Adding an extension box to a wired smart thermostat

Hello, Currently I have two thermostats wired to separate heating zones. I have a S plan setup with a boiler and a separate hot water tank. Currently the boiler comes on when the HW calls at any time. I want to use the extension kit to put time controllers on the HW for the boiler to reduce when it will be switched on.

The installer instructions I have found for an extension box and S-plan only refer to wireless thermostats. I'm not sure if the stats I have work in both configurations and what I should do with the wires from them.

Is there any instructions covering my setup. My thermostats have firmware 54.20 if that makes any difference.


  • Wired thermostats can be configured to operate wirelessly, allowing one of your current thermostats to link with the extension kit. The wiring changes are not minor (see below) and will need to be made by a competent electrician or heating engineer. You’re unlikely to get any instructions/support from Tado.

    1) One of your wired thermostats needs no changes.

    2) The second thermostat needs to be configured for wireless mode.

    3) The extension kit is installed and will control the HW zone and one CH zone.

    4) The extension kit HW relay controls the HW zone valve via the cylinder stat.

    5) The extension kit is wired to switch the CH zone valve that was originally switched by the wireless thermostat.

  • Thanks that is really helpful. I couldn't find anything to confirm that a wired one could be wireless too. I'm having my boiler serviced soon so may leave them to sort it.