Queensferry Plas Derwyn PRU HVAC, M&E

Client: Kier
Customer: Plas Derwyn & Queensferry CP
Service: HVAC Mechanical and Electrical Services
Project value: £1.3m
Project completion: October 2021

Kimpton were appointed by Kier Regional Building North West to deliver the mechanical and electrical services for a new Pupil Referral Unit at Plas Derwyn & Queensferry CP as well as for the extension and refurbishment of the existing Plas Derwyn & Queensferry CP Primary School.

The contract was awarded on a 60% Quality 40% Price weighting with social value commitments to maximise local supply chain spend and deliver training to local students.

Rear view of the three Mitsubishi CAHV ASHP units at Queensferry PRU by Kimpton

The three Mitsubishi CAHV ASHP units at Queensferry PRU by Kimpton

The new frontage of Queensferry PRU with HVAC by Kimpton - growing minds growing futures

View across the classroom to the three Mitsubishi CAHV ASHP units at Queensferry PRU by Kimpton

The classrooms with individual NVHR controls inside Plas Derwen PRU by Kimpton

Inside the main hall at Plas Derwen PRU Queensferry the natural ventilation system uses a roof mounted fan with mechanical services by Kimpton

Inside the plant room at Plas Derwen PRU Queensferry with HVAC by Kimpton

Inside the BMS at Queensferry Plas Derwen PRU by Kimpton

How does an air source heat pump work - Front view of the three Mitsubishi CAHV ASHP units at Queensferry PRU by Kimpton

View across the three Mitsubishi CAHV ASHP units at Queensferry PRU by Kimpton

The AHU Air Handling Unit on the roof of the Plas Derwen PRu Queensferry by Kimpton

Scope of Works

The work was all based around the existing Queensferry Campus in Deeside and was part of an overall £10.5m schools and community hub project by Flintshire County Council. The project was supported by the Welsh Government’s 21st Century Schools and Colleges programme and was designed to tick a lot of renewable technology boxes from ‘the ground up’. It was literally designed in, throughout every element of the build.

Perhaps the most visible renewable technology in use is the array of three Mitsubishi CAHV-P500 ASHP units mounted to one side of the playground area and next to the external pump house and cold water storage tank for the fire safety system.

Each of the three CAHV units has a 42.6kW output and combined, deliver nearly 130kW. The PRU building is fitted with a LTHW heating system throughout to maintain internal temperatures. This feeds LST radiators, fan convectors and radiant panels. When an ASHP heating system is designed from the ground up like this one, it’s usually far more effective in delivering on the claimed seasonal COP. With Lower temperature systems, the insulation of the building is critical in ensuring that the heat loss is negligible.

In education environments, we are also noting a huge growth in requirements for ventilation too. This build is no exception and is fitted with Breathing Building hybrid ventilation units. On warm days in the teaching spaces, the benefit of ventilation is obvious, but on a cold winters day, when fresh air is still required and temperatures need to be maintained, the hybrid mechanical ventilation system ‘mixes’ warm air with the cooler incoming fresh air to provide a healthy teaching environment, with no draughts or cold spots.

These systems are designed to maintain a CO2 concentration of no more than 1,000ppm for the full teaching day. It’s been shown in repeated studies that pupils are far more able to concentrate and stay healthy when CO2 levels are kept below this level.

In the school hall, the system is a hybrid ventilation solution. This comprises of roof-mounted aspirated terminals to displace cool air down into the building and move the warmer, lighter air upwards to atmosphere.

The kitchen, servery area and cooking range provide another challenge for heat retention, whilst maintaining valuable clean fresh air. There is additional mechanical supply throughout the area with a roof-mounted AHU to draw the hot air and cooking smells away from the school and teaching spaces.

At the centre of the whole installation is the plant room and BMS. To us, as mechanical engineers, this one looks like a work of art. It’s a tight space but the way the system has been designed maximises accessibility for future PPM.

For additional safety, there is also a sprinkler system throughout. This is fed by the external tank, located by the ASHP’s and the external pump room. A detection and prevention system manages all of this. It’s a comprehensive system that will ensure that if fire breaks out in one area of the school, it is very unlikely to spread and there will be plenty of time to evacuate anyone still present in the building.

Challenge

It was a complicated project, with a number of challenging requirements. However, with our engineers responsible for designing and implementing the layout of the plant room having more than 20 years experience in these types of projects, and the technical leads having a decade more, the project was handed over to Kier on programme ready for the start of the new term.