Anyone got a view?.. I’m pretty close to buying a Nest v3. Seems like the best.
I have just installed a Nest V3 onto a conventional boiler and it works a treat in HA.
Wiring it in was ok as I just removed the old controller and thermostat and apart from L&N I only needed to connect call for heat (3) & water (6) and water satisfied (4). Also jumpered the Live terminal to 2&5.
Old thermostat wiring was removed from the junction box and used to connect T1 & T2 on the heat link to the Nest downstairs in the hallway. Removed thermostat connection in the junction box was then jumpered across to complete the 3 port valve on my Y system.
Nest wiring diagram is here https://nest.com/uk/support/article/Which-cables-connect-Heat-Link-to-my-heating-system-and-the-Nest-Thermostat
Bertrum,
well done for putting yours in - do you like it - linked up to HA OK? How much did you pay for the nest - looks like they’re batting about £180 to £200.
thanks very much for this - you’re spurring me on (unintended pin there). I’m umming and erring as to if I should do it myself or “get a man in”… I want to do it myself and I have the feeling it’ll be straightforward… I’ll save £70 and will understand it more… and I want to do it ! haha…
I’m curious if you can give me a steer from the photos, perhaps if you think it’s doable? - I’m particularly interested to know if I can do it all from the side of the wall where the programmable controller is…? if I can tackle it from this controller side i wouldn’t need to mess with the rather scary wiring in the junction box by the boiler…
The room thermostat is operating at 240v currently and I’m aware I need to get that to 12v via the nest heat link during the install…
EXISTING SYSTEM summary…
Pressurised system
Greenstar 24i system erp condensing boiler
Pressurised tank with expansion vessel and immersion, thermostatstat on tank…there is a large junction box in this area on opposite side of wall to where the programmable controller is…
Honeywell st9400s hot water and CH controller (utility room, on other side of wall from where boiler and tank are).
Honeywell room thermostat (family room)
All the connections seem well labelled at the controller and room stat and I have my multi meter to check.
Here’s hoping for some info, all liability mine obv. :-).
cheers
here are the relevant pics…
that’d be helpful thanks, not sure I have quite the same wiring as you but I feel it’s doable with this wiring…so … going to pick up a nestv3 on the way home…
Hello bingobob,
Looking at your photos and there is no reason why you cannot do the same that I have however I notice that you do not have a HW satisfied wire which when we moved into this house we didn’t have one so I put it in - Cannot remember where it went in the junction box sorry but it went to the 3 port valve somewhere… I guess you need to have the CH on for the water to work ? It’s not a big problem it just means that I can have the heating and HW on together or on their own.
I had a bit of a bargain when I got my Nest. I just moved G&E to N Power and they are selling them for £129 so at that price it was a no brainer - came in 2 days as well 
As I mentioned last night the wiring would be very straightforward looking at your pictures
Live to live,
Neutral to Neutral
HW on 3 on yours to 6 on the Nest
CH on 4 on yours to 3 on the Nest
Run a live from the Live to 2 & 5 on the Nest
You will need to confirm where the stat goes in the junction box then remove then from there and place a wire to jumper where they went on the junction box. Once removed they got to T1 and T2 on the heat link. Earth wire is not needed for the Nest link.
I have added some pictures of mine including a wiring diagram that is next to the heat link.
***** As always this is done at your own risk and please take plenty of pictures before you remove wires and label each wire as they are removed so you can put it all back if it doesn’t work. Also remember that you are working on 230V so make sure the power is off and use a mains tester screwdriver to ensure that there is no power on any wire before your remove it *****
As a new user I can only send 3 pictures so screen shot of my phone cannot be uploaded yet but it works fine in HA although I use the data from the Nest to give data into HA. I generally use the Nest App to control the Nest but it can be done from HA easily enough.
Good luck and I’m sure it will go well.
Hi, thanks so much for this… really helpful, I feel I can get there with this… all the warnings headed and I won’t be touching it until I’ve got the power off… and absolutely I was thinking the same thing, I have the photos so can revert if necessary…liability all my own.
No hot water satisfied wire… Yes… I was curious about this also… Seems I haven’t got one. We can control the hot water and central heating on the programmer independently though, so not sure how that works!
