Building Condition Surveys
Scawby Academy Fire Safety Equipment Replacement

Dorchester Primary School – Air Source Heat Pump Installation


Eddisons were appointed by Hull Collaborative Academy Trust to undertake a PSDS Phase 3B application for one of their sites, Dorchester Primary School.

The Dorchester Primary School air source heat pump project reduces carbon dioxide emissions by utilising three low carbon air source heat pump systems to provide the building with heat energy. This system has now replaced fossil fuel burning, natural gas boilers. In addition, the installation of solar PV to the roof and improvements to the heating network were also undertaken.

Eddisons acted as Contract Administrator and coordinated the design and procurement processes as well as obtaining all statutory consents such as planning and building control. We also managed all environmental and structural implications, that had to be considered as part of the project.

The project was delivered from inception to completion and phased around a live school environment.


The new systems include DHW preheated by the ASHP system with top up via electric immersion heaters. The ASHPs use thermal energy extracted from the ambient air to heat LTHW to provide the building with heating. There are 6 plantrooms on site which will be paired up and supplied by 3no. ASHP systems with 2 duty assist heat pumps each.

All three systems consist of 2 x 55kW (nominal) Air Source Heat Pumps, an 800L buffer vessel, 300L expansion vessel and primary circulation pumps. Buffer vessels in each plantroom provides LTHW to heat a 200L preheat cylinder and for heating circuits. The preheat cylinders feed into 170L direct electric hot water storage vessels which raises the stored temperature to 55°C. The heat pumps are linked together to allow Master-Slave operation, where the master heat pump manages duty rotation and sequencing of the system.

Heat pump operation is monitored by the energy management system (EMS) to which they communicate via hardwired and optical interfaces (Modbus). Enable and set points are achieved through the EMS via the master heat pump. Each ASHP controls its respective condenser circulation pump. All secondary LTHW circulation pumps are monitored and controlled by the EMS. Enable, speed set point, fault and run feedback are communicated via hardwired connections between the pump and the EMS supervisory controls.

The solar panel installation consists of a Flat fix 100kw system, with each panel size at 232 x 425 watt panels. The panels generate energy to feed the ASHP’s and provide any excess energy as feed in tariff.


Our specialist project team successfully delivered the Dorchester ASHS project on time, within budget and to a high standard. It is the first school in Hull to have successfully received and delivered Salix Funding for an Air Source project of this size and nature. The building will optimise performance through a seasonal control strategy to enable adjustments to be made to the control philosophy, enabling maximum efficiencies.

Eddisons continue to work with HCAT in respect of similar projects and look forward to delivering more PSDS projects on behalf of Salix.

To further benefit the academy and assist in reducing their carbon footprint a solar array was also installed, utilising the existing scaffold and site welfare which enabled the works to benefit from a real terms cost saving should the install have been completed separately.

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