hackdroot wrote:My garage is finished and painted so I mentally walked through both options and it seemed easier to run a flex conduit outside the wall.
In that case, maybe so. I guess I assumed that if you were OK with exposed conduit, your garage probably wasn't finished and painted.
But now that you say your garage is finished and painted, I suggest considering concealing the wiring so it will look better.
Either way will work.
hackdroot wrote:You're correct and it appears that amazon has the same unit with the 6-50. I should just do the 50A breaker and #6 wiring instead though since it's recommended by the vendor in the product Q&A.
I'm surprised that Clipper Creek would suggest a 50 amp breaker for a 32 amp EVSE. A 40 amp breaker would be fine with #8 NM/2 on a 6-50 receptacle.
BTW, for a 50 amp circuit, if you run conduit the whole way, you could pull individual #8 THHN conductors, which have an ampacity of 50 amps. NM is limited in its ampacity to a lower value, so it would require #6 NM to get to 50 amps. You could e.g. run some FMC in the wall and transition over to EMT for the exposed run.
To answer your original question, if you want to run NM in the wall and transition to EMT exposed on the garage wall, yes, use a junction box, come into the back of the box with the NM (use a cable clamp), and run EMT out the side of the box. If you want to splice the NM in the junction box to individual THHN conductors, then there's a required minimum volume for the box: 15 in^3 for 8/2 NM, 21 in^3 for 8/3 NM, 25 in^3 for 6/2 NM, and 35 in^3 for 6/3 NM. [Edit: those numbers assume that any cable clamps are outside of the box. If there's a cable clamp inside the box, add 3 in^3 for #8 NM and 5 in^3 for #6 NM.]
Stripping the sheathing off the NM cable for the length of the EMT conduit run is a bit of a gray area, as the individual conductors in the NM cable typically aren't marked with their type, even when the manufacturer says they are THHN or whatever. Otherwise it would be the most convenient option.
Running the cable with its sheath through your EMT is another option, although it's not clear how to clamp the cable when it reaches the box with the receptacle (although you could omit the clamp where the cable emerges from the wall). You'd also want to upsize your EMT so the fatter cable will go through it more easily.