For protecting hot water heating registers against freezing. The device is intrinsically safe and has a sealable setpoint adjustment. For temperature measurement of non-aggressive gases in the duct, use the SW-200-12 thermowell, for temperature measurement in non-aggressive fluids use the TH-140 thermowell, in aggressive fluids use the NTH-140 thermowell. Mounting clamps, thermowells and protective coils are not included in the scope of delivery and must be ordered separately.