Nest 3rd Gen Install

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deanoMK

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Hello everyone.

I've just bought a 3rd Gen Nest and am going to attempt to install it myself.

I've currently got a Danfoss TP9000, controlling my Logic 15 regular boiler:
SAM_6778.jpg


Only trouble is, when I take the face off I'm greeted by this:
SAM_6781.jpg

SAM_6779.jpg


I really wasn't expecting to see three Neutral cables and three Live. My question therefore is, do I connect all three N & L to the Heatlink? I'm pretty sure in my quest to find an answer I've read that you should only connect 1 cable to each terminal on the heatlink. Which then leads to another question, how do I know which one to connect?

Here's a better pic of the cables: https://goo.gl/photos/BqmPVgJ3XeZYsQJDA

Many thanks,

Dean
 
They all still need to remain connected to each other, or something somewhere will no longer work.
If there's enough room for it in the hole behind the backplate you could use a terminal strip to connect the three wires for Live and the 3 for Neutral onto a single wire for each, to be connected to the heatlink L & N terminals. .
 
That's good to hear. Not sure if there is a lot of space but that does make things easier.

Am I right in thinking that 5 & 6 relate to the T1 and T2 on the Nest Thermostat?

Going by the danfoss, am I also right in saying that only 3 & 4 are currently connected, which according to the terminal identification is DHW on and HTG on, so where are the off cables?

Sorry if any of that sounds stupid, I'm a complete novice.
 
The T1 & T2 terminals are nothing to do with the existing wiring so don't connect them at all unless you know what's involved and there is suitable cabling available.
They would be used to get power and communications from the heatlink to the Nest thermostat, only if you were unable to use the plug in power supply unit.

It looks like your system doesn't need the heating Off and HW Off connections so don't worry about those either.
 
Well I wasn't intending on using the plug in power for the thermostat as I was simply going to be replacing the existing wall thermostat with the nest, which is where I thought the T1 and T2 connections come in.
 
Is there a wiring centre in the setup where the thermostats, motorised valves, programmer and boiler are all connected together? Near that would be the best place for the heatlink.
 
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Yes, it's all next to the hot water cylinder which is on the first floor, that's not likely to cause connectivity issues (by being on different floors) between the heat link and nest, is it?

Thank you for your help by the way.
 
If you can reuse the wiring from there to the old thermostat to carry T1 & T2, that will take care of the connectivity as well as provide power. Just don't send 230V to the Nest on those two wires by accident.

Post some pictures of the wiring centre and the old room thermostat connections if you need more help.
 
Just got home from doing this exact replacement. New build David Wilson home by any chance?

I used Wago connectors to join all the Lives together, all the Neutrals, all the Earths (in behind that backplate), then connected 3 to 5 and 4 to 6. I then took the existing programmer and backplate, and threw them in the bin. The connected wires were then pushed into the back box and a blanking plate fitted over the top

Up to the airing cupboard, remove the cover from your wiring centre and disconnect the wire connected to the brown leading to your heating valve controlling the part of the house you want Nest to control (you presumably have two thermostats, one upstairs and one downstairs?). Also disconnect the wire coming from your cylinder thermostat that ISN'T convected to the brown of the hot water valve (and also isn't the Earth or Neutral). These two wires lead to your remote sensor for your thermostat, and need to be connected to Heat Link (HL) T1 and T2. Your Nest will then replace the remote sensor using the two wires supplying it

Connect HL 3 to the brown of the heating zone valve you've just removed your new T1/T2 wire from. Connect HL 6 to your cylinder thermostat wire. Then it's L, 2 and 5 to the grey wires from your zone valves, N to Neutral and Earth to Earth. Power back on and away you go!
 
muggles said:
Just got home from doing this exact replacement. New build David Wilson home by any chance?

I used Wago connectors to join all the Lives together, all the Neutrals, all the Earths (in behind that backplate), then connected 3 to 5 and 4 to 6. I then took the existing programmer and backplate, and threw them in the bin. The connected wires were then pushed into the back box and a blanking plate fitted over the top

Up to the airing cupboard, remove the cover from your wiring centre and disconnect the wire connected to the brown leading to your heating valve controlling the part of the house you want Nest to control (you presumably have two thermostats, one upstairs and one downstairs?). Also disconnect the wire coming from your cylinder thermostat that ISN'T convected to the brown of the hot water valve (and also isn't the Earth or Neutral). These two wires lead to your remote sensor for your thermostat, and need to be connected to Heat Link (HL) T1 and T2. Your Nest will then replace the remote sensor using the two wires supplying it

Connect HL 3 to the brown of the heating zone valve you've just removed your new T1/T2 wire from. Connect HL 6 to your cylinder thermostat wire. Then it's L, 2 and 5 to the grey wires from your zone valves, N to Neutral and Earth to Earth. Power back on and away you go!
Click to expand...

It's a Taylor Wimpey, but I'm certain they're all the same these days! I've only got the one thermostat, which is downstairs in the open plan kitchen/living room. All other radiators are TRVs.

Here's the box next to the hot water cylinder:

IMG_20161129_205233.jpg


And this is the Thermostat (a Danfoss TS2):

IMG_20161129_204907.jpg
 
Yep, exactly as I expected. Your TS2 is currently directly connected to 5 & 6 on your old programmer. You want to remove this and use the wires to supply power to your Nest, which will happen if you follow my instructions above.

On your wiring centre image, counting terminals down from the top, I think left hand wires 5 & 6 will lead to your TS2 once you've connected 3 to 5 and 4 to 6 where your old programmer was. Buzz through with a multimeter to check. Disconnect these and connect them to T1 & T2 on the HL and use them to power your Nest by disconnecting your TS2 on the wall and replacing it with Nest. The terminals they were connected to are then used to connect HL/6 and HL/3 respectively. HL/L, HL/2 and HL/5 go to terminals 11 or 12 in the wiring centre (either will do), HL/N goes to 9 or 10 I think, although the picture's a bit dark so hard to be certain, and HL/Earth goes to 7 or 8
 
Thank you for that. I think I'm going to have to read it through a few times before attempting it.

When you say "once you've connected 3 to 5 and 4 to 6" does that mean what's currently DHW on (3) and HTG on (4), on the current programmer will go into slots 5 & 6? If that's the case, what would I do with the cables that are currently in 5 & 6, just tie them off?

Thanks
 
No, you connect the DHW On wire to the wire in 5, and the HTG On wire to the wire in 6. As I said, the aim is to do away with that programmer altogether and just fit a blanking plate over the hole where it used to be. Making these connections will provide a direct route from your TS2 location (where your Nest will go) to the wiring centre, and you're going to use those wires to connect into T1 and T2 in your Heat Link (and nothing else, otherwise your Nest will go bang)
 
Ah okay, that makes sense. Thank you. I'm going to knock up a wiring diagram later to try and get it crystal clear in my head, I'll post it up once I have to ensure everything is as it should be.
 
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