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Extension Kit connection with Smart Radiator Thermostats

Hi all,

i recently bought 5 smart radiator thermostats and one extension kit. It was basically a misunderstanding with the salesman. i was told that it is possible the following use case: you buy smart radiator thermostats and the extension kit and you could switch your boiler off whenever all smart radiator thermostats reach their set value, or on if only one of them needs hot water. Today I was told by tado support that I would still need the smart thermostat for this because it is the only thing that can communicate with the extension kit. In my case I do not need that smart thermostat. Simply, there would be no space where it can control any temperature because every room is already covered with smart radiators.

I suggest that you consider making this connection possible, because I believe it is like it is now only due to the history because you probably developed the smart thermostat first.

I would like what the others have to say.


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  • That does not sound right. I have smart radiator thermostats in all my rooms that demand heat via the extension kit.

    I do have a smart thermostat for the hot water but none of the radiators valves connect to it.

  • @AdyR So you want to say that smart radiator thermostats can communicate directly with the extension kit?

  • ChrisJChrisJ ✭✭✭

    As currently implemented if you want the Smart Radiator Thermostats to be able to 'call for heat' then you must have a Smart Thermostat even if none of the TRVs are 'connected' to it in the app (they do connect to it behind the scenes but in a different way).

    Maybe Tado could change this to have the TRVs communicate with the extension kit (depends on firmware, hardware capabilities etc.) but right now this is how it is. I appreciate that it is annoying to have to pay for the additional Smart Thermostat but if you do then it will work as you desire.

  • I am also curious about this. @AdyR says that Smart Radiator Thermostats can demand heat via the extension kit, while @ChrisJ says a Smart Thermostat is needed for the Radiator stats to talk to the extension kit. Unless I’m missing something, it’s not possible for both of these statements to be true.

    OK, so @AdyR has a Smart Thermostat installed for hot water, so it might be that, unknown to him/her, the Smart Thermostat is also allowing the radiators to talk to the boiler...

    BUT, I’m not convinced. Ever since I installed the system I wondered if the Smart Thermostat was actually necessary and I questioned Tado° about this and they insisted it was necessary, but the doubt has lingered for the last 2 years, while the Smart Thermostat has sat on a shelf doing absolutely nothing... unless it really is talking to the boiler? But if that is the case, as Tado° advised me, I have to wonder why things are operating just perfectly now that the batteries on the Smart Thermostat have finally run down?!
  • i am facing same issue, on app it suggest i should login online to register the extension kit. But then online i can't find any option to register this. I have 15 Smart thermostat installed but then not sure how they will communicate with the boiler if i don't have any extension kit?

  • This doesn’t sound quite like the issue I’m describing... but anyway, when you say you have 15 Smart Thermostats installed, I presume you mean “Smart Radiator Thermostats”? Do you also have a “Smart Thermostat” (square white box)? If so, is it connected to the boiler or not? I believe you have to have something connected to the boiler, so if it isn’t the Smart Thermostat then you need an extension kit.
  • Sorry to be away so long but as I understand it you NEED either the Smart Thermostat or and extension kit as something has to connect directly to the boiler by wire to switch it off and on.

    If you have just the Smart Thermostat then it replaces you original thermostat and the relay turns the boiler off and on.

    If you have the extension kit then that connects to the boiler and either the relay switches the boiler of and on or the serial communication sets the boiler temperatures for heating and hot water.

    Any extra Smart thermostats and Smart Radiator Thermostats connected to your account and will be able to demand heat as required via the hub to the boiler extension or the smart thermostat that is wired to the boiler.

    If you add more than one thermostat / radiator thermostat to a room you have to choose which one controls the room temperature (I believe the Smart Thermostat may take precedence).

    As far as I can see, the only way to control the hot water is via an extension kit that is connected with the serial link as I haven't come across any other way to wire into the hot water system to switch it.

    For my wet underfloor heating I use a Smart Thermostat where the relay controls the zone valve and the communication link controls the boiler via the hub / extension kit.

    When I first got my kit I had 6 Smart Radiator Valves, 1 Smart Thermostat and 1 Extension kit. The installer told me I didn't need the Smart Thermostat, as i had the Extension kit, but as I had it the best place to locate it was in the hall where there were no Smart Radiator Thermostats. The temperature in all the other rooms was controlled by the Smart Radiator Thermostats which could also demand heat if required.

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