Lee Common
In August 2024, we were approached by our client to quote for open-loop ground source heating for a house and annexe. The house had an internal area of approximately 433 square meters and the annex an area of approximately 90 square meters and we submitted a preliminary quotation accordingly.
Following further discussions, we obtained detailed floor plans, an EPC and SAP reports that allowed us to provide MCS approved calculations which were used to confirm the size the heat pumps. It was decided that a Kensa EVO 13-kW heat pump was best suited to heat the main house, with a 5-kW heat pump used for the annexe. With a guaranteed heat source temperature of 8-degrees, the outputs of these heat pumps increase by approximately 30%.
Our Firm Quotation contained just four items: (a) the construction of a water supply borehole to provide water from the underlying aquifer (chalk) for use as a heat source; (b) the installation of two borehole pumps to deliver the water to the heat pumps, the two borehole pumps being switched to run alternately as ‘duty’ and ‘standby’ to ensure a heat source in the event of a pump failure; (c) the construction of a soakaway to returned the cooler water to the aquifer; and (d) the installation of the heat pumps with buffer vessels and associated plant as required.
Our quote was accepted and we commenced works on site in September 2024. The water supply borehole and soakaway were completed in October, with water being pumped from the supply borehole directly into the soakaway to prove both an adequate heat source and an efficient soakaway. A log of the water supply borehole complete with pumping test results was sent to both the Environment Agency and the British Geological Survey for their records.
The borehole pumps provided ‘build water’ for the project and a sample of the water being abstracted was analysed at the laboratory of Affinity Water. It was agreed that particle and ultra-violet filtration should be installed along with a booster tank to provide a boosted potable cold-water supply and we vacated site, eventually returning once the plant rooms were ready for installation of the heat pumps and associated plant.
Both heat pumps and the relevant plant were installed in April 2025 as programmed. The system was tested and commissioned and a full handover pack provided to the client, which included the MCS certificate, information about the RECC, the insurance backed warranty and a maintenance agreement.
Our client had requested us to apply for the BUS (boiler upgrade scheme) following the installation. Details of this were sent over to the client and we successfully applied as the installer on the client’s behalf. The total comparison in cost savings for this project is yet to be determined due to the rising cost in energy
prices. Overall, this was an interesting project for us and our client was extremely happy with the installation.
“As we were constructing what was essentially a new build we had been considering our heating options. The area where the house is located does not have gas and the previous dwelling had oil powered central heating which I was not keen to continue with because of the price variations, inconvenience and green issues. While trying to install a new waste water treatment system we became aware that the soil was thick clay and any waste water would need a bore hole as surface drainage was virtually nil.
Up until this point we were considering an air source heat pump system despite not being overly impressed with their reputation. While they can heat in mid winter, the physics of the system means they are far less efficient when the air is cold – when you want the most heating. Knowing that we would probably need some bore holes for drainage and needed a heating system, we spoke to Frank who explained the benefits of an Open Loop system in comparison to other more popular options and how it would reduce our carbon footprint. The location of the property meant that we had relatively easy access to the chiltern aquafer which would provide both drinking water and the water required for the heat pumps. I was impressed with the technical knowledge of Paul and Malcolm in terms of the Heat Pump installation as a whole. We signed the maintenance agreement set forth by H D Services Ltd.
Overall the installed system is more efficient than air source heat pumps, requires less space than a closed loop ground source heat pump and also supplies all the water on site including drinking water.“
