Thread: Scorched grounding lug

In Canada, we keep grounds and neutrals separated even in the main service panel. The grounding bus is under a cluster of wiring on the left.

Some circuits were added, and this looked like a handy screw to mount a new lug.
I don't know what caused this much voltage on the grounds, but I'm happy the scorch marks are there to illustrate the screw up. I had no ground on one circuit in the new suite.

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The reason for those burn marks can be speculated forever. I'm "guessing" that the ground bar is/was full and that little lug was created as a "sub" ground bar for a place to terminate the last few circuit ground wires. Not legal, but probably functional.

My point is that hot spots were caused by this flaky connection. Square D provides mounting holes for these ground lugs up the sides of the panel.

Looks like a good way to start a fire.

I would wonder if this was caused by a fault condition or if an EGC is connected improperly to a downstream neutral conductor.

Would take a lot of current on those grounds to cause that, even with the paint acting as an insulator between the incorrect terminal and washer and the enclosure - that much current on a conductor which is not intended to carry any current is a bad thing.

That is what those look like when it takes a lightning strike - I've seen it several times after a lightning strike, even enclosure to cover through the screw and back to the enclosure through another screw.

I'd really suspect someone was working on something "hot" and caused a fault. There was a tiny contact at each of the two arc marks where the contact metal got vaporized.

I would guess none of the wires in the terminal are grounded any more with the contact points blown off and everything else painted. Prime example of why the screw is required to be in contact with the terminal and have at least two threads engaged in the metal cabinet.

I don't know how those lugs are listed up north but here it's for one wire only.

I found only one ungrounded circuit but there could be a dishwasher or some other dedicated circuit there that is no longer grounded. The large solid conductor supplies a remote panel, and those circuits tested grounded, but possibly not very well. The installer may have shorted a hot to ground as a test of his handiwork, who knows?

Bill, you are right. That is the wrong lug for that purpose, as well as being incorrectly mounted.

Originally Posted by John Kogel

My point is that hot spots were caused by this flaky connection. Square D provides mounting holes for these ground lugs up the sides of the panel.

Unlikely the schorches have anything to do with those ground wires John. They are insurance wires that only carry current in the event of a problem, which is rare. All those wires are bare, so no neutral wires. Many possibilities, but unless there was a fault already in play, those burns were caused by a hot that got away from somebody or by someone doing it for sport. As a young "lectrishun" on a weekend side job, I had to listen to the client complain about how expensive electricians are. Being on a ladder @ that time, I shorted out a hot wire in the box I was working on which made a mini spark show for him before the C/B tripped. He finally shut up and let me work.

I suspect that a hot got pinched or cut when the KO was made.