A Shocking Experience

Discussion in 'Hobby Electronics' started by fritz, Feb 20, 2011.

  1. fritz

    fritz Guest

    Several years ago I came close to getting electrocuted in the shower.
    While having a shower I noticed a strongle tingle when I touched the
    taps, so I checked with a DMM and found there was AC between the
    taps, showerhead etc and the wet floor. Strange, so we called in an
    electrician to check what was going on. Turned out the shower floor
    had a metal tub underneath - looked like lead - which extended up into
    the wall cavity. On the other side of one wall was the kitchen with
    a GPO near floor level for the fridge. The wiring was the old rubber
    insulated type which had gone brittle - and the edge of the tub was
    scraping the active ! So the wet shower floor was only insulated
    from the mains by the deteriorating rubber. The Sparky replaced the
    GPO wiring with TPS, bent the metal away from the GPO and said
    we were lucky the fault only showed a high resistance and the metal
    hadn't gone in another mm.
     
    fritz, Feb 20, 2011
    #1
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  2. fritz

    Sylvia Else Guest

    On 20/02/2011 9:09 PM, fritz wrote:
    >
    > Several years ago I came close to getting electrocuted in the shower.
    > While having a shower I noticed a strongle tingle when I touched the
    > taps, so I checked with a DMM and found there was AC between the
    > taps, showerhead etc and the wet floor. Strange, so we called in an
    > electrician to check what was going on. Turned out the shower floor
    > had a metal tub underneath - looked like lead - which extended up into
    > the wall cavity. On the other side of one wall was the kitchen with
    > a GPO near floor level for the fridge. The wiring was the old rubber
    > insulated type which had gone brittle - and the edge of the tub was
    > scraping the active ! So the wet shower floor was only insulated
    > from the mains by the deteriorating rubber. The Sparky replaced the
    > GPO wiring with TPS, bent the metal away from the GPO and said
    > we were lucky the fault only showed a high resistance and the metal
    > hadn't gone in another mm.
    >


    Many years ago I discovered that all the TV antenna sockets in a French
    apartment block were live. I told the manager, who called in an
    electrician who clearly didn't believe it and was muttering about small
    current leaks. It was definitely a case of "Pardon my French" when he
    realised that I was right. I knew I was - you can't normally illuminate
    an mains incandecent lamp by connecting it between an antenna socket and
    a hotwater radiator (hey - free power!).

    Turned out someone had put a screw into their wall, and it had
    penetrated a power cable and the antenna cable, but somehow managed to
    avoid shorting anything.

    I performed the experiment with the lamp because I'd been getting
    tingles from connections to a computer that was also connected to the
    TV. I had likely touched a live mains connection multiple times while
    myself being insufficient earthed for it to kill me.

    Sylvia.
     
    Sylvia Else, Feb 24, 2011
    #2
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  3. fritz

    keithr Guest

    Re: A Shocking Experience: bit OT

    On 24/02/2011 11:05 PM, Bruce Varley wrote:
    > "fritz"<> wrote in message
    > news:ijqp8c$ate$02$-online.com...
    >>
    >> Several years ago I came close to getting electrocuted in the shower.
    >> While having a shower I noticed a strongle tingle when I touched the
    >> taps, so I checked with a DMM and found there was AC between the
    >> taps, showerhead etc and the wet floor. Strange, so we called in an
    >> electrician to check what was going on. Turned out the shower floor
    >> had a metal tub underneath - looked like lead - which extended up into
    >> the wall cavity. On the other side of one wall was the kitchen with
    >> a GPO near floor level for the fridge. The wiring was the old rubber
    >> insulated type which had gone brittle - and the edge of the tub was
    >> scraping the active ! So the wet shower floor was only insulated
    >> from the mains by the deteriorating rubber. The Sparky replaced the
    >> GPO wiring with TPS, bent the metal away from the GPO and said
    >> we were lucky the fault only showed a high resistance and the metal
    >> hadn't gone in another mm.
    >>

    > I still get the shivers about this one, although it occurred many years ago.
    >
    > I was working with an American engineer on a plantsite in a country where
    > electrical licences hadn't been heard of at the time, we were commissioning
    > 440 volt drives in a sub. You check the wiring and insulation, do a dry
    > start with the main fuses out, then when it all looks OK, you ram the fuses
    > into the stabs and check the motor direction. I was working at one end of
    > the sub, and when I looked, my colleague was sitting on the floor looking
    > very shocked, although he was physically OK.
    >
    > What this guy was doing to save time was to defeat the door interlock by
    > pushing a welding rod into a little hole, so that he could open the door
    > with the isolator closed. in that condition the top fuse stab would have
    > been live at 440, right in front of his eyes. That way, he could do some
    > checks quickly. The plan was then to close the door, open the isolator,
    > reopen the door and insert the fuses.
    >
    > The guy had shoved the fuses into the stabs *with the isolator closed*. The
    > drives were in the 100 KW range, so the fuses were about the sizes of a milk
    > carton, with a ceramic body and metal ends that fitted the stabs. 3 times,
    > he did it without his hands touching the metal at the ends!!!
    >
    > I bet that's something he'll never forget.
    >
    >

    I knew a guy who tried the same idea with the interlocks on a 5MW peak
    primary radar modulator cabinet. The EHT supply was several hundred KV
    which arced over to the steel rule that he was carrying in the leg
    pocket of his overalls. They did manage to save his leg, but he never
    walked the same way again.
     
    keithr, Feb 24, 2011
    #3
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