12v PSU for 3rd Generation Nest Thermostat

[Grzyb]

Hi All,

In the Process of replacing our 26-Year Old Baxi Solo CH/HW Boiler with a Baxi EcoBlue Advance Heat one. Thought that I would also change the Landis & Gyr Room Stat & BG UP2 Programmer for a 3rd Generation Nest Thermostat with Heat Link....

Ideally, I'd like to fit the Nest Itself in the same place as the Original Room Stat, but the Room Stat is currently switching 240v, the Nest itself runs on 12v, I have identified the Wires that go into the Room Stat & they come from a 10-Way Terminal Block upstairs by the Hot-Water Tank...

My Question is, Can I power the Nest, using a 240v AC to 12v DC PSU, using the existing Wires that go to the Original Room Thermostat?

Most PSU's are rated as giving 12v 1A @ 12w, will that be OK, Or will I blow the nest?

The Heat Link will be going into the Kitchen, where the programmer was, so to make the Install as easy as possible, without having to Drill Floorboards, lift Laminate Flooring & run more cables, It would make life much easier, if I could use a 240v AC to 12v DC PSU to provide the nest with 12v using the existing Wiring to the Original Room Stat...

Thanks for any info that can be provided.....

 

[Razor900]

Put the heat link in the airing cupboard. You should have enough wires from the old programmer location for the boiler.

 

[D_Hailsham]

It would be more sensible to locate the Heat Link upstairs outside the airing cupboard, where you will find:.

either one motorized valve, like this:

View media item 5946
or two motorized valves, like this:

View media item 11762
The Heat link will control one of these valves which then controls the boiler.

The cable from the existing stat (currently carrying 240Vac) will go to the 10-way junction box. It can easily be used to carry 12V dc from the heatlink to the Nest.

Post a pic of the airing cupboard showing the pipe layout and motorized valves.

Also post a pic of the 10-way junction box with the lid off, so we can see the wiring.

 

[Grzyb]

Thanks for the replies.....

I will take your comments on-board in making the final decision....Yes, It would be easier, if the Heat Link is located in the Airing Cupboard, then it would be just taking the 12v Feed from T1/T2 of the Heat Link & using that on the Tails of the Old Landis & Gyr Room Thermostat....

The only thing that I would have to think about is what to do with the Old Programmer? I was hoping to Wire in the Heat Link into the Old Programmers location, in the Kitchen, otherwise, I'd either need to "keep" the UP2 in situ to "hide" an unsightly hole in the Kitchen Wall Tiles or try & find a "Blanking" Plate to Fit over....

But back to my OP, has anyone used a 240v AC to 12v DC PSU, to provide the necessary 12v to the Nest? Will 12v 1A Power Ouput be sufficient to Drive the Nest?

Some Photos enclosed & I can't count!!! It's an 8-Way TB. The Valve is a BGMVSP-23 Mid Position Actuating Valve

 

[flameport]

or try & find a "Blanking" Plate to Fit over....

A blank plate is 26p. http://www.toolstation.com/shop/p35507
Same size as the old programmer plate, and the screw holes will line up perfectly.

 

[Grzyb]

A blank plate is 26p. http://www.toolstation.com/shop/p35507
Same size as the old programmer plate, and the screw holes will line up perfectly.

Looks Like I have found the Perfect way Forward....Only £0.26 as well

 

[Gorners]

To answer your original question, I've been using a 240v/12v transformer for a couple of weeks to power the Nest, working absolutely fine. Had it confirmed in the Electrics UK forum before I did it - see thread below.

//www.diynot.com/diy/threads/reducing-230v-to-12v-for-nest.473505/#post-3799018

 

[Grzyb]

To answer your original question, I've been using a 240v/12v transformer for a couple of weeks to power the Nest, working absolutely fine. Had it confirmed in the Electrics UK forum before I did it - see thread below.

//www.diynot.com/diy/threads/reducing-230v-to-12v-for-nest.473505/#post-3799018

Thanks Gorners, That's exactly what I was after, whether it would be Possible....

 

[Agile]

As supplied the Nest is only powered from a 5 vdc supply!

Although they do mention 12 vdc in the leaflet.

Tony

 

[Gorners]

As supplied the Nest is only powered from a 5 vdc supply!

Although they do mention 12 vdc in the leaflet.

Tony

5v is supplied from the USB if you wish to power this way. 12v comes from the heat link.

 

[D_Hailsham]

The OP needs to trace all the wiring before deciding what to do. Programmer near boiler, thermostat in hall, wiring centre (seven! terminals) etc upstairs all say that there are a lot of wires running backwards and forwards. So it's more than just fitting the Heat Link in the place of the programmer.

 

[Grzyb]

The OP needs to trace all the wiring before deciding what to do. Programmer near boiler, thermostat in hall, wiring centre (seven! terminals) etc upstairs all say that there are a lot of wires running backwards and forwards. So it's more than just fitting the Heat Link in the place of the programmer.

Cheers...There's an 8th one all by it's lonesome, in the Top LHS of the JPEG.....Original Installer must've Cut it Off to fit into the JB....

 

[D_Hailsham]

Cheers...There's an 8th one all by it's lonesome, in the Top LHS of the JPEG.....Original Installer must've Cut it Off to fit into the JB....

I did wonder if that was another terminal block, but concluded it wasn't as there was plenty of room for an 8-way or even 10 way strip if installed vertically (or the box could be turned to landscape orientation).