Vaillant ecoTEC plus 837, BDR91 to nest Heatlink

14 Dec 2020
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United Kingdom
Hi all,

I have read through as many similar posts as I can in regards to my dilemma, I couldn't see anything that was similar to mine.

I have a Vaillant ecotec plus 837 with a Honeywell BDR91 and CM927. The vaillant is connected by a UK mains plug as opposed to it being hardwired with a 3amp fuse at the terminal block.

I want to replace the Honeywell BDR91 with a Nest Heatlink I have attached some pictures of the current wiring l.

How would I re-wire this to the nest Heatlink?
There seems to be 2 live and 2 neutrals. I get the A=2 B=3, but I'm stoked as to he 2 live and 2 neutrals wires


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You are correct about a&B to 2&3, but as for the lives and neutrals you will just have to follow the cables and see where they go, as for the plug that is bad and needs sorting

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