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Opentherm with Ideal Logic 30 Boiler

Hi everyone, I’m hoping somebody here might be able to offer some insight on a technical question I discussed with Tado customer support today.

I’ve currently got a setup consisting of two smart room stats, numerous smart TRVs and an extension kit. The boiler is being enabled by on/off control from the extension kit. I wanted to know the benefits of using the opentherm connection instead so contact Tado support. They have informed me that despite my boiler having opentherm capabilities, I am unable to connect it to my extension kit in this way. To quote their response: “ I've just checked your boiler and unfortunately we can not control this boiler using Opentherm. We can only control it via simple relay (On/off). This used to be possible, but connection to this interface needs an extra harness, which is why this interface is disabled for our devices.”

Does anyone know anymore about this or why opentherm can’t be used on my specific boiler model?

Just as some background, I’m a building management systems engineer, and I understand the principles of weather compensation, etc (although I must admit I don’t know a lot about opentherm protocol!).


  • jelockwoodjelockwood ✭✭
    edited February 6


    I cannot say for certain what Tado's reason is but I can say that On/Off control aka 'Call for Heat' control uses different wiring to OpenTherm.

    OpenTherm is a digital interface and only needs two wires and also runs at a different voltage. Call for heat is 220v and uses switches aka relays to turn that connection off. Typically you have wires for power, for the heating pump, and the heating mid-position valve, along with wires from the room thermostat to indicate whether heat is required or not.

    It could be that Tado are implying that the cabling to your Boiler needs to be replaced, or cabling within the boiler to link to their OpenTherm system.

    A possibly related example is that some Vaillant boilers can be fitted with a timer/controller on the front of the boiler and wirelessly linked to a matching room thermostat. With this example Vaillant setup there is no external wiring at all and hence nothing to link the Tado to. Perhaps they are viewing your setup as being like that.

    Here are some links that might help you.

    The wiring loom apparently comes with the Weather Compensator kit.

    Note: You do not want to fit the Weather Compensator itself as it would conflict with Tado's own OpenTherm control of the boiler.

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