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Knowledge document #3457
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Room temperature differs from the target temperature of the FRITZ!DECT radiator control

The radiator control, for example FRITZ!DECT 301, does not regulate the temperature according to the desired room temperature. The temperature either exceeds or drops below the specified comfort or cool-down temperature.

1 Checking the radiator valve

If the radiator valve cannot be moved easily, the radiator control either cannot open and close it completely, or it cannot open or close it at all. This prevents the radiator from warming up or cooling down. Therefore, check the valve pin:

  1. Remove the radiator control.
  2. Press the valve pin on the radiator several times with a solid object, for example a coin.
  3. Remount the radiator control.
  4. Once it is mounted, follow the instructions in the display of the radiator control.

2 Taking delayed display of measured temperature into account

Radiator controls measure and regulate the temperature every 2 minutes. However, since they operate according to the DECT ULE (Ultra Low Energy) standard, they only communicate with the FRITZ!Box every 15 minutes to save energy and minimize DECT radiation. This may cause a delay in the display of the actual temperature measured by the temperature sensor in the user interface of the FRITZ!Box.

3 Taking slow reaction time of heating system into account

Temperature-controlled heating systems tend to respond slowly. To prevent a room from overheating or cooling down too much, the radiator control does not immediately move the valve when there are slight deviations from the target temperature. Therefore, observe the heating behavior over a longer period of time by heating the room to the desired room temperature so that the heat can be distributed evenly throughout the room. The time it takes for heat to distribute almost evenly depends on the room height or presence of niches and bay windows, for example, and may take several hours.

4 Taking the settings of the heating system into consideration

Settings of the heating system, such as the flow temperature or a central night setback, can prevent the desired room temperature from being reached. For example, the radiator is heated up by a high flow temperature and radiates this heat even if the valve is already closed. A central night setback to a lower temperature can also prevent the desired room temperature from being reached although the radiator control correctly regulates the temperature.

5 Taking other heat sources into consideration

Please note that the room temperature is also subject to temporary fluctuations or fluctuations due to the time of day, regardless of heating output. For example, temporary exposure to bright sunlight or reduced ventilation can lead to an increase in room temperature, regardless of the temperature control by the radiator control.

6 Adjusting the measured temperature to room temperature

Since the temperature is measured directly at the radiator control, it may differ from the actual room temperature, for example in the middle of the room. You can set this temperature difference (offset):

  1. Adjust the temperature measured on the radiator control to the room temperature.