Wiring Loop Problem

Discussion in 'Electricians' Talk' started by Choppercollins, Jun 20, 2014.

  1. Choppercollins

    Choppercollins New Member

    I have a wiring problem I hope you can figure out.

    As you can see from the picture, I'm installing a new ceiling light. Having taken off the old fitting there were two wires which suggests that its at the end of a loop.

    I have therefore continued the loop with the two live cores and fixed up the neutral to the feeder wires of the light. The earth is pretty much as standard.

    In theory, this should work however it does not.

    The light switch works ok (suggests the loop is fine) and its not tripping the fuse box. Good so far.

    The problem is when the light switch is in the off position, the bulb is still lit (albeit dimly). To me it suggests that there is maybe a problem with the ceiling rose that's allowing power to come back down the circuit (hope that makes sense). The reason for my doubt is because the circuit worked ok before I changed the light so I question why it would be different now? I tried keeping track of how the previous light was wired but it was really old, gave no clues and I had bucket loads of dust and plaster board falling in my eyes.

    Any solutions (short of getting an electrician in)?

    Wiring loop.jpg
  2. unphased

    unphased Screwfix Select

    Is one of the cpcs not connected properly? (And the cpcs should have g/y sleeving.) Looks like the one on the right is not in the terminal. Are you sure the SL and N are the correct way around?
  3. Choppercollins

    Choppercollins New Member

    Thanks Unphased - Yeah its the angle of the photo but it is connected properly. The cpc is connected properly and doesn't have any sleeving (can only assume because the wiring is donkeys years old). Even if the earth isn't connected properly, that wouldn't cause the problem i have would it?

    Are you referring to the SL & the N from the light fitting? If so i've tried reversing but makes no impact at all and i still have the same problem.
  4. Sean_ork

    Sean_ork Screwfix Select

    check how its connected within the pendant or lamp holder
  5. Jitender

    Jitender Well-Known Member

    Just an idea, have you got a standard pendant (£3) you can temporarily connect. Maybe a possible faullt with the fitting?

    The flying earth suggests that it is a metallic fitting you have?
  6. Lectrician

    Lectrician Screwfix Select

    From your desccription, it sounds like your new wire is not in the photo?

    You have a neutral and a switch live backwards, putting your new light in series with the existing when the switch is off. Both would glow dimmly, although odd results can occur with energy saving lamps.

    You need to work out for sure which of the blacks is actually your neutral.
  7. Jitender

    Jitender Well-Known Member

    I renember wiring up a light at my home once, with the same symptoms i.e dim light when switched off. The fault was it was incorrectly wired!

    Have you got a tester to verify the wires?
  8. Choppercollins

    Choppercollins New Member

    Jitender - yeah i was thinking of trying something like that however, the fact there is still (some) power when the switch is off to my mind suggests there's something wrong with the ceiling rose?
  9. FatHands

    FatHands Well-Known Member

    Is the switch an on/off type or dimmer? If the latter, it could be faulty.

    The way to clarify what is what would be to turn off the lighting circuit and test.
  10. Cheburashka

    Cheburashka Active Member

    I don't fully understand what your trying to do, it sounds like your trying to fit an additional lamp somewhere and have connected it to the permanent live and the switched live? Is this right?

    If you have connected another lamp across the live and switched live, when the switch is off this additional lamp will then become in series with the first lamp and usually the lower wattage lamp will glow dimly as the other bulb/s are acting as a resistor.
  11. Lectrician

    Lectrician Screwfix Select


    Not if you are adding an extra cable to what we see in the pic. In that case, it is a classic sw live/neutral confusion.

    Nothing to do with a faulty ceiling rose.
  12. Choppercollins

    Choppercollins New Member

    Problem (kind of) solved.

    I tested all the whole circuit and the wiring was fine. The switch live was fine also. I wasn't adding in cabling or a new light. Just simply replacing an old fitting with a new.

    It was an LED buld that gave off a residual glow when the switch was off. Having replaced it with a halogen bulb, the light would fully switch off.

    What i dont understand is why there was residual current in the circuit to allow the LED to stay dimmly lit but that problem has been bypassed. The wiring in that part of the house is quite old and short of ripping down ceilings and walls I dont intend to find out now.
  13. seneca

    seneca Screwfix Select

    Led lamps require verrry little current to make them illuminate! Most likely cause is a bit of inductive pick-up between cables.
    FatHands likes this.
  14. Rulland

    Rulland Well-Known Member

    As Seneca, It's a common problem with LED fittings.
  15. Choppercollins

    Choppercollins New Member

    I wonder how much it would cost in £+p for the 4w LED lights (5 on one fitting) to be on permanently (albeit dimmed when should be off) compared with running 5x40w halogen on for a small amount of time, say 2-3 hours a day.

    I'll get my calculator!!
  16. Caddy

    Caddy Active Member

    You can fit a Capacitor across the Live & Neutral of the fitting to stop the lamps glowing when they are off
  17. unclemonkey

    unclemonkey New Member

    yes inductance(current caused by several cables running in close proximity to each other), either have to move cables (not practical) or fit capacitor at ceiling rose.

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