The existing heating system was heated by two boilers, one oil and one gas. These provided heat to the heating, hot water and outdoor pool heating systems for the property. There had previously been two air-source heat pumps contributing to these systems too, installed nearly 20 years ago but now redundant, and it was for this reason the client decided to explore their options with regards to ground-source heat pumps.
Although there is a large lake to the front of the property this was discounted early on as the build-up of silt over the years rendered it too shallow for a GSHP installation. The next possible location was “The Green” to the rear of the property and it was decided that this would be the best location for a borehole array to support the GSHP. After heat loss calculations were completed and technical surveys carried out and, it was discovered that there would be a limited electrical supply available for the GSHP due to onsite constraints and as such the GSHP would be slightly undersized for the load. For this reason it was decided to retain one of the existing boilers as a top up to the system in very low temperatures. This boiler would also then remain to service the hot water demand with the GSHP tasked with the heating and pool heating loads.
Drilling works for the required 16 x 145m boreholes was started in June by long term Isoenergy partner Synergy Boreholes, with headering works and plant room installation following on closely behind.
Due to a very tight existing plant room with no room for the installation of a GSHP and buffer cylinder, a new plant room for these items was constructed in a redundant space between two existing buildings. Pipework was then run into the existing plant room where, after some rearrangement, it was seamlessly connected to the original distribution circuits. A 90kW Viessmann 300-G Pro, twin compressor GSHP and 1,000 litre buffer tank were installed in the new plant room.
The system was commissioned and set to work at the end of October 2015 and metered data since installation shows that the system has been running at an SPF of 4.07. The client also now benefits from the Renewable Heat Incentive Phase 1 meaning that they will benefit from an income from the running of the GSHP for a period of 20 years. The estimated payback for the system is between 6 – 9 years dependent on the energy usage of the system.