Abstract: A method of compressor over temperature protection. The method comprises the steps of monitoring the temperature of oil entering a compressor, determining an oil temperature differential between the entering and exiting oil temperatures, comparing the oil temperature differential to first and second predetermined limits, terminating compressor operation if the first limit is exceeded by the oil temperature differential, and terminating compressor operation if the second temperature limit is exceeded by the oil temperature differential for longer than a first time period.

Abstract: A method and apparatus for monitoring oil charge loss for use with a refrigeration system. The refrigeration system has a compressor for compressing a refrigerant gas, an oil/gas separator for separating compressed refrigerant from lubricating oil, a condenser for condensing the compressed refrigerant gas, an oil cooler for cooling oil separated from the refrigerant, the refrigerant and oil both having known and differing coefficients of heat transfer, and an injection system for injecting the cooled oil into the compressor.

Abstract: A method of staging and modulating compressors in a multi-circuited refrigeration system including a plurality of condensing heat exchange circuits where each condensing heat exchange circuit includes a plurality of compressors. The method comprises the steps of: accumulating a first operative condition for each compressor; accumulating a second operative condition for each compressor; determining the status of each compressor in each circuit and designating therefrom a first list of circuits having compressors available to be turned on and a second list of circuits having compressors available to be turned off.

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: A method of staging a plurality of compressors in a refrigeration system. The method comprises the steps of: accumulating a first operative condition for each compressor; accumulating a second operative condition for each compressor; initiating operation of whichever compressor has the lowest accumulation of the first operative condition whenever a system controller calls for an increase in system capacity; and terminating operation of whichever compressor has the greatest accumulation of the second operative condition whenever the system controller calls for a reduction in system capacity.