Nest 3rd Generation Heat Link installation

7 Jan 2017
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United Kingdom

I'm trying to install a Nest Heat Link it to link to my Potterton Promax SL boiler, and worried I don't fully understand the wiring on the back of my old programmer!


I figure it should be fairly straightforward to swap over from my old programmer to the Heat Link, from seeing similar set ups:
Live Old to Live Nest,
Neutral Old to Neutral Nest,
Live Nest to Heating (2) and Hot Water common (5) nest

DHW ON (3) to Hot Water Call for Heat (6)
HTG ON (4) to Heating Call for Heat (3)

Is anyone able to confirm the above is correct?

However, I'm getting confused by the additional wires currently in neutral and live for my existing box, what needs to be done with these?
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Yes, you will also need to bypass the old room thermostat. If you fit the nest receiver at the position where the thermostat is wired back to you can reconfigure the wiring to power the nest controller. The extra lives and neutrals need to stay connected together as they currently are, or something will stop working!
Thank you Echo, I think I'm going to go for a Nest Pro as think there's a chance I'll mess it up sorting out the extra lives and neutrals!
I too have a promax sl and chose the simpler wireless nest thermostat option. it talks the the heatlink lovely. problem is I have 3 wires that go to the boiler. live. neutral and earth. i put live into 3 and neutral into 2 and earth into earth . nada. nest says running heat but it lies. heatlink live and green lighted. any ideas for connections please.
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I put live into 3 and neutral into 2

If you are referring to the Heatlink; There is only one Neutral terminal at the Heatlink labelled 'N'. But be careful! Sometimes unmarked blue (ie neutral) wires are used by unprofessional installers as a live conductor.

Heatlink terminals 2 and 3 are actually a switch and are electrically joined together when the Nest switches the Central Heating 'on'


To install a Nest safely, it is necessary to fully understand all of the existing wiring and what is does, as well as how the Heatlink actually works. From what you have written, I think you would probably better following the advice given by Nest in the instruction manual.

thank you very much. I appreciate the advice.. I spoke with nest service today and sent them the attached photo and said left cable was from fused spur and right dirty cable goes to boiler. thankfully they said it was correctly done. I'll speak to their boss tomorrow and he may advise a return. if so I may take the advert for 250 supply and for with a 5 yr guarantee of still available as the guarantee alone is worth the 90 on top of cost price.


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That's OK then. Really you have not put a neutral in terminal 2 as you said you had. The blue wire is not actually being used as a neutral.

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