EMS Bus wiring

Looking for wiring connections and setup for Worcester Greenstar CDi Classic to enable control using the EMS Bus (If possible) I have it connected using contacts at the moment.

Thanks in anticipation

Phil Holmes


  • Hi Phil,

    I can only confirm EMS is supported by Tado (I am using it with my Buderus heater). Did you try to use their step by step install guide?



  • PhilHolmes
    edited December 2019

    Hi Andrei

    Thanks for the response. It didn’t give me the option during the installation process. I found a document related to wiring a Vailent to eBus and a Worcester to WT-Bus but not a Worcester Greenstar CDi Classic to eBus. It may be the same but on my boiler I only have some contact marked up EMS BUS.



  • XeonJa
    edited February 2020
    I would also like to know this ems setup, I’m assuming it’s a setting within the thermostat. I know the the ht-bus is d16 or d17 on the thermostat and does this need a Worcester adapter converter thing
  • has anyone got EMS working with the worcester boiler

    i have just wired my extension kit up to the EMS bus, but on the tado docs it only mentions the HT-Bus with BBv on it , i tried D17 from there but that doenst work, the tado is powered up from the EMS bus ok, just not communicating properly which i assume is becuase of the D value in the thermostat setup

    Tado do you have some up to date instructions to wire and configure for EMS bus on worcester boilers.

  • Anyone scratching their head about why the worcester bb connection doesn't seem to work like I was, it does work! But you have to wire lr and ls together on the boiler, it's in the worcester wave setup instructions (wave setup seems v similar to tado, tado needs d17 to work). Good luck!
  • My Worcester Greenstar 8000 currently has switched 230v via a honeywell controller.

    I assume I could just swap that out and run 230v switched in the same way, connecting to ports 1,4 on relay 1

    But if the EMS Bus is a better option I assume I can do away with the wire that runs to 1&4 (leave the Ls to Lr pair in place for HW in the boiler) and just run 2 new wires from BUS1,2 to -.+ in my extender?

    Then setup my thermostat, tell it has has an extension kit and setup D17 ?

  • Nickholden
    edited October 2020
    I switched the high voltage wires to the bb connection then straight into the thermostat, imagine extension should work too. Yep did d17, believe tado will do hot water too in theory, although I don't have the water tank so haven't tried that via bb. To get bb working i had to hard wire lr and ls together, I'm in no way any boiler expert and was worried I was going to blow up the boiler 2bh but it showed what to do in manual (deffo check the boiler installation manual/professional).
  • After I changed my tado setup to d17 my trvs disconnected btw, had to contact support to connect them so they would call for heat. Caused some confusion while I was testing it as changing trv temp did nothing, only thermostat worked.
  • This is how mine was wired.

    So I moved the white cable that was coming in from the thermostat over to the two Orange connectors in the 1st picture. Wired the other end to + - on the extender - Setup D17 but it wouldnt control the central heating.

    Are you saying to put a live wire direct to the cental heating (similar to the black loop in the picture above for HW) ?

  • Im wondering if I have to install it like this (Random image found on internet for hive) so I bridge both CH & HW remove the extra blue bridge I have for the blue connector - "On/Off thermostat input" and connect the 2 bus connectors.

  • @RichB Did you try the wiring you found a picture of? I have just had my WB 8000 installed and the plumber left it with just the switched live for CH - while this works as the boiler does modulate based on water flow - I'm sure the two systems talking should be better...

  • Finally got around to wiring this in. Wired the digital side of the stat (+ & -) into BB on the boiler and put the link back in Lr and Ls. I then changed the config on the stat to D17. I found none of the radiator stats would fire the boiler when they called for heat, only the room stat. Put a call into tech support and they sorted it. Apparently the room stat didn’t have any heating zones assigned to it, so it thought it was a standalone room stat.

    I did rewire the room stat as the existing wiring was 240 volts and ran with other mains cables and I am unsure on what protocol the HT-Bus uses.

    Result so far is brilliant. The boiler seems to modulate the output (I have sensors on the flow and return) and if I select Care & Protect in the App it gives the percentage of heat going to each zone. Not sure if this did this before I altered the settings.

    Regards and stay safe


  • Hi @PhilHolmes,

    Thanks for posting your install process - very informative! I'm considering Tado and also have a Worcester Greenstar boiler (slightly different model to yours though). I think I'll run into the same problem with EMS integration though.

    Did Tado provide you with all the instructions you needed to get this set up correctly? Or was this all down to your own trial and error? I ask because whilst I'm pretty practical but certainly no heating/boiler engineer!

    One of the key attractions of Tado to me is the modulation of flow temp as the stat approaches target temp and if this functionality is lost with the installation of Tado I'm afraid it's not for me. Would be a hec of a lot easier if Worcester integrated opentherm protocols I'm guessing but alas that doesn't seem to be the case.

    Any advice for a Worcester boiler owner looking to install the Tado Smart Stat?



  • Hi Niall

    I’m not sure if it is true modulation. This is the boiler flow chart for 1 hour after the heating had gone off.

    I turned one of the zones on and TADO said it was 100% demand and went down to 80%. I will try to do some more testing with a better resolution on my logging software.

    Regarding the wiring, I did find a document on the web written by TADO but I didn’t find it on their site. I will try and dig it out for you.

    Regards and stay safe


  • Hi @PhilHolmes

    Could you post a photo of your wiring please?

    Looking to wire to do WB Greenstar CDi Compact boiler.

    Extension kit or wireless receiver or are they the same? Bit confusing.


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