NEST 3rd gen wiring to Vaillant combi 831

[Mr.Dips]

Hi, I was hoping if I could get some help please. Reading different threads and watching YouTube vids has confused me.

Could someone please help me to make sense.

I have the nest 3rd gen, and want to connect the heat link to the boiler and the thermostat on the wall

I have attached the pic of the board from my boiler and the nest installation guide.

Thank you all.

 

[ericmark]

I am not a central heating guy, so wait for other replies, but I would guess a shorting link goes where it says 24 volt RT and the cable is then re-used to where it says - + bus and other end goes to Nest heat link OT1 and OT2.

However not all ebus connections are OpenTherm, so step one is find if boiler in OpenTherm, and if so if the old connection to old thermostat which I assume is the 24 volt RT terminal is open or closed circuit.

My boiler is not modulating never mind opentherm enabled so never needed to work that out, clearly if it will run opentherm then that is better than simple on/off.

 

[stem]

The two wires in the 24v RT (Room Thermostat) here....

...go to Heat link 2 & 3 [After you have removed the old existing thermostat wires]

Then the Heat link requires an N and L supply from the boiler supply N and L to provide it with operating power.

Do not under any circumstances make the link between L & 2 shown in the diagram you have posted. If you do, you will be connecting 230V directly to 24v circuits and the result won't be good.

This is the diagram you should be looking at:

 

[Mr.Dips]

Thanks for your reply.

That confused me straight away as I question, why would you mention the OT1 and OT2 when in the diagram it's not used.

I think the method is.....

NEUTRAL from boiler doubles up and goes into HEATLINK NEUTRAL.

LIVE from boiler doubles up and goes into HEATLINK 3

use LIVE cable to connect HEATLINK LIVE to HEATLINK 2

I'm thinking it's as simple as that to connect the HEATLINK. But does it make sense?


Then after connect HEATLINK T1 & T2 to Nest thermostat.
There is a live and neutral already connected to the boiler 24V= RT which I'm sure is the one which leads to connect my current thermostat on the wall in the living room.

I think I need to disconnect the 2 cables in 24V= RT and connect then to HEATLINK T1 &T2.

Then connect the NEST THERMOSTAT onto the wall and connect the 2 wires coming from the wall... giving the connection from HEATLINK T1 & T2 to the NEST THERMOSTAT.


does this make sense?

Thank you!

 

[Mr.Dips]

I just read the previous post... so my method is incorrect?

 

[ianmcd]

Thanks for your reply.

That confused me straight away as I question, why would you mention the OT1 and OT2 when in the diagram it's not used.

I think the method is.....

NEUTRAL from boiler doubles up and goes into HEATLINK NEUTRAL.

LIVE from boiler doubles up and goes into HEATLINK 3

use LIVE cable to connect HEATLINK LIVE to HEATLINK 2

I'm thinking it's as simple as that to connect the HEATLINK. But does it make sense?


Then after connect HEATLINK T1 & T2 to Nest thermostat.
There is a live and neutral already connected to the boiler 24V= RT which I'm sure is the one which leads to connect my current thermostat on the wall in the living room.

I think I need to disconnect the 2 cables in 24V= RT and connect then to HEATLINK T1 &T2.

Then connect the NEST THERMOSTAT onto the wall and connect the 2 wires coming from the wall... giving the connection from HEATLINK T1 & T2 to the NEST THERMOSTAT.


does this make sense?

Thank you!

Please tell us that this is a wind up, you couldnt have got that more wrong, connect it like that and you better have lots of spare money

 

[stem]

NEUTRAL from boiler doubles up and goes into HEATLINK NEUTRAL.

OK.

LIVE from boiler doubles up and goes into HEATLINK 3

No for several reasons.

use LIVE cable to connect HEATLINK LIVE to HEATLINK 2

No. What do you not understand about.......

.....Do not under any circumstances make the link between L & 2 shown in the diagram you have posted. If you do, you will be connecting 230V directly to 24v circuits and the result won't be good.

Then after connect HEATLINK T1 & T2 to Nest thermostat.

