I had a little bit of a new experience today.

My new place has cables dropped from the ceiling, with receptacles
hanging somewhat above my height.

I was moving a crane and bumped into one of them, nothing big, just a
minor bump. Then I saw that the receptacle was on fire (or rather,
flames were coming out from inside), with small explosions inside.

I ran to the electrical control panel and turned off electricity to
the whole building. The fire stopped.

After a short while, I opened up the receptacle. It turned out that it
was full of grinding dust (! -- how did it get inside) -- and,
apparently, the dust shifted and shorted the contacts. It was a short
circuit, but with a lot of resistance from the dust, so it caught
fire, but did not trip a breaker.

I cut it off and taped the individual wires, but I am now thinking
that I need to take all of those things apart and blow them out with
compressed air.

Comments?

i

In article ,
Ignoramus23561 wrote:

I had a little bit of a new experience today.

My new place has cables dropped from the ceiling, with receptacles
hanging somewhat above my height.

I was moving a crane and bumped into one of them, nothing big, just a
minor bump. Then I saw that the receptacle was on fire (or rather,
flames were coming out from inside), with small explosions inside.

I ran to the electrical control panel and turned off electricity to
the whole building. The fire stopped.

After a short while, I opened up the receptacle. It turned out that it
was full of grinding dust (! -- how did it get inside) -- and,
apparently, the dust shifted and shorted the contacts. It was a short
circuit, but with a lot of resistance from the dust, so it caught
fire, but did not trip a breaker.

I cut it off and taped the individual wires, but I am now thinking
that I need to take all of those things apart and blow them out with
compressed air.

Comments?

Sounds like a plan. And, replace any worn outlets.

But don't trust that the outlets are really off just because the
switches claim this. Old factories accumulate odd wiring and
semi-broken breakers and switches.

Before disassembly, use a voltmeter to ensure that each and every pole
is unpowered.

You may discover a breaker that also needs to be replaced.

Joe Gwinn

On Sun, 02 Oct 2011 13:37:04 -0500, Ignoramus23561
wrote:

I had a little bit of a new experience today.

My new place has cables dropped from the ceiling, with receptacles
hanging somewhat above my height.

I was moving a crane and bumped into one of them, nothing big, just a
minor bump. Then I saw that the receptacle was on fire (or rather,
flames were coming out from inside), with small explosions inside.

I ran to the electrical control panel and turned off electricity to
the whole building. The fire stopped.

After a short while, I opened up the receptacle. It turned out that it
was full of grinding dust (! -- how did it get inside) -- and,
apparently, the dust shifted and shorted the contacts. It was a short
circuit, but with a lot of resistance from the dust, so it caught
fire, but did not trip a breaker.

I cut it off and taped the individual wires, but I am now thinking
that I need to take all of those things apart and blow them out with
compressed air.

Comments?

i

Yes.

Gunner

"In the history of mankind, there have always been men and women who's goal
in life is to take down nations. We have just elected such a man to run our
country." - David Lloyyd (2008)

Ignoramus23561 wrote:
I had a little bit of a new experience today.

My new place has cables dropped from the ceiling, with receptacles
hanging somewhat above my height.

I was moving a crane and bumped into one of them, nothing big, just a
minor bump. Then I saw that the receptacle was on fire (or rather,
flames were coming out from inside), with small explosions inside.

I ran to the electrical control panel and turned off electricity to
the whole building. The fire stopped.

After a short while, I opened up the receptacle. It turned out that it
was full of grinding dust (! -- how did it get inside) -- and,
apparently, the dust shifted and shorted the contacts. It was a short
circuit, but with a lot of resistance from the dust, so it caught
fire, but did not trip a breaker.

I cut it off and taped the individual wires, but I am now thinking
that I need to take all of those things apart and blow them out with
compressed air.

Comments?

i


Igor,
I think it would be wise to check all the electrical boxes and outlets
in the grinding area and maybe a couple in the rest of the shop away
from the grinding area to see if they are contaminated. If there is
that much grinding dust in the outlets, think how much was breathed in.
If you had 480 in the box it probably would have exploded. The call
that arc flash.

John

On Sun, 02 Oct 2011 16:08:33 -0400, Joseph Gwinn
wrote:

In article ,
Ignoramus23561 wrote:

I had a little bit of a new experience today.

My new place has cables dropped from the ceiling, with receptacles
hanging somewhat above my height.

I was moving a crane and bumped into one of them, nothing big, just a
minor bump. Then I saw that the receptacle was on fire (or rather,
flames were coming out from inside), with small explosions inside.

I ran to the electrical control panel and turned off electricity to
the whole building. The fire stopped.

After a short while, I opened up the receptacle. It turned out that it
was full of grinding dust (! -- how did it get inside) -- and,
apparently, the dust shifted and shorted the contacts. It was a short
circuit, but with a lot of resistance from the dust, so it caught
fire, but did not trip a breaker.

I cut it off and taped the individual wires, but I am now thinking
that I need to take all of those things apart and blow them out with
compressed air.

Comments?

Sounds like a plan. And, replace any worn outlets.

But don't trust that the outlets are really off just because the
switches claim this. Old factories accumulate odd wiring and
semi-broken breakers and switches.

Before disassembly, use a voltmeter to ensure that each and every pole
is unpowered.

You may discover a breaker that also needs to be replaced.

Joe Gwinn

Good statements all.

For Iggys application..he can buy 10 packs of 110vt outlets for less
than $6 at HomeDespot.


"In the history of mankind, there have always been men and women who's goal
in life is to take down nations. We have just elected such a man to run our
country." - David Lloyyd (2008)

On Sun, 02 Oct 2011 13:37:04 -0500, Ignoramus23561 wrote:

I had a little bit of a new experience today.

My new place has cables dropped from the ceiling, with receptacles
hanging somewhat above my height.

I was moving a crane and bumped into one of them, nothing big, just a
minor bump. Then I saw that the receptacle was on fire (or rather,
flames were coming out from inside), with small explosions inside.

I ran to the electrical control panel and turned off electricity to the
whole building. The fire stopped.

After a short while, I opened up the receptacle. It turned out that it
was full of grinding dust (! -- how did it get inside) -- and,
apparently, the dust shifted and shorted the contacts. It was a short
circuit, but with a lot of resistance from the dust, so it caught fire,
but did not trip a breaker.

I cut it off and taped the individual wires, but I am now thinking that
I need to take all of those things apart and blow them out with
compressed air.

