Trying to modulate a Worcester greenstar 440cdi ErP

Hi, I have recently had a new boiler fitted and for various reasons it had be a greenstar 440. As I understand it Tado is able to modulate Worcester boilers through HT-BUS / EMS-BUS. The problem I’ve got is that the person who fitted my boiler has connected in Relay mode as that’s how the previous one was done. I cannot for the life of me find a gas engineer or electrician who is willing to come and change it over to be HT-BUS for me. Does anyone if this is something I could try myself or would that not be advisable? My other thought was to find someone who will do a smart heating install of another system that modulates it, then after they’ve gone I can just swap it back for my Tado. Is anyone aware of any cheap systems that do this? Bosch Easy Control is maybe the only option?



  • You are supposed to have gas safe certification if you open the boiler up. If you have it or are willing to do it anyway it should be a fairly straightforward job. However only the Tado smart thermostat, eu wireless receiver and discontinued extension kit have digital connections. The uk wireless receiver doesn’t.

    Not all Worcester Bosch boilers are supported by tado for digital connections so check with them first.
  • Thanks for replying. Yeah I’m really reluctant to do it myself for fear of breaking the boiler and/or causing a safety issue. Just a shame so many UK gas engineers seem to want to avoid Tado.

    Regarding your other points I have an EU Tado and my boiler is definitely supported.

  • It is a surprisingly easy job (on most boilers). Unwire the relay connection, connect two wires to the digital connections and you’re done. Some ebus connections don’t even need separate power lines.
  • @johnnyp78 thanks for the reply. I’m definitely swaying more into the camp of doing it myself I think. After I remove the cables for Lr and Ls do you know if I just leave them empty or should I bridge them? Thanks
  • Check the manual. I’m not familiar with Worcester Bosch boilers but someone else may be.
  • The general consensus is that the EU Tado still doesn’t speak the EMS2 protocol that Worcester Bosch boilers require.