Extent of Damage from Arc?


Old 01-03-16, 03:59 PM
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Extent of Damage from Arc?

Location: Indiana, USA.

Hi, thanks in advance for your assistance.

I caused an arc (line-to-ground) with my voltmeter lead. The light switch was grounded and the hot line was secured to the light switch. The lead contacted both the hot line screw of the light switch and the metal side of the light switch, which was grounded, causing the arc.

The wire is 12 gauge, and the circuit breaker is 20 amp. The circuit breaker tripped "immediately". The metal side of the light switch is burned and the voltmeter lead tip is burned. Otherwise, once I reset the circuit breaker, everything seems to be okay (including the voltmeter and myself).

There are other receptacles, switches, and gang boxes between where the arc occurred and the circuit breaker. The damage (burns) appears to be localized to the location of the arc itself. However, I am concerned about possible damage somewhere else on the run.

I have heard that the copper wires used in home electrical systems can carry quite a bit more amps than for which they are rated, but just not for a very long time. Because the circuit breaker tripped quickly, I'm assuming the amperage over 20 amps was not sustained for long. Also, judging by the burn marks the heat dissipated quickly allowing the damage to be localized. I also cut into the hot line (right where it connected to the light switch screw) to make sure there wasn't any damage on the interior of the copper line. The copper line internal surface/cross-section looks a shinny copper. This further signals local-only damage.

I am aware of why an arc occurred, and I am aware of the danger of arcs. (I'm not an idiot, just did an idiot thing.)

I presume that if there were some poor connections up the line, then there possibly could have been more arcs?

I'm hoping that you all can put my mind to ease, so that I don't feel compelled to replace the entire run.

Do I need to be worried about any damage to other spots on the run other than where the arc occurred?

Thanks again for your assistance.
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Old 01-03-16, 04:09 PM
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The breaker should have tripped almost immediately before too much current would damage any other parts of the system. I would not worry about it.
Old 01-03-16, 04:10 PM
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For me, I just get *issed when I need to buy new probes. Replace the switch, trim the wire and reconnect.
Old 01-03-16, 04:35 PM
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There is probably no damage upstream to the breaker ...

Except ...

Any "push in and it sticks" backstab connections at receptacles daisy chained along the way might have been compromised.

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