When the process return water temperature required is equal to or higher than the ambient air temperature Free Cooling is not suitable. The system’s three way valve will continue to direct the fluid flow through the chillers’ compressors to be cooled to the required set point temperature.
Mid season operation
For mid-season operation the water is partially cooled by the compressor and partially by the ambient temperatures. The percentage of Free Cooling achieved mid-season is dependent on seasonal temperatures although partial Free Cooling commences when the ambient air temperature is 1oC below the process return water temperature. The water is partially cooled through the Free Cooler then flows through the chillers’ compressors to achieve the required set point temperature.
In winter, when outdoor temperatures are low enough, the water is chilled solely by the Free Cooling coil. This allows the chillers’ compressors to stop operating, saving significant amounts of energy. The only electrical power used in winter operation is for fan operation. This can be achieved once the ambient air temperature is 3oC – 5oC below the process supply water temperature.