Closed loop GSHP drilling and installation.
Drilling a GSHP borehole
Closed loop GSHP (Ground Source Heat Pump) boreholes are generally drilled to a diameter of either 125mm (5”) or 150mm (6”). The size of the hole is dictated by the size of the collection loops to be installed whether 32mm or 40mm. The hole is drilled using a variety of drilling tools from a simple drag bit through to high impact, high penetration Down The Hole Air Hammers.
Preventing GSHP borehole collapse
If the GSHP borehole collapses during drilling (common in sandy geology), temporary steel casing is installed into the borehole. These sections of steel casing are screwed together to form a continuous run of casing that supports the side of the borehole and enables drilling to continue into harder and self supporting geology. The requirement for casing can be established from the geological survey information supplied about the site.
Installing and equipping a GSHP borehole
Once the borehole is drilled to depth, the tools are removed from the hole, and the collection loop is installed. The loop is either 32mm or 40mm diameter pipe, this is usually specified by the heat pump manufacturer or supplier.
There are a number of methods used to make the installation as easy as possible such as weighting the end of the pipes to enable easier installation into the borehole. The two pipes are fusion welded onto a U bend creating a sealed and complete pipe; one side is flow and the other return. The pipe is filled with water and pressure tested upon completion of the installation to ensure that there are no holes or breaches within the pipe. Geologic recommend the installation of PE100 (quality mark) pipe which we stock in both 32mm and 40mm and comes to us pressure tested to 12bar. Once tested on site we seal the ends and certificate the pressure test.
Grouting and finishing the borehole
The installation is completed with the hole being back filled with a thermally enhanced bentonite grout. It is essential that the grout makes a good bond with the pipe and that no voids are left in the hole, as this will affect the thermal efficiency of the system. We ensure this is the case by mixing the grout at the head of the borehole and then pumping it down a pipe to the bottom of the borehole. As the bore fills, the pipe is slowly removed, this ensures that each section of the bore is filled. The borehole is grouted to the top and the tails of the pipe left about 1M above the ground for the installer to take them back to a manifold connection to the heat pump. Geologic can excavate the trench work and take the pipes back to the manifold if required.
Geologic can also install open loop GSHP systems
The installation described on this page is called a closed loop GSHP system. Open loop GSHP systems take water from one source (the borehole for example) and after pumping it through the heat pump, discharge it to a soak away area, which is an alternative service we provide, please contact us for more details.
Geological surveys for GSHP installation
To provide a quote for drilling we require geological information on the proposed site. If this information is not known by the customer we can prepare a basic geological survey for £65+VAT. All we need for this is the postcode of the site or a map reference/Google Earth pin.
We are experienced, accredited and fully insured
Geologic Boreholes are Corporate Members of the British Drilling Association. We hold both Public and Employers Liability Insurances. All our installations use only the best quality products and equipment.
Contact us for more information on GSHP installations
If you require any additional information or to arrange a site visit, please contact us.
