Abstract: A method of controlling a multiplicity of condenser fans in a refrigeration system comprising the steps of: calculating a first difference in state between a high pressure side and a low pressure side of the refrigeration system; determining an optimum state for the refrigeration system; determining a second difference in state between the first difference and the optimum difference; and controlling the multiplicity of condenser fans if the second difference exceeds a predetermined value.

Abstract: The determination as to whether an operational compressor in a multiple-screw compressor water chiller is fully loaded is made by sending a relatively long duration test pulse to the load solenoid of the compressor. If the compressor is fully loaded, no measurable change in the current drawn by the compressor motor will be measured since no slide valve movement will have occurred and no additional load will have been placed on the compressor. If, however, the compressor is not fully loaded at the time the test pulse is sent, the compressor slide valve will move to load the compressor to an extent such that a reliably measurable change in compressor motor current draw occurs.

Abstract: In a refrigeration system including an incremental expansion valve and an electronic controller for controlling the operation of the expansion valve, a method of controlling the expansion valve in response to a sensed condition of the refrigerant in the system. According to the method, the valve controller alters the control gain rate to provide compensation in the valve flow rate for changing refrigerant conditions in the system due to the staging of multiple condenser fans and flooding of the evaporator.