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A learning curve

The incorporation of a heat pump featuring inverter-driven compressor technology was one of the first installations of its type in the UK.

When the Building Services Department at Sheffield Hallam University set about refurbishing the newly acquired Arundel Building, there were certain specifics that needed to be taken into consideration when it came to upgrading the HVAC system.

These included keeping the size of the plant to a minimum for the restricted rooftop plant area, quick installation times to keep road closures to a minimum, good air quality for the building’s occupants and, most importantly, a reduction in the site’s energy costs to create a more sustainable university estate.

Lee Allen, senior building services manager at the university, is responsible for overseeing the refurbishment.

Explaining the project, he says: “The refurbishment has been divided in two phases, with the installation of the ventilation system occurring in phase one. From the outset, we decided to take a new approach, incorporating highly efficient mechanical equipment, alongside crossflow ventilation with new opening windows.

“This has been designed to allow the centralised ventilation system to be optimised for mixed-mode conditions. During our initial discussions with Fläkt Woods, we were keen to incorporate the new ReCooler heat pump unit into the AHU, instead of installing a separate wet heating coil or DX coil.

“It’s a really neat and tidy package, but also offers COPs that are far higher than the alternatives. The energy-saving potential of the device is hugely important in our drive to create a more sustainable estate.”

Comprising an eQ Air Handling Unit (AHU) and integral ReCooler HP, the new equipment has replaced a natural ventilation setup in order to supply up to 2.5 m3/s of conditioned air into a variable air volume (VAV) system.

The incorporation of the new ReCooler HP is one of the first inverter-driven compressor technology installations of its type in the UK and works in conjunction with Fläkt Woods’ VAV boxes and associated controls.

The Fläkt Woods ReCooler HP unit provides heating and cooling from a built-in reversible heat pump and recovery wheel.
The unit has been designed to provide a number of key benefits, including quick and simple installation, extremely high efficiencies and all-year-round energy recovery.

The unit also uses a DC inverter scroll compressor, which ensures it achieves a COP up to 6.5, as well as full control of output from 10 per cent to 100 per cent. This is claimed to allow the Recooler HP to deliver the exact temperature required to maintain occupants’ comfort levels more effectively than traditional fixed speed systems. Plus, the inverter drive allows the unit to work at part load, ensuring the perfect balance between reliability, efficient heating and cooling.

Individual control

The ventilation system has been designed so that each floor in the five-storey building is divided into six zones, where the ducting will serve individual VAV boxes with temperature and CO2 control.

Powering the ventilation system is Fläkt Woods’ eQ range of highly efficient AHUs. Available in 21 sizes with flow rates from 0.1 m3/s to 12.5 m3/s, the eQ unit is ideal for a wide variety of commercial applications, including schools, offices, retail outlets and hospitals.

All models incorporate a Centriflow plenum fan with an impeller design to provide the highest efficiencies on the market.

In addition, the eQ units are provided with integrated controls, corrosion protection and built-in cooling systems with latent energy recovery.

The contractor for phase one of the project was Rotherham-based Lyndhurst Cooling and Heating Services. Commenting on Fläkt Woods’ products, managing director Russ Oliver says: “This installation is the first of two projects that we have carried out for Sheffield Hallam University incorporating the ReCooler HP unit.

“After using a crane to lift the equipment onto the roof of the building, the unit was successfully connected to the ventilation system without any issues and, so far, we’ve been really impressed with the quality and performance of the equipment.

“We’re also looking forward to evaluating the success of the units over the next year, especially their energy-saving potential.”

Phase two of the project – including the design and build of the interior and the connecting of all services – was scheduled for completion in January 2015.

Due to success of the ReCooler HP unit at the Arundel Building, Sheffield Hallam University are in discussion with Fläkt Woods about similar applications, as Peter Wilson of Fläkt Woods explains: “The university has involved us in the planning and plant sizing stages of new projects, in order to maximise both energy recovery and reduction of total running costs across its ventilation equipment.

“These include a new-build project that uses a mix of indirect humidification and ReCooler HP, allowing the total cooling load of the AHU to be reduced by more than 50 per cent.” 

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