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Panelboard Cabinet Holes


Jerry Simon
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While there probably is a standard for enclosures, and it probably does include restrictions on the placement and sizing of these openings, I don't know what those would be. The 9/16" noted in the book is just an example of a largish opening that doesn't need to be covered. The general rule is that knockouts always need to be covered - either by having clamps or bushings and wiring run through them, or by having knockout covers installed. Holes that the manufacturer made to accommodate mounting hardware do not need to be covered, even though they can get to be quite large. 

That said, in my reports, I don't recommend covering mounting holes unless I think that a mouse can get through or, more to the point, if I see evidence that mice have gotten through. 

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2 hours ago, Jim Katen said:

From another Eaton panel (the example in Electrical Inspection of Existing Dwellings is also an Eaton panel) earlier this week. This hole, at .65" is slightly larger than 5/8". 

My guess is that a mouse would have to be pretty darn motivated  to get through this hole. 

RIMG0171 (Medium).JPG

Maybe, maybe not.  I've been fighting those suckers for five years.  EVERYTHING sealed outside, but finally had to spray-foam my wooden knee walls that they kept chewing through.  Little assholes.

Mouse Holes

I originally was concerned about arcing/burning inside the panelboard that could escape through the openings.

 

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On 8/23/2020 at 3:01 PM, Jim Katen said:

From another Eaton panel (the example in Electrical Inspection of Existing Dwellings is also an Eaton panel) earlier this week. This hole, at .65" is slightly larger than 5/8". 

My guess is that a mouse would have to be pretty darn motivated  to get through this hole. 

RIMG0171 (Medium).JPG

Your vernier digital indicator is off. The scale shows 15mm and .60 inches. .60 inches which is almost exactly correct. 16 mm is almost exactly 5/8 inches. 16.5 mm =.65 inches 

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Good observation, but you can't go by the rule markings in this view. The front section of the digital display has some thickness, so with the camera slightly to the right, there's some parallax error. I zeroed out the digital reading before measuring it. It should be pretty darn accurate. If I were to move the camera to the left, it would show .65 on the rule as well. 

Actually, here's a previous attempt at a photo where the lighting was messed up. The camera is even further to the right and the parallax is slightly greater. 

RIMG0169 (Medium).JPG

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I finally got around to looking, and it has no brand or manufacturer name on it. No country of origin. No model number. Just "Electronic Digital Caliper" and "Carbon Fiber Composite Digital Caliper." I got it from Amazon several years ago just so that I could use it in live electrical panels. I think it cost $8. Interestingly, it's in perfect agreement with my expensive metal Starett calipers - and it's easier to read. Of course, there's some flex in the carbon fiber, so you have to be very gentle when taking readings, but otherwise it's been a great tool. 

 

 

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