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GANAPATHI RAO
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 Posted: Wed Apr 27, 2011 8:20 am Post subject: NEED OF LABLES AND COLOUR CODES |
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| Justmanuals wrote: | | sflsan wrote: | First off, how am I going to die?
And second off, who ever said I wasn't going to label it? |
Well, how about if you're out sick one day and some unsuspecting geek comes along and uses it? |
First off and Second off please read the following lines:
EARTHING SAVES EARTHLINGS!
On a sunday afternoon I got a call from my friend asking if
one gets shock if one touches the ground pin on 3 Pin Plug
of a power cord which is connected to a printer. Without
giving any room for analysis I said it is preposterous! But
when he said his employee got a nearly fatal shock I immediately
rushed to his shop, where he showed me the damaged equipment
which had fallen out of the table when the employee tried
retreiving his hand when he experienced the shock. He
supposed to have fallen on the floor pulling down the printer
along. Somehow I got scared before touching any of the equip-
ment and asked if he has a line tester and as expected he did
not have one. At that moment I saw a pendant holder with a
bulb hanging from false ceiling. I took out that to test the
earthing. As a standard procedure I did lamp test between
Neutral-Ground and Phase-Ground. Alas! Bulb did not glow in
both cases. Now was a testing time for me. I want to find
out the correct limbs, Phase & Neutral without taking a risking
of touching and went out to shop for a line tester, on return
I thought of taking a coffee break and over the coffee I pondered
about the situation. Yes! there was lightning bolt of realisation.
The problem boiled down to: The printer was connected with a
power cord and the printer inturn connected to a DTP PC which
was switched off. Why the boy should get such a shock? Yes!
The PC though not switched is plugged into the wall socket which
has faulty earthing (later on found to be Phase), and as with SMPS
signal ground and power ground are shorted and when the machines
are interconnected the faulty current of one m/c flows into the
other. Hence whatever the boy considered as earth pin turned out
to be having Phase. But I wondered who would carry out such
dangerous and careless wiring. Anyway I went back to the shop
with line tester, located phase pin. Now I took the test lamp
and connected between the phase and ground the lamp did not light
but as I connected the lamp between neutral and ground there it
was, lamp was lit. I wondered if I had mistakenly connected
neutral and ground at first and then Phase and ground. I did a
double check with the line tester again. It was correct and I
had located the phase pin properly. The lamp was lit when I
connected it between Neutral and Ground! Can you Imagine? One
thing came to mind if the shop is connected with multi phase
and got a negative answer from my friend. The line tester tested
positive on the supposed to be Ground pin. But I wondered why
did this not happen when I did lamp test before going out of the
shop. I asked my friend if he switched on/off some switches, he
said yes he switched on all the switches in the process of locating
switch to his photocopier machine. Now with lamp connected between
neutral and ground I asked him to put off the switches one by one.
There it is! One of the switches did the magic. The lamp went off.
As I had seen enough of wrong wiring in the shop I could not risk myself
working with live wires and switched off the mains, opened the panel
and saw to my horror the ground pin from the wall socket was landing
on this switch which was connected to phase instead of ground. Further
investigation I found that whoever did the wiring did not follow any
colour code but used yellow, red and blue wires at his will and would
have got confused while giving finishing touch. He had used blue wire
for phase for some points and for Ground for some points. The entire
staff would have been electrocuted had there been earth leakage in any
of the equipment. But I wondered why this particular operator alone
got the shock. It was obvious, the PC and printer in question alone
were on that wall socket with the faulty connection. After isolating
the problem I asked my friend to get the whole shop rewired with proper
colour coding, but whether or not you call it coincidence he had to
shift the shop elsewhere before the wiring was corrected. Whatever
happened to the next occupant we should find from Chitragupa's records.
My friend was taken aback at this horrible wiring he even forgot to
thank me for the job I did, but asked me how much I should paid, but
I refused because I was happy that I saved lives of my friend and his
staff. |
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