reverse-acting thermostat

Definition

(Noun) A thermostat that decreases or switches off its output as its set-point is reached. The thermostat that controls a typical house furnace is reverse-acting since it switches the furnace OFF or de-energises as the set-point is reached. The opposite to this is a direct-acting thermostat, which energises equipment as the set-point is reached. For example, an air-conditioner or a refrigerator.