OT : Paging the electricians

Discussion in 'UK Motorcycles' started by Steve, Feb 7, 2010.

  1. Steve

    Steve Guest

    I'm trying to fit a new ceiling light and have replaced the old wall
    dimmer switch with an on/off switch.There's only 1 switch in the room.
    At the ceiling end are 2 sets of cables that did have the Live's
    twisted together and seemed to be switched on the Neutrals.
    This doesnt work with the new light and I can't get any combination of
    wires to work.One of the Live's is permanantly live.
    I haven't a clue as to why there are 2 sets of wires apart from
    perhaps there used to be another wall switch before I moved in.
    Any ideas or should I just GAMI?

    Steve
     
    Steve, Feb 7, 2010
    #1
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  2. Did the switch work with the old light?

    If so then the connections at the light are wrong (he said, stating the
    obvious).

    From memory the way a single switch works is that you have the lighting
    ring spurred to the 'connection block' in the light. The neutral and
    earth are connected directly to the light (in as far as the earth is
    used...). The live goes to a connection block where it goes to the
    switch (so you've got the two red wires twisted together. The black
    from the switch then comes back to feed the live connection of the lamp.

    So the two sets of cables in the ceiling sound right for a single switch
    system. The live being constantly live is the cable from the ring, the
    live not live is the feed to the switch.

    You're connecting something incorrectly (again, stating the obvious) or
    maybe something is fucked.

    Stand in a bucket of water, wet your thumb and try that in the socket in
    case the bulb is fucked.
     
    stephen.packer, Feb 7, 2010
    #2
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  3. Steve

    A.Lee Guest

    The wiring sounds correct.
    It is a 'loop-in' circuit, where one side of the light fitting is always
    live, as is one side of the switch. They get swapped around over time,
    so it could be a switched live or neutral. Either way, it should still
    work.
    There will be 6 wires from 2 cables (or 4 wires if no earth) going into
    the ceiling fitting.
    One of these cables is the 'loop' which will always be live, this comes
    from your fusebox/rcd, then goes to each light fitting in turn,
    eventually returning to the fusebox. That means one side of the light
    fitting is always live, even when the switch is off. The other cable at
    the ceiling goes to the switch.
    So at the ceiling, you'll have 4 connections,- the outer ones are
    usually one wire from the loop cable, one from the switch cable, the
    light is attached to these.
    Then one of the middle connections is where the the other wires from the
    loop and switch are joined together.
    The 4th connection will be the earths joind together.

    If you have put it back as before, then the only problem will likely to
    be a poor connection, or a faulty new fitting (it happens).

    It is a really simple circuit, so shouldnt be hard to trace the fault.
    HTH
    Alan.
     
    A.Lee, Feb 7, 2010
    #3
  4. Steve

    A.Lee Guest

    This is slightly wrong after reading it again, if it is a loop-in
    circuit, there will be 3 cables at the light fitting. It makes no
    difference to you anyway, as the connections will be the same.

    Alan
     
    A.Lee, Feb 7, 2010
    #4
  5. If you smell smoke, this warning has come too late ;-)
     
    The Older Gentleman, Feb 7, 2010
    #5
  6. Steve

    Owain Guest

    Join the 2 reds together with a chocolate block

    One black to one side of the lampholder, the other black to the other
    side.(The black coming from the switch is a switched live and should
    really have a red sleeve or piece of red tape on it)

    Owain
     
    Owain, Feb 7, 2010
    #6
  7. Steve

    Pip Guest

    Switched neutral, Shirley.
     
    Pip, Feb 7, 2010
    #7
  8. No, it's a neutral-coloured wire but carrying the switched live. Often
    two/three core is used and the black/blue is the return live from the
    switch. Even if single-core is used throughout, it's not uncommon for
    some lazy **** to have used reds or blacks for everything. In such cases
    the live wires should be tagged with a red sleeve or tape.
     
    Grimly Curmudgeon, Feb 7, 2010
    #8
  9. Think it probably is a switched live. They often seem to use the normal
    T+E cable with the red picking up 'live' from the lighting ring and the
    switch then switches this to the black to provide the live to the light
    unit.
     
    stephen.packer, Feb 7, 2010
    #9
  10. Steve

    Steve Guest

    Yep - my fuckwittery strikes again.There are 2 wires in the switch and
    3 holes.
    All sorted now :)

    Steve
     
    Steve, Feb 7, 2010
    #10
  11. Excellent.

    Now look at your email (assume you still read the Elefantentreffen
    list).
     
    stephen.packer, Feb 12, 2010
    #11
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