Opentherm and power supply for Tado Extension Kit

Hi all,

I decided to try to use Tado smart thermostats. My current setup with an existing thermostat is simple 24V on/off control. My boiler supports support OpenTherm connection though. Will it make any difference by connecting Tado Extension Kit via OpenTherm or it's better to stay with existing low voltage connection scheme? As I understand Tado devices are already "smart" enough and there will be no real effect in using OpenTherm?

Another question, if I decide to connect via OpenTherm to my boiler I have to provide separate power supply for the Extension Kit. Will it be sufficient to just to wire extension kit (N and L) to regular 230v electric outlet?



  • Hi Alexander,
    Opentherm has a big advantage over on/off control if your boiler supports modulation (can provide a fragment of its maximum power). For example if only a room must be heated by only 2 degrees and the external temperature is high, etc the Tado algorithm might ask the boiler to run at only 10% of its nominal power. This means both energy savings and greater confort (as the room temperature can be kept almost constant).
    Regarding your second question, the Opentherm BUS works with only two wires that both power the thermostat (extension) and cary the digital control signals.
  • Hi Andrei,

    Thanks for your answer!

    I will try to connect the extension kit via to Opentherm BUS when I get it in my hands.

    Although one thing is not clear yet. In the manual available on Internet ( it's clearly stated: "The Extension Kit requires a separate 230 V power supply at N and L for OpenTherm installations". I got this link not via official site but just googled it so it might be outdated. I'm a bit confused now.


  • Hi Alexander,

    Sorry for misleading you. I have a similar BUS (EMS from Buderus) that also provides power to the Extension Kit and I wrongly assumed that it the case for all digital connections.
    Also, I just remembered that the Extension Kit comes with a 4 wire cable that you can use to also power it directly from the boiler if it has a power out terminal.

Sign In or Register to comment.

Howdy, Stranger!

It looks like you're new here. If you want to get involved, click one of these buttons!