The thermostat is the "brain" of the cold room: it reads the room temperature with a sensor, compares it with the set point and the differential (hysteresis, usually 2 K) and switches cooling on and off. Simple mechanical thermostats only open and close a contact; digital cold room controllers (Dixell, Carel, Eliwell, Danfoss) bring the compressor, evaporator fan, defrost heater and alarm outputs together in one device.
The main values set on a digital controller: room temperature and hysteresis, defrost type and interval (for example every 6 hours, 30 minutes maximum, 8 °C termination temperature), drip time after defrost, fan delay, high and low temperature alarm and door-open alarm. A wrongly set defrost interval leads both to icing and to wasted energy; the product’s temperature and humidity requirement should be taken from the food storage conditions guide when setting it.
Sensor placement matters: the room sensor goes not in front of the evaporator discharge but at a point representing the average room air; the defrost sensor goes between the evaporator fins. Remote monitoring systems record the thermostat’s values continuously and send a notification to your phone on a deviation; these records are requested in food safety inspections.