Ground Source Heat Pumps - FAQ
Q. What is a ground source heat pump, and how does it work?
Q. What type of building is suitable for heat pumps?
Q. What size heat pumps does IHS supply?
Q. What's a closed loop system?
Q. What's a trench system?
Q. Will a trench system affect my lawn?
Q. What if I don't have enough room for horizontal loop?
Q. Do you install or supply only?
Q. What is the procedure for obtaining a quotation?
Q. What do I need to know about purchasing a micro-renewable system?
Q. What planning permission is required to install a micro-renewable system?
Q. What financial incentives are available for IHS heat pumps?
Q. Some electrical terms used in connection with heat pumps
Q. What is COP and why does it matter?
Q. What is a ground source heat pump?
In the UK, the temperature of the earth below the frost line is an average of 8ºC at a depth of between 1.5 to 2 meters. Ground source heat pumps extract this energy from water or soil to provide heating and hot water. Similarly, during the summer, heat can be transferred back into the ground and act as a cooling mechanism. Heat pumps run on electricity and can produce up to five times their own power in heating. This is produced by a rise in pressure caused by an electrically powered compressor. Heat pumps have been heating homes and offices throughout countries such as Sweden, Norway and Austria for years. As long as refrigeration has existed, so have heat pumps!
Almost 75% of the energy required for heating can be taken from the soil (which costs nothing) to provide heating and hot water. Depending on the method of installation, for every unit of electricity used, you achieve 4 to 5 units out.
A heat pump consists of four simple components - an evaporator, a compressor, a condenser and an expansion valve.
Just like your domestic fridge working in reverse, the working fluid in the system is converted to gas by evaporation and at the end of the cycle, back to a liquid by compression. The result is an output temperature of 35ºC- 45ºC. This is ideal for underfloor heating in a solid floor construction. In this case, for every 1kW of electricity you use to power the system, you get up to 5kW out. Heat pumps can achieve a temperature of 60ºC but at a reduced efficiency output of 2.5kW.
All ground-source heat pumps have two parts: a circuit of underground piping outside the house and a heat pump unit inside the house. The outdoor piping system can be either an open or closed loop system. An open system takes advantage of the heat retained in an underground body of water. In a closed-loop system, heat is collected from the ground by means of a continuous loop of piping buried underground.
Back to Top
Q. What type of building is suitable for heat pumps?
We can design heat pump systems for most building types - domestic and commercial; new and older builds. The ideal situation in which to extract maximum return from a heat pump is a new building (or newly renovated building that's up to current building regulations) that's properly insulated and has underfloor heating.
However, it is still possible and practical to install a heat pump into an older, less well insulated building - even one without underfloor heating. Bear in mind though that this is not the most ideal situation for obtaining optimum return from the heat pump.
Most radiators would need to be either doubled in size or converted to aluminium to compensate for the lower water temperature and increase output temperature.
For further information about heat pumps in older buildings, please click here.
Back to Top
Q. What size heat pumps does IHS supply?
IHS heat pumps are available in a broad range of size suitable for single and three-phase electricity supply. Manufactured by IDM Energie in Austria, all units are high quality heat pump systems designed to deliver high efficiency and faster payback. Hot water is delivered from between 45ºC to 49ºC (up to 55°C in HGL systems).
| IHS Ground, Water & Air Source Heat Pumps Model Overview | ||||
| Heat Pump Type | Heat Source | Model | Size | Notes |
| Ground & Water | Soil, Water | Terra Compact | 10 & 12kW | Single phase connection. Smaller dimensions than Terra S unit. |
| Terra S/W | 7kW, 8kW, 10kW, 12kW, 15kW | For single phase electric supply. | ||
| Terra S/W | 7kW, 8kW, 10kW, 12kW, 15kW, 17kW, 19kW, 26kW, 30kW, 37kW, 45kW | For three phase electric supply. | ||
| Terra Twin | 20kW, 24kW | Single phase connection. Twin compressor unit. | ||
| Terra Max | 50kW, 60kW, 70kW, 90kW, 130kW | 3-phase connection required. For larger installations. Twin compressor unit. | ||
| Heat Pump Type | Heat Source | Model | Size | Notes |
| Air | Air | Terra CL | 8kW & 10kW | Single phase connection. |
| Terra CL | 12kW, 15kW, 20kW, 25kW, 30kW | Three phase connection. | ||
| Terra ML | 6kW | Single phase connection. Suitable for smaller properties. | ||
| Terra ML | 12kW | Three phase connection. Suitable for smaller properties. | ||
Q. What's a closed loop system?
The term "closed loop" is used to describe a geothermal heat pump system that uses a continuous loop of special buried plastic pipe as a heat exchanger. The pipe is connected to the indoor heat pump to form a sealed, underground loop through which an antifreeze solution is circulated. Unlike an open-loop system that consumes water from a well or open water source, a closed-loop system recirculates its heat-transferring solution in pressurised pipe. A closed-loop system can be installed ((horizontally)) (trench system) or ((vertically)) (borehole).
Back to Top
Q. What's a trench system?
Most closed loop is laid horizontally in the ground adjacent to the building. But any area near a home or business with appropriate soil conditions and adequate space will suffice.
Ground loop pipe is normally laid to a depth of 1.2 meters (single trench) or 1.8 meters (double trench) in trenches of 1 meter wide and 1 meter apart.
