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I need some advice on installing a 3rd generation nest

Discussion in 'Plumbing and Central Heating' started by NGreen18wood, 7 Jan 2017.

  1. NGreen18wood

    NGreen18wood

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    I have a grasslin tower chron QE2 and a mechanical Honeywell thermostat. Is it easy to fit the nest

    upload_2017-1-7_19-0-8.png

    upload_2017-1-7_19-0-30.png
     
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  3. Dan Robinson

    Dan Robinson

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    FFS.
     
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  4. NGreen18wood

    NGreen18wood

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    Any help would be appreciated.
     
  5. jackthom

    jackthom

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    Should be ok with a Nest but need a bit more info about the system.
    Is there a 3 port valve ( looks likely from the wiring ) and do you have a room thermostat?
    Some pictures of the room thermostat wiring and the internals of the main wiring centre would be useful.
     
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  6. muggles

    muggles

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  7. Davidl66

    Davidl66

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    Remove wires from timer .
    Live goes to live neutral goes to neutral
    From live link to 2 and 5
    Then from old timer put 4 of old timer into 3 of nest =ch on.
    Then 3 of old timer into 6 of nest =Dhw on
    Then 1 of old timer to 4 of nest = Dhw off.
    Remove wired room stat and connect common and sl together = 1 &3 .
    Then you can have the nest as a wireless set up only .
    Wired set up is more complicated . To do by yourself
     
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  8. TheKeymeister

    TheKeymeister

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    As above for the wiring

    Only problem I had was it all ran back to a junction box by the hot water cylinder and it took a bit of testing with a multimeter to work out where the room stat was wired in to bypass it, nothing in my system followed any y plan diagram I could find online pin or colour wise, but I got there in the end.

    Also the terminals on the Nest heat link are very small so it can be a bit fun trying to loop between the live to the two commons. I ended up using crimped on ferrules to get around this as I had the kit lying around.
     
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  9. NGreen18wood

    NGreen18wood

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    Thank you for your help. I have been busy on another project

    The part I didn't understand was this
    Remove wired room stat and connect common and sl together = 1 &3 .

    Also I was asked to include the wiring for the main box and the thermostat

    Your help is appreciated
     

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  11. TheKeymeister

    TheKeymeister

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    Disconnect the room stat, it looks like its the grey wire in pin 10 and one of the browns in pin 9

    Move the white wire to the 3 port valve to pin 9

    Room stat is then bypassed

    You will also want to remove the neutral and earth going to the old room stat as well. Follow the brown and grey wires back and you'll be able to find which black and green/yellow one it is. Once finished tape it up or cut it off so it can't touch anything and become live.

    You could use those wires to power the Nest stat if you're putting it in the same place as your wired stat, and you have two spare cores between the heat link and the wiring centre, I didn't, so I've just got my Nest stat plugged in.
     
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  12. NGreen18wood

    NGreen18wood

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    I have posted some photos on line. I am going to fit it on Saturday
     
  13. NGreen18wood

    NGreen18wood

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    Thank you I am going to fit it on Saturday
     
  14. NGreen18wood

    NGreen18wood

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    Thank you for your help!! Nest is working!!
     
  15. NGreen18wood

    NGreen18wood

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    I thought the working was working but it isn't unfortunately. I can only get heating and hot water when the nest isn't connected. Any suggestions???
     
  16. Echo the husky

    Echo the husky

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    Photos of the wiring please!
     
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  17. NGreen18wood

    NGreen18wood

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    All sorted now
     
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