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  1. sweet212
    Offline

    sweet212 EF Member

    Location:
    wiltshire
    Evening all,

    Visited a customer yesterday who said their lamps were blowing regularly in the living room light fitting. I took the light fitting down and visually it looks fine. Its a metal fitting with 3 arms with an SES lamp holder on each. I removed the lamps and insulation tested the fitting with 999+Mohms as the result. All good. I then turned my attention to the wiring. R1 R2 from the light point to the board was 0.62. Insulation res for the circuit was 999+Mohms L-N, L-E, N-E, (lamps removed). Zs from the light was 0.88. Supply polarity is fine and the Ze is 0.22.

    However there is a voltage of 58V showing from the SW line to earth when the switch is turned off.

    The feed has been taken to the light point in t&e and a 3core cable has been taken to the switch. This is a permanent live, neutral and SW line back to the light. A live and neutral is needed at the switch due to a t&e leaving it to feed the kitchen light switch. I disconnected the 3 core either end and insulation res tested it. Again 999+Mohms was the result. When the permanent live is connected at the light point the SW line in the cable becomes live at 58V even though is completely disconnected each end.

    I am returning tomorrow to have another look.

    Any input would be helpful.

    Regards

    James
     
  2. Leesparkykent
    Online

    Leesparkykent You Rock Gmes Staff Member Trusted Advisor

    Location:
    Kent
    Capacitive coupling.
     
    • Agree Agree x 5
  3. sweet212
    Offline

    sweet212 EF Member

    Location:
    wiltshire
    Yes that is my thinking, but Ive not seen it on this scale. It is possible though because the permanent Line and SW line are the red and yellow cables. This will be my first port of call in the morning.

    Thanks

    James
     
  4. telectrix
    Online

    telectrix Scouser and Proud of It Trusted Advisor

    Location:
    cheshire/staffordshire
    Business Name:
    Telectrix
    take an analogue meter with you.
     
    • Like Like x 1
  5. Murdoch
    Offline

    Murdoch Electrician's Arms

    Location:
    Woking
    Regular blowing of bulbs should be remedied by fitting led bulbs .... Or not buying them from cheap outlets
     
    • Agree Agree x 7
  6. wirepuller
    Offline

    wirepuller Trusted Advisor

    Location:
    south uk
    One of the most common domestic calls is 'lamps blowing all the time, must be the wiring'
    99% of the time it's rubbish lamps and can be diagnosed and advised upon without a visit.
     
    • Agree Agree x 7
  7. PEG
    Offline

    PEG Trusted Advisor

    Location:
    Manchester
    Hi James,what device was used to measure that voltage?
     
    • Agree Agree x 1
  8. davesparks
    Offline

    davesparks Trusted Advisor

    Location:
    guildford
    Why are you doing all those tests when the problem you've been asked to look at is the lamps blowing?
     
    • Agree Agree x 1
  9. Lucien Nunes
    Offline

    Lucien Nunes Mercury Arc Rectifier Trusted Advisor

    Location:
    London
    Indeed. What was the supply voltage?
     
    • Like Like x 1
  10. andyb
    Offline

    andyb Electrician's Arms

    Location:
    West Sussex
    Lamps blowing will be one of 4 things
    1, Rubbish lamps (most common reason)
    2, Poor light fitting design, not letting heat escape.
    3, High voltage.
    4, They don't keep blowing, the customer dosn't remember which lamps they change.
     
    • Like Like x 4
    • Agree Agree x 1
  11. KEV 1 N
    Online

    KEV 1 N Regular EF Member

    Location:
    Durham
    Yeah, I often get asked "why do my bulbs blow all the time?" Usually there cheap pound shop stuff or the lights are on and off a lot. Wiring shouldn't cause them to blow, although if there's a lot of vibration on the ceiling above, that may affect the life of an incandescent bulb (I mean lamp, bulbs go in the garden!)......tell them to get LED lamps..
     
    • Like Like x 1
  12. Strima
    Offline

    Strima Electrician's Arms

    Location:
    St Neots
    Bulbs grow, lamps blow...
     
    • Like Like x 1
    • Funny Funny x 1
  13. andyb
    Offline

    andyb Electrician's Arms

    Location:
    West Sussex
    • Like Like x 1
    • Agree Agree x 1
  14. anthonybragg
    Offline

    anthonybragg Electrician's Arms

    Location:
    NORTHAMPTON
    Business Name:
    CHARLTEC ELECTRICAL LTD
    I assume that the lamps are of the halogen type and therefore the SES screw cap expands and contracts with the heat generated when left on for some time. This makes a small gap between the live contact pin and poor contact reducing lamp life.
     
  15. HandySparks
    Offline

    HandySparks Trusted Advisor

    Location:
    Hampshire
    Business Name:
    Neish Electrical Services
    What do you think the mechanism would be for the reduced life under these circumstances?
     
    • Like Like x 1
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