I did a stupid thing

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 second. 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 the wall?
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j j wrote:

There was a connection to either the return or ground, perhaps through the outlet's mounting frame or the box.
I don't think the blade

I doubt it. If it had that enough current in it to melt the blade you'd see evidence of the current in the plaster.

No. Just be more careful in the future.
RB

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We all do 'stupid' or non-thinking things from time to time. What is important is that we learn from them. Des

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j j wrote:

There was a short.

It touched something hot and a neutral or ground. The box, if metal or the cable if metal would be ground and there may have been a pipe or other ground in the area not part of the box.

If you hunt around you should be able to find a burn mark somewhere. No need to, likely everything is OK.
--
Joseph E. Meehan

26 + 6 = 1 It's Irish Math
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I'll bet that the drywall knife shorted the hot screw to the case of the box.
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 box.
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 fast-blow fuse.
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.
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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.
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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.
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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)
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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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no it is Siemens
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