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Advice replacing light switch

Discussion in 'Electrics UK' started by _tony_, 15 Aug 2019 at 8:24 AM.

  1. _tony_

    _tony_

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    Hi,

    I'm looking to replace a single dimmer light switch. When I took off the existing one the wiring looks like:

    IMG_20190811_121303.jpg IMG_20190811_121308.jpg

    I was expecting one terminal to have a brown wire and one to have a blue, but that doesn't seem to be the case. As you can see as all of the wires going in to the terminals are brown. Unfortunately I can't just mimic which wires go in to which terminals on the new one, as my current one doesn't have any labels on the terminals. How can I figure out which wires go in to the live and switch live (that's how they're labelled on my new dimmer) terminals?

    Cheers,

    Tony
     
  2. stem

    stem

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    A switch breaks the live supply to a light. So the wires in both terminals will all be lives. Sometimes an installer will use a cable that has blue and brown wires, and there is nothing wrong with this. However as the blue wire is not being used as a neutral and it should be identified as a live by having a brown sleeve on it.

    In your case, the wires are brown to start with, so even better. One terminal will be for the permanent live supply and the other the switched live to the light. With some dimmers it doesn't matter way way around the wires go, but if yours does, testing them with a multimeter will enable you to identify which is which. However, the two wires in the same terminal will need to stay connected together.

    You can find an explanation of lighting circuits in the wicki here.

    Before fitting the dimmer you should make sure that the lights you have are suitable for operation with it, and there seems to be a loose earth wire that I suspect has come from the metal back box, and if so should be reattached.
     
  3. bernardgreen

    bernardgreen

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    The Live and Neutrals supplies from the CU are looped from room to room ( switch to switch ) at the switches and not ( as in most houses ) at the ceiling rose.

    Ensure you mark the Switch Live brown wire so you know which is the Switched Live when fitting the new switch,

    The Switched Live wire goes to Switched Live on the new switch
    The other two Brown wires gor to the Live terminal on the new switch

    upload_2019-8-15_8-40-23.png
     
  4. _tony_

    _tony_

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    Thanks for the advice and for getting back to me so quickly!
     
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