Patent ID: 6185946
Filing Date: 2001-02-13
Classification: F04D,F25B,Y02B

Abstract:
A system comprising at least two variable speed chillers arranged in parallel, each chiller including a refrigerating cycle that includes a variable speed compressor, an evaporator, a condenser, and a refrigerant expansion device, and wherein the speed of all operating chillers is coordinated by a common controller to meet a cooling load, comprising:means for transmitting a first control signal from each chiller to the common controller to communicate speed of the corresponding chiller;means for transmitting a second signal from each chiller to the common controller to communicate a current head of the corresponding compressor;the controller including first means responsive to the first control signals and the second control signals from all of the operating chillers for determining a current operating point of the system without regard to load;the controller further including second means for selecting a specific number of chillers such that the selected number of chillers in operation at the current operating point of the system would be operating a closely as possible to their predetermined natural curve of operating efficiency; andthe controller further including third means for adjusting the number of chillers on-line such that it equals the selected number of chillers, thereby improving overall operating efficiency of the system, while still enabling the system to accommodate the load by adjusting speed of the adjusted number of on-line chillers.