Heat Pump Installation

eco hometec ground source heat pump installation

Before deciding which type of heat pump to install i.e. a ground source or air source, careful considerations need to be made. Not all locations are suitable for a ground source heat pump.

If a ground source heat pump is installed with ground loops in an area of ground that is either too small or unsuitable then the performance of the heat pump will be impaired. Predicted CoP's will be lower, the heat pump will use more electricity and subsequent running costs and CO₂ emissions will be higher than predicted. This section of our website is designed to bring to your attention the pitfalls, leaving you better informed and able to make the right choice.

Unfortunately it is a fact that heat pumps have been installed in locations that were completely unsuitable. The reasons for this are stated below.

The UK heat pump grant scheme

Historically the grant scheme was exclusively for ground source heat pumps. In situations where an air sourced heat pump would have technically been the best choice a ground source was installed purely to secure the grant making proposal look more financially attractive. Had the long term operating costs been factored in then a different decision might have been made.

Available land for ground loops

The energy that heats the water/glycol mix, as it circulates through pipework buried under the ground, comes directly from the sun. In effect your piece of land is a giant solar collector. The bigger the piece of land, the greater the exposure to the sun, the more energy it will retain and return to your heat pump.

Solar energy also reaches the land carried by water. Rain as it falls through the atmosphere is warmed by the sun and in turn permeates through the ground warming the soil. Consequently a piece of land covered by an impermeable layer of concrete e.g. a car park will not recover as much energy if rainfall is unable to penetrate through to the ground.

Underground water movement is a good source of energy. Water, as it drains through land, will carry with it heat energy. Consequently land at the bottom of inclines will offer more energy.

Soil types will affect the amount of energy available. Light sandy soils will drain water away quicker and with the energy it carries. Wetter soils will store and retain more energy.

Finally the golden rule is not to try an extract more energy than is available. Ground collectors that expose larger surface areas to a small area of land should be avoided. Trying to extract more energy than is available will result in the ground temperature dropping and in extreme cases freezing solid.

Ground source heat pump efficiencies are at their highest when the temperature of the water/glycol mix is at its highest. Careful thought, design and installation of the ground loops is vital if efficiencies are going to be maintained throughout the heating season.

Underground collectors can be installed in two ways. Either as a horizontal collector, set in a depth of 1.5 to 2m under ground level or as a vertical one set in one or more boreholes.

Bore holes being significantly deeper than pipes in shallow trenches are less susceptible to seasonal temperature changes and the energy available to the heat pump is more even throughout the heating season.

When compared to an installation using horizontal collectors are, vertical bore holes and their collectors experience less seasonal temperature changes and earth-water heat pump can achieve higher COP's.

Ground Heat Collection Method Classifications

Geothermal Probes (closed loop) - These systems circulate heat collection fluid around a circuit flowing continuously from the Heat Pump and down the pipes set within the borehole. This fluid extracts Heat from the ground via the geothermal probes set within the borehole and brings the heat energy back to the Heat Pump.

Boreholes (open loop) - Here ground water from an underground source is pumped up from the source to the Heat Pump, the heat is extracted and the water is then piped back down onto the ground.

Horizontal Thermal Probes (closed loop) - These systems can be referred to as slinky type collectors and are positioned to a depth of 1.5 metres below ground level horizontally within the grounds of the property. These horizontal collectors collect heat from the ground but also take heat via solar gain from the atmosphere i.e. the ground temperature increases and is regenerated on a daily basis via solar energy.

Energy Piles (closed loop) - This method uses the piling base underneath a property to extract heat from the ground by placing collection pipes within the piles which then act in the same way as the Geothermal Probes shown above.

Each method of heat collection can be used depending on the space available and the efficiency demands of the project. In general terms to give more uniform operating temperatures and security of performance the deeper the heat is collected from the ground the better.

Boreholes with a closed loop Geothermal Probe system as the one shown below will extract heat from the ground at depths of up to 100 metres; however boreholes at any depth from 10 metres to 100 metres allow varying amounts of heat to be extracted reliably using heat energy from the earth.

Ground source heat pumps use a buried ground loop which transfers heat from the ground into a building to provide space heating and domestic hot water. As well as ground source heat pumps, air source and water source heat pumps are also available.

Air Source Heat Pumps

Air source heat pumps absorb heat from the outside to heat buildings. There are two types of air-source heating systems. Air-to-air systems provide warm air, which is circulated to heat the building.

The other type, air-to-water, heat water and they can be used not only for heating and hot water production but are equally suitable for example heating swimming pools.

Benefits - The benefits of air source heat pumps are similar to ground-source heat systems. Firstly, neither type of system requires the use or storage of external fuel. The systems instead run on electricity, which eliminates the need for a gas connection or storage of oil/solid fuel. Air source heat pumps present an advantage over ground source heat pumps because they require less space to install. Instead of requiring the installation of buried underground coils, air source systems can be fitted using much less space.

An air source heat pump has three main parts:

The internal part - comprising of compressor, condenser, water heater, control system, control panel and other heat pump components, should be situated in a suitable internal space, utility room, garage, or plant room are typical locations. All the components should be housed in an acoustically insulated casing.

The external part - the heat pump evaporator, should be positioned outside the building in a convenient location not too far away from the internal unit.

The location must ensure a free flow of air through the evaporator and be able to drain the water freezing on the evaporator that melts away during and ice de-frosting cycle.

Please browse our website for more information about eco hometec and our range of Ground Source & Air Source Heat Pumps then click here to submit your plans or contact us on Freephone 0800 8620278 to speak to one of our team or e-mail us at sales@eco-hometec.co.uk.