ᐅ The mixer valve is not receiving a signal to open.

Hello everyone!

We recently bought a house and now have the following issue:

The heating system is a Eurocontrol KM. In the basement, I have underfloor heating, and on the ground floor, radiators. The radiators work perfectly fine. However, the mixing valve for the underfloor heating does not receive a signal from the heating system to open. If I open the mixing valve manually, the heating system immediately sends a signal to close it.

During the relay test, the mixing valve opens and closes as expected.
The outdoor sensor shows accurate values (currently 4°C (39°F)).
The flow temperature sensor also shows correct values (currently 18°C (64°F)).
For testing, I set the heating curve very high. At 0°C (32°F) outside, the flow temperature should be set to 80°C (176°F).
The heating is set to continuous operation.

When I turn the dial and increase the temperature setpoint from 22°C (72°F) to 24°C (75°F), the mixing valve opens briefly, then closes again. The same happens when I set it to 26°C (79°F). This also occurs in manual mode...

Since I have a heat exchanger, I have a mixing valve (Brötje SQA 31.1) and two circulating pumps (Grundfos Alpha 2 and Brötje CP43). There is no maximum thermostat.

Thanks for your help!

Hello

Is the mixer in the underfloor heating circuit or in the boiler circuit?
Are both pumps running, or is it possible that heat is not being transferred in the circuit?

Olli

The mixer is in the boiler circuit. All pumps are running. In the meantime, I have switched to manual operation. Now everything is warm. However, this cannot be a permanent solution...