I tried to use a refrigerator with a thermostat to cut the power off when unit reached 50 degrees F. When power cut off at 50 F the unit continued to cool for a few minutes and was getting down to 45F before stabilizing and eventually reaching 50F. I do not know if a gradual change of 4 to 5 degrees would be problematic but all the eggs I had were in that unit and I abandoned the project. The refrigerator I was trying to use was a convection type. I built a room 3x6x8 feet well insulated and cooled it with a window style air conditioner. If it had been old style refrigerator with fan blowing air over coils I think it would operate within a closer range.