NEST Thermostats Installation

6 Apr 2021
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United Kingdom

Hi All

I am looking at installing a 3rd gen Nest

I need some help been looking through all your posts and can’t find an installation that has the same wiring as I have so any help would be great.

This is what I think I need to do?

N - N
L - L
3 - 6
4 - 3

I am planning on leaving the old thermostat wiring in place just linking out the wires so that it permanently calling, will this work?

Then go wireless with the Nest thermostat.
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Seems like it will work, however Nest isn’t completely wireless.
Hi Chris

Thanks for the reply I was a little confused as the system doesn’t have any off signal wire, I am presuming that if there is no “call” signal on 3&4 then it’s in an “off” state?

My understanding is that the Thermostat (sensor) can be wireless I have a stand and USB power supply, the heatlink will need to be hardwired.
Yes it doesn’t need on off, because it’ll be done automatically, as it’s similar to a switch. Yes heatlink can be done on a usb, but you’d have to unplug it and plug it back in again should you want to change rooms. The nest thermostat can go where the hard wired stat is currently, just connect the 2 switch wires to T1 and T2.
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Hi Chris

sorry maybe my terminology is incorrect.

I will be replacing the Drayton LP255 with the Heatlink.

I can use the current Thermostat as its 240V, Nest is a Max 24V I plan to link this out so it’s permanent “calling”

I then plan use the Nest Thermostat completely Wirelessly being powered USB on mains power.
Ok no harm in doing that, but I think you’ve misinterpreted what I was suggesting. If you didn’t want to use the usb plug, you can site the Nest thermostat where the existing 240vac thermostat is. Basically what you would need to do is figure out the live in and call wires and connect these up to the T1 and T2 in heatlink, then connect the same wires up in the Nest thermostat backplate T1 and T2 and the heat link will provide the correct voltage.
Got you! That was my first plan to be honest, Then I 2nd guess myself.

Thanks for your help, will report back how I get on.
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