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Hi guys. Just bought a Honeywell CM700 series wireless room stat/programmer with BDR91 relay box/receiver to link with Worcester Bosch 28CDi combi boiler.
Using a 4-core will take L/N feed from boiler to L/N in receiver and route the Ls/T1-A and Lr/T2-B.
But there are 2 L terminals in the receiver, which one do I use? See wiring diagram picture attached. The one on the left of right?
If boiler was powered through the programmer, then I understand. As it is, I’m taking the feed from the boiler.

Thank you in advance

image.jpg
 
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telectrix

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if you mean the 2 L terminals in the boiler, they are (or should be ) linked in the boiler, so the left one is Lin to boiler and right one is Lout to receiver. check with a meter.
 
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  • #4
if you mean the 2 L terminals in the boiler, they are (or should be ) linked in the boiler, so the left one is Lin to boiler and right one is Lout to receiver. check with a meter.
Cheers telectrix. The two L terminals I’m referring too are in the BDR91 room stat/programmer. One of these will link to the L from the boiler, But which one?
Note: I’m piggy backing N/L from the boiler.
 
Take a permanent live and neutral to the receiver. Link the second L in the reciever to terminal A. Then terminal B to Lr in boiler.
Remove the link in the boiler

Or do what buzz said didnt see his comment before posting
 

Corbs

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(PF Mod)
two options

option one requires two cables

one cable perm live, neutral, and earth from the boiler fused spur (live to live, neutral to neutral, link live to A)

another cable from the receiver b port to boiler lr

option two 5 core cable from the boiler

boiler side Ls to live, Ns To neutral, earth to earth, link live to a, B to Lr on boiler

both acceptable but if you need to remove the cover / case of the boiler with tools eg screwed on you need to be registered / qualified
 
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  • #7
Thanks Corbs. Option two is most likely, my query was whether I needed to link receiver ‘L out’ to receiver A. Your response answers that, thank you.
Now I have to buy10m because it’s not sold in 1m lengths!

Thanks all
 

Corbs

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(PF Mod)
Thanks Corbs. Option two is most likely, my query was whether I needed to link receiver ‘L out’ to receiver A. Your response answers that, thank you.
Now I have to buy10m because it’s not sold in 1m lengths!

Thanks all
I think b and q sell it in 5m 0.75mm is good enough while being easy to work with
 
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  • #10
Thanks guys, yep definitely H/R cable/flex. Will check bandq and all the other usual haunts.
Although, if I reroute existing cable so the fused spur connects to the relay box/receiver and the boiler is then powered from the relay box/receiver I will only need a 2-core for the relay box/receiver to boiler connection. Just as in the wiring diagram as intended. Meaning I could utilise existing cables.
Hmm choices choices.

Cheers guys, much appreciate your input.
 
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  • #12
Fortunately, non of the wiring goes through the closed/sealed section of my boiler. At least no wiring that I need access too. I’ve checked and it’s all accessible and runs under the boiler unit into and out of the front panel. The biggest pain would be removing the existing cable run to the old room stat.

Thanks for all the comments and advice guys.
 

davesparks

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Take a permanent live and neutral to the receiver. Link the second L in the reciever to terminal A. Then terminal B to Lr in boiler.
Remove the link in the boiler

Or do what buzz said didnt see his comment before posting
That is not in accordance with manufacturers instructions and can result in problems with the warranty in the future.
 
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  • #15
Thank you all for your input and support. Job completed, working a treat (so far) and old unsightly thermostat n wiring removed.
All the best.
 
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