Case Study

Heat pumps for schools 

REI looks at the installation of a renewable heating system, specified and installed at a school in Milton Keynes as part of a development project to expand the premises. 

Check out our most recent case study on how a school in Bletchley, Milton Keynes, incorporated renewable heating technologies in its new extension. This project, completed by Modplan Mechanical & Electrical Installations Ltd, showcases the integration of air source heat pumps and underfloor heating to enhance sustainability and reduce carbon emissions.

A recently completed extension project at a school in Bletchley, near Milton Keynes, saw the development of an additional building at the school’s premises. Modplan Mechanical & Electrical Installations Ltd and its sister company designed, specified, and installed the heating system fitted in the extension at Milton Keynes PRU School.

Modplan worked closely with the school and the local council to specify a renewable heating system that would fulfil the new building’s space heating and hot water requirements and help the school lower its carbon emissions.  

The extension project commenced in 2023 and included adding over 380m² to their premises with the addition of two new classrooms, a sports/dining hall, storerooms, a medical room, a quiet room and a plant room. Modplan’s sister company were the main site contractor, and they carried out the heat loss calculations for the new building to determine the size of the heating system that would be needed. The system specified included two air-to-water source heat pumps, a hot water cylinder and underfloor heating throughout the new floor area.  

Heat loss calculations

“Modplan joined this school project once the heat loss calculations had been completed and the system specified,” explains Harry Townsend, managing director at Modplan.  

“We then worked with the school and Milton Keynes Council to confirm the choice of products we would install. Here at Modplan, we have been fitting Grant’s air source heat pumps and cylinders regularly over the last 12 months, with the Aerona³ being our preferred brand of heat pump. We, therefore, selected two Aerona³ 13kW air source heat pumps alongside a QR 210ltr single coil cylinder.” 

The Aerona³ 13kW heat pumps installed, which are twin fan units, have an excellent Seasonal Coefficient of Performance value of 5.40. The Aerona³ 13kW model is highly efficient, reliable, and easy to install. It is also Connect and Notify approved, Quiet Mark accredited, and supplied with a seven-year guarantee when installed by G1 installers, such as Modplan. 

“The Aerona³ heat pumps have been installed as part of an S-Plan system minus the radiator circuit, with the two heat pumps supplying the underfloor heating system and hot water,” continues Harry.  

“Another benefit of Grant heat pumps is that they are supplied with schematic drawings to suit different types of systems. For our installation team, having these schematics readily available to refer to and use is a really useful resource when on site.”  

Fully modulated heat pumps

A plant room was created to house the ancillary products that support the wider heat pump system. Here, Modplan has installed the hot water cylinder, a combined volumiser/low loss header, and the heat pump controller, along with the system pipework and connections.  

The Quick Recovery hot water cylinder that was installed at the school is a single coil model and it is ideally suited to a heat pump system, featuring a large internal coil to facilitate the efficient transfer of heat to the water contents. With clearly labelled tappings, the QR cylinders have been designed to make connecting the cylinder to the system simple and easy.  

The Grant combined volumiser/low-loss header, which was also fitted, is a unit that creates hydraulic separation to help maintain the correct flow rate through the heat pumps. It also provides a suitable volume of system water to allow the heat pumps to fully modulate.  

Costs within a set budget

“We like the low-loss headers designed and supplied with these systems,” explains Harry. They are compact in size, enabling us to fit the unit in most airing cupboards or plant rooms even when we are facing space constraints.  

“We have used other manufacturers who supply large buffer tanks, making some installations almost impossible. Having the hydraulic separation, air vent and backup immersion heat source all in one compact low-loss header is a big plus for us with these systems. 

“The installation time for this heat pump system was approximately two weeks,” continues Harry. “This included fitting all the primary pipework, completing the plant room installation, setting up the Aerona Remote Controller and testing and commissioning the heat pumps and system.” 

Modplan Mechanical & Electrical Installations Ltd are G1 Installers, having completed heat pump training at Grant UK’s Training Academy. Alongside the support provided through this training and the resources that accompany the products, as Harry explains, Modplan likes working with Grant’s renewable products for several reasons. 

“We find the Aerona³ R32 heat pump range straightforward to fit, and the units are installer-friendly. They are affordable as well, something which was particularly important for this project which needed to come in at costs within the set budget. The support from the Grant staff is good and the products are in stock and readily available to order from our local merchant as well. We have also not experienced any issues with Grant products after installation, something which gives both our team and our customers peace of mind.”  

This heat pump system installation was completed in February 2024, and the new extension will be officially opened by the Milton Keynes PRU School later in the year.  

For further information about Grant’s renewable heating range, please visit