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Nest 3rd Gen learning thermostat installation help

Discussion in 'Plumbing and Central Heating' started by veeg33, 24 Nov 2018.

  1. veeg33

    veeg33

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    Hello all, good evening.

    Newbie here with 1st post in this forum.

    I'm average to good with DIY and keen to learn more (installed 4 cameras CCTV, loft ladder, loft boards and build in wardrobe) Hopefully I can install the Nest in my house rather than getting a Pro Installer.

    I'm in a new build house (2yrs old) with the current setup. Boiler in the garage (Worcester Greenstar Ri), hot water tank upstairs in a little room (tank and a shelf) with a Danfoss WB12 junction box, 2 zone heating (lounge and whole house), Danfoss tp9000ma-si programmer/thermostat on ground floor next to the stairs.

    My assumption is one of the cables (5 cores) that goes into the WB12 goes down to the Tp9000ma-si but I have doubt as the cables that goes into the Tp9000ma-si doesn't match those in WB12. Pics attached. In the Tp9000ma-si, there are Earth, N(blue) , L (dark brown) and 2 signal for Heating On (4, brown) and Water On (3 Black). However the outer sheath on the tp9000ma-si is grey and WB12 is white. Hence my doubt it wasn't the same?

    My plan is to add the Heat Link at the WB12, replace the Tp9000ma-si with the Nest thermostat, disconnect all the wires that goes down to the programmer but select 2 to connect to Heat Link T1 and T2 so that I can power up the Nest thermostat downstairs.

    Any advise will be much appreciated bearing in my it will be my own responsibility to ensure safety and won't be taking anyone else responsible for any damage.

    If I'm wrong where should the Heat Link be? I don't want to replace the Tp9000ma-si with the Heat Link and add the Nest thermostat on top of it or somewhere else.

    Many thanks in advance.
     

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  3. stem

    stem

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    Sorry, but your enquiry doesn't make too much sense which is probably why no one has replied earlier. Also, installing a Nest on a two heating zone + hot water system is complex and quite difficult to describe over a forum, because considerable rewiring may be required.

    You say that you have "two heating zones (lounge and whole house)" yet you only mention one thermostat "on the ground floor next to the stairs" What zone is this thermostat controlling? where is the thermostat for the other zone located? Is it also a Tp9000ma-si?

    With two heating zones, you will also need two Nest thermostats with two Heat links, one for each zone. One of the Heat links will also have control of the hot water, so will need to replace whatever is presently providing time control of the hot water, but you don't give any information about the hot water control at all.

    The details you give about the wiring doesn't help unfortunately. The number of wires in a cable, the colours of the wires used for the various functions and how they are connected would be based on the personal preferences of the installer, the layout of your home, the various components used, and the cables to hand. It's what is connected to each end of each wire that is important.

    To install Nest on this type of system, you will need to be electrically competent with a working knowledge of the various components making up your heating system and how they relate to each other. It's not just a matter of saying move wire from A to B. I don't know your skill & ability level, but this could well be one for a professional install.
     
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  4. veeg33

    veeg33

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    Hi Stem,

    Many thanks for your reply. I've managed to figure it out and installed it without problems.:) And apologies for not very good discription in 1st post.

    I have 2 zones in my house ie to controller/programmer. 1 for lounge only (just heating) and 1 for whole house (heating and hot water). The house programmer/thermostat is TP9000ma-si, and this is located at the bottom of the stairs. I also found out that I'll need another Heat Link for lounge which I can't justify another £150. Btw, I bought the Nest on Black Friday deal at screwfix for £150 including a free stand worth £40. I'm planning to sell the stand as I've hard wired it.

    Here's what I did:
    1.) Track the house programmer/thermostat wires. I found another junction box in the airing cupboard upstairs, all the connections here are then connected to the hot water tank (My assumptions are both lounge and stairs programmer goes into this, which is correct after I've tracked them). Managed to track N, L and 'hot water On' and 'heating On' wires that goes from the junction box to the programmer/thermostat downstairs. I did this by swith off the mains, disconnect 1 wire, mains back on and test. Eventually I've tracked all the wires and lable them up.
    2.) I added additional wire to the juntion box to connect to Heat Link which I wanted it be in the airing cupboard and the Next thermostat to replace the current programmer/thermostat (TP9000ma-si) at the bottom of the stairs. I used the existing 'hot water on' and 'heating on' as 12v power supply from Heat Link to the Nest Thermostat. I also disconnected the N and L as I believe if the 240v is still connected, this will affect the 12v power, which I don't want to blow up the Nest Thermostat
    3.) I wired the Heat Link as per diagram for S-plan heating.
    4.) Once everything is wired up (including the Nest Thermostat on the wall) and I'm happy with the wiring, I switched the mains back on everything switched on.
    5.) 15-20mins setting up the Nest thermostat and connecting to my home wifi.

