Nest Protect Wired Installation

sipxstream · Nov 20, 2023

Hello,

I have a wired version of a Google NEST Protect (Smoke and CO detector) which I need to install in my garage.

We've recently moved into a new house. My garage is very long, and the way the power that comes into it is split a bit weird, or at least to me anyway:

The 1st half of the garage, the lighting circuit is taken from a feed from the 1st floor's lighting circuit. On the consumer unit within the house, it's on the 6A circuit for all of the 1st floor lighting.

The 2nd half of the garage has power coming in from the CU on it's own 16A MCB, and then loops from socket to socket, which I don't think returns back to the CU (TBC) . Along this leg of the chain, the feed also splits off and goes into an FCU which powers the lights for that end of the garage.

The garage doesn't have separate consumer unit installed.

I would say that the NEST needs to be installed somewhere in the middle of the garage, but I don't know which feed is best to take power from, or if I can just simply take a junction from wherever it needs to come from. The NEST is double-insulated, so there's no need for a CPC - only L + N.

Also, in my house, the power for the lighting circuits are at the switch (I believe the correct terminology is the 2-plate method?)

Geoff1946 · Nov 20, 2023

Take it from either lighting circuit.

sipxstream · Nov 20, 2023

Thanks for your help, Geoff.

Thinking about it even more, I don't think I can take power from the 2nd lighting circuit:

The 2nd lighting circuit's lights are turned on/off by the FCU, so that'd mean that I'd need to keep the FCU (and therefore the lights) on permanently for the NEST to be constantly powered on?

Perhaps the 1st lighting circuit might be better. If I cut into the cable before it reaches the light socket, and use Wago terminals to take a junction from it to where the NEST is to be installed, do you think this would be ok?

I'd put all of the joins into a WAGO box, zip-tie it so that it becomes maintenance-free and then fix the Wago box to the ceiling joist (the ceiling's not plaster boarded yet)

Mike P · Nov 20, 2023

I wouldn’t cut/break into the lighting circuit, just take a feed from a pedant or switch if its 2 plate!

sipxstream · Nov 20, 2023

Yes, it's 2 plate.

There's already 2 cables in the switch - one for the incoming power to the switch, and one going out to the light fitting. So, from my understanding of what you said, it would be best to add a 3rd 1.5mm cable from the switch, taking the permanent live, neutral, and CPC to the NEST?

Many thanks.

Mike P · Nov 21, 2023

sipxstream said:
Yes, it's 2 plate.

There's already 2 cables in the switch - one for the incoming power to the switch, and one going out to the light fitting. So, from my understanding of what you said, it would be best to add a 3rd 1.5mm cable from the switch, taking the permanent live, neutral, and CPC to the NEST?

Many thanks.

Yup!