Air-cooled water chillers for free cooling offered highly efficient performance and lower investment costs

CKW Fiber Services, Lucerne, Switzerland

CKW Fiber Services Ltd is a reliable provider of telecom and IT infrastructure services to businesses and is the digital hub in central Switzerland. It had been operating two data centres, but increasing demand made it necessary for a third centre to be built. With 1,200 m2 of space, it could accommodate 300 data racks. Since the total cooling capacity of 1.1 MW was above the new limit of 400 kW, the unit had to use either natural refrigerants or hydrofluoroolefins (HFO) such as R1234ze, which has low environmental impacts. The global warming potential (GWP) had to be less than 7 and the local noise level regulations, stipulating 58 dBA at a distance of 10 metres, also had to be respected.

Risk of runaway installation costs

A set-up with water-cooled machinery and free cooling from external systems was planned to achieve these values. Because the data centre was supposed to be fitted out with compact air-cooled chillers, there was a risk that the actual investment costs for the new system would be substantially higher than estimated. The client needed a highly-efficient installation that would meet the requirements without investment costs running away.

Rigorous efficiency requirements

The engineers at Swegon-owned BlueBox in Veneto, Italy suggested that the client invest in equipment built around its KAPPA REV unit, with free cooling and ultra-quiet performance (*LGW FC + SLN). Kappa REV is an energy-efficient unit with screw compressors, tube heat exchangers and HFO refrigerant.

Compact design freed up space

The Energy Efficiency Ratio (EER) ratings achieved with KAPPA REV are so good that all the requirements can be met. Moreover, the unit operates with a built-in hybrid system for free cooling in the spring and autumn, which minimises the client’s  costs. Its compact design also made it possible to free up 200 m2 of internal space where more data racks could be installed.

Efficient solution with free cooling reduced costs significantly

The investment costs for the installation were CHF 400,000 less than originally quoted, thanks largely to the free-cooling solution. With the help of the BlueBox solution, in which a free-cooling module in the stand-by machine achieved a very high degree of efficiency, TFT was obtained when the outdoor temperature was just 11°C, i.e. the temperature at which free cooling meets all the cooling requirements (Total Freecooling Temperature).