Flexicom CX with Google heat link thermostat help

10 Dec 2022
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United Kingdom
Hi, so we recently moved into a new house and the boiler is like nothing I'd seen before. I'm trying to install my Google Nest learning thermostat 3rd gen and having a hard time finding an input for the Live & Neutral wires. I've attached both nest and boiler manuals, I just can't work it out and with a new baby on the way, I am under a lot of pressure to get the central heating sorted. Please if anyone has had this combination of boiler and thermostat I'd love to hear how you've configured it.

Thanking you.


  • Nest-Thermostat-Installation-Guide-UK.pdf
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  • flexicom-cx-instn.pdf
    10.4 MB · Views: 10
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Maybe you should explain to whoever is putting you under pressure that removing the cover forms part of the combustion circuit and should only be opened by a competent person who can check for safety afterwards. Quite easy to wire up, L and N can be piggybacked from the boiler and then it’s just the switching wires.
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There's a bit of a contradiction in your post. You refer to a "Google Nest learning thermostat 3rd gen" but the manual you've posted is another version. However regarding your question about N&L that bit is the same.

Usually, the easiest and safest way to DIY is to re-route the wires from the existing room thermostat to the Nest (Nest terminal 2 'Heating Common', and terminal 3 "Heating Call For Heat" are where the switching wires from the old thermostat go). If the old thermostat was battery operated and so doesn't have a 230V supply to it, then, as has been said, N&L can be picked up from the 3A fused spur. That way you don't need to open up the boiler and so avoid having to get an RGI in to reseal and carry out the necessary safety checks.
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