I have often thought of potential problems associated with the grounding continuity of the majority of bus plugs I see, especially in older facilities. The way they are bolted on through the paint, I don't see how the ground continuity is even close to acceptable. I think some manufactures have nuts that dig into the paint, but that is only on one side; and those special nuts always end up lost and replaced with standard nuts.
And today I have proof. I was relocating an unused 200A switch and the head of the 1/4-20 bolt was all melted/welded. I attribute this to the paint under the head of the screw causing excessive heat and arcing under a fault condition. Does anyone else notice this as a chronic problem? Sometimes I think about installing a bonding jumper from the switch to the duct, but usually I'll just try to scrape the paint. What about you?
I have noticed sqD switches have spring steel clip that digs into the paint, which is a good design.
And today I have proof. I was relocating an unused 200A switch and the head of the 1/4-20 bolt was all melted/welded. I attribute this to the paint under the head of the screw causing excessive heat and arcing under a fault condition. Does anyone else notice this as a chronic problem? Sometimes I think about installing a bonding jumper from the switch to the duct, but usually I'll just try to scrape the paint. What about you?
I have noticed sqD switches have spring steel clip that digs into the paint, which is a good design.
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