Concentric Knockout question

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Old 08-18-14, 12:07 PM
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Concentric Knockout question

I had to use the concentric knockout in 2 1900 box for a circuit I ran with 1/2 emt. Is using the 1/2" hole on these concentrics any less secure than using the ones that don't have them?

Secure from a strength perspective and from a grounding perspective.

I was going to go as far as replacing the box to avoid using them... hopefully that wasn't necessary.
 
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Old 08-18-14, 12:20 PM
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It is not necessary. You do not have to bond around the concentric KO's with what you are doing. If you were installing service equipment, that would be a different story.

From a strength perspective, I guess they would be less strong. The KO's are designed for EMT. However, if you're concerned with strength perhaps you should be looking at rigid metal conduit instead of EMT.
 
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Old 08-18-14, 02:02 PM
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Once installed the box should have no stress on it so the knockouts should not be an issue.
 
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