IHS does not recommend a tightly coiled "slinky" system.
IHS provides a full trench layout diagram.
Back to Top
Q. Will a trench system affect my lawn?
Properly installed ground loop has no adverse effect on grass, trees or shrubs. Naturally, there will be temporarily bare areas caused by initial disruption but nature's ability to regenerate is unbeatable!
It's another reason we don't recommend the "slinky" system of laying pipe. This method is often presented as a means of overcoming shortage of space and avoiding drilling expensive boreholes. As a large concentration of pipe continues to draw heat from a confined area, the ground will eventually lose most of its heat. Indeed, you will sometimes see areas where the grass has died away altogether as all remaining energy has been sucked out of the ground. Another nasty result can be the ensuing increased electricity bills as the system isn't being given any "free" heat at all.
Back to Top
Q. What if I don't have enough room for horizontal loop?
Ground loop systems can also be installed vertically in a closed or open well. The pipe is installed in a specially drilled borehole. Boreholes can be expensive to drill and you should always work with an experienced driller who has a good reputation. We recommend a small group of drilling companies - please contact us for details.
Back to Top
Q. Do you install or supply only?
Here at Invisible Heating Systems we design, supply, install and commission ground and air source heat pumps and solar systems. We are a fully MCS-accredited company. In the case of our underfloor heating system, we can either recommend and installer, or if you would prefer to install the underfloor heating yourself we can guide you through the process with the help of our installation manual and the accompanying CAD drawings.
Back to Top
Q. What is the prodecure for obtaining a quotation?
The earlier you plan your heating system and the better informed you are, the more likely it is that you'll acquire a well designed, environmentally and commercially sound heating system that suits your needs and is best for your home or office.
In order for us to give you a quotation for a heat pump (or any other system), we ideally need a full set of architects' drawings showing full side elevations and glazing details. Additional useful information includes number of bathrooms, floor construction and proposed floor coverings. Do you have a swimming pool that needs to be heated also? Have you a tennnis court? (We can even investigate heating your swimming pool from your tennis court!) If you have a plot map, we'd love to see it. The more relevant information that you give us, the more we can tailor a heating design specially for you.
On receipt of your drawings, we will prepare an indication of costs which will give you a very good overview of the heating systems we recommend. This will help you make the most informed decision possible about the choices available to you. Our design team are happy to help you with any queries you may have.
Back to Top
Q. What do I need to know about purchasing a micro-renewable system?
If you decide you want to take things further, we will organise a site visit by a qualified installer (IHS has built up a comprehensive network of installation engineers who have worked with us over a number of years and have all been trained in the installation of our systems). We would then prepare a final quotation including installation costs.
If you're thinking of installing a ground source heat pump or indeed, any renewable system, you should contact the following:
- Local planning authority (if you're in any doubt that you'll need permission to carry out the work)
- Your electricity provider - to obtain information about cheaper electrical tariffs (eg Economy 10, 7 or other eco tariffs). We've received additional information about Economy 10 in Scotland. Click here for further information.
- Investigate the financial incentives that may be available.
Q. What planning permission is required to install a micro-renewable system?
Planning requirements for ground and water source heat pumps is generally not required but if you have any doubts, please contact your local authority. Planning permission is still required everywhere for air source heat pumps. Please click here for further information.
Back to Top
Q. What financial incentives are available for IHS heat pumps?
Yes, conditions apply. See our grants information.
Back to Top
Q. Some electrical terms used in connection with heat pumps
See also frequently used terms.
Single phase electricity
This is the electrical engineering term for a normal simple circuit, with one live wire and one neutral (or return) one.
Most domestic loads are single phase.
Three phase electricity
Three phase electricity has properties that make it very desirable in electric power systems. Power transfer into a linear balanced load is constant, which helps to reduce generator and motor vibrations. They can produce a magnetic field that rotates in a specified direction, which simplifies the design of electric motors.
Three-phase electricity is desirable for heat pump installations above 12kW but absolutely necessary for heat pumps with an output of 24kW and more.
Click here for further information about economy tariffs.
Back to Top
Q. What is COP and why does it matter?
COP or Coefficient of Performance is the means of stating the ratio of the heat output by the particular technology relative to the amount of energy it uses to operate.
If you're looking at installing most renewable systems into any property, its performance will be dependant on a range of factors.
All the points we've outlined below are equally important to ensure your heat pump performance, that its efficiency is maximised and that running costs are minimised in the long term.
- Method of construction; concrete and screeds are the ideal partner when combined with underfloor heating and heat pumps.
- Up to standard insulation and U-values.
- Correctly fitted insulation; careless installed insulation will allow heat to excape and renders the insulation job worthless.
- Amount of ground to install trenches - IHS do not recommend using the slinky method in a trench system!
- Method of heat delivery and how well the system is installed and integrated
- System programming and sizing.
If the above elements are in place, a heat pump from IHS should deliver the following efficiencies
- Efficiency/COP with trenches - 1:4.4
- Efficiency/COP with closed loop (borehole) - 1:4.4
- Efficiency/COP with open well - 1:5.5
- Efficiency/COP Air Source Heat Pump - 1:4.2
Expected COP is taken as an annual average return - obviously in winter it may be lower and higher in the summer.
Back to Top
