Hot water issues after trv install

I have a tado system with an extension for my hot water which is in a cylinder. Had it a few years and all works fine. I have hot water on for 40mins a day and that’s enough to keep it hot. The extension is linked to the tado thermostat which controls my upstairs system.

Last week I purchased a load of tado TRVs and since then my hot water is hit or miss.

Sometimes I have hot water sometime times I don’t.

My theory is that the call for hot water turning on is not resulting in a trigger to the boiler. I think when I do have hot water it’s a coincidence that it’s at the same time that the main bedroom is calling for heat or perhaps another radiator upstairs.

No idea why this would now be a issue?


  • Just confirmed that for some reason activating hot water is not triggering the heat you don’t hear the click. Turned all the thermostats down and the. Activated it and no joy.

    Also I’m the hot water is says it’s run by the extension and downstairs thermostat.
  • No reply from Tado either here or via support. Managed to get luke warm water. Oh the days when tado had a great helpline and you could speak to someone 😡
  • We see, to have the opposite problem. Hot water (and boiler) always on. Heating on smart schedule generally working but can’t seem to do the same thing for the hot water - ie can’t control it at all. No answer for, Tado either. This has been going on for weeks - so we are not saving any energy !!! Hate to think what my gas bill is going to be.

  • 96mgb
    edited December 2020
    Still no reply from tado
  • I have this same issue

  • Jurian
    Jurian | Admin

    As far as we are aware, there are no known issues with the extension kit and the hot water control.

    How does tado control hot water and heating in the Extension Kit ?

    The Extension Kit uses the normal dual channel UK backplate.

    All tado does, to activate the hot water is to connect the number 3 wire with the live wire (L).

    All tado does, to activate the heating is to connected the number 4 wire with the live wire (L).

    In some cases, there might be an issue with the wiring or with the 3 port valve, and this could lead to issues where the hot water can only heat up when both the number 3 and 4 wire are connected to the live wire.

    If this is the case, there is something wrong with the wiring or 3 port valve.

    The best way to go forward: Get an experienced heating electrician to take the tado Extension Kit from the wall, to manually connect the number 3 and 4 wires with live. To see if the heating system is able to produce hot water by ONLY connecting the number 3 wire with the live wire.

    If that is not the case, he needs to do a full check of the system because something is not right with the heating system (tado has been excluded from the equation since the Extension Kit has been taken from the wall).

  • I just replied to your post in the Boiler Room section -

    Tado is not so straightforward as this in a low voltage installation (I have Vaillant eBus) and there's way more than just 'Connect 3 or 4 with live'.