Ground Source Heat Pumps - FAQ

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Ground Source Heat Pumps - FAQ Call: UK 028 9099 6697
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Frequently Asked QuestionsGround Source Heat Pumps

How efficient is a ground source heat pump system?
Modern systems are very energy efficient. For each kilowatt of electricity used to run the heat pump, three to four kilowatts of heat are delivered to the building.
Why have I never heard of these systems before? Are they new?
Around the world, particularly in the USA and several parts of Europe, the use of GSHP systems is common. The ground source heat pump was actually invented more than 50 years ago, and continuous development has greatly improved its efficiency and reliability. It is now a proven, cost-effective, safe and environmentally friendly alternative to fossil fuels.
How large are these units?
A typical heat pump unit for a domestic dwelling is about the same size as a large fridge.
Can it supply hot water for the house?
Yes. Some domestic systems are able to heat domestic hot water via a modern high efficiency indirect water cylinder. In lower rated units an immersion heater can boost the temperature which can be done at night using off peak rates.
Can the systems provide cooling?
Yes. There are reverse-cycle heat pumps that can deliver both heating and cooling.
Can I use a standard domestic electricity supply?
Yes. There are a number of heat pumps that have been specifically designed to run on a standard UK single phase supply. However, if you do have access to a three-phase supply, which is essential for the larger units, then this is a preferable option.
I am currently designing a new house which will be extremely well insulated. Would a ground source heat pump system be worth considering?
Yes, absolutely. Almost all new houses in the UK designed to meet or exceed the 2006 Building Regulations should be able to install a ground source heat pump system. These mandatory regulations have been designed to conserve fuel, reduce heat losses and ensure greater energy efficiency, & so will ensure that all modern properties need less heating. This means that the size of heat pump is smaller, will need smaller ground loops and will therefore cost less.
My architect suggests I install underfloor heating in my new house. Is this OK?
Yes. Ground source heat pump systems are ideally matched to modern low temperature underfloor heating.
I have an older style property. Can I still fit a GSHP system?
Yes, you can, but your building must be well insulated for you to gain most benefit. The cost of a system is directly related to its size and with heat losses being fairly high from older buildings, this can add substantially to the capital cost of installation, upgrading insulation levels is usually money well spent. Regrettably, many older buildings can never be made sufficiently energy efficient to use a modern heating distribution system such as low temperature underfloor heating, or low temperature radiators.
Can radiators be used inside my house instead of underfloor heating?
Yes, but you will need radiators correctly sized for the typical 45°C to 50°C water temperatures obtained from GSHP systems. If your house is really well insulated they may be suitable, but check to see how big they would have to be and the space they would take up. There is also a range of skirting radiators, these are very efficient and essentially can be fitted in situations where underfloor is impractical such as retro-fit installations. Upstairs is usually less of a problem as bedrooms are normally kept at lower temperatures.
Could I install the heat pump outside or in my car-port, garage or basement?
Yes. There is generally no problem in doing so and it normally means the pump is nearer to the pipe connections on your ground loops, which often makes the whole system easier to connect. Some home owners have made up a small, well insulated, external enclosure for the pump unit.
How big are the trenches?
The typical heating-only installation for a medium sized, new build detached house would need at least two narrow trenches, each 300 mm wide and 40 to 50 metres long and 1.8 metres deep. The trenches can be straight or curved and laid in any direction to suit your site, providing they are always a minimum of 5 metres apart. A standard excavator, such as the type used to dig conventional foundations and footings, can dig the trenches. Once completed, and the ground loops pressure tested and buried, your renewable energy collection system can basically be forgotten. However, its location needs to be recorded to avoid accidentally digging it up!
Can I install trenches on a downward sloping site?
Yes, provided you can physically dig the trenches, a moderate downward slope is not a problem. Consideration needs to be given to purging air from a system with ground loops higher than the heat pump.
I have a large plot of land but the ground is quite hard. Can I dig a shallower trench?
Yes, the ground loop coils can be laid so that they lie horizontally in the trench rather than vertically. This would need a wider but shallower trench depth to at least 1.2 metres. However, this is not as satisfactory as a deep trench in which the coils are vertical and you will need a special slinky configuration and probably longer trenches.
I have some very wet land. Can I use this?
Yes, wet land is better at conducting heat so, as long as you can physically dig a trench, its ideal.
I have a large pond. I have a stream. Could this be used?
Yes, it is possible to use very large ponds and fast flowing streams as an energy heat source
Are Ground Source Heat Pumps dangerous? What about servicing and maintenance?
There are no hazardous gas emissions, no flammable oil, LPG or gas pipes, no flue or chimney and no unsightly fuel tanks. GSHP systems have absolutely NO site emissions. There is no need for regular servicing or annual safety checks and maintenance is very low.
How do running costs compare with conventional alternatives?
It depends what you are comparing. In a modern, well insulated house, a Ground Source Heat Pump system can offer very high efficiency and moderate running costs. An oil-fired boiler would cost considerably more to run, and electric heating would be at least three times as expensive. It is true that the very best of the modern condensing gas boilers may only be a little more expensive to run but that is on current gas prices, which are set to rise. Also, all fossil fuel boilers need regular servicing and maintenance.
Are these systems expensive?
The initial purchase costs of a ground source heat pump system will be quite a lot more than a conventional oil or gas fired boiler. The initial one-off expense is offset by the lower running costs, lower maintenance and low servicing requirement. There is also the security of knowledge that the majority of your heating and cooling energy comes out of your ground, is under your control and will not increase in price.
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