Tado Extension kit to replace controller

I have a glow worm 15hxi boiler heating both central heating and hot water, controlled with a Siemens RWB9 controller. I already have a Tado thermostat and numerous smart radiator thermostats.

i am wanting to swap out my controller to enhance my control of the hot water.

Can I use the Tado extension kit to replace my controller?

and do I have to install it in the same location as the existing controller or could I move it local to the boiler?

Best Answer


  • Germán
    Germán | Admin
    edited August 2019

    Hello RichardW

    Technically it would be possible for you to replace the RWB9 with the Extension Kit.

    However, as you are using the Smart Thermostat together with Smart Radiator Thermostats, this change may not be so convenient for you.

    Our Smart Radiator Thermostats are able to call for heat from the boiler because it not only opens the radiator valve, but also asks the Smart Thermostat **or** the Extension Kit to send a demand for heat to the boiler.

    It is not possible, however, for the Smart Radiator Thermostat to ask the Smart Thermostat to ask the Extension Kit to call for heat.

    Therefore, as in your heating system the Smart Thermostat is unable to call for heat without a timer or programmer set to on, if you add the Extension Kit, we couldn't offer you the independent behaviour that you are currently experiencing with your Smart Radiator Thermostats.

    You can discuss with an electrician or heating engineer to have your heating system rewired so that it functions with the Smart Thermostat being directly able to call for heating from the boiler. This option is also the answer to your question about placing the Extension Kit in a different location than the Siemens controller, as this would already require to rewire the system.

    You may consult with your heating engineer about this possibility, having the Extension Kit installed next to the boiler just for the Hot Water, and leaving the heating control directly in the Smart Thermostat as it is now.

    Kind regards,


  • Thank you for your response.

    I am wanting the extension kit to give me on/off control for my central heating ( it is in permanent on mode with the tado devices installed) and control to adjust the time for my hot water heating. This is the same as the existing controller but with the added extra that I can remotely adjust the hot water timing.
    The hot water timer in the Siemens controller has recently failed and I need to replace it.
    Is this possible?
  • Thank you very helpful. I understand now
    Have a good day