AskCodeMan

Does this violate Section 300.15?

My 2 cents worth: Yes, no and maybe.
A) Maybe, but most likely ok. Assuming the following: 1) That is an AC connector and AC cable. 2) The cable is supported properly. 3) The EMT ends in a properly attached box. 4) Coupling passes (see letter 'C')
There would be an arguable point ref the grounding path. AC uses the armor. Therefore we have to look at the integrity of the path through all the pieces and material changes (cast->steel->cast->steel). A discussable point.
B) Yes. IF: 1) that's MC cable with an MC connector. 2) The cable is supported properly. 3) The EMT ends in a properly attached box. 4) Coupling passes (see letter 'C')
Then I'd say it's legal because the the coupling and EMT are both ok to contain "loose" conductors. The EMT in this case is protection only, not ground path. EMT would be grounded at the end where it goes to the box.There is a potential question on the sharp exposed threads within the coupling at the gap but I'd say that was irrevelent because we have the same issue when two pipes are joined.
C) Maybe, but most likely illegal. The final "it depends". Is the coupling listed for the attachment of any fitting, or only for the joining of two threaded pipes? I don't know for sure but I'm betting it's only for pipes, therefore illegal.
What do you think?
Steve

BTW they make a fitting that has a UL and can be obtained at the DIY stores that has a set screw EMT on one side and a connector on the other. Never saw one with AC connector but have used one with NM connector. This eliminates the coupling.