Panelboard Cabinet Holes

[Jerry Simon]

You guys flag these three small open holes on the back of a main electrical panelboard's metal cabinet as needing to be sealed?  Cabinet is not mounted flush against foundation wall (one could stick their pinkie into the larger hole).    Same holes at top of cabinet if you're familiar with this brand.

[Jim Katen]

Unless I figure a mouse can fit though, I don't mention it. 

[Bill Kibbel]

Same as Jim.  If a critter can't fit, you must omit.

[Jim Katen]

3 hours ago, Bill Kibbel said:

If a critter can't fit, you must omit.

Unless the slit, is not legit

And was commit, ed by a twit

Who used a bit, to bore the slit

As an aftermarkit, retrofit. 

- Jim-Manuel Miranda

 

 

[Chad Fabry]

I can't prove it, but I think I read in the book that the maximum allowable size is 9/16"- I'm pretty sure it's in EIED by Hansen and Katen

[Marc]

I'll betcha its a standard for enclosures, not a code cite.

I don't write them, unless its an open knockout or otherwise a cable opening.

Edited August 18, 2020 by Marc

[Jim Katen]

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. 

[mtwitty]

Even if the mouse gets in, a trap is waiting for him.

[Marc]

Poor thing. He's beautiful.

Edited August 20, 2020 by Marc

[Jim Katen]

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. 

[Jerry Simon]

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. 

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.

 

[Tom Breslawski]

1/4 inch hardware cloth.

[Jim Katen]

2 hours ago, Tom Breslawski said:

1/4 inch hardware cloth.

For large openings. 

For small openings, stainless steel wool works great. The mice will not chew on it because it makes their fillings hurt. 

[Chad Fabry]

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. 

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 

[Jim Katen]

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. 

[mtwitty]

Cool micrometer. What brand is it?

[Jim Katen]

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.