Case Study: Heat Pump
Our client reached out to us to explore potential solutions for decarbonising their traditional gas-fired wet heating systems at two hospitals near Salisbury. Following their successful PSDS funding application. We embraced the challenge and carried the project from the initial conception stage, all the way through to commissioning. We evaluated various low carbon heating technologies suitable for the site and determined that integrating additional air source heat pumps into the existing system would be the most effective approach. This setup would enable the heat pumps to meet the heating demands while retaining the gas system as a backup during the colder winter months.
Project
Delivery
Initially, we did a feasibility study to investigate the various solutions for decarbonising the systems. Both sites used standard gas-fired boilers and wet heating systems. One location had independent gas-fired water heaters that provided self-sufficient hot water, whereas the other relied on indirect hot water, which required the gas-fired boilers to be operational. We found that the heat-only site required a hybrid heating system, whilst the other site would benefit from a standalone heat pump to control the building's heating load. This was especially efficient because the underfloor heating could handle the lower temperatures produced by the heat pumps, allowing us to keep gas heating for the hot water and air handling unit circuits.
Site 1
At Green Lane, we implemented the hybrid solution by building a large new plant area to accommodate two 135kW heat pumps, complete with concrete bases and sound-deadening fencing. The heat pumps required a new 400A electrical connection from the hospital's main incoming supply, which was 100 metres away, necessitating extensive foundation and panel changes. We created a new heating circuit from the heat pumps to two 2000L buffer vessels, which we linked to the existing heating system using a 3-port control valve. We modified the Building Management System (BMS) to enable an automatic changeover, allowing the system to run mostly on heat pumps for the majority of the year. If the building struggles to achieve the necessary temperature, the gas-fired boilers will automatically activate and take over.
Site 2
Fountain Way required a higher boiler temperature all year since hot water was provided by indirect coils. We installed a 70 kW heat pump at this location to provide an independent heating circuit that interacts directly with the existing underfloor heating system, providing complete comfort heating for the wards and reception area. The renovation also includes custom compounds, noise-reducing fencing, a new mains electrical supply and panel alterations on the opposite side of the building. We connected the heat pump circuit to a 100L buffer vessel, which fed straight into the building's underfloor heating system. In addition, we added an auto-changeover valve and upgraded the BMS controls to enable seamless interaction with the system, allowing for automated changeover.