Comments?

i

So was it was one of those hanging metal box thingies, with an ordinary
receptacle mounted in the box?

If so then whacking the whole thing off was probably more than was
necessary: replacing the receptacle and blowing out the dust (and the
dust in all the other receptacles as well) is probably more "right".

--
www.wescottdesign.com

On Sun, 02 Oct 2011 13:37:04 -0500, Ignoramus23561
wrote:

I had a little bit of a new experience today.

My new place has cables dropped from the ceiling, with receptacles
hanging somewhat above my height.

I was moving a crane and bumped into one of them, nothing big, just a
minor bump. Then I saw that the receptacle was on fire (or rather,
flames were coming out from inside), with small explosions inside.

I ran to the electrical control panel and turned off electricity to
the whole building. The fire stopped.

After a short while, I opened up the receptacle. It turned out that it
was full of grinding dust (! -- how did it get inside) -- and,
apparently, the dust shifted and shorted the contacts. It was a short
circuit, but with a lot of resistance from the dust, so it caught
fire, but did not trip a breaker.

I cut it off and taped the individual wires, but I am now thinking
that I need to take all of those things apart and blow them out with
compressed air.

Comments?

i
Hey Iggy,

If grinding dust was a liquid it, it would be hydraulic fluid !!! A
little bit goes a long ways, and it will get everywhere!!!!!!!!!!!
Nice building, but be ready for lots of exciting things because of the
grinding dust. Well maybe not exciting, but interesting.

Take care.

Brian Lawson.

On 2011-10-02, Tim Wescott wrote:
On Sun, 02 Oct 2011 13:37:04 -0500, Ignoramus23561 wrote:

I had a little bit of a new experience today.

My new place has cables dropped from the ceiling, with receptacles
hanging somewhat above my height.

I was moving a crane and bumped into one of them, nothing big, just a
minor bump. Then I saw that the receptacle was on fire (or rather,
flames were coming out from inside), with small explosions inside.

I ran to the electrical control panel and turned off electricity to the
whole building. The fire stopped.

After a short while, I opened up the receptacle. It turned out that it
was full of grinding dust (! -- how did it get inside) -- and,
apparently, the dust shifted and shorted the contacts. It was a short
circuit, but with a lot of resistance from the dust, so it caught fire,
but did not trip a breaker.

I cut it off and taped the individual wires, but I am now thinking that
I need to take all of those things apart and blow them out with
compressed air.

Comments?

i

So was it was one of those hanging metal box thingies, with an ordinary
receptacle mounted in the box?

No, it was a "female connector".

If so then whacking the whole thing off was probably more than was
necessary: replacing the receptacle and blowing out the dust (and the
dust in all the other receptacles as well) is probably more "right".


Well, I kept it. Going through all of them means a few wasted
hours. But I guess I have to bite the bullet and do it.

i

Whether single or poly-phase, circuit breakers don't sense fire.

As John said, 480V will leave a very memorable and lasting impression.
I saw such "ball lightning" events when I was in the maintenance dept of a
steel wire mill facility, and in a new area that had only been in operation
for over a year.

You can expect to be showered with grinding dust any time anything
structural is disturbed.
All of the overhead pipes, cables, rafters/stuff are likely to be loaded
with that dust.

By the staining on the walls, it looks like that business had been there for
quite a while.. the yellowing is likely from evaporating (and/or misted)
coolant.

Anything valuable or pristine should be kept under cover.. and it's not a
good place for kids to hang out.
Aluminum oxide dust is bad enough to inhale (and conductive), but silicon
carbide dust is very nasty, in case you haven't been reading those caution
labels or MSDS info sent with SiC products.

Those hanging receptacles may not be installed properly. The best type of
cable to use is the stuff designed for hanging switches/etc (such as on a
hoist) which has an internal steel cable for securing at each end, which
prevents stretching of the conductors.
The boxes shouldn't have been the common type (covered in knockouts) for use
in that kind of shop, and the box connectors should've been the sealing
type.
Details like these will give you an indication of what can be expected when
you need to use, or make changes to, the electrical circuits.
When you see improvised/improper installations, it's likely because the
installer didn't know any better (unqualified inexperienced), and/or because
no one would spend the money to do the job correctly.

A much better installation is to install posts with the boxes mounted to
them.

--
WB
..........


"Ignoramus23561" wrote in message
...
I had a little bit of a new experience today.

My new place has cables dropped from the ceiling, with receptacles
hanging somewhat above my height.

I was moving a crane and bumped into one of them, nothing big, just a
minor bump. Then I saw that the receptacle was on fire (or rather,
flames were coming out from inside), with small explosions inside.

I ran to the electrical control panel and turned off electricity to
the whole building. The fire stopped.

After a short while, I opened up the receptacle. It turned out that it
was full of grinding dust (! -- how did it get inside) -- and,
apparently, the dust shifted and shorted the contacts. It was a short
circuit, but with a lot of resistance from the dust, so it caught
fire, but did not trip a breaker.

I cut it off and taped the individual wires, but I am now thinking
that I need to take all of those things apart and blow them out with
compressed air.

Comments?

i

Ignoramus23561 wrote:
I had a little bit of a new experience today.

My new place has cables dropped from the ceiling, with receptacles
hanging somewhat above my height.

I was moving a crane and bumped into one of them, nothing big, just a
minor bump. Then I saw that the receptacle was on fire (or rather,
flames were coming out from inside), with small explosions inside.

I ran to the electrical control panel and turned off electricity to
the whole building. The fire stopped.

After a short while, I opened up the receptacle. It turned out that it
was full of grinding dust (! -- how did it get inside) -- and,
apparently, the dust shifted and shorted the contacts. It was a short
circuit, but with a lot of resistance from the dust, so it caught
fire, but did not trip a breaker.

I cut it off and taped the individual wires, but I am now thinking
that I need to take all of those things apart and blow them out with
compressed air.

Comments?

i


Well I would probably commit overkill myself and grab a manlift and a
pressure washer and give all the open utilities a good bath. Wash down
the pipes/conduits and let the place dry out. While it's drying I would
check EVERY outlet and switch in the place for wear/damage/proper
installation. Then paint the walls with some good white paint. Dryloc
wouldn't be a bad thing to keep moisture out.

