Originally Posted by
hyperion
You need to know/guess the the difference between the evaporating temperature and the air off temperature in comparison to the achieved room temperature. As a rough guide the evaporating temperature will be 8degK lower than room temp. So your suction pressure could be about 18 psig at 2degC, so set your pressure switch to cut out at 15psig. You may need to do a little fine tuning to make sure that it is working correctly and allowing the system to get down to temperature and operate on the room thermostat.