The iO HVAC Controls FS-38 Suction Line Freeze Thermostat is a protective temperature switch designed to monitor the suction line of air-conditioning systems. It senses refrigerant line temperature and opens the cooling control circuit when the temperature falls to 38°F, helping prevent evaporator coil freeze-up; it closes again at 50°F. Designed for residential and light commercial A... https://www.partshnc.com/io-hvac-controls-fs-38-suction-line-freezestat