NEST 3rd gen wiring to Vaillant combi 831

[stem]

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

Yes

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

It means that the Heat link requires a mains voltage supply to power it (230V) and that the boiler generates 24v for it's control. As the switch connected to terminals 2 & 3 is voltage free it will switch 24v quite happily. Remember the diagram I posted.

Notice it is called "LOW VOLTAGE" at the top. The 24v for boiler control is what it is referring to. But the N & L terminals still need to be connected to 230v, because that's what the heat link needs to provide it with operating power.

This is why it is important that the two voltages are kept separate and why I told you under no circumstances should you link terminals L and 2.

 

[Mr.Dips]

Hi,

I would just like to say

BOOOOM!!!

thanks alot STEM!!!

I just need to rewire to make tidy and re-drill holes in wall as not so secure... But works!!!

Thanks again!!!

 

[stem]

I just need to rewire to make tidy and re-drill holes in wall as not so secure

Good I'm glad you clarified that. There's a fair bit to do. You should make sure the outer cable sheaths are secure under the cable clamps and also add an earth connection to the earth terminal next to T1 & T2.

... But works!!!

Of course, what else did you expect.

 

[Mr.Dips]

Ok.. thanks..

I will ensure the cable sheaths are further in the heatlink to clamp.

Regards to the diagram

It doesn't show to connect earth.

Can I ask why you say I should connect one?

And is it all good doubling up the earth from the boiler along side the L & N which I have already doubled up.

Thanks!

 

[stem]

From the Nest instructions.

The diagrams are just schematics. Earth connections are there for safety rather than provide any operating functionality as such. Their addition is down to general electrical competence and good practice, which is probably why it's not shown with a wire connected on the diagram you posted. However, the little earth symbol at the side of the terminal indicates it has an earth connection made to it.

And yes you can connect it to the boilers earth terminal.