Double thermostat ATHs 270U

The ATHs 270U surface mounted thermostat consists of two separate measuring and switching systems in a thermostat housing. It works as a safety temperature limiter STL with manual reset and as a temperature monitor TM with automatic restart after hysteresis. In this way, the ATHs 270U "monitors" the set temperature, switches the device off when the set temperature is exceeded, and then switches it on again automatically after a hysteresis. The ATHs 270U is TÜV tested according to DIN EN 14597 and encapsulated according to IP54. The temperature range of the TM and STL is + 20 ° C to + 150 ° C.

Technical description


The surface mounting thermostat works on the principle of liquid expansion. If the temperature changes in a liquid-filled sensor system - consisting of a sensor, capillary and membrane - the volume changes. The resulting stroke of the membrane actuates the microswitch by lifting. Only the temperature sensor is used to record the temperature.

Switching function (STL and TM)

If the temperature at the temperature sensor exceeds the set limit, the sensor plunger of the microswitch is relieved and the circuit is opened.

TM with automatic restart

If the value falls below the set limit (by the hysteresis), the microswitch is automatically returned to the starting position.

STL with mechanical lock and restart lock

When the set limit is exceeded, the circuit is opened and the microswitch is locked mechanically. After falling below the limit by approx. 10% of the temperature range, the microswitch can be unlocked by removing the cap nut by pressing the restart button.

Switching element

Encapsulated microswitch with single-pole changeover contact and restart lock (opens when the temperature rises) at STL. The TM has an encapsulated microswitch with a single-pole changeover contact.


The unbreakable thermostat (STL), with enhanced safety according to DIN EN 14579, opens the circuit when the measuring system is destroyed and remains mechanically locked in this position.