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Re: NST's ARE ALL DEADLY !!!!!!!!

At 04:27 PM 03/06/2000 +0000, you wrote:
snip....
>
>2. The HARD bites I got while changeing the NST setup were under the 
>following conditions.
>
>The control panel was completely shut down and the key was on a necklace 
>around my neck. The Emergency Stop button was down, the Fire button was up 
>(both open).
>
>I was standing on wet concrete pavement outdoors in a city park.
>
>Problem: We only switched the hot side, as is the norm. We do not switch the 
>Neutral side for safety reasons.
>
>In this event the suspected cause of my bite was the Neutral in the park 
>floating to about 60VAC and grounding itself out...though me!
>
>The panel is being redesigned, and we now unplug the panel from the source, 
>and the NST from the panel before makeing adjustments.
>
>
>Safety through fear, pain, and respect. :)
>
>Chris B.
>
snip....

Hi Chris,

I have always switched the neutral and hot using a DPDT relay (contactor).
This removes all possibility of the AC sneaking around things.  Only the
ground is left intact when the power switch is turned off.  This also
provides safety if the neutral and hot wires are switched as they often
are.  I used to switch the AC line (variac side) into the ground too just
to be real sure, but occasionally the contactor would switch late blowing
it up.  However, even the ground wire can be hot if there is a wiring
problem.  You could run a small ground rod at the park too just as a
backup.  Best to meter the unknown AC outlets in such locations too just to
be sure they are wired and operating correctly.  Floating neutrals can be
very dangerous.  Be sure to let the park people know about it.  You can
also wire small AC lamps (neon) between the ground and neutral, ground and
hot, neutral and hot, to make like a little AC line tester on your control
box.  This can be useful if you are constantly plugging it into unknown
sources.

Glad your OK!!  People get killed by such things...

Cheers,

	Terry