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Honeywell sundial rf2 to nest v3.

Discussion in 'Plumbing and Central Heating' started by Craig Hayes, 15 Oct 2021.

  1. Craig Hayes

    Craig Hayes

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    Hello,

    Im in the process of replacing honeywell sundial rf2 (DT92E & ST429C ) to Nest V3 S Plan.

    Ive successful ( i think) wired up the nest link correctly.
    N to N
    L to L
    Jumper from live to 2 then 2 to 5
    Heating into 3
    Water into 6
    E to E


    The nest thermostat is up and running looking nice and pretty but......
    When i call for heat, my worcester bosch fires up, the temp goes up a 5 to 10 degrees, then the heat stops and drops but the boiler still keeps running / blue light of the worcester bosch stays on.
    The app and thermostat turn the boiler on and off, but as before no heat.

    Same with the water.

    I looked at the wiring diagram and numerous pics on this site but, i just cant figure out what's wrong. Ive trawled this site to no gain.

    Any thoughts or advice would be greatly appreciated. If you require further pics or info please let me know.

    Regards

    Craig
     

    Attached Files:

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  3. Craig Hayes

    Craig Hayes

    Joined:
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    Hello,

    Im in the process of replacing honeywell sundial rf2 (DT92E & ST429C ) to Nest V3 S Plan.

    Ive successful ( i think) wired up the nest link correctly.
    N to N
    L to L
    Jumper from live to 2 then 2 to 5
    Heating into 3
    Water into 6
    E to E


    The nest thermostat is up and running looking nice and pretty but......
    When i call for heat, my worcester bosch fires up, the temp goes up a 5 to 10 degrees, then the heat stops and drops but the boiler still keeps running / blue light of the worcester bosch stays on.
    The app and thermostat turn the boiler on and off, but as before no heat.

    Same with the water.

    I looked at the wiring diagram and numerous pics on this site but, i just cant figure out what's wrong. Ive trawled this site to no gain.

    Any thoughts or advice would be greatly appreciated. If you require further pics or info please let me know.

    Regards

    Craig
     

    Attached Files:

  4. Agile

    Agile

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    Presumably the boiler temperature knob is turned up to a typical position? Usually about 2/3 of maximum.
     
  5. Craig Hayes

    Craig Hayes

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    Hello, its set at 70 deg.
     
  6. CBW

    CBW

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    Have you decommissioned the previous thermostat and receiver? You don’t show the Nest wiring? How is the Nest powered?
     
    Last edited: 17 Oct 2021
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  8. Craig Hayes

    Craig Hayes

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    Hello,
    Yes ive decommissioned the old planner and stat.
    Tried to show the wiring best as possible.
    As before ive gone
    N to N
    L to L then jumper to 2 then 5
    Ch in 3
    Hw in 6
    Regards
     

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  9. ianmcd

    ianmcd

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    did you link the L & SL on the old stat wiring ?
     
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  10. Craig Hayes

    Craig Hayes

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    I havent altered anything. Basically ive removed the programmer and then wired up the nest link with the wires removed from the programmer. Sorry and ive used jumper wires on the link.
    Regards
     
  11. ianmcd

    ianmcd

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    but if you have an old existing thermostat, you will have to turn it fully up or link the two switching wires
     
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