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Discuss Strange Earth Leakage Trips in the Electrical Forum area at ElectrciansForums.co.uk.

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  1. Mick Sulley
    Offline

    Mick Sulley New EF Member

    Location:
    Melton Mowbray
    I have an odd situation in that I get random earth leakage trips which happen occasionally when I turn off an outside light. I have a standard split board, half earth leakage protected, half not. Trips happen maybe once every 50 times that outside light is switched off, never when it is switched on and never when anything else is turned on or off.

    I really don't understand how tuurning something off can cause a trip, can anyone explain how this can happen and what I can do to fix it.

    Thanks
    Mick
     
  2. 123
    Offline

    123 Electrician's Arms

    Is it a Double Pole switch or Fused Spur that controls this outside light by any chance?
     
    • Like Like x 2
  3. dmxtothemax
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    dmxtothemax Regular EF Member

    Location:
    Australia
    Business Name:
    David Haddock Electronic Repairs
    QUOTE - [ I really don't understand how tuurning something off can cause a trip, can anyone explain how this can happen and what I can do to fix it. ]
    Technical term for it is "back EMF".
    When ever you turn off a reactive load
    then a voltage spike is generated by collapsing magnetic field in the smps ( in this case ) which can cause problems.
    Some form of filter will usually fix it,
    Try some clip on ferrite cores.
     
  4. snowhead
    Online

    snowhead Respected Member

    Location:
    Mildlands
    What sort of light is it;

    LED?
    Halogen, open or glass covered?
    Tungston lamp?
    How old is it?

    Depeneding on what type it is , have you looked inside the light is there any condensation?
     
  5. Mick Sulley
    Offline

    Mick Sulley New EF Member

    Location:
    Melton Mowbray
    Thanks for the replies.
    It is a standard single pole light switch, SWA cable to 3 light fittings each with a 21 watt 2D folded florescent lamp.
    Ferrite cores
    - Where should I fit them, at the switch or at each light, does it matter?
    - Does it matter what size?
    - On live, neutral or both?
     
  6. marconi
    Offline

    marconi Respected Member

    Try changing the switch first for a new one with a quick click on or off action.

    Some pictures of behind the switch and of how the SWA is terminated at its beginning, the 3 outside lights and end would be useful.

    Are the fittings of the correct IP and do they require and earth or not?
     
  7. Lucien Nunes
    Offline

    Lucien Nunes Mercury Arc Rectifier Respected Member

    Location:
    London
    Do the fittings have wirewound (magnetic) ballasts or electronic? If wirewound, what I suspect is happening is that the insulation is low somewhere, and the back-EMF mentioned above is causing it to break down to earth when current flowing through the inductance of the ballast is interrupted. The voltage rises almost instantaneously until an arc occurs at the switch, but if the insulation is low due to moisture, it might result in a brief spike of leakage.

    If the insulation is good and the fittings sound, try fitting a snubber network (capacitor and resistor in series) across the fitting nearest the supply end of the cable
     
    • Informative Informative x 1
  8. Mick Sulley
    Offline

    Mick Sulley New EF Member

    Location:
    Melton Mowbray
    Thanks for the reply Lucien Nunes, can you give me a bit more info on the snubber network? What value and type capacitor? What value resistor?
     
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