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Smart Thermostat Permanently calling for heat

Hi everyone,

This is slightly different from everyone else's fault regarding calling for heat when not required, so thought I better to start a new thread.

Like a lot of you, I have heating coming on all night, even though every Radiator Thermostat and the Smart Thermostat are well below the temperature.

I checked and found the heating valve off the boiler was permanently open. I replaced it with a new one and had the same result. I bought a new heating controller and still have the same result.

Because I have wired my heating/hot water system with a 13 amp socket for ease of working on it, I turned it off and the heating valve closed correctly.

Turned the power back on and the valve opened.

I have now removed the Smart Thermostat and the valve closes. On the back of the Smart Thermostat you can see the pins that are for Common, NO - Normally Open and NC - Normally Closed. You get this information off the back plate still on the wall.

When no heat is required the NO should be open.

I found with every Radiator Thermostat turned to it's lowest temperature and off, along with the Smart Thermostat, there was still continuity across the NO pins. This should only happen when a thermostat calls for heat, which in turn will change the valve to open and start the boiler.

This means that it is very likely the Smart Thermostat which is at fault.

I have been in communication with Tado, but to be honest I am at a loss to describe just how bad some - but not all - of their support staff are. The one I am currently dealing with kept asking the same question. "Tell us the time and date the heating came" Even though I kept explaining that it was happening all night and turning on for 30 - 60 seconds every 2 - 3 minutes. To be more accurate than that we would need to synchronise our clocks!

I have fed this information to them and explained that as an electronics engineer, this was straightforward and as I had explained from the beginning, almost certainly a Smart Thermostat fault.

Annoyingly, I threw away my old thermostat recently!

Unless I have missed something, what I need from Tado is a replacement Smart Thermostat!


  • samdsamd ✭✭✭
    edited May 1

    @G2EWS You said

    I have now removed the Smart Thermostat and the valve closes. On the back of the Smart Thermostat you can see the pins that are for Common, NO - Normally Open and NC - Normally Closed. 

    It may be my misunderstanding of your wording but should you not connect NO and Comm only?


    Hi Samd,

    Thanks for replying.

    Interesting thought, but the three wires were connected on my old thermostat.

    However, the problem is that the NO is permanently closed on the Smart Thermostat even without being connected, so it is probably irrelevant.




    A quick follow up.

    I bought a cheap manual thermostat and wired it up. Now the boiler turns on and off based on the temperature setting.

    I did expect this, but definitely need it installed until Tado get the broken Smart thermostat sorted.


    Well my thoughts on Tado's technical support which were poor at best, took a nose dive yesterday.

    They told me they would get back to me next week. Basically, if I had not bought a manual thermostat, I would either be without heating or would have continued to experience heating all day and night.

    Sorry Tado, your products are good, but you seem to not want to know customers when it comes to a difficult fault that falls outside your experience. I believe you need proper technical support engineers and not just people who come back with statements from a book of 'how to look after customer faults with Tado'

  • Hi i’m experiencing a similar issue but it’s my hot water that is permanently on. As soon as the thermostat in the tank calls for heat the boiler fires up and this happens constantly every hour or so through the night. My hot water extension kit seems to have constant on signal for water even when I turn off the hot water. when i remove the extension kit the boiler shuts off and valve closes as soon as it’s back on it sends a signal to turn on hot water again. I’m having the same issue with their technical support aswell.They take ages to respond and have asked the same questions over and over but not given me any solution.It’s been almost 2 weeks now and still they haven’t actually helped at all.
  • Hi,

    I don't have the extension kit so have no idea how it works. But I guess something is calling for heat. If you have removed the extension kit, is there a wiring diagram? Does it show how the thermostat will take a normally open - NO - contact to closed? If so, check to see if the NO contacts are closed even if your thermostat is not calling for heat. Based on what you have stated it is going to show a closed contact, if so then it is U/S and needs to be replaced. For what it is worth I started up a new conversation with support to get away from the incompetent person I was talking to!

    For me, after spending a lot of time trying to get sense out of anyone, I eventually got hold of a sensible person and they confirmed my Smart Thermostat was broken. A new one arrived yesterday and will be installed by me later today.

  • Hi G2EWS

    Did the new thermostat resolve the problem in the end? Keen to know as have a similar issue that’s been bugging me for ages.

    Many thanks
  • Hi TJ,

    Sorry for the delay, only just spotted your post.

    Yes, it has solved the problem and I have a correctly operating Tado system now.

    Do you have a multimeter, so you can remove the Smart Thermostat - after turning off the power of course - then check the continuity of the NO contact?

    Best regards


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