Nest Thermostat 3rd Gen and Vaillant Ecotec Plus 831

[Stanquest]

1 to 5 are OK

6) You can power the Nest directly using the 'usb' lead power adaptor. No need for T1 & T2 to be connected if not required.
If the Grey and Black wires do go all the way from the boiler to the wall thermostat directly you could use them to carry the power using T1 & T2, provided there is enough spare cable at the boiler end to reach the heatlink.

As for hot water, it's a combi and only provides hot water when you open a hot tap. There's just no need for any other timing control from the Nest.

Thanks for confirming this.

The Grey and Black wires don't go all the way to the Vaillant thermostat unfortunately. Only the Live and Neutral, please see attached picture.

I was hoping I could replace my current Vaillant thermostat with the Nest one using the trim plate provided and the Live and Neutral wires in the wall to carry power and connecting to T1 and T2 in the Nest thermostat. The question is: where will I get the power from in the boiler to still be able to use the existing L and N in the wall to power the Nest thermostat? Any idea? Or I my making things complicated and confusing?

I don't want to place the Nest thermostat any where else in the house using the USB power adaptor as I plan to use my Alexa devices and Nest App to control it.

 

[jackthom]

All I can suggest is try and trace the mains power wiring back from the old Vaillant thermostat to see where its hooked up to the house mains wiring.
Normally this would be taken from somewhere close to the boiler.
If it does come from the same spur as the boiler it can be disconnected from the mains and possibly used for the T1/T2 connections.
Don't connect up the Nest thermostat itself to these wires until you are absolutely certain you have ditched the correct mains cables.


What sort of room is behind the wall currently carrying the Vaillant thermostat? If it's out of sight, eg a storage area, there may be other ways of getting power to the plug in usb adaptor.

 

[Stanquest]

All I can suggest is try and trace the mains power wiring back from the old Vaillant thermostat to see where its hooked up to the house mains wiring.
Normally this would be taken from somewhere close to the boiler.
If it does come from the same spur as the boiler it can be disconnected from the mains and possibly used for the T1/T2 connections.
Don't connect up the Nest thermostat itself to these wires until you are absolutely certain you have ditched the correct mains cables.


What sort of room is behind the wall currently carrying the Vaillant thermostat? If it's out of sight, eg a storage area, there may be other ways of getting power to the plug in usb adaptor.

You're an absolute genius!

The Vaillant thermostat is located by the entrance and backing my neighbour - to test where its source of power supply is, I turned off the boiler's main switch located near the boiler like you said and the Vaillant thermostat also went off. I opened up the socket, see attached picture. It would appear that this mains is powering three things... correct?

You said I shouldn't connect the nest thermostat to the wires in the wall until i disconnect them from the mains socket... I can't know which it is as all goes into the wall. So what do I do now to use the Nest thermostat on the wall?

Thanks for your response.

 

[Dan Robinson]

This is verging on the point of being dangerous.

 

[jackthom]

Even if you did find out which one of those power cables goes to the thermostat will you be able to pull the cable out of the socket backplate and safely get access to it somewhere where it can be connected to the Heatlink?

 

[Dan Robinson]

The thermostat is powered from the boiler.

OP has opened a fused spur on the ring main.

Call a professional for your own safety.

 

[Stanquest]

Even if you did find out which one of those power cables goes to the thermostat will you be able to pull the cable out of the socket backplate and safely get access to it somewhere where it can be connected to the Heatlink?

Answer is no. I don't know which of them heads to the thermostat. There are three grey cables in there, one of them goes to the thermostat. Which? I have no clue.

 

[Stanquest]

The thermostat is powered from the boiler.

I don't think so... I think it takes it power from the mains socket (as in the picture) like Jackthom also pointed out. I could go into process of elimination by removing one live after another to identify which powers up the thermostat.... I'll wait for Jackthom's suggestion before doing that at all.

 

[jackthom]

I don't think so... I think it takes it power from the mains socket (as in the picture) like Jackthom also pointed out. I could go into process of elimination by removing one live after another to identify which powers up the thermostat.... I'll wait for Jackthom's suggestion before doing that at all.

As I said earlier would that actually help?

You may then have the problem of locating the path of that cable in the wall or under floorboards etc in order to pull through enough of it to connect to the Heatlink.

 

[Hot&Cold]

This is verging on the point of being dangerous.

Diynot.com advice
Electrics in the UK

Caution
If unsure you should seek expert advice rather than risk accidents.

 

[Stanquest]

As I said earlier would that actually help?

You may then have the problem of locating the path of that cable in the wall or under floorboards etc in order to pull through enough of it to connect to the Heatlink.

Hmmm... I'm starting to feel that I may have to settle for not using the Nest thermostat on the wall and use the USB power anywhere in the house. And the current Vaillant thermostat will be redundant on the wall.

 

[Dan Robinson]

Have you even bothered with the manuals for which you were so cock sure of yourself over?

I can also indeed follow picture manuals;

Because.....

WTF do I know? I only do this for a living.

 

[Stanquest]

Have you even bothered with the manuals for which you were so cock sure of yourself over?



Because.....

View attachment 133417

View attachment 133418

WTF do I know? I only do this for a living.

I would be grateful if you would kindly explain what the diagram is supposed to tell me.... in English please.

Dan, your contributions would be so highly respected and cherished if and only if, you could portray them in a positive and meaningful manner... food for thought for you! Take cue from Jackthom.

 

[Dan Robinson]

The connection is the same for both thermostats.

 

[Dan Robinson]

These pictures are showing you what you have now.

Put that fused spur back in the wall and call someone that knows what they are doing.