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.

About the only way to be somewhat sure is to get a Megger and throw
1000V or more of Hi-Pot Test at a controlled current capacity on it,
and see what happens.

And even then it might fool you. This is when you energize the
circuit using a load bank resistor and a much smaller than normal fuse
that has a high enough arc-fault rating to clear the line if something
goes seriously wrong. If it holds, then you can put the big fuses in.


The factory has a mix of bakelite and nylon body connectors. I bought
8 new nylon body connectors to replace the old bakelite connectors.

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.

If you have a receptacle drop hanging in a machine shop environment,
you should be using the yellow plastic boxes that are sealed from
casual crap entry. Not all that expensive, and they'll keep most
everything outside that needs to be.

Hubbell Kellems 3000H - double sided with 2 Duplex receptacle plates.
There are "Wet Rated" flap covers too - 3056H on 3099H bare box.

http://www.hubbell-wiring.com/catalog.aspx Section F Watertight
Devices.

Best practices would be using the raintight Pin And Sleeve cord cap
devices hanging from the ceiling that can be washed-down with the
covers closed - go look at any McDonalds and they use them on all
their gear. But they are a bloody fortune - those you find in an
auction lot or on eBay..

And the upper cord grip going into the boxes on the rafters needs to
have a woven wire cord grip so all the strain isn't on the SO cord
sheath all in the one spot with the rubber grip gland, but spread out
on the sheath and conductors. Those boxes should be sealed up too,
even if it's just a careful application of caulking to the covers and
all the holes in the boxes.

-- Bruce --