I had someone put a screw into an 800 amp branch circuit cable when replacing the panel cover. does anyone know of a publication or standard that states to inspect behind the screw holes before replacing panel? this person did no work on the system, simply removed the front panel did a visual for available breaker positions and replaced the panel. He recieved only lightly singed eyebrows and a stain in his shorts.
This is not an answer to your question but a related story.
We opened up a 200A 208/120 panel about a year ago to add a couple of circuits. Started wiggling wires in the panel and found one wire that we couldn't move. Investigated and found out that a company that had installed some steel shelving in the storage room behind the panel had screwed their shelving into the "metal wall panel" in the closet. Of course the metal wall panel was the back side of the electrical panel.
They had put a self tapper right into the neutral feeder. Talk about luck.
Sorry for the continued sidetrack. Common sense really is rule #1, but you won't find that written anywhere. I never replace the cover on anything without double-checking clearances of screws. I don't care if I just took the cover off two minutes earlier.
What amazes me is when the factory screws get lost and someone replaces one or more with 2" sheet metal screws. Talk about blind luck!
If a cover on a piece of equipment is removed the one reinstalling it has the responsibility to make sure screws do not penetrate any insulation and if dealing w/ a older panelboard where they use concealed clamps to hold the panel front to also make sure they don't pinch anything. You take it off, you are responsible to see that everything is clear to replace it.......
As stated by others, there is no documented text in the NEC, but there is some "hinting" done in a few of the Switchgear installation manuals I have read over the Years.
On one of the bulleted lines, there is a paragraph describing to "Check For Pinched Wires When Replacing Covers".
And, as stated by others, it's something to commonly think of when replacing covers, and such.
When dealing with large Feeders in switchgear sections, the Conductors tend to naturally want to spring right against the brackets where the screws for covers are affixed to. This is apparent prior to installing the covers, and steps should be made to secure the Conductors away from the landing brackets (to avoid a Ground fault issue from a Bolt/Screw penetrating a Conductor's insulation).
With Panelboards, Branch Circuit Conductors should be routed away from possible conflicting areas, such as where the Mounting Holes are located, or where captive clamps will engage the Enclosure.
Screws / Bolts of proper length should be used, and these should have "Dull" or rounded ends.
There are times when a Panelboard was made up in an "Ugly" fashion! These Panels resemble a tightly packed Bird's Nest inside. Typically, the Covers on these Panels will "Spring Off" when the screws are loosened! Re-installing the Covers on these Panels is a challenge, to avoid pinching Conductors, or driving a screw through Conductors.
Scott " 35 " Thompson Just Say NO To Green Eggs And Ham!
They could fix this problem if the cover mounted on studs with wing nuts or knurled caps instead of screws that penetrate the wiring cabinet. It would be easier to put on too since it would hang there until you got the nuts started.