Then I would probably set up an area where you can inspect/test incoming
gear. Another where you can strip stuff for parts (and dispose of the
common/worthless pieces) Another area for crating/palletizing and shipping.
Barcode software and inventory tracking is not expensive these days.



--
Steve W.

Ouch!

I suspect the rubber boot that seals the top connector
was not tight against the wire or even there.

Dust just floated in and filtered down.

Or maybe you were not using plastic covered connectors.

Martin

On 10/2/2011 1:37 PM, Ignoramus23561 wrote:
I had a little bit of a new experience today.

My new place has cables dropped from the ceiling, with receptacles
hanging somewhat above my height.

I was moving a crane and bumped into one of them, nothing big, just a
minor bump. Then I saw that the receptacle was on fire (or rather,
flames were coming out from inside), with small explosions inside.

I ran to the electrical control panel and turned off electricity to
the whole building. The fire stopped.

After a short while, I opened up the receptacle. It turned out that it
was full of grinding dust (! -- how did it get inside) -- and,
apparently, the dust shifted and shorted the contacts. It was a short
circuit, but with a lot of resistance from the dust, so it caught
fire, but did not trip a breaker.

I cut it off and taped the individual wires, but I am now thinking
that I need to take all of those things apart and blow them out with
compressed air.

Comments?

i

Ignoramus23561 wrote:


After a short while, I opened up the receptacle. It turned out that it
was full of grinding dust (! -- how did it get inside) -- and,
apparently, the dust shifted and shorted the contacts. It was a short
circuit, but with a lot of resistance from the dust, so it caught
fire, but did not trip a breaker.
Wow, this is one of the most scary sorts of electrical problems, the
latent high-resistance short. Fortunately, in this case, if it happens
in the dangling cords, it is at least somewhat likely to turn into a
major short and trip the breaker before it spreads. But, you are
right, you should examine all of these connectors for dust and any
other deterioration. I'd turn off breakers to every unused receptacle,
and then only turn them on as you get them cleaned out. It may also be
there's a lot of dust in the junction boxes up on the ceiling, too, and
maybe in every other electrical box and panel.

Ugh, this might be a mess to clean up!

Jon

On 2011-10-03, Steve W. wrote:
Ignoramus23561 wrote:
I had a little bit of a new experience today.

My new place has cables dropped from the ceiling, with receptacles
hanging somewhat above my height.

I was moving a crane and bumped into one of them, nothing big, just a
minor bump. Then I saw that the receptacle was on fire (or rather,
flames were coming out from inside), with small explosions inside.

I ran to the electrical control panel and turned off electricity to
the whole building. The fire stopped.

After a short while, I opened up the receptacle. It turned out that it
was full of grinding dust (! -- how did it get inside) -- and,
apparently, the dust shifted and shorted the contacts. It was a short
circuit, but with a lot of resistance from the dust, so it caught
fire, but did not trip a breaker.

I cut it off and taped the individual wires, but I am now thinking
that I need to take all of those things apart and blow them out with
compressed air.

Comments?

i


Well I would probably commit overkill myself and grab a manlift and a
pressure washer and give all the open utilities a good bath. Wash down
the pipes/conduits and let the place dry out. While it's drying I would
check EVERY outlet and switch in the place for wear/damage/proper
installation. Then paint the walls with some good white paint. Dryloc
wouldn't be a bad thing to keep moisture out.

I am afraid that this washing down of dusty electrical outlets may
create more problems.

Then I would probably set up an area where you can inspect/test incoming
gear. Another where you can strip stuff for parts (and dispose of the
common/worthless pieces) Another area for crating/palletizing and shipping.
Barcode software and inventory tracking is not expensive these days.


This is the hope, indeed.

i

On 2011-10-02, Gunner Asch wrote:
On Sun, 02 Oct 2011 16:08:33 -0400, Joseph Gwinn
wrote:

In article ,
Ignoramus23561 wrote:

I had a little bit of a new experience today.

My new place has cables dropped from the ceiling, with receptacles
hanging somewhat above my height.

I was moving a crane and bumped into one of them, nothing big, just a
minor bump. Then I saw that the receptacle was on fire (or rather,
flames were coming out from inside), with small explosions inside.

[ ... ]

After a short while, I opened up the receptacle. It turned out that it
was full of grinding dust (! -- how did it get inside) -- and,
apparently, the dust shifted and shorted the contacts. It was a short
circuit, but with a lot of resistance from the dust, so it caught
fire, but did not trip a breaker.

[ ... ]

Sounds like a plan. And, replace any worn outlets.

[ ... ]

Before disassembly, use a voltmeter to ensure that each and every pole
is unpowered.

You may discover a breaker that also needs to be replaced.

[ ... ]

Good statements all.

For Iggys application..he can buy 10 packs of 110vt outlets for less
than $6 at HomeDespot.

I don't think that he actually stated that these were 110 VAC
outlets. They may have been 240 VAC single phase or 240VAC three phase.

And hanging outlets are likely to use twist-lock connectors to
keep the cord's weight form unplugging the equipment. I don't think
that you can get 10-packs of twist-lock outlets for that little -- even
in 110 VAC size.

Enjoy,
DoN.

--
Remove oil spill source from e-mail
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On Sun, 02 Oct 2011 20:31:54 -0500, Ignoramus23561
wrote:


Well, I kept it. Going through all of them means a few wasted
hours. But I guess I have to bite the bullet and do it.

i

Its hardly wasted when you prevent arc flash or a fire.


"In the history of mankind, there have always been men and women who's goal
in life is to take down nations. We have just elected such a man to run our
country." - David Lloyyd (2008)

Ignoramus23561 wrote:

After a short while, I opened up the receptacle. It turned out that it
was full of grinding dust (! -- how did it get inside) -- and,
apparently, the dust shifted and shorted the contacts. It was a short
circuit, but with a lot of resistance from the dust, so it caught
fire, but did not trip a breaker.


I'm glad there wasn't an explosion. A long time ago, at a company long auctioned off, a
30A 480V twist lock cord fell into a mop bucket. In addition to the bang that sounded
like a rifle shot (wires slapping in conduit), a marathon splice block that was part of
200 amp run to the panel this cord was attached to exploded along with tripping the 4000A
breaker in the boiler room.

All that from a little 10 ga SO cord and water.


Wes

On Oct 2, 11:00*pm, Wes wrote:
Ignoramus23561 wrote:
After a short while, I opened up the receptacle. It turned out that it
was full of grinding dust (! -- how did it get inside) -- and,
apparently, the dust shifted and shorted the contacts. It was a short
circuit, but with a lot of resistance from the dust, so it caught
fire, but did not trip a breaker.

