Potterton ProMax and NEST Installation advice

[Tim Price]

Hi all,

Thank you in advance for anyone who is able to provide some advice to me.
I am not an electrician nor a plumber but I feel competent when it comes to these sort of things.

I am looking at installing a NEST into my house to start turning my home into a smart home (im an IT manager nerd) and I just want to make sure I know exactly which wires to put where.

I am going to get the 3rd Gen NEST and I have a Potterton Promax HE Plus combi boiler and a wall mounted thermostat powered by batteries.

This is the wiring guide on the boiler plate:

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Followed by the wires into the boiler itself:

Finally the wires to the thermostat:

Thermostat is running on battery at the moment but ideally I would like to install the Nest unit here (I know it requires power)

Finally is the wiring diagram for the Nest itself:

So on assumptions:
I do all the sensible stuff like power off, isolate etc.
Then remove the cables from the left hand side.
Using some new 3core I wire the live and neutral from the boiler into N/L on the heat link. I leave all the hot water alone as it is always on (I believe)
I am unsure which cable is the call for heat? Is it the black one from the thermostat into the switched line in 1?

I am assuming that the Earth & Grey cable in Live out 2 are going through to the thermostat.

Basically I would like some advice when it comes to the wiring so that I doing do something bad.

Thanks,

Tim

 

[buzzlightyear]

basically what it says on the tin!

 

[davesparks]

You’ll need to find the wiring centre then identify and disconnect the current thermostat cable there, then alter/extend it in a manner which complies with the regulations to use it for the 12V power to the nest stat and connect it to the heatlink.

Then you’ll need to bring the L, N, E and S/L connections at the wiring centre out to the heatlink in a manner which complies with the regulations.

There is no reason to open the boiler casing to do any of this.

Don’t use the L in to the boiler for the common connection at the heatlink, this must come from the correct terminal in the boiler otherwise you could bypass the fuse protection in the boiler and create a dangerous situation.

Take great care when doing this as you can verily easily damage your £200 thermostat beyond repair or more seriously you could receive a fatal electric shock.