Wiring Nest Gen 3 Heatlink to Vaillant Ecotec 831

[a_w]

Hi all,

New to this forum.

I have recently moved in to our first house so getting in to DIY. My first project was to get the Nest Gen 3 Thermostat set up and working.

This is the exact wiring of my PCB Board:

Full manual here: https://www.vaillant.co.uk/downloads/ecotec-installation-and-servicing-manual-261417.pdf

So here's what I've done so far:

Taken the L&N from X1 above. Powers the heat link fine.

I have tried the Heat Link connected to:

X100 Blue - gives me Nest working perfectly but NO hot water
X100 White - gives me hot water but NO nest
X100 Pink - gives me hot water but random, erratic heating (not following nest at all)

What have I done wrong?

The manual also mentions on page 30:

> If you connect a 230 V AC time and temperature control to the boiler, then remove the bridge at input 24 V = RT (X100 or X106) if a bridge exists.
> If you connect a weather compensator or room temperature control via eBUS, then bridge input 24 V = RT (X100 or X106) if no bridge exists.
> I If using low voltage (24 V) controls connect these in place of the bridge marked RT 24 V (X100 or X106).

The cable I have tried on X100 is connected to ports 2 and 3 on the nest, as per: https://nest.com/support/images/mis...Nest-Learning-Thermostat-Install-Guide-UK.pdf

I thought I was okay with this but apparently not!

What way should I have this wired up?

Any help is greatly appreciated!

(I have tried searching the forum but there doesn't seem to be a definitive answer for my type of boiler)

Thanks

 

[Dan Robinson]

There are hundreds of threads on this boiler.

Also several stating the need to carry out your 26.9 checks.

 

[a_w]

There are hundreds of threads on this boiler.

Also several stating the need to carry out your 26.9 checks.

I've read every thread that concerns an Ecotec and Nest. None of them answer my question(s).

Edit: however, if you see any that might help me out. Please post them below!

 

[fezster]

https://www.diynot.com/diy/threads/nest-thermostat-3rd-gen-and-vaillant-ecotec-plus-831.494890

 

[a_w]

https://www.diynot.com/diy/threads/nest-thermostat-3rd-gen-and-vaillant-ecotec-plus-831.494890

Different PCB wiring I'm afraid!

Mine looks like this:

 

[a_w]

View attachment 134621

I just asked a simple question, something that, I assume, you could have answered in 30s:

Where do I connect the heatlink 2&3 to?

Edit: forgot to hit quote.

 

[stem]

With some boilers, you have to remove a combustion chamber cover or sealed boiler case to access the wiring terminals. I believe that yours does fall into that category. If so, it is unlikely that you will get any advice. See here. for an explanation why.

 

[muggles]

As Stem suggests, you won't get any advice on wiring this up here, as you need to remove the safety room sealing cover from your boiler in order to do so, which is against forum rules. Having doing that, the regulatory 26.9 checks then need to be carried out before the boiler is used again, and this can only be done by a Gas Safe Registered Engineer. The only advice we can give in order to comply with forum rules is to call a GSR to wire it up and carry out the vital safety checks for you