Abstract: A method is provided for operating a refrigerant vapor compression system, for example an air-cooled chiller or air-cooled condensing unit, at optimal energy efficiency rating. The method includes the steps of: determining the instantaneous values of a plurality of selected operating parameters of the system's refrigeration unit, calculating a desired control parameter set point indicative of an optimal energy efficiency rating for the refrigeration unit as a function of the selected operating parameters, sensing the instantaneous value of the control parameter, comparing the sensed instantaneous value of the control parameter to the calculated control parameter set point, and adjusting the operating speed of the condenser fans associated with the air-cooled condenser of the refrigeration unit in response to that comparison.

Abstract: A method is provided for operating a refrigerant vapor compression system, for example an air-cooled chiller or air-cooled condensing unit, at optimal energy efficiency rating. The method includes the steps of: determining the instantaneous values of a plurality of selected operating parameters of the system's refrigeration unit, calculating a desired control parameter set point indicative of an optimal energy efficiency rating for the refrigeration unit as a function of the selected operating parameters, sensing the instantaneous value of the control parameter, comparing the sensed instantaneous value of the control parameter to the calculated control parameter set point, and adjusting the operating speed of the condenser fans associated with the air-cooled condenser of the refrigeration unit in response to that comparison.

Abstract: The invention uses a variable speed drive (VSD) only on a range of capacities corresponding from zero to standard point conditions, and if conditions correspond to higher than rated point current, the VSD is disconnected and the compressor is connected directly on line. This approach allows using a smaller size VSD. At the same time, if there are several compressors operating in the same machine, only one VSD is needed. The VSD drives a first compressor from zero to the speed corresponding to the line frequency. Controls then switch the first compressor to direct on line (DOL) and disconnects the VSD from the first compressor. The VSD is then available to drive a second compressor. This process can be repeated through multiple compressors.

Abstract: An algorithm calculates, in real time, the overall heat transfer coefficient for an air-cooled chiller system and compares this value to a reference value corresponding to a new machine operating with a clean condenser. Based on this comparison, an indication is displayed to inform a user of the degree of degradation in condenser performance.