Free cooling is an economical method of using low external air temperatures to assist in chilling water, which can then be used for air conditioning systems. It is the production of chilled water without the use of a chiller and can be used generally in the late fall, winter and early spring.
When the ambient air temperature drops to a set temperature, a modulating valve allows all or part of the chilled water to by-pass an existing chiller and run through the Free Cooling system, which uses less power and uses the lower ambient air temperature to cool the water in the system.
Ambient Temperature above 40ºF
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 chiller’s compressors to be cooled to the required set point temperature.
Mid Ambient (Between 15ºF to 40ºF)
The water is partially cooled by the compressor and partially by the ambient temperatures. The percentage of Free Cooling achieved is dependent on seasonal temperatures, although partial Free Cooling commences when the ambient temperature reached 32ºF. The water is partially cooled through the Free Cooler then flows through the chiller’s compressors to achieve the required set point temperature.
Low Ambient (Below 15ºF)
When outdoor temperatures are low enough, the water is chilled solely by the Free Cooling coil. This allows the chiller’s compressors to stop operating, saving significant amounts of energy. The only electrical power used in winter operation is for fan operation.
Notes: The operating sequence above serves as a general guideline only. The ambient temperature for free cooling to commence can be reset by user.