I'm glad there wasn't an explosion. *A long time ago, at a company long auctioned off, a
30A 480V twist lock cord fell into a mop bucket. *In addition to the bang that sounded
like a rifle shot (wires slapping in conduit), a marathon splice block that was part of
200 amp run to the panel this cord was attached to exploded along with tripping the 4000A
breaker in the boiler room.

All that from a little 10 ga SO cord and water.

Wes

My friend had a 440 motor or line short right in front of him in an
elevator motor room. He was temporarily blinded for a couple days. He
said it felt like someone poured sand in his eyes.
Karl

On 3 Oct 2011 04:42:06 GMT, "DoN. Nichols"
wrote:

On 2011-10-02, Gunner Asch wrote:
On Sun, 02 Oct 2011 16:08:33 -0400, Joseph Gwinn
wrote:

In article ,
Ignoramus23561 wrote:

I had a little bit of a new experience today.

My new place has cables dropped from the ceiling, with receptacles
hanging somewhat above my height.

I was moving a crane and bumped into one of them, nothing big, just a
minor bump. Then I saw that the receptacle was on fire (or rather,
flames were coming out from inside), with small explosions inside.

[ ... ]

After a short while, I opened up the receptacle. It turned out that it
was full of grinding dust (! -- how did it get inside) -- and,
apparently, the dust shifted and shorted the contacts. It was a short
circuit, but with a lot of resistance from the dust, so it caught
fire, but did not trip a breaker.

[ ... ]

Sounds like a plan. And, replace any worn outlets.

[ ... ]

Before disassembly, use a voltmeter to ensure that each and every pole
is unpowered.

You may discover a breaker that also needs to be replaced.

[ ... ]

Good statements all.

For Iggys application..he can buy 10 packs of 110vt outlets for less
than $6 at HomeDespot.

I don't think that he actually stated that these were 110 VAC
outlets. They may have been 240 VAC single phase or 240VAC three phase.

And hanging outlets are likely to use twist-lock connectors to
keep the cord's weight form unplugging the equipment. I don't think
that you can get 10-packs of twist-lock outlets for that little -- even
in 110 VAC size.

Enjoy,
DoN.

True indeed. I hadnt read it in that light. Not at all.

Good reality check and thanks!

Gunner

"In the history of mankind, there have always been men and women who's goal
in life is to take down nations. We have just elected such a man to run our
country." - David Lloyyd (2008)

On Sun, 02 Oct 2011 23:41:21 -0500, Ignoramus23561
wrote:

On 2011-10-03, Steve W. wrote:
Ignoramus23561 wrote:
I had a little bit of a new experience today.

My new place has cables dropped from the ceiling, with receptacles
hanging somewhat above my height.

I was moving a crane and bumped into one of them, nothing big, just a
minor bump. Then I saw that the receptacle was on fire (or rather,
flames were coming out from inside), with small explosions inside.

I ran to the electrical control panel and turned off electricity to
the whole building. The fire stopped.

After a short while, I opened up the receptacle. It turned out that it
was full of grinding dust (! -- how did it get inside) -- and,
apparently, the dust shifted and shorted the contacts. It was a short
circuit, but with a lot of resistance from the dust, so it caught
fire, but did not trip a breaker.

I cut it off and taped the individual wires, but I am now thinking
that I need to take all of those things apart and blow them out with
compressed air.

Comments?

i


Well I would probably commit overkill myself and grab a manlift and a
pressure washer and give all the open utilities a good bath. Wash down
the pipes/conduits and let the place dry out. While it's drying I would
check EVERY outlet and switch in the place for wear/damage/proper
installation. Then paint the walls with some good white paint. Dryloc
wouldn't be a bad thing to keep moisture out.

I am afraid that this washing down of dusty electrical outlets may
create more problems.

Then I would probably set up an area where you can inspect/test incoming
gear. Another where you can strip stuff for parts (and dispose of the
common/worthless pieces) Another area for crating/palletizing and shipping.
Barcode software and inventory tracking is not expensive these days.


This is the hope, indeed.

i

Washing them down? Turn off the power, open the covers and simply blow
them out with a good deal of compressed air, then reclose.

Washing them down?? Get grinding dust wet? Oh you are far far braver
than I am. Id never intentionally create concrete in electrical outlets.

Let us know how that works out, will ya?

Gunner

"In the history of mankind, there have always been men and women who's goal
in life is to take down nations. We have just elected such a man to run our
country." - David Lloyyd (2008)

" writes:


My friend had a 440 motor or line short right in front of him in an
elevator motor room. He was temporarily blinded for a couple days. He
said it felt like someone poured sand in his eyes.

OSHA has gotten religion on the arc flash issue. The #1 chance
for such that will kill folks is when you close a large
main/sub-main breaker. They can and do explode outward with
enough force to blow apart cabinets, taking out the chump
standing there closing the breaker.

There's now many types of motor/hydraulic powered breaker
closers. They attach with magnets, the arm is on the
handle. You stand 20 ft away behind Lexan etc and push
the button.

There's also required "arc-flash clothing" -- I think the point
being it won't catch fire and melt onto the skin, but I'm not
sure on this.

In residences, the NEC has spec'ed arc sensing breakers for
bedrooms/living rooms, I think. These can be a PITA as
brush-type motors [Skilsaw, etc] can trip them.


--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

On 2011-10-03, Gunner Asch wrote:
On Sun, 02 Oct 2011 23:41:21 -0500, Ignoramus23561
wrote:

On 2011-10-03, Steve W. wrote:
Ignoramus23561 wrote:
I had a little bit of a new experience today.

My new place has cables dropped from the ceiling, with receptacles
hanging somewhat above my height.

I was moving a crane and bumped into one of them, nothing big, just a
minor bump. Then I saw that the receptacle was on fire (or rather,
flames were coming out from inside), with small explosions inside.

I ran to the electrical control panel and turned off electricity to
the whole building. The fire stopped.

After a short while, I opened up the receptacle. It turned out that it
was full of grinding dust (! -- how did it get inside) -- and,
apparently, the dust shifted and shorted the contacts. It was a short
circuit, but with a lot of resistance from the dust, so it caught
fire, but did not trip a breaker.

I cut it off and taped the individual wires, but I am now thinking
that I need to take all of those things apart and blow them out with
compressed air.

