Connecting a Honeywell Lyric T6R to a Bosch 35cdi

[Andypthomas]

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

[Edinburgh2000]

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.

[Andypthomas]

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

[Edinburgh2000]

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.

[Andypthomas]

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?

[Edinburgh2000]

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).

[Andypthomas]

Permanent live is connected to ST12 and also I have a connection from A & B from receiver box to Ls & Lr respectively.
The only diference I can see is that if using a wired thermostat it connects to Ns on boiler (see diagram) but a wireless unit, Lyric T6R, just shows two wires ( A & B) and no connection to Ns
This is whats confusing me as the boiler doesnt fire up but the heat demand indicator lights up on the receiver box. I am starting to wonder if I have a faulty Lyric receiver box

2019-04-04_1249.jpg

[Edinburgh2000]

The only diference I can see is that if using a wired thermostat it connects to Ns on boiler (see diagram) but a wireless unit, Lyric T6R, just shows two wires ( A & B) and no connection to Ns.

The Ns terminal on the ST8 block is only there for the old-fashioned mechanical thermostats, which take their power supply from the boiler. Their connections would be a live from the boiler (Ls), a neutral from the boiler (Ns) and a switched live (return) (Lr). Your Lyric receiver has its own power supply so does not need to take a neutral from the boiler.

I am starting to wonder if I have a faulty Lyric receiver box

Could be. Do you have a circuit tester? If so, you could disconnect the wires from the receiver to the boiler and then check if the receiver's relay is working correctly. Check the continuity between terminals A and B when the heat demand indicator is off (should be infinite resistance, i.e. no continuity) and then when the heat demand indicator is on (should be very low resistance, i.e. high continuity). If that is working correctly, then you should check the cable that you are using between the receiver and the boiler.

[Andypthomas]

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?

[Edinburgh2000]

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.

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?