Nest Install, 2 Wire, Replacing existing stat...

[twixx]

Fellow DIYnotters... I'm in the UK and have been waiting since the US launch to get my hands on a Nest. With the recent UK launch my order went straight in...

I've currently got a Saunier Duval Themaclassic F30e installed with a Honeywell T6651a thermostat. This operates using the 2 wire (two wire) method. Which feeds back to the voltage free connections in the boiler.

I understand the Nest has no polarity at the stat end, from this I gather it is irrelevant which wire (blue/brown) goes into T1/T2. The same would then hook back to the Heat Link.

Regarding the Heat Link, Neutral and Live are fairly straight forward.

1,2,3 is where I am confused. Are these left empty? Or do I need to tap in to existing wiring?

The wiring diagrams are available on Page 27/28 of the manual; here.

 

[ALCPlumbing]

I can't see 1, 2 & 3 on the wiring diagram for the boiler.

 

[twixx]

I can't see 1, 2 & 3 on the wiring diagram for the boiler.

That was where I was lost, I assume therefore, there is no requirement to connect Call for Heat/Common/Satisfied, and that all comms are done via T1/T2?

 

[ALCPlumbing]

Yeah it just completes the circuit when there's a heat demand and breaks it when it's satisfied. That's if you're using the voltage free connection. If you're not sure call a gas engineer as you can blow the circuit board if you connect mains to the volt free connection in the boiler. Let me check the nest wiring diagram as I've not installed one.

 

[ALCPlumbing]

That's a bit beyond my electrical knowledge mate. Call an electrician.

 

[twixx]

The UK Nest is slightly different (completely different) to the US model. There's not much online about this new Heat Link they provide, as such I've snapped the manual which might help you/others...

 

[mogget]

I had a quick look at the Nest manual the other day out of curiosity, but I can't find it again now. I have to say it was clear as mud.

As far as I can make out you would re-use the existing wire to the room stat to supply 12v from the heat link to the Nest. Then you use the volt free contacts in the heat link to switch the boiler. The live and neutral 230v power the heat link which also powers the Nest.

But bear in mind this is only from memory, I can't find it now.

 

[mogget]

Aha, you've posted some snaps.

2 and 3 are the volt free contacts for the boiler, these switch your boiler.

N and L power the heat link.

T1 and T2 are the 12v to power the Nest.

Do NOT link N / L to anywhere else on the Nest system!

 

[twixx]

Aha, you've posted some snaps.

2 and 3 are the volt free contacts for the boiler, these switch your boiler.

N and L power the heat link.

T1 and T2 are the 12v to power the Nest.

Do NOT link N / L to anywhere else on the Nest system!

That makes sense, so at the minute the Blue & Brown connecting my stat, runs back to the voltage free connection on the boiler. So, remove from the volt free end on the boiler, and drop in to T1/T2 on the heatlink.

Then run new copper from the volt free connection on the boiler, to 2/3 on the heatlink...

Having a certified electrician run the power...

 

[mogget]

Yep that sounds right to me, looking at the diagram, but I've never installed one.

I do know that it's imperative to use the existing stat wire only to supply 12v from the heat link, and nothing else.

 

[ALCPlumbing]

That's more like it. The diagram I got up on the internet must have been the US one as it made no sense to me. The diagrams you have put up make perfect sense. I'm not familiar with your boiler. Is it a combi or do you have zone valves?

 

[twixx]

Yeah the US one wasn't really UK friendly... They've obviously been working on this solution for a while, as they've always been silent when quizzed when the UK would get it.

The Saunier Duval Themaclassic F30E I have is a combi, no zones - single stat. Apparently the boiler is horrible and should be replaced... but, it's plodding on for now. Touch wood.

Anyhow, thanks to your help (and patience), I'm now up and running!

 

[Geordieboy44]

Hi guys

In process of buying a house with a Potterton Heatmax Combi boiler that has NO room thermostat.

Been looking at the nest but struggling with the installation of the Heat Link.

My bolier states that the room thermostat MUST be suitable for 230v switching, but looking at this thread it & reading up on nest it needs to be 12v max?

Any help on wiring the heatlink is much appreciated.

Pic below from the boiler manual showing electrical connections.

Untitled

• Geordieboy44
• 24 Sep 2014
• 1

Any help greatly appreciated.

Thanks in advance

Dave

 

[kedzis]

Has anyone wired Nest Heat Link with Baxi boiler?

Baxi Combi 105E thermostat wiring

• kedzis
• 28 Oct 2014
• 2

When i look at my combi boiler connections and Nest manual the most appropriate would be to to connect LOW Voltage Option not as Switched Live in Nest manual.

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• kedzis
• 28 Oct 2014
• 2

What would you recommend?

 

[jackthom]

Yes use the nest as in the LOW voltage diagram even though it will actually be switching live to the switched live wire.

Are you removing the external timeswitch (if there actually is one) and connectiing the heatlink directly to boiler terminals 1 & 2 ?