What is believed to be the largest air-cooled chiller project in the UK using hydrocarbons as a refrigerant has been delivered by Cooltherm for a leading pharmaceuticals company. The 1MW cooling plant is based on two 500kW Geoclima screw chillers, and runs on high efficiency propane. The ultralow Global Warming Potential (GWP) solution was selected as a result of the end user’s policy of moving away from use of HFC refrigerants by the end of the 2015-16 financial year. It replaces a conventional cooling system based on HFC R407C refrigerant, which had also become unreliable before reaching the end of its anticipated operational life.
Excellent energy efficiency Rob Young, Cooltherm director who headed the project, said: “In additional to its low GWP characteristics, the design was chosen for its excellent energy efficiency and ability to meet the electrical load limitations of the site, which were an issue and a potential restriction on the higher cooling capacity required of the replacement system.” The plant is optimised to cool the building’s tw wings using one chiller, with the second chiller coming onstream automatically when load and ambient temperature increase, ensuring peak demand is met. When conditions allow, and the load reduces, the system automatically reverts to default one-chiller mode.
Low propane charge The propane chillers were lifted into position in a two-stage process, one from a public road at an extended radius which used a specialist mobile tower crane. “Given the time of year, we had some concerns about high winds given the succession of storms during the lead up period. However, on the day we had a 90 minute period of calm, enabling us to safely complete the lift.” The chillers are designed to operate on a low charge of propane given their size, and are equipped with high performance brazed plate heat exchangers, which boost efficiency further. They are also fitted with automatic water isolation valves to prevent water mixing across the system.
Cooltherm provided a turn-key design and installation package, with chillers installed within the original footprint within the chiller compound. The company worked closely with the end user throughout, providing technical consultancy support at every stage of the project.
Following its success, Cooltherm is working on a second project on the site to replace an existing data centre cooling system which runs on HFCs. Because of the difficulty of using long pipe runs for propane, the company is designing a mini propane-based chilled water CRAC system, to replace the existing HFC plant.
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