Nest 3rd Gen Thermostat - Replace Undefloor Heating Thermostat

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Hi all

I bought a Nest thermostat for the single zone underfloor heating we have

We have an existing thermostat for the undefloor and the plan was to just replace that with the nest just to control the underfloor heating

I have another nest wired up to the boiler and that works really well - heatlink etc all good

My idea was to just replace the thermostat for the underfloor heating
However im not sure if Ive made a mistake though as there are only two wires on the back of the nest and the one we have now has four

So it maybe that Ive jumped the gun here and I might have to re-sell

20211228-133547.jpg


Can anybody help
Thanks
 
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@tododo please specify exactly which Nest thermostat you have.

your existing thermostat has three wires and an earth. If your new stat only has two wires (I assume it’s battery powered) you only need to connect the live (brown) and call for heat (black) wires. The grey is the neutral. Put that in a bit of insulated terminal block it isn’t needed. Ditto for the earth wire. Put that in a separate bit of terminal block.
 
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