Installing 12v supply for nest thermostat

[Phil_D]

im having a new kitchen fitted Monday and have decided to mount a nest thermostat on the wall.

When the sparky was there doing the electrics we spoke about this and he said he can chase in a spur from a nearby socket, which he has done.

The nest arrived today and it says you can’t run it off a 230v supply, needs a 12v supply. Anything I can do here with the spur I currently have? How would a 12v supply usually be wired in to the mains?

 

[WorkshopChris]

Can you use the new cable to feed the 12v to thermostat all depends if the other end of the cable is somewhere convenient to feed 12v from a plug top transformer. OK if somewhere hidden but not really something you might want in the middle of a wall.

 

[lshigham]

Poor show from the sparky not checking the voltage first! Mines fed from a 12v led driver in a deep double pattress by the consumer unit, as I couldn't get another cable up to the attic. You might be able to hide something like that above the ceiling or a wall unit?

The nest only uses 300 odd mA so very little load.

 

[Phil_D]

So here’s what’s going on with the current wiring

So far left is light switch with the thermostat cable poking out next to it. Two double sockets above worktop height to the right of that. There will be bass units along this wall.

Would it be possible to take a spur down from the left hand double socket to a 12v transformer mounted at below plinth level, then connect the twin and earth which has been chased into the wall for the thermostat to that?

 

[brightspark]

drop supply from socket in 2.5mm cable down to a 13 amp spur behind plinth out to transformer and connect your thermostat cable to it . it will still be accessible and hidden

 

[Phil_D]

drop supply from socket in 2.5mm cable down to a 13 amp spur behind plinth out to transformer and connect your thermostat cable to it . it will still be accessible and hidden

Ok cool, but to save me messing about with any more chasing in and refilling, could I just stick a junction box on one of the socket supplies that is already at under plinth height and then stick the transformer on this?

 

[brightspark]

Ok cool, but to save me messing about with any more chasing in and refilling, could I just stick a junction box on one of the socket supplies that is already at under plinth height and then stick the transformer on this?

yep as long as its through a 13 amp switch spur with 3 amp fuse fitted

 

[slim_boy_fat]

Anything I can do here with the spur I currently have?

Install a shaver socket? [I understand VERY little about elektrickery/electronics. ]

 

[Kayos]

Nest base unit had 12v output, I use the old stat wires to feed the nest round when I do them

If no existing supply I either plug them in with usb on the stand or run a thin cable

 

[Phil_D]

Nest base unit had 12v output, I use the old stat wires to feed the nest round when I do them

If no existing supply I either plug them in with usb on the stand or run a thin cable

I wanted to go for no visible wires and seeing as I was having a bunch of stuff chased in I thought this would be worth doing, defo don’t want any visible plugs or wires etc

 

[Phil_D]

yep as long as its through a 13 amp switch spur with 3 amp fuse fitted

Nice one. As it will all be accessible under plinth I’ll just get the sparky to do it when he’s in for the second fix after the kitchen is in.

Why does the supply to the transformer need to be switched by the way?

 

[WorkshopChris]

I wanted to go for no visible wires and seeing as I was having a bunch of stuff chased in I thought this would be worth doing, defo don’t want any visible plugs or wires etc

I am not familiar with the nest but you might need to dig the wall out a little directly behind where its going to sit and solder and heat shrink 2 lengths to light flex to the T&E or you might have a job terminating the T&E and getting the next back to the wall, depends how heavy the terminals are, it takes quite a bit of force to push the T&E back when you only have a short length to move.

 

[brightspark]

Nice one. As it will all be accessible under plinth I’ll just get the sparky to do it when he’s in for the second fix after the kitchen is in.

Why does the supply to the transformer need to be switched by the way?

because its on to the ringmain at 32 amps and transformer only 3 amps .isolation u can just use a 13 amp fused spur if u wish but switched is better if u need to do testing as they are double pole . a fused spur is only single

 

[Luke]

I am not familiar with the nest but you might need to dig the wall out a little directly behind where its going to sit and solder and heat shrink 2 lengths to light flex to the T&E or you might have a job terminating the T&E and getting the next back to the wall, depends how heavy the terminals are, it takes quite a bit of force to push the T&E back when you only have a short length to move.

The mounting ring is only approx. 4-5 mm thick, so it does help to have some room behind. There's a round cavity where the terminals are that helps - it will take a small loop of each of the cores.

 

[lshigham]

The mounting ring is only approx. 4-5 mm thick, so it does help to have some room behind. There's a round cavity where the terminals are that helps - it will take a small loop of each of the cores.

As Luke says no problem terminating 1.0 T+E in the back I used a little heatshrink on the earth as there's no earth terminal