On 10/16/2015 05:10 PM, dpb wrote:
On 10/16/2015 4:29 PM, Texas Kingsnake wrote:
Hi there. Back again with a new problem.

My wife was doing the laundry and I was working near the circuit breaker
panel. When she turned the machine on I heard a loud buzz from inside
the
box. Less than a second long. I had her turn the machine off, took off
the panel cover and watched as she turned the machine back on. I saw
arcing
at the left-handed side of the panel at the point where the heavy black
cable from the street enters the box. I had her turn the machine on and
off and it happened again. Then I pushed the black wire right where it
enters the clamp and it hasn't happened again, despite having all the
same
lights and appliances on.

I am thinking the clamp has loosened over time. I am going to get a
well-insulated screwdriver, put on very heavy rubber gloves and am
going to
try to tighten the clamp which may have not been tightened in 40 years.

Does the power *really* need to be killed at the meterhead? I've changed
out breakers without killing main power (so much frikkin' stuff needs
to be
reset after a power shutdown that I hate doing it)?

Anything else I should consider? Is the washine machine motor about
to fail
and is drawing a huge amount of current at startup? How do you even
measure
the inrush(?) current in such a case. Would pressing on the wire near
the
clamp cure it temporarily or is some other process in play?

What would account for it happening twice and then not happening
again. The
only real intervening act was to push on the wire jacket at the point it
enters the clamp on the circuit panel. Very strange.

Sounds quite plausible and yes, simply pushing on the wire could easily
have broken the point at which the arcing was happening.

It's certainly possible to just tighten the connection w/o cutting
power; I'd be much more comfortable going on if I had seen the actual
condition of the wire and connection before I just went on, however. If
it was actually arcing to that point, good chance there's some built up
corrosion and/or arc damage that should be taken care of.

Particularly if the external feed is Al instead of Cu, I'd not even
think of not doing the above, cleaning it all up well and replacing the
antioxidant.

--



I worked on high power circuitry for 38 years and cleaning a bad
connection is not the answer.


Believe me I've tried. Once a connection has been burned and tarnished
no amount of cleaning can ever again provide a satisfactory connection.
All connectors and wires must be replaced...or if the wire/cable is long
enough...cut back to good , fresh copper.


For low power circuitry, cleaning is probably OK though.