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Lightswitch with just 2 red wires?

Discussion in 'Electrics UK' started by Jonathandelorean, 10 Apr 2021.

  1. Jonathandelorean

    Jonathandelorean

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    I'm looking to swap my single lightswitch over to a dimmer, but after opening it up I see there's just 2 red wires. There is an earth which is connected to a screw in the back box but that's it.

    One of the red wires is connected to a terminal labelled "Top" and the other is connected to an unlabelled terminal.

    I was expecting to see a neutral wire as the other switches I've changed all have neutrals. The new dimmer has 3 terminals (L1, L2 and Com).

    Just wondering which way to wire this up?
     
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  3. AndyPRK

    AndyPRK

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    Use com

    And one of the L terminals.
     
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  4. flameport

    flameport

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    Unlikely, switches do not generally have neutral terminals.
    Black wires are not necessarily neutral either.
     
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  5. Jonathandelorean

    Jonathandelorean

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    Aah ok I had assumed the black wires in the other switches were neutral
     
  6. Jonathandelorean

    Jonathandelorean

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    That's great, thank you - does it matter which of the red wires I use in which terminal? There's no visual way of differentiating between them.
     
  7. EFLImpudence

    EFLImpudence

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    I shall use my new graphic.

    upload_2021-4-10_18-58-20.png
     
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  8. AndyPRK

    AndyPRK

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    No.

    You could put Top into Com though.

    If the switch works backwards you need to use the other L terminal
     
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  9. EFLImpudence

    EFLImpudence

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    No, it doesn't matter.
     
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  11. Jonathandelorean

    Jonathandelorean

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    Thanks for the responses folks!
     
  12. Sureitsoff?

    Sureitsoff?

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    or turn the switch upside down!
     
  13. AndyPRK

    AndyPRK

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    It's a dimmer
     
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  14. securespark

    securespark

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    When you think about that statement, if it were true, the switch would be connecting the live wire directly to the neutral wire every time you closed it.

    What would happen then?
     
  15. Jonathandelorean

    Jonathandelorean

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    Ah.. actually that's a good point... :oops:

    I've always just changed switches on autopilot and never really paused to think much about it. I feel a bit silly now!!!
     
  16. securespark

    securespark

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    :)

    No need. It's a common misunderstanding.
     
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