“Run a live from the Live to 2 & 5 on the Nest”… Just checking I understood that… basically I just run a wire between those points on the heat link…a jumper wire I suppose to connect them together ?
bb
Yes. Didn’t have time to remove the cover of the heat link as work again but I ran a link from the Live to 2 and then a link from 2 to 5. All this does is to put a 230v feed on pins 2 and 5 that the heat link will internally connect to 3 & 6 which feed the HW and CH.
I also labelled each wire that I removed just in case I needed to revert back if it doesn’t work or I move and want to put the old system back.
You will need to work out which are the 2 active wires from your thermostat as well as I see you have 3 and the earth - is the one to power a light when the thermostat is in the on position ?
Good Luck.
Got it. Helpful thanks…
Room thermostat is just the dial (no light on it) so not sure why it has the extra wire in play. I’m more comfortable with this side of things as if I’ve got it I’m really just repurposing a pair of these thermostat wires for the 12volt feed from the heatlink… So as to have the Nest thermostat powered nicely on the wall.
Whichever way I go with this I’ll report back, even if I bail out and call in a pro! (Hopefully not)…
Thanks again…
1 Like
This is the wiring on my old controller - same as yours except the extra wire for HW satisfied
Just looked at a PDF of your Thermostat Honeywell T6360B and it seems that wires 1&3 are what you need to use. Wire 2 is used for a light in certain models and I can see where the light would’ve gone on yours.
I’m ashamed to say I took the cowards way out and got a man in. I first tried to do it myself following the wiring diagram you kindly provided and it was going pretty well, I think I was very close but I wasn’t having the confidence that I needed that everything was going to be just right. At that point I decided the best thing to do was get the Professionals involved and a guy came along and did it. Cost but at least I’m more confident that it’s wired correctly. love the device, is amazing and it’s learning at the moment I think so I guess it will get better with the temperatures over time but it seems really well built and very much a quality device. I think it’s the best one and better than the others like wave and netamo and hive etc. Just wanted to say thank you for going to all that trouble with the photos and the wiring explanation. I didn’t quite make it maybe next time.
Already got the thing hooked up to home assistant - that was very easy!
Anyone got any good tips what do to do next!
I figure the motion sensor in it is pretty amazing so I plan to use that to trigger some HA stuff…
Would like to use it initially to have an “away” mode for the house if it hasn’t been activated for couple of hours…
That’s ok - better to be safe than sorry. Glad you’ve got it all sorted. At least you have a bit more knowledge if you ever think of doing something similar in the future.
Hi @BertrumUK
Thanks for the above. Can you help me clarify what to do when removing the old stat please.
From the above, I believe you took the old stat wires out of 4 and 5 from the junction box.
Where did you then put the jumper wire? Between 4&5?
Thanks for your help in advance.
Hello Adam,
If you look at the picture that I posted in link 8 -
at the bottom you can see my note that I linked 3&4 together as this was where the old thermostat was wired into. This is for a Y plan system.
Normally the thermostat switches 230v into the 3 port valve so with it linked out the Nest heatlink will inject the 230v and switch the valve depending on whether hot water/heating or both are selected.
If you need further help then just ask.
Thanks @BertrumUK, really appreciated.
A final naive question, did you take the wire from the Thermostat to no. 5 out as well?
This is my only area of confusion as I initially thought from the image you mention that the thermostat was connected to 4 (in) and 5 (out). Therefore, I was thinking that I just needed to jump between 4&5, rather than 4&3.
Thanks again.
Hello Adam,
My Thermostat only had 2 wires from it to the old controller via the 10 way junction box. It was connected to 3&4 in the junction box so I removed it from there and replaced both connections with a link connecting 3&4 together. The wires from the thermostat were then connected to T1 and T2 in the heatlink to provide a 12v feed to the Nest downstairs in the hallway.
If you have 3 wires on your thermostat then I guess the extra wire is for neutral and isn’t used. Normally terminals 1&3 are used in the mechanical thermostats.
If you have 3 wires then let me know what the make and model is so I can see which wires you will need to jumper ?
@BertrumUK Thanks so much. I have two wires from/to my thermostat and they go in to 4&5. Therefore, I will put a jumper between 4&5 instead. I’ll post what i do just so you can see. Thanks again.
1 Like
Hi @BertrumUK, hope all is well.
As promised, please find attached pic’s of my junction box, thermostat, programmer and general set-up.
Any further advice would be appreciated.
Thanks again.