1. A refrigeration system control device using fuzzy logic for controlling a plurality of refrigeration compressors such that the closest capacity is selected to match the load to each of a plurality of evaporators comprising: a control having an input adapted to be connected to a means to sense the temperature in the controlled space wherein a control signal is indicative of the maximum refrigeration load of the controlled space; a means for determining whether the primary control variable in said space is above or below a single predetermined desired target; a pressure sensing means connected to the refrigeration system in a manner which allows generating a signal responsive to the suction pressure of the refrigeration system; a means for generating a signal indicative that the temperature in said space is above a predetermined high alarm setpoint or below a low alarm setpoint, said signal causing disconnect of said temperature control signal from the control device and allowing the control to use a signal from the pressure sensing means as the control signal; a signal means to indicate that said controlled space is in defrost, such means causing disconnect of said temperature control signal from the control device and allowing the control to use a signal from the pressure sensing means as the control signal; a timer having an adjustable timing interval based upon the error in the control signal of the device and the single predetermined desired target for that control signal and the rate of change of the control signal; a selection means consisting of fuzzy logic rules and membership functions for determining, after said timer interval has elapsed, the closest combination of available compressors which will match the load; an output being an electric signal adapted to selectively energize or de-energize said combination of the plurality of refrigeration compressors.