On 2011-10-07, Bruce L. Bergman (munged human readable) wrote:
On Thu, 06 Oct 2011 14:31:45 -0500, Ignoramus15921
wrote:
On 2011-10-06, Jim Stewart wrote:
Ignoramus29750 wrote:

Sounds like GE did a bad job on this Electrocenter.

Sounds dubious that the busbars "slid down". Busbars
have to be bolted solid in numerous locations to withstand
the forces generated by the magnetic fields created
from a short circuit. More likely would be a piece of
wire or other debris fell across them.


I have learned a lot of very fascinating stuff recently. Thanks a lot.

There are procedures for initial power-up of gear that's new and being
energized for the first time, and for gear recently moved and being
reenergized. The main rule is to check for outright shorts and
crosses before you power it up, and then be careful bringing it up to
operating voltage.

It might pass an ohm-meter test when you check for shorts, but have
compromised insulation or a piece of trash that will flash over at
full voltage. 120/208/240V isn't so likely to have flash-over
failures, but you go to 440V and up and it starts being a real
possibility.

I've had them at 120 VAC. A standard duplex outlet, where the
grounded mounting strap was attached to the Bakelite body with drive
screws. One of the screw cavities apparently had a void near the end
which opened into the area where the hot and neutral conductors were
living. No problem until a thunderstorm induced a high enough voltage
spike to start an arc inside the outlet -- coating it with carbonized
Bakelite. It tripped the breaker (of course), and when I got home and
switched the breaker back on, there was a bzzzzttt-snap! and it tripped
again. I walked through the house until I smelled the burnt Bakelite,
and dug my way into the outlet. (It has one of those 6-way trapezoidal
expanders/surge suppressors screwed into it. The hot pin was welded to
the connector inside the outlet, so I had to pull hard enough to break
the pin loose to get the outlet out and replace it. After that, I could
turn the breaker back on. (I was working against time there, because
it was getting dark while I was yanking it apart. :-)

[ ... ]

The more important thing is to keep the trash from getting in the
boxes again. Unless you start doing grinding and sharpening in that
shop again, your main worry is getting the historic accumulation of
old swarf out of the existing boxes.

Again -- these are not duplex outlets in boxes, but rather
single outlet which mounts onto the end of the cord. Probably
twist-lock connectors, even for 120 VAC drops. Probably something like
the L5-20R shown in the right-hand photo of this URL:

http://www.lockingpowercords.com/Products/79-20a125v-locking-power-cords.aspx

Enjoy,
DoN.

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