We don't do a lot of refrigeration but do get the opportunity occasionly.
Most of the controls I have seen are 120/208 with the compressor controlled by a pressure switch. The evaporator is controlled by a themostat that switchs the freon solenoid valve and may control the evaporator fans. One compressor can serve several evaporators.
Often these systems are a conglomeration of used equipment. Usually what I do is ask the refrigeration tech. how he want the system to work and then set up the controls to make that happen. Sometimes they want the evap. fans to run continuously, sometimes they cycle with the thermostat.
Often there is no electrical tie between the compressor and evaporator. Defrost timers, heaters etc. are another matter.
These are really very basic control systems but it can get confusing because lack of schematics.
Good luck!
GJ
