Vaillant EcoTEC plus 832 and Nest

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I know you all must be sick of nest wiring questions but just wanted clarification if anyone could help me please. Here is what I propose.

1. LNE from 3 amp fused spur to boiler power terminal.

2. 2 core from L & N on boiler power terminal to L & N on heat link.

3. 2 core from 24 volt RT on boiler to terminals 2 & 3 on heatlink (obviously remove link on boiler).

Would anyone mind confirming whether this is correct please.

Thank you very much in advance
 
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The wiring sounds OK to me as you describe it. Obviously don't link terminal (2) to (L) as is done when switching 230V.

However, if you have to remove a room sealed cover to get to the wiring terminals with your particular boiler, it's not a DIY job and should be done by a Gas Safe engineer who can check it is sealed up again properly afterwards.
 
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Stem is correct - wiring on these boilers isn't a DIY job, as it requires removal of the room-sealing cover in order to access the wiring terminals. Removing and refitting this cover should only be carried out by someone who is capable of completing the safety-critical 26.9 checks on completion, IE a Gas Safe Registered Engineer, and the boiler should not be operated until these checks have been completed and passed.
 
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Hi Stem, thanks for your reply. Not sure what you mean by don’t link terminal 2 to L. I would be linking terminal 2 to one side of 24V RT.

Regarding Gas Safe, I own a gas safe registered company and have a registered employee who will be doing installation. We just don’t usually get involved in the wiring as elec contractors on site usually do it.
 
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Sorry for the confusion. When the Heat link is used with 230V often terminal (2) is linked to the Heat link (L) terminal, and there are a lot of diagrams that show this. But as you are using 24v do not do it!

How you describe it is correct, with only the two wires from the boiler going to the two terminals 2 & 3
2 core from 24 volt RT on boiler to terminals 2 & 3 on heatlink (obviously remove link on boiler).

I mentioned it because I have had to sort out a couple of installations where DIYers had seen the 230V instructions and added the link to the (L) terminal when wiring up to a boiler with 24v control. The consequences weren't good.
 
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Hi, sorry I’m back.

When I take my live and neutral from the boiler to the heat link. Do I literally connect onto the live and neutral terminals on the boiler with a second cable? (so there will be 2 cables in the same terminal) or is there somewhere else on the boiler to take it from?

It looks like I’d struggle to get 2 cables into the boiler terminal.
 
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It doesn't matter which point the N & L are physically connected to, provided that the Boiler and the Nest are both supplied via the same 3A fused spur. For example:
  • The 230V supply can go to the Nest Heat link first, and then out to the boiler (although the Nest terminals are a bit tight for space too)
  • The Nest Heat link can be wired directly to the 'load' side of the fused spur via a dedicated cable and the boiler can be wired directly to the 'load' side of the fused spur by a second cable.
  • The fused spur can be wired to a junction box that then has two separate feed cables. One out to the boiler and one to the Heat link.
What size of cable are you using? I would have thought it would be possible to get two 1.5mm cables connected to the boiler terminals.
 
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Two 0.75mm cores is about the limit for the Vaillant terminal block.
Twin 0.75mm bootlace ferrule is a snug fit into terminal block although an external wiring box would be the better option.
0.75mm 5 core mains flex will be fine.
 
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Thanks Gents, I’ll let you know how I get on. Chubby plumbers fingers aren’t the best when it comes to wiring.
 
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