Developing a natural refrigerant heat pump scheme in the centre of Bolton
A secondary school in Bolton town centre had no ground to spare for heat pumps. Working with Eddisons, we developed a propane (R290) scheme on the roof, laid out around the safety zones a natural refrigerant needs, feeding the existing plantroom on the second floor.
Rooftop heat pump compound and pipework, from the issued design
The site
The school is a multi-storey building in the centre of Bolton, surrounded by roads and car parking. Heating came from three 225 kW gas boilers in a plantroom on the second floor. We put the heat pump load at around 230 kW.
There was no space at ground level for that much plant without losing parking or play space, so the heat pumps are on the roof.
Propane heat pumps
We specified propane (R290) heat pumps. It is a natural refrigerant with a very low global warming potential and no phase-out risk under the F-gas rules. It is flammable, so each unit needs a clear zone around it, and on a roof those zones set the layout.
The compound was laid out around the manufacturer's exclusion zones, with an acoustic screen and a structural assessment of the roof. The pipework runs down to the existing second floor plantroom, so no new plantroom was needed. A buffer vessel allows the system to use cheaper electricity.
Electricity supply
The school had an agreed supply capacity of 320 kVA against a recorded peak of 95 kVA. We made the case to the network operator on that basis, and the scheme was accepted without a reinforcement cost. The design also covered cooling for the prayer room, and the site is connected to Jupiter Performance.
Concept sketches
Photographs
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