Installing nest thermostat to replace old thermostat


I have brought my nest thermostat to a new home. In the old home, it was very easy to install, no existing thermostat, only a few connections.

In the new home with the new boiler, I am out of my depth... but I cannot afford to pay for professional installation at this time. I am an absolute novice, but I know to isolate power before starting etc

I do not care about wiring the Nest to the power supply, only removing the old thermostat wiring from the boiler, and attaching the heat link in its place.

Attached is the wiring on the boiler as it is now - which seems quite simple, but I'm just not confident in what to change. Also attached is the wires I have connected to the Heat Link itself. (They're not currently connected to one another)

I would greatly appreciate your assistance here because the old thermostat is very temperamental and I the wifi enabled heating control will really help me out

Thanks in advance


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Distinguished Member
I can make a reasonable guess based on your pictures but it would be a guess without knowing more.

My guess would be the top left connection is the power supply, top right is power to the boiler, bottom left ones to the stat and bottom right is the switching from the boiler.

I wouldn't be comfortable saying anything else without seeing the wiring connections at the boiler, can you gain access and post a picture of those.

You're right in that I think this will be quite simple once we have more info.
Hello! Thanks for your helpful reply. I tried to get a decent pic of the inside, the black flex leads into the controls, the white flex leads to a loom with lots of wires coming off it. The grey flex goes into the walls and I think is definitely connected to the old thermostat


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