    Now the Heat Link is hidden in the airing cupboard, Nest thermostat is next the bottom of the stairs. I just need to remove it again one day to paint the wall around it as it was a new build and I have yet to paint proper paint on it.

    It could be easier if is replaces the programmer/thermostat TP9000ma-si with Heat Link and have the Nest thermostat either next to the Heat Link (which won't look neat, I don't want to replace 1 device on the wall with 2 devices) or have the Nest thermostat plugged to a USB power supply and find a suitable place for it (which again I'll end up having 2 devices in around the bottom of stairs).

    Overall, I'm really happy this Nest, the temperature seems to be more stable compared to the old thermostat. Heating is just nice in the house now where the old one, temp always goes up higher than I wanted it to or if I set it lower, it just won't get to the right temp. And not forgetting the mobile app........heating on when I was about to set off from office, got home to a nice and warm house. :) And the best part, I was quoted by my nearest Nest Pro Installer - £100. However, things could have gone wrong but I think I'm pretty good/confident with DIY and everything is pretty much a calculated risk before I start the job.
     
  5. stem

    stem

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    OH dear. I'm sorry but what I can read sounds like a bit of a bodge up. You have only replaced one of your two heating zones with the Nest, so you can't control the other heating zone or the hot water via the app. I am in half a mind to think your post is a wind up.
    The "heating and hot water" can't be one zone, the hot water should be wired to be totally separate from the heating
    1) Zone 1 - Lounge Heating - with its own thermostat
    2) Zone 2 - Rest of house heating - with its own thermostat
    3) Hot water System

    That bit sounds reasonable.

    This bit's not so good. "An additional wire to the Heat link" is meaningless, it could be an earth wire for all I know. The old thermostat cable should be completely disconnected first before using in for 12v. Once the thermostat cable has been disconnected the live switching wires need to be bridged to maintain the circuit. Otherwise the heating won't come on.

    Don't know how you managed that. The S-Plan always has at least two motorised valves (heating & hot water. Or, Heating Zone 1 and heating Zone 2) you have only wired up one.

    If I read that correctly then you still have the original programmer still connected to the bit of the heating now controlled by the Nest......hope they don't interfere with each other!

    Except for the heating zone that isn't connected to it.

    It will probably cost you more than that to have it put right.

    No comment!
     
  6. veeg33

    veeg33

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    LOL, let me try again. I'm not so much of an heating/electric engineer hence my explanations might be different from the common heating/electric world.

    I have 1 programmer/thermostat next to the stairs that controls hot water and heating (whole house except lounge). And another in the lounge just to control heating. I didn't replace the programmer in the lounge as I don't feel the need for it as the control/thermostat is just next to the sofa. Hence I don't consider this a bodge up. For example, if I swap a few sockets with wireless/App controlled unit that I use regularly, I won't be swapping all the sockets in the house.

    The programmer/thermostat next to the stairs has wires up to the junction box in the airing cupboard and from junction box to the hot water tank + electric valves. All I did was disconnect all of them at the junction box, replace with new wire to connect like for like to the junction box and the other end of the new cable to Heat Link which I planned to place inside the airing cupboard. If this make sense? Hence the original wires from junction box to programmer downstairs are now redundant. Since I place the Nest Thermostat replacing the existing programmer/thermostat next to the stairs, I used 2 of the 5 redundant wires to power up the Nest thermostat (12v). I took the 12v power from Heat Link, run it into the junction box, then connect it to the 2 of 5 redundant wires going downstairs.

    In summary, I now have Nest working (manually or Mobile App) to control hot water and heating for whole house, the existing controller in the lounge is still controlling the lounge heating.

    P/S - I also posted my neighbourhood Facebook page and one of my neighbour has this installed by a Pro Installer. I went over last night have a look and they have the Heat Link replaces the programmer/thermostat next to the stairs and uses the Nest stand/USB adaptor to place the Nest Thermostat on a shelf which the need to another cable from the USB adaptor. I've spoken to him and he said they weren't offered other options to hide the Heat Link in the airing cupboard.
     
    Last edited: 28 Nov 2018
  7. stem

    stem

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    You have a programmer in the lounge! Very unusual. Most people have the thermostat in the lounge and site the programmer out of sight somewhere such as in the kitchen.

    Anyway, you are happy with what you've achieved, you live there, I don't so that's fine. :)
     
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