What is a Ground Source Heat Pump System?
Ground source heat pumps work by harnessing the natural heat underground to provide homes with an efficient source of heating and hot water.
Temperatures underground sit at between 10-15°C and no matter the time of year, the temperature at this level stays the same so you can use the system in all seasons.
How ground source heat pumps work
Ground source systems are made up of 3 different parts that work together to harness heat from the ground and transfer it into the home:
This is a pipe buried underground, usually in the garden, either in a horizontal trench or a vertical borehole. A horizontal trench goes 2 metres below ground level, while boreholes are drilled further down to between 15 and 150 metres. More heat can be extracted from the ground with longer loops but the space available will determine the most suitable ground heat exchange loop.
Circulating around these pipes will be a mixture of water and antifreeze. The natural heat underground is absorbed by the fluid which then goes through a heat exchanger into the heat pump.
Once the liquid from the pipes, heated by the ground, reaches the heat pump it's able to increase the temperature further before circulating it around the home. To do this, the heat pump compresses refrigerant gases which gets hot and then transfers the heat, using a heat exchanger, to the heating system around the home.
Heat distribution system
At this stage, the heated water is passed around the home to radiators or underfloor heating. If the system is being used to generate hot water then the water is sent to the cylinders used for water storage.
All of these parts work together to create a highly efficient heating system.
Horizontal trenches and vertical boreholes
The underground pipes can be fitted horizontally or vertically, this will be different depending on the space available around your home. Vertical boreholes go straight down into the ground and could be as deep as 15 – 100 metres. Horizontal systems, on the other hand, are much shallower but cover more area. A vertical system is likely to cost more to install but be more efficient in the long run.
Installation costs will vary from installer to installer so to ensure that you get the best possible installation price, you should get quotes from at least 3 different engineers.
Best heating systems for a heat pump
As mentioned earlier, ground source heat systems operate at a low temperature which make them more suited to underfloor heating that radiators. Radiators require a higher temperature of around 70 degrees to heat rooms, while underfloor heating tends to function at around 30 degrees. If you'd prefer radiators over underfloor heating then you might want to consider fitting larger ones.
Should you be interested in underfloor heating, you can either have it installed all around your home or have a combination of underfloor heating and radiators.
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How efficient is ground source?
Ground source heat pumps use electricity, which can be expensive to run, to pump water around the pipes but they generate heat from a renewable source. While they may require electricity, a well insulated ground source system will provide around 3-4 more kilowatts of energy for every kilowatt of electricity used. That equates to an efficiency of around 300%.
They're a very efficient way of heating your home and not only will you be making back the cost of the system in savings from your energy bills, you can receive government payments through the Renewable Heat Incentive (RHI).
Maintaining a heat pump
While ground source heat pumps require little in the way of maintenance, it's important to keep an eye on how they're performing. The Ground Source Heat Pump Association states that safety checks aren't required and professional maintenance is only needed every 3-5 years.
Manufacturers may require their ground source heat pumps to undergo certain service maintenance during the warranty period, so always make sure you check with them.
How long do ground source heat pumps last?
Not all heat pumps will have the same lifespan as this vary depending on the type of heat pump and how well it is maintained. Some can last for as long as 25 years but others might need replacing after about 10 years. Either way, ground source heat pumps are a lengthy investment that will be able to heat your home efficiently for a number of years.
Is ground source right for your home?
Before having a ground source heat pump installed, you'll need to ensure that your home is suitable for the installation. Firstly, your home must have enough space in the garden for either a horizontal trench or vertical borehole and this may require access for various machinery.
To get the most out of a ground source heat pump your home should be well insulated and free from draughts that could cancel out the heat being generated.
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