That depends what happens to the wire on each side of the whole. If you
run several cables through the same set of holes it has the effect of
bunching the cables together. The ampacity of cable is given in free
air. If air cannot readily circulate around each cable the conductor
ampacity of the cable should be derated. By how much is a matter of
interpretation. That is a job for the Authority Having Jurisdiction
You've probably forgotten more than I know. So, I would just suggest you
ask the local building codes people or inspector, as this is a way to meet
him/them and let em know you intend to do it right. They like those kinds
of builders. I'm in the middle of an addition, and I've called mine about
six times so far. He said he would rather a phone call than declining
approval because someone just didn't get a simple but important item right.
I live in a small town. Things may be different where you are. Even though
there are national standards, sometimes those little localities can and do
have their weird ways of doing things.
You don't live in Toquerville, Utah, too, do you? Same thing here. No
house delivery of mail. Everyone has to go to the post office. UPS goes to
post office. But the inspector is a nice guy, and if you approach him
right, he'll point you AWAY from the cliffs.
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