Case Study

Grant Aerona³ heat pumps specified for school in Milton Keynes

Grant Aerona³ heat pumps specified for school in Milton Keynes
Credit: Modplan
The two Aerona³ 13kW heat pumps installed at the school

A renewable heating system including the installation of two Aerona³ air source heat pumps, a QR hot water cylinder and a low loss header has been specified and installed at a school in Milton Keynes as part of a development project to expand the premises.

The Project
Property: school building
Heat source: air source heat pump
Products installed: two Aerona³ 13kW air source heat pumps, QR 210ltr single coil cylinder, Grant combined volumiser/low loss header

In February, an extension project completed at a school in Bletchley, near Milton Keynes, which saw the development of an additional building at the school’s premises. The design, specification and installation of the heating system fitted in the extension at Milton Keynes PRU School was carried out by Modplan Mechanical & Electrical Installations Ltd and their sister company. Working closely with the school and the local council, Modplan specified a renewable heating system that would fulfil the new building’s space heating and hot water requirements while also helping the school to lower its carbon emissions.

Specifying the heat pump system

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

“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 twelve months with the Aerona³ being our preferred brand of heat pump to install. We therefore selected two Aerona³ 13kW air source heat pumps alongside a QR 210ltr single coil cylinder.”

The Aerona³ 13kW heat pumps installed at the school are twin fan units with an excellent Seasonal Coefficient of Performance value of 5.40. Connect and Notify approved, Quiet Mark accredited and supplied with a 7 year guarantee when installed by G1 installers, such as Modplan, the Aerona³ 13kW model delivers efficiency, reliability and ease of installation.

“The Aerona³ heat pumps have been installed as part of a 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 the schematic drawings to suit different types of systems so for our installation team, having these schematics readily available to refer to and use is a really useful resource when onsite.”

The plant room – cylinder, pipework & low loss header

To house the ancillary products supporting the wider heat pump system, a plant room was created as part of the extension. Here, Modplan have installed the hot water cylinder, the combined volumiser/low loss header, the heat pump controller along with the system pipework and connections. The Quick Recovery hot water cylinder installed at the school is a single coil model which is ideally suited to a heat pump system as it features a large internal coil to facilitate efficient heat transfer 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.

A Grant combined volumiser/low loss header was also fitted as part of this installation. This unit 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. “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 back up 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.”

Why the installers chose Grant products for the project

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, there are several reasons why Modplan like working with Grant’s renewable products, as Harry explains.

“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.”

The installation of this heat pump system was completed in February 2024 with the new extension being officially opened by the Milton Keynes PRU School later in the year.

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

Grant Aerona³ heat pumps specified for school in Milton Keynes
Credit: Modplan
The plant room installation including a low loss header and QR hot water storage cylinder
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