The adjustment knob (director) must be set higher than the desired room temperature.
  • Incoming and outgoing (shifted) phase are reversed. That way the feedback resistor is constantly connected to the power supply and drops the temperature in the room. Otherwise the temperature fluctuation is very high (approx. 5-8K)


  • The heat output is too low for the room. This is why the duty cycle of the controller is too high, the feedback resistor is switched on for too long, reducing the temperature in the room.


  • Foreign sources of heat influence the controller (e.g. the sun, television, lamps etc.). The controller is affected by these foreign sources of heat and registers the room as being warmer than it is, not heating the room sufficiently.
The adjustment knob (director) must be set lower than the desired room temperature.

The controller is behind a curtain (for example) or mounted on an outer wall or near a door. The controller registers the room as being cooler than it is, overheating the room

The room is not getting warmer.
  • The actuator is faulty, the actuator is not opening the valve.
  • Severe dirt from the construction site may have accumulated on the controller. The contact cannot close because of this.
  • The controllers for two rooms are switched on in series. These rooms only get warm when both controller contacts are closed.

Future guidance:

  • It is important to be aware that response times are very long, especially for floor heating. So the room is heated very slowly and cools down very slowly (sunshine, for example, can lead to overheating). You also cannot expect a cool room to reach the desired room temperature just a short time after turning up the adjustment knob on the controller.

  • In well-insulated rooms, you should also be aware that the temperature takes a long time to cool down. So sometimes you may find that at night, though “lowering mode” (e.g. 4 K lower) has been selected, the temperature only lowers slightly and the heating is thus not activated for a long time.


  • It is very common for the function of bimetallic controllers to be impaired or completely inactive due to penetrating dirt, which accumulated from the construction site. Therefore, you should always wait until after any necessary scraping, painting or wallpapering to mount it. Avoid all drilling debris.
The temperature fluctuation in the room is very high (approx. 5 – 8 K).
  • The neutral conductor N is not clamped to clamp 4 of the controller.
  • The neutral conductor N is clamped to clamp 4 of the controller but not in the correct place (distributor box, safety box).