Heat pumps replace gas boilers at Surrey offices

UK: The refurbishment of a landmark 70,000ft² Surrey office block has seen gas-fired boilers and air-to-water cooling systems replaced with Mitsubishi Electric heat pumps and AHUs.

The owners of the Omnibus Building in Reigate, built in 2001, sought a new low carbon solution to replace the aging major components of the building’s existing systems.

Fareham-based decarbonisation specialists Internal Environments worked closely with the building owners, the Skelton Group, to identify how the old system could be replaced with a fully electric system. 

They opted for two of Mitsubishi Electric’s Climaveneta air-source heat pumps, which offer simultaneous heating and cooling, and three Climaveneta water-source heat pumps. The building also benefits from WizardX-G07 E-OU air handing units, which are fed heating or cooling from six Mr Slim air conditioning systems.

“We evaluated various systems and determined that a four-pipe heat pump providing simultaneous heat and cooling would be the optimal solutions to achieve our client’s need for a low-carbon, low energy system,” said Chris Roy, Internal Environments’ sales director.

The four-pipe heat pump chillers now supply heated water at 45°C and chilled water at 6°C flow temperature. The team from Internal Environments worked closely with Mitsubishi Electric to carry out thermal modelling to show that a temperature of 45°C would heat the offices using the existing fan coil ceiling units when the ambient temperature is around 6ºC-7°C and above.

To supply heating on colder days, the EW/HT water-to-water heat pumps boost the water temperature from 45°C to 75°C when necessary.

Disruption for occupants was minimised and refurbishment was prioritised over replacement where possible. “We thoroughly evaluated the existing fan coil units, and given that they were in good condition, decided that a refurbishment would be more environmentally friendly than a replacement,” said Chris Roy. 

The result is a fully decarbonised, future-proof system, maintaining the comfort of current and future occupants and delivering an EPC of A.