Replacing Honeywell T40

[InThrees]

Hello, realise there are a few posts related to this subject but want to double check my understanding with regards my specific system.

I want to replace with a Google thermostat e heat link.

The attached photo represents how mine is wired. My interpretation is the yellow wire is being used as the Com and the red wire the No, and the yellow/green earth being earthed. The blue (neutral?) isn’t connected to anything.

My assumption is I can follow Google’s advice and connect my heat link using the wires as identified above as the Com and No in the new set up. Is that correct?

Many thanks.

 

[stem]

Quite common situation, usually a 'lazy install'. There should be a neutral connection made to the Honeywell terminal 2, but as you state it's not been connected. The old dial thermostat will work without it, albeit not as accurately as it would with it. So, it's quite possible that the other end isn't connected to anything either.

As you are installing a Nest-e which is battery operated you don't need a neutral. The red wire (Live) would normally go to COM and the yellow (Switched Live) to NO.

Although the original installer even got that transposed. It doesn't really matter though it will work either way around.

 

[InThrees]

Great, thank you for advice and quick response!