OK

There is a live and neutral already connected to the boiler 24V= RT which I'm sure is the one which leads to connect my current thermostat on the wall in the living room.

Indeed, which is why I said....

....The two wires in the 24v RT (Room Thermostat) here....

...go to Heat link 2 & 3 [After you have removed the old existing thermostat wires]

 

[Mr.Dips]

Thanks stem. Appreciate your help.

Regard to the 24v rt.

Do I disconnect the wires. Then.

Connect with new cables from the 24V r boiler to the heatlink 2 & 3?

Thus leaving 2 free cables which I disconnected for them to go into Heatlink T1 & T2.


Does this make sense?

 

[ianmcd]

@stem has to be a wind up , have a good idea who it is , sadly some complete bell ends on here looking for attention

 

[Mr.Dips]

STEM, thank you.

You made it sound so simple. Guess this is from me focusing on the wrong diagram.

Are you sure the diagram you told me to follow is for the VAILLANT ECO 831 BOILER?

is it literally as simple as doubling up the N & L from the BOILER to HEATLINK N & L. Then disconnect the current wires which go into the 24V RT and connect them directly into HEATLINK 2 & 3? Or get new cables for the HEATLINK 2 & 3 to connect to the 24V r?

I want to connect the NEST THERMOSTAT onto the wall in the living room

If what I said so far is right. Then I will assume the wires I disconnected from the 24V r will go into the HEATLINK T1 &T2 ?

 

[stem]

It's quite simple. Disconnect the old thermostat from the 24v RT terminals, and connect them to the Heat link terminals 2 & 3 instead, it doesn't matter which way around they go, it is simply an on/off switch.

The Heat link N & L also connect to the boiler main N & L supply

If you wish, you can now use the old disconnected thermostat cable to connect T1 at the Heat link to T1 at the Nest thermostat. and T2 at the Heat link to T2 at the thermostat.

ianmcd thinks your post it a windup, and he is a respected poster. However, I'm giving you the benefit of the doubt, so in the spirit of the forum, I hope that you post is genuine.

 

[Mr.Dips]

Guys this is not a wind up nor am I a bell end.
Just a novice. Mr.paranoid better to be safe then sorry kind of guy.

Again thanks for your time and patience. I can understand the frustration when you know what your explaining which I'm trying to understand. Also am trying to understand why to gain knowledge.

Stem, I would like to go through the below one last time.

It's quite simple. Disconnect the old thermostat from the 24v RT terminals, and connect them to the Heat link terminals 2 & 3 instead, it doesn't matter which way around they go, it is simply an on/off switch.

When I disconnect the wires from the 24V RT. I need to add 2 additional cables from the 24V RT to HEATLINK 2 & 3.
Keeping the disconnect wires available to put into HEATLINK T1 & T2.

Thanks again!!!

 

[stem]

This is is a cable, it can have several wires in it.

and this is a wire

There are two terminals marked 24v RT. One of the terminals connects to Heat link terminal 2 and the other to Heat link terminal 3. You can use two wires from the same cable to do this.

The Heat link also needs 230V connecting to N and L. This can come from the boiler N & L

 

[Mr.Dips]

Amazing Stem!!! I understand finally... I think LOL.

Just wanted to clarify regarding wires from the RT to understand how to connect the thermostat. As you agreed I need to add 2 additional wires makes me understand the disconnected ones are available for the thermostat.

So........

NEW WIRE - BOILER N to HEATLINK N
NEW WIRE - BOILER L to HEATLINK L
NEW WIRE - 24V RT to HEATLINK 2
NEW WIRE - 24V RT to HEATLINK 3
.....

Disconnected original 2xwires which were from 24V RT can go into the HEATLINK T1 & T2.

I didnt know theres a difference of cable and wire. Now I know. Thanks.

I referred all as wires to have a better understanding.

 

[Mr.Dips]

Does it matter that above HEATLINK 2 & 3 it says 100-240V? And the BOILER RT says 24V...

Can you tell me what these mean please.

Thanks so much!!!