Replacing Drayton LP111 with Center BDR91 - HELP!

6 Jan 2022
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United Kingdom
I'm looking to replace my fixed boiler control unit with a wireless thermostat (so that i don't manually have to switch boiler on & off). Need some help in understanding how to rewire my existing control unit (Drayton LP111) with the wireless thermostat (Center BDR91). I've added all the images i have of the wiring. Hopefully i can get some help on this



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Have you worked it out by now? :)

If you would still like some help (and I'm only a DIY'er, so feel free to ignore!), first, has your existing timer been working properly?
If it has, you just need to transfer the old wiring to the new backplate.

...And ignore the 'typical' circuit diagrams - if your old system worked, you don't want to mess with the wiring! :)

Your existing LP111 is single channel.
It has a live and neutral terminal (obviously!)
Terminal one is a common.
Terminal three is a (switched) normally open contact.
You also have a Live link to common.

So, transfering to your new system

L -> L
N -> N
Terminal 1 -> A
Terminal 3 -> B
Plus an additional link from the 2nd L -> A

There is now an earth wire that won't have a place in the new back plate; you need to safely terminate this in something like a single terminal block.

I hope that makes sense and good luck! :)

Ps LP111 manual attached.


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