Comments?

i


Well I would probably commit overkill myself and grab a manlift and a
pressure washer and give all the open utilities a good bath. Wash down
the pipes/conduits and let the place dry out. While it's drying I would
check EVERY outlet and switch in the place for wear/damage/proper
installation. Then paint the walls with some good white paint. Dryloc
wouldn't be a bad thing to keep moisture out.

I am afraid that this washing down of dusty electrical outlets may
create more problems.

Then I would probably set up an area where you can inspect/test incoming
gear. Another where you can strip stuff for parts (and dispose of the
common/worthless pieces) Another area for crating/palletizing and shipping.
Barcode software and inventory tracking is not expensive these days.


This is the hope, indeed.

i

Washing them down? Turn off the power, open the covers and simply blow
them out with a good deal of compressed air, then reclose.

Washing them down?? Get grinding dust wet? Oh you are far far braver
than I am. Id never intentionally create concrete in electrical outlets.

Let us know how that works out, will ya?

I will. I was not going to wash them down.

i

On Mon, 3 Oct 2011 03:23:42 -0700 (PDT), "
wrote:

On Oct 2, 11:00*pm, Wes wrote:
Ignoramus23561 wrote:
After a short while, I opened up the receptacle. It turned out that it
was full of grinding dust (! -- how did it get inside) -- and,
apparently, the dust shifted and shorted the contacts. It was a short
circuit, but with a lot of resistance from the dust, so it caught
fire, but did not trip a breaker.

I'm glad there wasn't an explosion. *A long time ago, at a company long auctioned off, a
30A 480V twist lock cord fell into a mop bucket. *In addition to the bang that sounded
like a rifle shot (wires slapping in conduit), a marathon splice block that was part of
200 amp run to the panel this cord was attached to exploded along with tripping the 4000A
breaker in the boiler room.

All that from a little 10 ga SO cord and water.

Wes

My friend had a 440 motor or line short right in front of him in an
elevator motor room. He was temporarily blinded for a couple days. He
said it felt like someone poured sand in his eyes.
Karl

Just servicing kitchen and hallway exhaust fans can be a heart-stopper
when it's a high-rise Condo in West Hollywood and the common
"Mushroom" fans on the roof are 1-HP 480V 3Ph.

Renewable fuses in a motor control center, and the only way to find
out if you'd fixed it was to throw the switch and try it - if the
fuses didn't go off like a shotgun blast and the motor started, then
you were done.

And you make DAMN sure they are locked off/tagged off and well and
truly dead before sticking your hands in...

Iggy: Don't screw around with this - take some time, get a Dust
Collector system or a good Shop Vac with a HEPA element and your big
air compressor, use a cross-draft and blow it toward the vacuum hose.
Clean up and out EVERYTHING in the shop area, starting with the
rafters and working down. Take apart the light fixtures, the boxes
for the building wiring, everywhere.

And your last stop is to pick a nice day, have Con Ed (or whoever) pop
the fuses out and kill the power to the Main Service for the day, and
you pull the covers and clean it out too. (Bring in a gas powered
compressor and a generator.) If that sucker burns up, you'll be in a
world of hurt. That grinding dust can be miserable stuff when it gets
inside electrical gear.

-- Bruce --

On Sun, 02 Oct 2011 22:29:50 -0700, Gunner Asch wrote:

On Sun, 02 Oct 2011 20:31:54 -0500, Ignoramus23561
wrote:


Well, I kept it. Going through all of them means a few wasted hours. But
I guess I have to bite the bullet and do it.

i

Its hardly wasted when you prevent arc flash or a fire.

Yup. The best fire insurance in the world isn't as good as not having
your shop burn down in the first place.

--
www.wescottdesign.com

On 2011-10-03, David Lesher wrote:
" writes:


My friend had a 440 motor or line short right in front of him in an
elevator motor room. He was temporarily blinded for a couple days. He
said it felt like someone poured sand in his eyes.

OSHA has gotten religion on the arc flash issue. The #1 chance
for such that will kill folks is when you close a large
main/sub-main breaker. They can and do explode outward with
enough force to blow apart cabinets, taking out the chump
standing there closing the breaker.

So, why exactly do they explode? Can you explain?

There's now many types of motor/hydraulic powered breaker
closers. They attach with magnets, the arm is on the
handle. You stand 20 ft away behind Lexan etc and push
the button.

There's also required "arc-flash clothing" -- I think the point
being it won't catch fire and melt onto the skin, but I'm not
sure on this.

In residences, the NEC has spec'ed arc sensing breakers for
bedrooms/living rooms, I think. These can be a PITA as
brush-type motors [Skilsaw, etc] can trip them.

Ignoramus19762 fired this volley in
:

So, why exactly do they explode? Can you explain?

Rapid heating (to plasma temperatures) of the air. It gets heated to
several thousands of degrees in a few tens of microseconds. That releases
a physical shock wave (due to the expanding ball of super-heated gas -- if
you don't know them read the Gas Laws) equivalent to a small charge of
explosives.

LLoyd

On 2011-10-03, Lloyd E. Sponenburgh lloydspinsidemindspring.com wrote:
Ignoramus19762 fired this volley in
:

So, why exactly do they explode? Can you explain?

Rapid heating (to plasma temperatures) of the air. It gets heated to
several thousands of degrees in a few tens of microseconds. That releases
a physical shock wave (due to the expanding ball of super-heated gas -- if
you don't know them read the Gas Laws) equivalent to a small charge of
explosives.

Right, but why does the arc flash in the first place?

i

Ignoramus19762 fired this volley in
:

Right, but why does the arc flash in the first place?

All electricity needs is a low-enough resistance path to start flowing,
and as it raises the temperature of its surrounds (say, by fusing the
metal grinding dust that started the connection), the air itself becomes
a conductor.

A "spark" is nothing more than the voltage overcoming the insulation
resistance of the air; when it begins to flow through the air, it heats
the gasses to plasma temps, and that's what you see as the "spark". If
something like a filament of lathe turning can assist in starting that
current flowing, all the easier for a big, fat arc to form.

Such an arc can form from having foreign material between the leads (like
your 3ph box), or it can form from having two high-voltage leads too
close together. Excess humidity shortens the required gap.

The "classic" man-killer short happens when an inattentive technician
creates a dead-short with a tool, then the tool AND the air around it
vaporize into plasma.

