we're doing renovations
I was trying to clean some plaster that was next to a power outlet and I
used the same metal "thing" used to spread the plaster on the wall. (it's a
thin metal blade)
the plaster broke and the metal blade went in the power outlet area and
touched the hot screw, making some spectacular sparks and basically
destroying (vaporising) a small piece of the metal blade.
the breaker did not trip. the whole thing only lasted a fraction of a
also, the blade only touched the black wire screw (hot) and did not short
hot with neutral or ground. the screw that holds the black wire is not
melted, just black on one side
#1 why would there be sparks if there was no short? I don't think the blade
touched the box of the outlet because the box is deeper inside the wall. the
blade was touching the wall.
is the wall acting as a ground?
#2 I opened the outlet. all the wires in the house are new. I looked at the
wires for the hot, neutral and ground and all look fine, no melting and no
marks whatsoever. the plastic insulation is the same way it was the day the
wires were installed. the only evidence that this happened is on the screw
that holds the wire in the outlet. I still have power to the circuit.
could this have caused any permanent or serious damage to the wires inside
I'll bet that the drywall knife shorted the hot screw to the case of
If the drywall knife was already in contact with the box when it hit the
screw (most likely), you may only find scorch marks on the screw, not the
If the contact was for a _very_ short interval, it's entirely possible
that the breaker wouldn't trip. The sharp edge of the knife acted as a
If the screw head is heavily damaged, you should replace the screw, but
outlets are so cheap, and these screws are special alloys, so it'll
usually be easier to replace the whole thing unless you have another
outlet you can cannibalize. If only one screw is in use on the hot side,
just move the wire to the other screw.
If it's just a little cosmetic soot on the top of the screw, don't worry
about it. Do check that you can loosen the screw with a screwdriver - it
_may_ have fused threads.... Better to replace it now if it's fused.
If the wire on the screw is partially damaged (ie: got melted),
clip off the end and re-strip/reconnect the wire.
Fortunately, wire tends not to get damaged from this sort of short except
where badly knicked, or if it is the point of contact for the short.
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.
it's only soot. I unscrewed it to look at the copper wire beneath it, there
were no marks on the wire.
I think the blade must have been in contact with the outlet's metal bracket,
the part that holds the plastic cover.
While it is possible that the contact was so brief that the breaker didn't
have time to open, any time I have had sparks (which sadly is more than a
couple) the breaker has opened. Unless you want to test it and ascertain
that it is functioning okay, I would replace it.
the contact was very brief, I was going back and forth with the blade at the
time and I obviously stopped as soon as I saw sparks flying
the breaker is a Siemens and it is new, as is the panel and the wiring. I
assume the breakers all work (I can't really test any of them, I won't shrt
out wires to see if the breakers open up)
I have a a couple screw drivers and several pairs of wire snips with the
tell-tale 'weld mark' from coming in contact with wires I'd thought were
cold. I agree, the breaker generally has always blown (except the one that
was the buss to the metal breaker box, that one about broke my arm instead!)
If you aren't comfortable replacing the breaker yourself, I'd have an
elecrician in to do it.
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