In article .com,
wrote:
What do I need to do to transition at the point where the Romex exits
the wall and enters the conduit?

I have the same situation with some #6 stranded wire I'm running for a
subpanel out to the garage. It's 50ft of three wire in a black jacket
and I wanted to run it in from the back through the joist cavity. But
the back of the subpanel I have does not have a rear knock-out, so I
have to run the feeder in through the top of the panel, which leaves
the cable exposed on the wall.

If anyone can advise, I don't want the cable exposed on the wall. I'm
thinking of having a metal conduit run from the panel up to a j-box in
the corner of the wall/ceiling. Run the cable into the j-box from the
ceiling with the jacket on. Out the other side of the j-box through
conduit, to the sub-panel. Does this make sense? I'd remove the outer
jacket from the cable run into the conduit.

Do they make j-boxes that big for #6 stranded (heat concern?) or is
there some kind of transition device used to go from sheathed cable to
conduit?

Thanks!

They make direct EMT-to-Romex fittings. I have only ever seen them in
1/2", to small Romex; the Romex clamp (officially known as NM cable,
BTW) is 3/8", and suitable for 14-2, 12-2, and maybe even for 14-3 and
12-3. The next large solution has already been mentioned: Use an
EMT-to-threaded connector, followed by a threaded coupling, followed
by a clamp for the Romex.

To make sure you hide all the cable in the wall, drill a hole deep
enough that the first 1/2" or 1" of the EMT is hidden in the wall. By
the way, drywalling around the EMT will be no fun, hard to get it nice
and smooth.

There is one more annoying little issue: the EMT has to be grounded,
at the minimum by being connected to a grounded metal box on at least
one end. If you use an EMT-to-NM fitting, or the method with the
threaded coupling, there is no place to attach the ground, so you
better hope you can ground from the other end. Also, the NEC allows
small sections of unstripped Romex in conduit only. If you have a
long run in conduit, you shall strip the outer jacket off; the
conductors used inside the Romex are perfectly happy to continue on
inside the conduit.

For the rear exit from the subpanel: What I've seen done is simply to
drill or punch a hole in the back of the subpanel. Do the experts
think that this is legal? We did this to two of our panels, and
passed inspection, but that means nothing (could be that our inspector
was a fool or sloppy).

Getting a J-box for three strands of #6 cable is trivial. Just look
up the rules in the NEC for required cable volume per conductor. I
would use at the very minimum a 4" square box, because #6 cable is
stiff enough that working with it in anything smaller is an incredible
pain, and has the risk of chafing the insulation. In general, using
bigger boxes makes life much more pleasant.

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Ralph Becker-Szendy