LLoyd

Ignoramus19762 wrote:

OSHA has gotten religion on the arc flash issue. The #1 chance
for such that will kill folks is when you close a large
main/sub-main breaker. They can and do explode outward with
enough force to blow apart cabinets, taking out the chump
standing there closing the breaker.

So, why exactly do they explode? Can you explain?

I can't but I stand to the side of control panel boxes when turning on the main
disconnect. One time seeing a Hoffman box open from the arc flash was enough for me. No,
I didn't do the work, I was a by stander.

Wes
--
"Additionally as a security officer, I carry a gun to protect
government officials but my life isn't worth protecting at home
in their eyes." Dick Anthony Heller

On 2011-10-03, Wes wrote:
Ignoramus19762 wrote:

OSHA has gotten religion on the arc flash issue. The #1 chance
for such that will kill folks is when you close a large
main/sub-main breaker. They can and do explode outward with
enough force to blow apart cabinets, taking out the chump
standing there closing the breaker.

So, why exactly do they explode? Can you explain?

I can't but I stand to the side of control panel boxes when turning
on the main disconnect. One time seeing a Hoffman box open from the
arc flash was enough for me. No, I didn't do the work, I was a by
stander.

Scary.

Can this happen with 240v 3 phase?

My building has only 240v. 800 amps service.

i

Ignoramus19762 fired this volley in
:

Can this happen with 240v 3 phase?

My building has only 240v. 800 amps service.


240 VAC (in any phase configuration) is less dangerous than, say 440.

But with 800amps of ability to deliver current, you have a great
potential for plasma-like arcs.

Just protect yourself.

LLoyd

On 2011-10-03, Bruce L. Bergman (munged human readable) wrote:
Iggy: Don't screw around with this - take some time, get a Dust
Collector system or a good Shop Vac with a HEPA element and your big
air compressor, use a cross-draft and blow it toward the vacuum hose.
Clean up and out EVERYTHING in the shop area, starting with the
rafters and working down. Take apart the light fixtures, the boxes
for the building wiring, everywhere.

My plan has solidified.

I would do the following.

0. Put on eye protection.
1. Kill all power to the building.
2. For every hanging connector:
- Get a ladder under it and climb it
- Open up the connector
- Clean with a bristle brush
- Close it
- Raise it up by at least 2 feet, forming a loop

I figure, if I need to ever hook up a machine to a hanging connector,
I can always get a ladder in place, it will not be very frequent.

I want to make sure that when I drive a crane, forklift, or my truck
around, I do not hit those connectors.

i

On Mon, 03 Oct 2011 16:05:07 -0500, Ignoramus19762
wrote:

On 2011-10-03, Wes wrote:
Ignoramus19762 wrote:

OSHA has gotten religion on the arc flash issue. The #1 chance
for such that will kill folks is when you close a large
main/sub-main breaker. They can and do explode outward with
enough force to blow apart cabinets, taking out the chump
standing there closing the breaker.

So, why exactly do they explode? Can you explain?

I can't but I stand to the side of control panel boxes when turning
on the main disconnect. One time seeing a Hoffman box open from the
arc flash was enough for me. No, I didn't do the work, I was a by
stander.

Scary.

Can this happen with 240v 3 phase?

My building has only 240v. 800 amps service.

i

Fault current in your building will be well in excess of 10,000A.
Ordinary domestic fuses can't interrupt that kind of current. You do
need to treat industrial power with respect, but it's not particularly
scary compared to anything else that can get you. Getting blinded by
vaporized metal is a risk. I don't use cheap meters on anything higher
than 120VAC (and gingerly on that). Electrocution risk is no higher
than working on home 240VAC.

On Mon, 03 Oct 2011 11:44:48 -0500, Ignoramus19762
wrote:

On 2011-10-03, Gunner Asch wrote:
On Sun, 02 Oct 2011 23:41:21 -0500, Ignoramus23561
wrote:

On 2011-10-03, Steve W. wrote:
Ignoramus23561 wrote:
I had a little bit of a new experience today.

My new place has cables dropped from the ceiling, with receptacles
hanging somewhat above my height.

I was moving a crane and bumped into one of them, nothing big, just a
minor bump. Then I saw that the receptacle was on fire (or rather,
flames were coming out from inside), with small explosions inside.

I ran to the electrical control panel and turned off electricity to
the whole building. The fire stopped.

After a short while, I opened up the receptacle. It turned out that it
was full of grinding dust (! -- how did it get inside) -- and,
apparently, the dust shifted and shorted the contacts. It was a short
circuit, but with a lot of resistance from the dust, so it caught
fire, but did not trip a breaker.

I cut it off and taped the individual wires, but I am now thinking
that I need to take all of those things apart and blow them out with
compressed air.

Comments?

i


Well I would probably commit overkill myself and grab a manlift and a
pressure washer and give all the open utilities a good bath. Wash down
the pipes/conduits and let the place dry out. While it's drying I would
check EVERY outlet and switch in the place for wear/damage/proper
installation. Then paint the walls with some good white paint. Dryloc
wouldn't be a bad thing to keep moisture out.

I am afraid that this washing down of dusty electrical outlets may
create more problems.

Then I would probably set up an area where you can inspect/test incoming
gear. Another where you can strip stuff for parts (and dispose of the
common/worthless pieces) Another area for crating/palletizing and shipping.
Barcode software and inventory tracking is not expensive these days.


This is the hope, indeed.

i

Washing them down? Turn off the power, open the covers and simply blow
them out with a good deal of compressed air, then reclose.

Washing them down?? Get grinding dust wet? Oh you are far far braver
than I am. Id never intentionally create concrete in electrical outlets.

Let us know how that works out, will ya?

I will. I was not going to wash them down.

i

But..but you said you were going to wash them down..check up about 20 or
so lines.

VBG

Gunner

"In the history of mankind, there have always been men and women who's goal
in life is to take down nations. We have just elected such a man to run our
country." - David Lloyyd (2008)

On 2011-10-03, Gunner Asch wrote:
On Mon, 03 Oct 2011 11:44:48 -0500, Ignoramus19762
wrote:

On 2011-10-03, Gunner Asch wrote:
On Sun, 02 Oct 2011 23:41:21 -0500, Ignoramus23561
wrote:

On 2011-10-03, Steve W. wrote:
Ignoramus23561 wrote:
I had a little bit of a new experience today.

