Horizontal Ground Loops
Horizontal ground collectors consist of polyethylene pipe installed a
minimum of 1.5 metres below the surface, for example under a garden or
field. There a number of variations for this array.
Closed loop vertical bore holes
Bore holes around 150mm wide are drilled at depths of up to 150 metres
and loops of pipe inserted in each borehole which is then filled and
sealed with a thermally enhanced grout. This is a more expensive
method than horizontal ground collectors but boreholes can be installed
where ground space is more limited and they can be put under a building.
The number of boreholes required varies according to the geology of the
area, the heating demands of the property and the size of the ground
source heat pump. There have been occasions in the past where the ground
has been so unstable we have installed air source units as the alternative.
Open loop systems
In an open loop (or water to water) ground source heat pump array,
ground water is abstracted, usually from an aquifer or possibly from a
river and passed through the heat pump before being returned to the ground.
A constant supply of water is needed. This type of ground source heat pump
system is highly efficient because of the relatively high temperature of
ground water, but the installation can be more complex and require
regulatory approval. Open loop ground source heat pump systems are usually
confined to larger commercial buildings rather than domestic properties.