Opentherm, is it working?

Hi I've recently discovered that my baxi boiler is opentherm ready.

I noticed that my installer had set up my extension kit as a relay instead of opentherm. I opened it up and wired it in as described on the tado app.

My only concern is I don't know if it's working or not. I'm hearing my boiler run almost constantly since changing it round?
My living room (thermostat) and bedrooms (tado TRV) are over heating the room by at least 1.5° instead of a maintained temperature.

I've also noticed a significant jump is kWh used after the switch with nominal change in ambient temperature.

Could really use some insight/help before I pull my hair out :anguished:



  • Montage
    Montage ✭✭✭

    Did you reconfigure it?

    You can usually check settings with the Tado Pro app.

  • I tried to but it wouldn't allow me as I have an extension kit with the old style bridge, the serial number was not recognised. I contacted tado themselves and they explained that it was already configured.

    I found it quite odd as surely I should be able to adjust the maximum and minimum flow temps.
  • do you have manual temp dials for heating and water on your boiler? ive found mine will only react to those even when I use OT

  • Hi yes I do but I've read on here that the tados opentherm communication will over ride this
  • Montage
    Montage ✭✭✭

    I'd expect that Tado would control the heat calls to the boiler using OT. I'm not sure I see the value in them exposing that to a customer.

    Boilers seem to vary regarding whether the boiler settings will be overridden under OT control. There is no 'one' method.

    Tado (themselves) may be able to reconfigure your system settings for flow temp calls.

    In general, I'd expect the boiler to stay on for longer periods, but at lower flow temps.

  • double check with tado if they have configured OT correctly. for my setup, the first person i spoke to had changed it but then when i spoke to another assistant the next day, they said that one of my wireless temp sensors had been configured incorrectly to use OT aswell as the extension kit.

    the boiler will run longer in OT mode.

    in the colder temps, my boiler is more or less running all day. i have my max temp flow set to 60C and my boiler can modulate down to 3.5 i believe.

    also, not sure how true this is but tado should "learn" how much it needs to heat the room up by etc so may take a few days to settle down with the overshooting.

    if not, you might need to balance your heating system.

    someone posted this from another thread i read:

    Balancing Heating Systems: The Ultimate Guide (