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Moving to Opentherm Control

toekneeheart
toekneeheart ✭
in General Questions & Topics

Hi All,

I've got myself a bit confused and hoping the wise heads in the forum can assist.

We've had a Tado V3+ system with multiple TRVs for a few years now. It has worked well. I installed it myself and it was the zenith of my DIY career 🤣. This was in combination with a Worcester Bosch Greenstar 18i System Boiler that was in place when we moved into the house.

Sadly this recently died and needed replacement. After much reading, we plumped for a Viessmann Vitodens 100-W (B1KF) Combi Boiler. This was based on the understanding that it was a solid Opentherm compatible boiler whereas the new Worcester Bosch models do EMS2 which Tado doesn't speak.

We also moved to a combi system because we wanted the extra space freed up by losing the hot water cylinder and to be rid of the very loud shower pump we had. Install went well but the engineers were somewhat mystified by the Tado. Eventually they managed to wire it so it works.

My understanding however is that our existing setup won't do Opentherm and it simply will do relay on-off at this point. So I've bought the Tado Add-On Wireless Receiver (EU) to replace the existing UK Wireless Receiver. But at this point I am a bit bamboozled about what to plug into what.

This is what my current Wireless Receiver looks like:

old_wireless_receiver.jpg

And this is what the new one looks like:

new_wireless_receiver.jpg

I originally thought that this would be fairly simple!

Any advice would be MUCH appreciated! Cheers!

Answers

  • CiupaSs
    CiupaSs ✭
    edited November 2024

    for opentherm, it is digital 36v but if you put there these 2 cables from 230v you will destroy it

    take a picture of your boiler cables, and how they are connected inside

    cover your serial number and auth code

    you need to connect 2 cables from the opentherm boiler to 36v on your receiver and configure it in the Tado Pro app for opentherm

  • toekneeheart
    toekneeheart ✭

    Thanks for the reply and sorry for taking a while to reply. Christmas was a busy time!

    I've had a look now and understand a little more.

    Our boiler is located in the loft space above our kitchen. My existing controller (The UK one without Opentherm support) is installed some distance away, in a small utility room. I gather that some installs place the controller next to the boiler but that is not the case in our house. This is where the existing controller sits:

    IMG_0589.jpeg

    I've had a look inside the boiler and based on the boiler wiring diagram, it appears that to wire for Opentherm, the digital connectors need to be attached to the 5th & 6th connectors on the white block I have circled below.

    IMG_0591.jpeg

    I am beginning to think that the only way to do this is to relocate the new EU Tado receiver to the loft so that it is next to the boiler? Is that correct? Secondly, in Opentherm mode, does the EU Tado receiver require separate power, or is this provided over the digital connections? I only ask, because I am not sure quite where I would wire it in up in the loft…

    This is definitely at the edge of my abilities! Advice appreciated!

  • hugbilly
    hugbilly ✭✭✭

    Is it not possible to run a new twin core cable from the receiver to the boiler for the low voltage control, or, are there any spare cores in the existing cable you could use ? The black switched live will, I presume, be redundant once you change to OpenTherm ?

  • Dapplefrost
    Dapplefrost ✭
    edited January 5
    @toekneeheart did you get it sorted in the end and did you need to use the plug? I'm struggling to find any threads where anyone has talked about if they put the UK plug on, used an adaptor or didn't use a plug at all and just wired the EU receiver into the boiler for power 😅

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