My new place has cables dropped from the ceiling, with receptacles
hanging somewhat above my height.

I was moving a crane and bumped into one of them, nothing big, just a
minor bump. Then I saw that the receptacle was on fire (or rather,
flames were coming out from inside), with small explosions inside.

I ran to the electrical control panel and turned off electricity to
the whole building. The fire stopped.

After a short while, I opened up the receptacle. It turned out that it
was full of grinding dust (! -- how did it get inside) -- and,
apparently, the dust shifted and shorted the contacts. It was a short
circuit, but with a lot of resistance from the dust, so it caught
fire, but did not trip a breaker.

I cut it off and taped the individual wires, but I am now thinking
that I need to take all of those things apart and blow them out with
compressed air.

Comments?

i


Well I would probably commit overkill myself and grab a manlift and a
pressure washer and give all the open utilities a good bath. Wash down
the pipes/conduits and let the place dry out. While it's drying I would
check EVERY outlet and switch in the place for wear/damage/proper
installation. Then paint the walls with some good white paint. Dryloc
wouldn't be a bad thing to keep moisture out.

I am afraid that this washing down of dusty electrical outlets may
create more problems.

Then I would probably set up an area where you can inspect/test incoming
gear. Another where you can strip stuff for parts (and dispose of the
common/worthless pieces) Another area for crating/palletizing and shipping.
Barcode software and inventory tracking is not expensive these days.


This is the hope, indeed.

i

Washing them down? Turn off the power, open the covers and simply blow
them out with a good deal of compressed air, then reclose.

Washing them down?? Get grinding dust wet? Oh you are far far braver
than I am. Id never intentionally create concrete in electrical outlets.

Let us know how that works out, will ya?

I will. I was not going to wash them down.

i

But..but you said you were going to wash them down..check up about 20 or
so lines.

VBG

Where exactly did I say that?

i

On Mon, 03 Oct 2011 10:10:51 -0700, "Bruce L. Bergman (munged human
readable)" wrote:

On Mon, 3 Oct 2011 03:23:42 -0700 (PDT), "
wrote:

On Oct 2, 11:00*pm, Wes wrote:
Ignoramus23561 wrote:
After a short while, I opened up the receptacle. It turned out that it
was full of grinding dust (! -- how did it get inside) -- and,
apparently, the dust shifted and shorted the contacts. It was a short
circuit, but with a lot of resistance from the dust, so it caught
fire, but did not trip a breaker.

I'm glad there wasn't an explosion. *A long time ago, at a company long auctioned off, a
30A 480V twist lock cord fell into a mop bucket. *In addition to the bang that sounded
like a rifle shot (wires slapping in conduit), a marathon splice block that was part of
200 amp run to the panel this cord was attached to exploded along with tripping the 4000A
breaker in the boiler room.

All that from a little 10 ga SO cord and water.

Wes

My friend had a 440 motor or line short right in front of him in an
elevator motor room. He was temporarily blinded for a couple days. He
said it felt like someone poured sand in his eyes.
Karl

Just servicing kitchen and hallway exhaust fans can be a heart-stopper
when it's a high-rise Condo in West Hollywood and the common
"Mushroom" fans on the roof are 1-HP 480V 3Ph.

Renewable fuses in a motor control center, and the only way to find
out if you'd fixed it was to throw the switch and try it - if the
fuses didn't go off like a shotgun blast and the motor started, then
you were done.

And you make DAMN sure they are locked off/tagged off and well and
truly dead before sticking your hands in...

Iggy: Don't screw around with this - take some time, get a Dust
Collector system or a good Shop Vac with a HEPA element and your big
air compressor, use a cross-draft and blow it toward the vacuum hose.
Clean up and out EVERYTHING in the shop area, starting with the
rafters and working down. Take apart the light fixtures, the boxes
for the building wiring, everywhere.

And your last stop is to pick a nice day, have Con Ed (or whoever) pop
the fuses out and kill the power to the Main Service for the day, and
you pull the covers and clean it out too. (Bring in a gas powered
compressor and a generator.) If that sucker burns up, you'll be in a
world of hurt. That grinding dust can be miserable stuff when it gets
inside electrical gear.

-- Bruce --

Ive replaced a surprising number of 3ph and single phase outlets,
connectors and boxes in the 15 yrs Ive been repairing
machinery...replacements necessary because of metallic/conductive dust
in the boxes etc.

Some were quite spectacular...in both initiation and later investigation

Gunner

"In the history of mankind, there have always been men and women who's goal
in life is to take down nations. We have just elected such a man to run our
country." - David Lloyyd (2008)

On Mon, 03 Oct 2011 16:58:34 -0400, Wes
wrote:

Ignoramus19762 wrote:

OSHA has gotten religion on the arc flash issue. The #1 chance
for such that will kill folks is when you close a large
main/sub-main breaker. They can and do explode outward with
enough force to blow apart cabinets, taking out the chump
standing there closing the breaker.

So, why exactly do they explode? Can you explain?

I can't but I stand to the side of control panel boxes when turning on the main
disconnect. One time seeing a Hoffman box open from the arc flash was enough for me. No,
I didn't do the work, I was a by stander.

Wes
================

Hey Wes,

Our "rule" was: Stand off to the side of the disconnect (ie..not "in
front" of the cabinet door), one hand in pocket, other hand on the
lever, face away before throw. I've had three occasions to be happy I
did, although I still get a ringing in my left ear.

Somebody mentioned replaceable link fuses....they are not legal here
in Ontario anymore, but I have a long wonderful (nobody actuall "hurt"
story) about them when 200 amp links were tripled up, and the 575 volt
elevator motor was a dead short. We couldn't find the disconnect at
all or about 4 feet of the bus duct feeding it, but we did find two
ends of the fuses (that's how we knew about the tripling) and it took
out the whole powerhouse because it made every disconnect along the
way go short...sort of a ripple effect. You could hear them popping
every few seconds throughout the building. By the way, it was the
building maintenance electricians that had done the tripling, and they
should definetly have known better...I say that, becuase they get to
work with hot supplies most of the time, versus construction
electricians who really don't work hot as much.

And for Iggy...I've seen 120 volt hanging cables that were in very
damp conitions shorted, and they arc and catch fire and burn like a
dynamite fuse or like a July 4th hand-held "sparkler"...they don't
blow a fuse for about 5 feet.

A point to note that amazes me some people don't know.... with
electric current, the point of HIGHEST resistance will be the point of
highest heat(ing). Think about it.

