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Electric Shock from Old P.I.R. Floodlight.

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Today I was asked to investigate why an old outside P.I.R. tungsten halogen floodlight did not work. It had been installed on a 70s holiday chalet. The owner had installed it himself and admitted that he did not know much about electrics. I used my aluminium ladder to access it, the ladder has plastic feet and it stood on a concrete surface. When I went up to the floodlight my Voltstick suggested that the supply cable was dead. But when I touched the fitting I got a shock, this before I had removed the terminal box  cover. Anyway, after turning off at the consumer unit I noticed that the owner had fitted the live supply wire into the earth terminal. That was the cause of the shock I imagined. Anyway I removed the old floodlight and was going to fit a new L.E.D. one. I tested at the supply cable but there was no supply. All M.C.B.s were on and the R.C.D. was on as well. So how did I get a shock if the supply cable was dead? A charged capacitor perhaps? Or induced Voltage? No switch was found that controlled this cable.


I got a reading of about 2 Volts from the main P.M.E. earth terminal and a temporary earth rod bashed into the lawn.


There are three 11kV overheads about 30 metres away from this chalet.


Any ideas please?


Z.
  • 0
    How many times over the years have you found a fluorescent light batten fitting with the choc block terminals held in place by the central connection being made onto a tab of the steel enclosure to hold it in place and provide an earth terminal with this terminal actually having been used as a live terminal for the circuit conductors?


    I have found that arrangement many times, well into double figures.


    These days I use a fibreglass ladder, but when I did or if I do use an aluminium ladder I use a two pole voltage tester between the fitting and the ladder.


    One particular occasion comes to mind, a damp evening as it was getting dark, I put an aluminium ladder up the wall and tested between it and a light fitting that was not working,the tester showed full mains voltage and I packed up and went home saying I will come back in day light when it’s not raining.


    Those bits of plastic on the ends of a ladder are not electrical insulators and should not be considered as such.


    Andy Betteridge
  • 0
    How can a lamp work if live wiring is connected to the earth terminal? I presume you mean it's used to park the incoming live and the choke input otherwise can't see how it would light up.
  • 0
    Kelly, I have seen the central terminal of a 3 terminal block in a fluorescent batten fitting used as a loop in Line as in a ceiling rose. As the central terminal is connected to the metal fitting's body the whole fitting sits there live if not earthed correctly. So a person touching it may get a bad shock. The fitting works correctly as the switched line and neutral are correctly connected. As the fitting is normally secured to a wooden or plasterboard ceiling there is no earth return so the protective device(s) do not operate. A typical D.I.Yers bodge.


    Z.
  • 0
    I have come to the conclusion Watson, that the chalet owners fitted a hidden supply switch and deliberately wired the Live to the earth terminal in the metal floodlight to do away with me. This is the only plausible explanation. They turned on the supply as I went up the ladder. When they heard me cry out they concluded that I had fallen from the ladder, but when I entered the chalet and saw me still alive and unhurt, they immediately turned off the hidden switch. There can be no other explanation. None at all. I expect that after my demise they would have sold my vehicle and tools at Camden Market.


    "When you have eliminated the impossible, whatever remains, however improbable must be the truth".


    Z.
  • 0
    How have you eliminated the possibility of the flood light being fed from a forgotten RCD fused connection unit tucked away in a corner somewhere - which then tripped automatically when you received your shock?

       - Andy.

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