i worked the industrial side of the business most of my life (30yrs) and doing the residential on weekends and such. finally decided to retire into res. only. suprise! anyway, i have a question regarding a post in the photo section of the forum. why can't the header above the dist panel (flush mount) be drilled to allow a conduit with branch circuit cables to pass through?
another question; is there a size limit on the nm feeder cable, to a panel that is run between 2x4 studs unprotected by conduit? (top or bottom entrance to the panel)
thx for any feedback. ken m

Hi Ken;
do you mean this one? https://www.electrical-contractor.net/ubb/Forum4/HTML/000035.html

hey sparky, yes that is the one. i have seen different methods. i.e., several holes drilled in the header and individual clamps at the box, like the photo portrays and a 2' or a 2-1/4" pvc or emt conduit run from the panel thru the header an the branch cables passing thru. i'm familiar with the 24" nipple rule and max # of cables. are there any other reasons why the conduit thru the header is not nec worthy?
providing the cables are secured prior to entry into the conduit and a sealer is used. thx., ken m

Ken,

373-5(c) requires that "cables shall be secured to the cabinet..."

There is an exception for surface mounted cabinets, but there are 7 items that must be complied with to do it right.

As far as the max size cable is concerned, you have 1 inch in the center of a 2x4 to use without needing nail protection, see 300-4(a). You might, if you hold your mouth just right, get #2 aluminum SER cable to go through a 1" hole. I certainly wouldn't want to run this size cable through too many holes, my back hurts just thinking about it.

Tom

Uh...

We're allowed to go larger then 1" if we use "anti-nail plates" though, right? I get mine at a hardware store, the type plumbers use...

What about protection between the framing members (in the stud-bay voids) ? Do we have to sheet the entire run with 1/16" Galvanized steel?

are there any other reasons why the conduit thru the header is not nec worthy?
providing the cables are secured prior to entry into the conduit and a sealer is used.

I don't know the rationale behind this particular code. It would seem a captive panel would be accessible if it were so.

Good point Virgil,

We should use diamondplate on the outside to protect from the siding guys !
More than once I've seen them nail right through the panelboard into the Busbars! And once put a screw into the SE cable (Underground service). Like the 4th of July!!

Bill

Be careful about using a plumber's nailplates. They may be too thin. UPC requires steel plates to be not less than 18 gauge.That's .0478" instead of .0625"

Good point Phil!