iwire said:
Yes, but the question remains ..... why?
Why is it OK for SE but not NM?:-?
I'll take a stab at it.
It could be that, when the rule was made, NM cables contained undersized EGC's (i.e., the ones with EGC's), which would not be protected by the branch-circuit OPD.
As for the only-from-the-main-panel rule, it's a dilemma we face when we render a main panel into a sub-panel: where do we land an SE's neutral doing double duty?
We're supposed to replace a cable, receptacle, and cord being used this way, but on the occasion we don't, the bare conductor is connected as a neutral, not as an EGC.
What's the point? I don't know.
Except that an SE cable's bare conductor is clearly designed and approved for use as a current-carrying conductor; an NM's is not.