Nest Thermostat E Installation issue

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I thought this would be super simple as the E is battery powered so just isolate power and connect the two wires.

No instructions I can find have mentioned anything about switches but my existing thermostat has TWO and the Nest install guide can't cope with two.

Here is what I see:

PXL_20210324_183419068.jpg


Could someone please explain what I need to terminate and why it's such a mess in there?!
 
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Oh hang on I think I misunderstood the instructions.

So now I think terminate everything in earth/l/n and the black wire in B is NO and the grey wire is COM?

And I'm done?! Easy!
 

CBW

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Decommission the live, neutral and earth, put wires a and b into switching (common and n/o usually).
 
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A&B go to NestE NO&COM everything else needs to be safely isolated or totally disconnected, they are the 240v supply to your existing stat and as you say the nest E is battery powered
 
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CBW

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Oh hang on I think I misunderstood the instructions.

So now I think terminate everything in earth/l/n and the black wire in B is NO and the grey wire is COM?

And I'm done?! Easy!

Yep, grey com and black no.
 
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Right, I thought I did it all properly and the Nest E is connected to the Heat Link fine but nothing will turn the boiler no - Changing the temp doesn't and putting the hot water on doesn't. The boiler has no power at all.

I terminated all L/N/E wires but I assume that's what's caused it? Do I need to put each L/N/E in it's own block to create the power circuit for the boiler?
 

DP

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I thought you were suitably advised on your previous post on this setup:whistle::whistle::whistle::whistle:
 
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Ha, so did I. I did what I thought I was told and I then thought it worked as the heat link and therm both linked and said it was working.

It was only when my wife tried to shower this morning did I realise how much trouble I was in!

What I posted just above sorted it - All done now! Heat and water both working. I had just assumed it was working yesterday as the therm was saying it was heating and even giving a time until it hit heat. I was too tight to actually leave the heating on to find out.
 

DP

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Ha, so did I. I did what I thought I was told and I then thought it worked as the heat link and therm both linked and said it was working.

It was only when my wife tried to shower this morning did I realise how much trouble I was in!

What I posted just above sorted it - All done now! Heat and water both working. I had just assumed it was working yesterday as the therm was saying it was heating and even giving a time until it hit heat. I was too tight to actually leave the heating on to find out.

Clearly you had a Ferrari with high performance engine and you have stuck a Lada engine in it without first studying the workshop manual :whistle::whistle::whistle:
 
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I terminated all L/N/E wires but I assume that's what's caused it? Do I need to put each L/N/E in it's own block to create the power circuit for the boiler?
what difference would putting them in terminal block make ?
 

CBW

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I’m guessing the boiler l-n-e was fed via the existing thermostat?
 
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I’m guessing the boiler l-n-e was fed via the existing thermostat?
but only single wires into each terminal, if that was the case it would need two wires in each terminal, as there are two earth wires the L&N may well have been joined somewhere else in which case isolating the single L&N in the thermostat wouldnt make any difference
 
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CBW

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Looks like there’s a red wire and blue wire, so must not be connected? I see the brown and Black are connected.
 

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