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light switch

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  • 12-03-2007 11:29am
    #1
    underpants
    Registered Users Posts: 213 ✭✭


    so the dimmer switch for the living room broke and I went to replace it but it looked like it was wired up using only the brown (live) cables.

    When I took off the switch what I found was 3 brown cables connected to the light switch, 3 blue cables all connected together in to a piece of plastic and not being used, and 3 green/yellow cables also connected into a small piece of plastic and not being used.
    The light did work before so I'd presume this was right.

    But before I opened it I expected to find one earth, one live and one neutral cable. not three of each. Why would there be three of each??
    Then I thought I'd have to connect a live cable and neutral cable to the light switch to make a circuit???!

    So what should I do??
    I'm thinking that I should just use one neutral cable and one of the live cables and connected those the the light switch and just ignore everything else and hope nothing blows up.
    Does anyone actually know anything about electricity and can help cause as you've probably already guessed.... I have no idea!


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    #2
    ifah
    Registered Users Posts: 576 ✭✭✭ifah


    the electrician who wired your house probably use T+E and looped them through the switch box instead of bringing individual live feeds down to each switch - just wire the new switch back the same way as the old one. - Leave the Neutral and earth alone. The circuit (live to neutral will be managed at the ceiling rose) will short if you connect neutral through the switch.


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    #3
    underpants
    Registered Users Posts: 213 ✭✭underpants


    ifah wrote:
    the electrician who wired your house probably use T+E and looped them through the switch box instead of bringing individual live feeds down to each switch - just wire the new switch back the same way as the old one. - Leave the Neutral and earth alone. The circuit (live to neutral will be managed at the ceiling rose) will short if you connect neutral through the switch.

    ok, so I should only use the live wires. Then the next problem is that the old light switch had 3 connections for wires where as the new one only has 2.
    But there are 3 live wires....
    So can I just use any 2 of the 3 live wires? And then just leave the 3rd wire unnconnected? or should I put two live wires into one connection and the 3rd wire into the second connection? so that all wires are used.


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    #4
    eoghan.geraghty
    Registered Users Posts: 419 ✭✭eoghan.geraghty


    As ifah said, leave the blues (neutral) and green/yellow (earth) alone.
    The 3 browns (lives) are: live supply,live loop to next switch,switch wire to light.
    Have a phase tester ready and know how to use it. Any diy shop should have one for about 4 euro.
    Turn off the power to the circuit with the MCB ( fuse).
    Seperate the 3 browns, turn on power, with a phase tester you can determine which brown is live supply. It will be the only on which lights up the tester.
    Turn off the power.
    Join the live supply to either of the remaining browns.
    Turn on the power.
    If living room light turns on, this 2nd brown is the switch wire and should go into the L1 terminal.
    If not this brown is the loop supply to next switch and should go into the Com terminal along with the live supply.
    Turn off the power again and finish connecting the switch.
    If you are still unsure after reading this or are not confident working with live electricity you should ring an electrician.


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    #5
    underpants
    Registered Users Posts: 213 ✭✭underpants


    eoghan.geraghty wrote:
    As ifah said, leave the blues (neutral) and green/yellow (earth) alone.
    The 3 browns (lives) are: live supply,live loop to next switch,switch wire to light.
    Have a phase tester ready and know how to use it. Any diy shop should have one for about 4 euro.
    Turn off the power to the circuit with the MCB ( fuse).
    Seperate the 3 browns, turn on power, with a phase tester you can determine which brown is live supply. It will be the only on which lights up the tester.
    Turn off the power.
    Join the live supply to either of the remaining browns.
    Turn on the power.
    If living room light turns on, this 2nd brown is the switch wire and should go into the L1 terminal.
    If not this brown is the loop supply to next switch and should go into the Com terminal along with the live supply.
    Turn off the power again and finish connecting the switch.
    If you are still unsure after reading this or are not confident working with live electricity you should ring an electrician.


    Great, that seems simple enough. I've never heard about this type of wiring before. Seems a bit complicated for no reason. But your post seems to explain everything clearly so I'll give that a go.
    Thanks for your help!


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