A Shocking Experience

[fritz]

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.

 

[Sylvia Else]

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.

 

[Bruce Varley]

"fritz" <yaputya@microsoft.com> wrote in message
news:ijqp8c$ate$02$2@news.t-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.

 

[kreed]

On Feb 20, 8:09 pm, "fritz" <yapu...@microsoft.com> 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.

I remember when I was young, some guys in a grocery store trying to
move a display refrigerator that would have been about
10' long, and 4' H x W. At one point one guy collapsed on the floor

Turned out that he had dropped it onto/ran over a live power cable,
and he got a massive shock as he was still firmly holding onto the
metal unit from moving it.

I presume now that it was turned off and unplugged (therefore no earth
to it) and must had cut a live cable that was feeding something else .
They got everyone out, an ambulance came, we heard the next day that
he didn't make it. The floor was likely damp and this didn't help
either.



Just because something is unplugged, doesn't mean that it is totally
safe, as if metal it may touch other live things.

 

[keithr]

On 24/02/2011 11:05 PM, Bruce Varley wrote:

"fritz"<yaputya@microsoft.com> wrote in message
news:ijqp8c$ate$02$2@news.t-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.