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Thread: 3rd Gen Uk spec nest install help and advice much appreciated

  1. #1
    Junior Member

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    3rd Gen Uk spec nest install help and advice much appreciated

    Hi, New to all things thermostats but happy to take on a DIY challenge, but within the constraints of my ability, hence the request for guidance.

    I have the 3rd generation uk Nest that I wish to install. The wiring I am seeing is nothing that was expected. Pics below.

    I have a timer for the CH and hot water - even though the HW is via a combi boiler.

    There is a dial Thermostat next to the timer/controller

    The timer/controller has one twin and earth to it from the boiler with one wire direct to the HW connector and the other via the thermostat to the CH connector (I see the thermostat as being a temp switch to the controller.)

    So the controller has live and neutral to it for power then two wires from the boiler to HW and CH. The two wires from the boiler are not carrying mains current so i am assuming they are switch wires being made by the timer controller?

    Thats where I have got to ..... it could be I need the help of a professional - please say so but if there is an obvious connection(s) to the Nest wireless controller then I'm happy to receive suggestions. I am ok to leave the timer controller in situ with it on for both hot water and CH and passing whatever switching wires is needs to the Nest wireless controller. I know I will need to give the Nest wireless controller 240v.

    Any advice/guidance?Click image for larger version. 

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    Last edited by Yellownev; 04-20-2017 at 05:48 AM.

  2. #2
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    It is a simple configuration if you remove both the programmer and the thermostat. Just a bunch of wires to sort out.
    I adapted the drawing from the installation manual to reflect your system.
    Click image for larger version. 

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  3. #3
    Junior Member

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    Quote Originally Posted by Stuff View Post
    It is a simple configuration if you remove both the programmer and the thermostat. Just a bunch of wires to sort out.
    I adapted the drawing from the installation manual to reflect your system.
    Click image for larger version. 

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    Many thanks my friend for being so helpful. I used this schematic and have got the system live. Not 100% sure on the hot water as it is a combi boiler and last night it seemed to be working ok but this morning no hot water unless I hit the button on the nest wireless unit to manually overide ?

  4. #4
    Junior Member

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    Since you were able to override that means the wiring and hardware should be good. Either the schedule is not set or the thermostat does not know the correct time. Since it gets the time via wifi did you get that set up? Otherwise give Nest a ring.

    Take a look at https://nest.com/uk/support/article/...-water-control as "By default the 3rd-gen Nest Learning Thermostat will heat your hot water from 06:00 to 08:00, and from 16:00 to 22:00."





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