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Help replacing old thermostat with new

Discussion in 'Electrics UK' started by Noisy76, 4 Oct 2020.

  1. Noisy76

    Noisy76

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    Hi, I have a new thermostat for our central heating which I'd like to install, however I'd like some guidance on wiring it in.

    I have some experience in electrical work, and have taken precautions to isolate the wiring, and checked with my multimeter, so everything is safe to work with.

    IMG_20201004_133515.jpg

    This is the old thermostat and wiring.

    IMG_20201004_133614.jpg

    This is the new one, and instructions. I assume the existing live and neutral go to pins 7 and 8 as shown, but then does the control wire go to one of 3 and 4?

    Thanks for your time.
     
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  3. 333rocky333

    333rocky333

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    i woild say yellow goes to 6, but wait for a second opinion
    To use 3/4 you would need to link one of them to 7
     
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  4. EFLImpudence

    EFLImpudence

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    Yes.

    No, it goes to 6
     
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  5. Noisy76

    Noisy76

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    Thanks. I had assumed 5 and 6 were for hot water systems as it says on the top of the page "Wiring Diagram Water"
     
  6. EFLImpudence

    EFLImpudence

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    It's just a switch. The other diagram just says 'boiler'.
    There are no water connections on the old thermostat. Do you have a combi boiler?

    Do you mean that the new thermostat has separate settings for hot water and central heating?

    If so, then you can use 4 for Yellow but you will need a link wire from L to 3.
     
  7. EFLImpudence

    EFLImpudence

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    I think the 'water' reference is a confusion.

    This is what you should be looking at:

    upload_2020-10-4_19-41-37.png

    You don't need 8 for the Neutral to the valve.
     
  8. EFLImpudence

    EFLImpudence

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    Rocky seems to be beating me to it. I didn't see your replies.

    Sorry Rocky.
     
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  10. Noisy76

    Noisy76

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    Thanks. so just to clarify, Live and Neutral to 7 and 8, and control (yellow wire to 6)? I'm a bit confused now!
     

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  11. EFLImpudence

    EFLImpudence

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    Yes.

    It just sends 240V to the boiler as did your old thermostat.

    3 & 4 would be used for 12V or 24V boilers.

    If you have a combi boiler you won't have a valve. As I said the instructions are confusing.
     
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  12. 333rocky333

    333rocky333

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    I wasnt too sure, maybe a picture of the front may help

    Is it one of these
    [​IMG]
     
  13. Noisy76

    Noisy76

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    Yes
     
  14. Noisy76

    Noisy76

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    Thanks all, it's working perfectly
     
  15. EFLImpudence

    EFLImpudence

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