Wiring nest thermostat, I'm missing something obvious here!

[DanMcLiverpool]

I've had a look at the likes of the following:

In summary - run a 5 core from viessman boiler to a nest heatlink. Live and neutral to power it, then 2 cores for the control of it (plus earth).

All good, but I can't see a mains out from my boiler? And it matches the board on that YouTube video yet he's managed to power his heatlink from it?

I'm missing something here. I'm happy to power the heatlink by a plug instead and use 2 cables instead of the one 5 core, but just wanted to double check I'm not missing something here.

Note: The mains in the first pic is the mains IN not out.

Pics attached

 

[DanMcLiverpool]

Ah, do I have 2 cores into 'L' for both the power and control?

 

[Lister1987]

Iirc you don't need to touch anything in the boiler, it should lal be done from the exisiting wall mounted thermostat.

Try this:

 

[DanMcLiverpool]

Iirc you don't need to touch anything in the boiler, it should lal be done from the exisiting wall mounted thermostat.

Try this:

Thanks lister, should've mentioned mate - there's no existing thermostat. You can tell this from the link that's in the boiler (so that it's permanently on).

 

[Lister1987]

Thanks lister, should've mentioned mate - there's no existing thermostat. You can tell this from the link that's in the boiler (so that it's permanently on).

stupid question. does the veissman boiler manual give any help?

 

[DanMcLiverpool]

stupid question. does the veissman boiler manual give any help?

It's a good shout mate, I don't know where that is. I'll google it.

It doesn't look like I'm going to be able to (safely) terminate 2 cores into the `L` of the boiler without cramming, so I'm leaning more towards me having to deal with the permanent supply to the heatlink separately, which is fine - just wanted to check I absolutely had to.

 

[DanMcLiverpool]

I've come to the conclusion it needs to look something like this:

Take the perm L and N from the boiler, loop the live over and take the switched live back to terminal labelled 1 on the boiler.

Means my overpriced 5 core was a waste of money!

This still leaves me really confused as to how he's done it in the video though!

 

[James]

without checking the boiler manual, here is how i think it should be done.

3 terminals marked (96)

L live out to thermostat- use brown and grey (sleaved brown)
N Neutral ot to thermostat- use blue
1 call for heat signal to boiler- use black (sleaved brown)

at heatlink end
N-BLUE
L-BROWN
2-GREY (SLEAVED BROWN)
3-BLACK (SLEAVED BROWN)

it will just make it a bit easier to put 2 wires in L out at the boiler end than it is to try and get 2 in the L terminal of the heatlink.

Before doing this, you need to check the boiler manual and confirm that terminal 1 expects a 230v call for heat signal.