Heating comes on when it shouldn't

My CH is set to off, but comes on every time Tado switches the HW on. Tado app doesn't recognise this and on the app it shows CH is off but all radiators are hot.
I suspect faulty 3-port valve but not sure, how do I check? Worcester Greenstar Boiler. Wireless thermostat, extension kit and internet bridge all paired and working. Have reset the system many times but prob persists.

Best Answer

  • RetsimLegin
    Answer ✓

    In my experience, my three-way valve has been the most unreliable part of my system, going back before I had Tado when the boiler timer and thermostat were simple switches.

    If you feel confident at working with live mains power without killing yourself, probably the easiest way to check that it's not Tado misbehaving is:

    • set the Tado system up so that the Hot Water is on; the heating should be off, but is erroneously on as well (so, as you describe)
    • CARE: remove the front cover from the Wireless receiver (the thing that typically sits adjacent to the boiler)
    • CARE: use a mains voltmeter (ideally) and check voltage between the two terminals Supply (N) and CH (NO) terminals. Or a mains tester screwdriver (etc) to check for live power on the CH (NO) terminal. If Tado is behaving correctly and the heating should be off, the CH (NO) terminal should be dead. Confirm by testing CH (NC) which should be live.

    If that's correct then it's not Tado at fault; if CH (NO) is live when it should not be, then I'd suggest Tado is at fault.

    DO NOT try this unless you are confident you won't kill yourself; mains power needs treating with a huge amount of respect!


  • That is very helpful, thanks. I'm very competent with electricity and will perform the tests you advised.
    Thanks again.