Replace Drayton with Nest - wiring?

Ali81 · 22 May 2021

Hi, I'm not sure if my programmer can be replaced with a 3rd gen Nest? Google website says my wiring means no, but I don't believe that's true. Do I need to modify any wires or add anything?

I know there's threads discussing similar, but I'm still not sure. I have a Drayton (British Gas UP2) linked to a Glow worm Flexicom 18sx condensing boiler. There is no thermostat.

There's 2 black wires in N
2 red in L
1 red in 1
Nothing in 2 - I don't know why?
1 blue in 3
1 yellow in 4
Earth

Any help much appreciated

Photos:

ericmark · 22 May 2021

Very likely you can fit Nest Gen 3, but as it stands I can only guess what your system is. I am using it with a C Plan and the instruction book does not cover that option, but need more info, are there any valves or pumps?

Johnmdc · 22 May 2021

Yes it can. Looking at the wiring it is almost certainly a Y plan system.
Both blacks in N to N on Nest heat link.
Both red in L to L
Red in 1 to 4
Blue in 3 to 6
Yellow in 4 to 3
Then you need to put a link in from L to 2 and from 2 to 5.
You might find it easier to put one of the reds in L and the other in 5 then there is only two wires in each of the three terminals L, 2 and 5. Because the terminals are quite small and you may struggle to get three wires in the L terminal.
Don't worry that there is no wire in terminal 2 on your existing UP2 it is very rarely required.

ianmcd · 22 May 2021

yep as @Johnmdc says you have a Y plan, just follow Y plan instructions for your nest

CBW · 22 May 2021

Ali81 said:
There is no thermostat.

You will probably be better off plugging into a socket outlet then, unless you can get wiring to heatlink and thermostat positioned in appropriate location?

Ali81 · 23 May 2021

Johnmdc said:
Yes it can. Looking at the wiring it is almost certainly a Y plan system.
Both blacks in N to N on Nest heat link.
Both red in L to L
Red in 1 to 4
Blue in 3 to 6
Yellow in 4 to 3
Then you need to put a link in from L to 2 and from 2 to 5.
You might find it easier to put one of the reds in L and the other in 5 then there is only two wires in each of the three terminals L, 2 and 5. Because the terminals are quite small and you may struggle to get three wires in the L terminal.
Don't worry that there is no wire in terminal 2 on your existing UP2 it is very rarely required.

Thank you. It seems pretty straightforward. What do I do with the Earth wire when I remove the black backplate from the UP2?

Ali81 · 23 May 2021

Chris_W said:
You will probably be better off plugging into a socket outlet then, unless you can get wiring to heatlink and thermostat positioned in appropriate location?

Yeah, I think so. That's my plan just now to wall mount and plug in if possible, and then hide the wire later

Ali81 · 23 May 2021

ericmark said:
Very likely you can fit Nest Gen 3, but as it stands I can only guess what your system is. I am using it with a C Plan and the instruction book does not cover that option, but need more info, are there any valves or pumps?

I'm not sure what pump there is in the loft, but the system looks like It works like a Y plan, though there are two wires to neutral and two to live, which I don't see on some examples online.

CBW · 23 May 2021

Ali81 said:
What do I do with the Earth wire when I remove the black backplate from the UP2?

Terminate safely in heat link or connector block.

ianmcd · 23 May 2021

Ali81 said:
I'm not sure what pump there is in the loft, but the system looks like It works like a Y plan, though there are two wires to neutral and two to live, which I don't see on some examples online.

nothing to worry about just make sure you keep them the same

Ali81 · 18 Jun 2021

So, a bit of a story with getting this sorted. Due to my property having some wiring issues I didn't want to try install it myself straight away. I tried to get a Nest Pro to install it, but didn't hear back, so I asked my electrician to do it while he was visiting sorting out my consumer unit. Turns out it wasn't as easy to figure out! It had an issue with the hot water always being on, with radiators working fine. After a lot of frustration, a more experienced with Nest electrician from the same company had a look, and said all the wiring looks fine... so we thought it was probably a PCB issue on the heatlink. So my Drayton was put back on.

I contacted Google, they sent some info, and I realised that maybe the Bacteria Prevention option was automatically on, meaning that when it thinks the water hasn't been heated for a while it will heat it up, regardless if you have it set to off. Not wanting to pay for another electrician, I just installed it myself and sure enough the bacteria thing was enabled. It now works fine.

Google could make it a bit clearer that this thing might be on automatically, and it might have saved me the extra 3 hours of electrician to pay

Usually I would have figured this out, but I don't remember reading anything about it on the installation. I remember seeing it during setup and I just ignored it as I assumed it would be off, then forgot about it. At least I'm now a pro at this Nest stuff!

Seán Corduff · 24 Oct 2021

Johnmdc said:
Yes it can. Looking at the wiring it is almost certainly a Y plan system.
Both blacks in N to N on Nest heat link.
Both red in L to L
Red in 1 to 4
Blue in 3 to 6
Yellow in 4 to 3
Then you need to put a link in from L to 2 and from 2 to 5.
You might find it easier to put one of the reds in L and the other in 5 then there is only two wires in each of the three terminals L, 2 and 5. Because the terminals are quite small and you may struggle to get three wires in the L terminal.
Don't worry that there is no wire in terminal 2 on your existing UP2 it is very rarely required.

Hi. I’ve a similar looking system, however you have an extra wire. I was wondering if my system is compatible with the nest, and any help would be appreciated. (I’m a complete Noobie btw!!)

Ali81 · 24 Oct 2021

Your wiring does look a bit different, and I don't know if it is compatible. Hopefully someone here will know what type of setup you've got

ianmcd · 24 Oct 2021

You need to start your own post, not Hi-jack an existing post, it is against site rules for good reason, there is no system that cant be adapted to use nest

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Replace Drayton with Nest - wiring?

Ali81

ericmark

Johnmdc

ianmcd

CBW

Ali81

Ali81

Ali81

CBW

ianmcd

Ali81

Seán Corduff

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