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Replacing Drayton LP241 band thermostate with Gen 3 nest

Discussion in 'Plumbing and Central Heating' started by ZeroNero, 25 Jan 2020.

  1. ZeroNero

    ZeroNero

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    Hello people

    I am taking on replacing my Brother in-laws LP241 with a gen 3 Nest and have a couple of questions I hope someone can assist with.

    I am comfortable with the wiring I need to do replacing the drayton programmer with the nest unit, but just for confirmation;

    N - N
    L - L
    Drayton 1 - Nest 4
    Drayton 2 - Nest 1
    Drayton 3 - Nest 6
    Drayton 4 - Nest 3
    bridging Nest L - 2 & 2- 5

    The area I have questions about is the thermostat. I need to remove the existing and replace with the nest as the kit does not have the table stand or the power cable, so I need to feed it from the cables in the wall.
    The wires from the thermostat go upstairs to the junction box, which is located in the same cupboard as the hot water tank and I will not have a wire long enough to bell out the cable end to end. As you can see from the picture, the original installer has gone off reservation, I have a strong suspicion that the thermostat wires, red, yellow and blue are coming in second from left and terminating in 8 & 13. I plan to check the switched live (yellow?) by having the heating on, thermostat turned down/off which should show zero volts and then turning on the thermostat which should then liven up terminal 8. For the red wire in terminal 13, I was going to check live with the drayton unit on which would show live and then turn off the drayton unit and this terminal should go dead, will this work to properly identify the cables??

    Once properly identified and considering I need a power supply to the nest thermostat, I was going to remove and cap off the yellow wire, leave the blue neutral in place, move the white cable in 8 - 13. The issue I have is I am not sure where the red wire goes as I need this for a permanent live to the nest thermostat, can it stay where it is as it will be live whenever the nest wall unit is live??

    Any help would be greatly appreciated, thanks in advance
     
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  3. ZeroNero

    ZeroNero

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  4. ianmcd

    ianmcd

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    NO NO NO dont do that or you will blow the thermostat, the thermostat power comes from T1 & T2 from the nest heat link, it is a 12V supply , DO NOT put live and neutral to the thermostat
     
  5. ZeroNero

    ZeroNero

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    Thanks Ian

    Realised that when I took everything out of the box and realised it needed a 12v supply, lucky escape

    Got much bigger problems, the power wires that feed the drayton/nest control unit are completely dead, all of the circuit breakers are back in and absolutely no power.
     
  6. ianmcd

    ianmcd

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    which boiler do you have
     
  7. ZeroNero

    ZeroNero

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    The boiler is a glow worm ultimate 60FF
     
  8. ZeroNero

    ZeroNero

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    To get it all working I've had to force a feed in from a cable plugged into a nearby socket
     
  9. The Novice

    The Novice

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    The boiler or the Drayton?
     
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  11. ZeroNero

    ZeroNero

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    I have the nest wired up, but to get it powered I have had to force a power feed in from a cable plugged into a 3 pin socket.
    All the circuit breakers are in and the power cables in the wall are dead. Will have to get a sparks in as my skills are challenged with this one
     
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  12. The Novice

    The Novice

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    Have you tested the wires? Did the Drayton work?
     
  13. ZeroNero

    ZeroNero

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    My multi meter went pop when I was testing the old thermostat wires earlier
    I can pretty much guarantee that they are dead as the nest did not power up with just the power wires coming from the wall and it does if I power it from a plug socket.
    Strangely the Drayton did, is it possible for it to function from the battery back up?
     
  14. The Novice

    The Novice

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    I wouldn’t have thought so, it might be that you blew the 3a fuse.
     
  15. ianmcd

    ianmcd

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    You can not leave it like that, you have popped the fuse on the fused spur, it is 3 Amp do not put a 13 Amp in there, reading your posts you really should get someone that knows what they are doing
     
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  16. ZeroNero

    ZeroNero

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    You are a legend, the fused switch for the boiler is probably powering the controller too. Will change the fuse out and see
     
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  17. ZeroNero

    ZeroNero

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    Have no intention of leaving it like that, was just to test the nest was working as I couldn't test the cables, due to my multimeter packing up earlier
     
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