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How to wire extension kit to simply turn the mains power to the boiler on or off.

I have a very old oil boiler which only has a simple power supply to the boiler and a stat on the boiler itself to control the temperature of the boiler itself.

Their are NO room stats or and other control equipment. If it's cold I turn power to the boiler on and adjust the stat depending how hot I want the water in the boiler / radiators to be.

So I plan to cut the mains cable to the boiler and wire through an extension kit which of course if then wirelessly connected to the Tado smart room stat.

I just need to know what the wiring diagram should be. It should just be simple L+N+E in and Earth common with a switched Live (or Neutral or both) but I am unsure what each of the connectors in the ext box do.

Tado just tell me to remove the old unit and wire accordingly but I don't have an old unit.

Any help would be much appreciatted.

Kind Regards



  • The extension kit requires Live and Neutral. Due to the extension kit being made of plastic the Earth is not used, but there is a terminal to hold the unused wire. The extension kit is single pole, meaning it only switches the Live supply. You will need to use terminal 4 ‘CH ON’ to switch your boiler on. And select jumper position 2 for 230V relay control.

    You must protect the extension kit with a fuse. I’m not an electrician but I suggest a double pole switched Fused Connection Unit (FCU) is fitted between the extension kit and your consumer unit. Fit the FCU with a 3A or 5A fuse.

  • Thanks very much for that, it's much appreciatted. It's as I though but wanted to check. I got my new unit on Monday the old one packed up and I had to buy a new unit although I'll get a 50% refund when I send it back.

    Tado Support have been useless.

    I'll give that a try

    Thanks again.

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