Minimum or maximum thermostat for supply air monitoring and fan control in ventilation and air conditioning systems. Type-tested by TÜV in accordance with DIN EN 14597. For hot air heaters in accordance with DIN 4794. Sensor break: In the event of sensor damage or sensor break, contacts 1 and 4 of the fan open. Intrinsic safety/cold protection: The appliances are intrinsically safe, i.e. if the sensor medium is lost, e.g. due to sensor breakage, the burner is switched off. As temperatures below freezing produce the same effect by reducing the volume of the sensor medium, the devices are adjusted by means of the “cold screw” so that they only switch off the burner at temperatures below -15 °C. The appliance can only be switched back on manually at temperatures higher than approx. -5 °C using the manual reset button. Overheating protection: The appliance protects against uncontrolled overheating caused, for example, by heat build-up or gradual capillary filling loss in the event of invisible damage to the sensor or capillary tube, etc. When a temperature of 220 °C is reached, the safety slot in the sensor melts and the appliance switches the burner off to the safe side due to loss of the filling medium. The burner cannot be switched on again. The appliance is then unusable and serves as proof that an excess temperature of at least 220 °C has been reached. Overheating protection thermostat for electric heating coils and direct-fired air heaters in oil and gas operation.