Nest thermostat wiring help

RichHat

RichHat

RichHat

Associate
Joined
21 Feb 2019
Posts
8
Hello,
I've just got a Nest thermostat but struggling with the wiring.
I have a logic combi boiler and dual zone heating so have two esi zone valves located in the cupboard upstairs. I don't have a hot water tank.
I understand I have to wire the valve to the heat link but not sure on what wire goes where?

The ESI valve colour wires are:
Blue - neutral
G/Y - earth
Grey - live
Brown - ? (Currently switched live off wire from thermostat
Orange - ? (Wires into black from boiler thats room stat/timer

Sorry I don't know how to add photos.

Any help is greatly appreciated

Thank you
 
Looks like your heating is zoned into two. You need to pick which zone you want to run from the Nest and have the heat link switch the correct zone valve instead of whatever control you have currently.
The switching wire from the heat link needs a 240v common (2) and the output (3) connects to the brown of the zone valve. The current control needs disconnecting, unless you are wall mounting the Nest thermostat and then you need to use the existing wires and remove from the wiring center and attach to T1 & T2 < Do not power these wires from any other source, you will fry your Nest!
Should be the diagram on page 22, just ignore the hot water valve and stat wiring.

Ideally you should have two Nests installed, one for each zone.

Mick
 
Thanks for the reply Mick.

Sorry I forgot to mention that it would be just the one zone controlled with the nest being downstairs, we rarely use the heating upstairs so doesn't warrant a nest just yet.

So brown wire into 3
Grey wire (current live) into 2, does that need a loop from live input power too?
Does the orange wire now become redundant?

Thanks
 
You shouldn't need to touch anything other than the brown:

The brown is the live to power the valve open, it'll be switched via the output from the programmer, via the appropiate roomstat, presently.

The blue is neutral and the g/y earth for the valve motor, but these are already connected to neutral and earth so no need to touch.

The Orange and Grey are a microswitch on the valve head, its switched when the valve opens, its purpose is to switch the boiler (and any pumps) on when any valve opens. The orange traditionally feeds the boiler switch live while the grey is connected to permanent live, again there should be no reason to touch this.
 
Adam_151 said:
You shouldn't need to touch anything other than the brown:

The brown is the live to power the valve open, it'll be switched via the output from the programmer, via the appropiate roomstat, presently.

The blue is neutral and the g/y earth for the valve motor, but these are already connected to neutral and earth so no need to touch.

The Orange and Grey are a microswitch on the valve head, its switched when the valve opens, its purpose is to switch the boiler (and any pumps) on when any valve opens. The orange traditionally feeds the boiler switch live while the grey is connected to permanent live, again there should be no reason to touch this.
Click to expand...

Ahh I understand it now, so all other wires stay on the current terminal block other than the brown that wires into 3 on the heat link? And a live from L into 2 on the heat link?

Thanks
 
Yes, but just to be explicit... there also needs to be L+N linked from the wiring centre permanent feed upto L-N on the heat link terminals.

Not sure how you are doing it, but I'd get a piece of four core flex (Dont try and drag unsheathed cores out the wiring centre into the heatlink - That will make a dog's dinner of it all :p)

At the heatlink connect brown to L, Sleeve/tape grey as Blue and connect to N, G/Y to earth and Black sleeve brown and put to 3. Use a scrap of brown to link 2 to L.

Run the other end to existing wiring centre, Brown to the live feed in (should be where the greys are already, but leave them in as well). Mark grey as blue and in with the neutrals, Earth in with the earths, Mark black up as brown and put in a currently empty terminal. Find the brown from the value you want it to operate and disconnect that from where it is presently and put it in the new terminal you have just put the black into.
 
Adam_151 said:
Yes, but just to be explicit... there also needs to be L+N linked from the wiring centre permanent feed upto L-N on the heat link terminals.

Not sure how you are doing it, but I'd get a piece of four core flex (Dont try and drag unsheathed cores out the wiring centre into the heatlink - That will make a dog's dinner of it all :p)

At the heatlink connect brown to L, Sleeve/tape grey as Blue and connect to N, G/Y to earth and Black sleeve brown and put to 3. Use a scrap of brown to link 2 to L.

Run the other end to existing wiring centre, Brown to the live feed in (should be where the greys are already, but leave them in as well). Mark grey as blue and in with the neutrals, Earth in with the earths, Mark black up as brown and put in a currently empty terminal. Find the brown from the value you want it to operate and disconnect that from where it is presently and put it in the new terminal you have just put the black into.
Click to expand...

Brilliant thank you so much
I've got some 5 core flex and it'll be a nice neat tidy job :)
 
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