Excalibur recently completed a project to optimise the performance of four 600kw single circuit air conditioning screw chillers at a London University.
Typical of many buildings, the chillers operate efficiently at full load, however these conditions rarely occur, and all four chillers had been running at part load to satisfy the building’s cooling demand.
To optimise part load efficiency inverter control was installed to two of the four screw compressors, (replacing their inefficient slide valve capacity control), electronic expansion valves were also installed, and condenser water temperature optimised to allow floating head pressure operation.
The inverter controlled chillers now operate efficiently at part load with the non-inverter chiller operating at 100% capacity when building demand requires.
The project achieved a 30% reduction in absorbed power while also reducing compressor operation, associated maintenance costs and noise levels in the plantroom.