always advisable to consider where to accommodate the it and tanks at an early stage of the design which Fervo would be pleased to discuss this with you.
Ground source heat pumps are built to last and with relatively few moving parts with life expectancies well over 20 years. Warranties, depending on manufacturers, vary from two to seven years.
Ground loops frequently come with warranties of 50 years. It is always advisable, as with any heating system to have a ground source heat pump serviced annually which Fervo can arrange.
Most heat pump systems are “weather compensated” to keep your indoor climate at a constant level of comfort. When the weather turns colder the GSHP will work harder to produce just sufficient heat to maintain your desired indoor temperature. This is all done automatically.
No, in most instances planning permission is not required.
If you have any other questions regarding ground Source Heat Pumps or would like to discuss how you can incorporate into your project, please contact us