Take care.

Brian Lawson.

Brian Lawson fired this volley in
:

A point to note that amazes me some people don't know.... with
electric current, the point of HIGHEST resistance will be the point of
highest heat(ing). Think about it.

I did. It doesn't. I'm a career electrical engineer, now 'converted to
the dark side' (explosives industry).

IF you even understand Ohm's law, consider that a few hundred megohms in
series with (even) a 575V main won't conduct enough current to even warm
up.

That's a "HIGH" resistance. A complete "open" with no conduction at all
would be the "HIGHEST" resistance. And in that case, no current would
flow, at all. No current, no power dissipation -- no heat. So
obviously, the point of highest resistance does NOT create the highest
heat.

Try this, instead -- a resistance of _exactly_ what will dissipate the
maxiumum POWER across a shunt is the one that will be the point of
highest heat(ing). (hint... heat is energy... power dissipated as heat)

Think about it. If that doesn't work, try looking up Ohm's law and the
power vs. resistance vs. current formulae.

It's a bit amazing to me that the trades still allow this kind of myth to
perpetuate, and even allow them to be the basis of training their
apprentices. But they do; even today, so don't feel deprived.

The Navy was full of this stuff, too. That's one reason why all I ever
wanted out of the Navy was ME.

LLoyd

On 2011-10-04, Lloyd E. Sponenburgh lloydspinsidemindspring.com wrote:
Brian Lawson fired this volley in
:

A point to note that amazes me some people don't know.... with
electric current, the point of HIGHEST resistance will be the point of
highest heat(ing). Think about it.

I did. It doesn't. I'm a career electrical engineer, now 'converted to
the dark side' (explosives industry).

IF you even understand Ohm's law, consider that a few hundred megohms in
series with (even) a 575V main won't conduct enough current to even warm
up.

That's a "HIGH" resistance. A complete "open" with no conduction at all
would be the "HIGHEST" resistance. And in that case, no current would
flow, at all. No current, no power dissipation -- no heat. So
obviously, the point of highest resistance does NOT create the highest
heat.

Try this, instead -- a resistance of _exactly_ what will dissipate the
maxiumum POWER across a shunt is the one that will be the point of
highest heat(ing). (hint... heat is energy... power dissipated as heat)

Think about it. If that doesn't work, try looking up Ohm's law and the
power vs. resistance vs. current formulae.

It's a bit amazing to me that the trades still allow this kind of myth to
perpetuate, and even allow them to be the basis of training their
apprentices. But they do; even today, so don't feel deprived.

The Navy was full of this stuff, too. That's one reason why all I ever
wanted out of the Navy was ME.

LLoyd

Brian Lawson is correct for a series circuit.

i

On Mon, 03 Oct 2011 19:09:42 -0500, the renowned "Lloyd E.
Sponenburgh" lloydspinsidemindspring.com wrote:

Brian Lawson fired this volley in
:

A point to note that amazes me some people don't know.... with
electric current, the point of HIGHEST resistance will be the point of
highest heat(ing). Think about it.

I did. It doesn't. I'm a career electrical engineer, now 'converted to
the dark side' (explosives industry).

IF you even understand Ohm's law, consider that a few hundred megohms in
series with (even) a 575V main won't conduct enough current to even warm
up.

That's a "HIGH" resistance. A complete "open" with no conduction at all
would be the "HIGHEST" resistance. And in that case, no current would
flow, at all. No current, no power dissipation -- no heat. So
obviously, the point of highest resistance does NOT create the highest
heat.

Brian is correct, given the assumption of a simple series circuit.
Consider a series circuit of several resistors. It's a series circuit,
so the current is the same in each. The power dissipated by each
resistor is I^2*R. So it's easy to see that the highest value resistor
dissipates the most power. For example, the wires, which have low
resistance, dissipate little power.

Try this, instead -- a resistance of _exactly_ what will dissipate the
maxiumum POWER across a shunt is the one that will be the point of
highest heat(ing). (hint... heat is energy... power dissipated as heat)

That's the answer to a different question. The maximum power you can
deliver is when a resistor is equal to the total source resistance )of
the line, transfomer, etc. If the power line has a 0.2 ohm source
resistance (1200A short circuit current at 240VAC) then the maximum
power would be delivered (until the breaker blows) by a 0.2 ohm load
(144kW dissipated in each of the load and in everything else).

Think about it. If that doesn't work, try looking up Ohm's law and the
power vs. resistance vs. current formulae.

It's a bit amazing to me that the trades still allow this kind of myth to
perpetuate, and even allow them to be the basis of training their
apprentices. But they do; even today, so don't feel deprived.

The Navy was full of this stuff, too. That's one reason why all I ever
wanted out of the Navy was ME.

LLoyd





Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

On Mon, 03 Oct 2011 15:30:44 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

Ignoramus19762 fired this volley in
m:

Right, but why does the arc flash in the first place?

All electricity needs is a low-enough resistance path to start flowing,
and as it raises the temperature of its surrounds (say, by fusing the
metal grinding dust that started the connection), the air itself becomes
a conductor.

A "spark" is nothing more than the voltage overcoming the insulation
resistance of the air; when it begins to flow through the air, it heats
the gasses to plasma temps, and that's what you see as the "spark". If
something like a filament of lathe turning can assist in starting that
current flowing, all the easier for a big, fat arc to form.

Such an arc can form from having foreign material between the leads (like
your 3ph box), or it can form from having two high-voltage leads too
close together. Excess humidity shortens the required gap.

The "classic" man-killer short happens when an inattentive technician
creates a dead-short with a tool, then the tool AND the air around it
vaporize into plasma.

LLoyd

Plus a whole lot of copper vapor. Blown switchgear at my old company
has vaporized pounds of copper. This was more often 2300V than 480V,
but either one will blow the doors way off. We had to watch movies of
phase to phase faults in our training to work in energized enclosures.
I was approved solely due to the large number of VFD's I had and
needed to program in 480V enclosures. Contrary to normal plant
practice, I used low voltage control circuits. I didn't want live 120
V. stuff behind me on the door to the enclosure when I was inside
programming stuff.

Highest voltage I ever personally switched was 15000 V. Hated that
****.

And I never had to deal with grinding dust in my stuff. Water once, a
lot of it, but no conductive dust. Yuk. By the way, I was a chemist,
not an electrician. That's R&D for you.

Pete Keillor