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Thread: Connecting a Honeywell Lyric T6R to a Bosch 35cdi

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  1. #1
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    Default Connecting a Honeywell Lyric T6R to a Bosch 35cdi

    Hopefully someone can help.

    I have a Honeywell Lyric T6R Smart Thermostat (wireless) and trying to connect it correctly to my Worcester 35Cdi Combi Boiler.

    The wiring diagram mentions connecting it , via A & B on Receiver Box tp T1 & T2 on the boiler, which I think means Ls & Lr (see B in photo )

    Heat demand lights up on the receiver box but boiler doesn't fire up.

    Is the diagram wrong or have I connected the wires to the wrong terminals on the boiler? I HAVE removed the jumper link bween Ls & Lr.


    IMG_0300.jpg

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    Quote Originally Posted by Andypthomas View Post
    Is the diagram wrong or have I connected the wires to the wrong terminals on the boiler? I HAVE removed the jumper link bween Ls & Lr.IMG_0300.jpg
    Have you really connected the 230V supply into the T1 terminal on the boiler? I do not know about the 35Cdi boiler but my Worcester GB162 operates on 24V. I have a relay that closes the contacts between T1 and T2 on your diagram to switch the boiler. The boiler has a permanent 230V supply, and through a transformer provides its own 24V power supply for its control systems. Closing the 24V contacts between T1 and T2 makes the boiler fire. It should not have 230V anywhere near those terminals.

    Forgive me if your boiler is completely different, but that hand-drawn link from the 230V supply to your terminal T1 just looks wrong.

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    Thanks for your reply.

    After talking with a guy from Honeywell he suggested the link but I mentioned to him that that is ALSO shown on another section for Basic boiler or S plan (omitting wire B)
    Trouble is I cant see a T1 or T2 on my worcester boiler

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    Quote Originally Posted by Andypthomas View Post
    Trouble is I cant see a T1 or T2 on my worcester boiler
    I think this is the manual for your boiler. In which case, yes, T1 and T2 on your diagram are Ls and Lr in Figure 13. Apologies. I had not appreciated that the 35CDi can be operated at 230V. I am assuming that you have separately provided a permanent live and neutral supply to the boiler (ST12 in Figure 11)? In which case, you still don't need that hand-drawn link on your diagram between the live 230V supply and A/T1.

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    Many thanks for the manual. The boiler works fine when link is refitted between Lr &Ls and using the Worcester wireless thermostat. I have removed its batteries so it doesnt interfere and also the Lr, Ls link. It looks like , as in Fig 13, I may have to connect a Neutral feed between my Honeywell receiver box and Ns on the boiler?

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    Quote Originally Posted by Andypthomas View Post
    It looks like , as in Fig 13, I may have to connect a Neutral feed between my Honeywell receiver box and Ns on the boiler?
    Referring to the manual again, you should have a permanent power supply (live, neutral and earth) to the ST12 terminals in Fig. 11 (item 1). That is the only neutral that the boiler needs. Fig. 8 also shows the mains connections, with the earth fixed to the earth screw (item 3 in Fig.11).

    The boiler control runs through terminals Lr and Ls in the ST8 terminal block in Fig. 11 (item 4), shown in detail in Fig.13. With no thermostat, the supply just runs through the link. You can replace the link with a mains thermostat, such as the receiver box for the Lyric T6R. You just need to connect Ls and Lr in the ST8 block to A and B respectively in the Lyric receiver, exactly as the diagram you posted (without any hand drawn link).

    Providing a link to the mains live or neutral anywhere other than through the ST12 terminals is bad practice as you would be bypassing the fuse (item 2 in Fig. 11).
    Last edited by Edinburgh2000; 4th April 2019 at 10:24 AM.

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    Removed two wires from Lr & Ls ( from the Lyric receiver) and measured the continuity
    With on demand OFF there is infinity and when demand light is on the relay energises and there is continuity between the wires
    I assume therefore the Lyruc is working but possibly some issue in the boiler circuit board?

    Is there another link I should remove to “disconnect “ the boiler wireless thermostat?

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    Quote Originally Posted by Andypthomas View Post
    Removed two wires from Lr & Ls ( from the Lyric receiver) and measured the continuity
    With on demand OFF there is infinity and when demand light is on the relay energises and there is continuity between the wires
    I assume therefore the Lyruc is working but possibly some issue in the boiler circuit board?
    It does sound as though the Lyric is working OK. What happens if you replace the jumper between Lr and Ls on your boiler (ST8)? The boiler should be fooled into thinking heat is being demanded. Your test shows that the Lyric effectively is acting like that jumper and shorting out the Lr and Ls terminals when the thermostat demands heat. If the boiler works with the jumper, then it should work with the Lyric.

    Quote Originally Posted by Andypthomas View Post
    Is there another link I should remove to “disconnect “ the boiler wireless thermostat?
    What do you mean by the 'boiler wireless thermostat'? What thermostat is that?
    Last edited by Edinburgh2000; 4th April 2019 at 10:27 PM.

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    Believe it or not I think I have sorted it
    With your help and measuring the continuity I started to think what else is preventing it from firing up - esp when it worked with the jumper lead between ale and Ls

    As I don’t have a physical timer clock on the boiler but a wireless receiver I had a ‘ BINGO” Moment - What if I disconnected this and did it interfere with the Lyric?

    Receiver removed and is working fine now
    Just need to obtain a blanking plate

    Many many thanks for you invaluable help mate 🤝

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    Quote Originally Posted by Andypthomas View Post
    Receiver removed and is working fine now
    Glad it's sorted. Well done. Cheers!

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