Please be patient folks, this is the first time I've tried asking a question here :-)
I use full conduit wiring (usually 3/4" EMT) for new stuff in my shop/garage areas. The new stuff sometimes has to connect to NM cable wiring. I usually formally transition to my new EMT conduit wiring in a metal box, with the NM coming in thru a knockout and clamp in a protected way (e.g., thru the back of a 4 square box that is surface mounted on a sheetrock wall).
But, this isn't always reasonable. So I have some questions about what is and isn't allowed when using EMT as protection for NM cable as it approaches a box.
When using EMT for protection of NM cable, is it OK to attach the EMT sleeve to the box using a box connector, just as one would in full EMT conduit wiring?
If attaching the protection with a box connector is OK, how is the requirement met for securing the cable within 12" of the box (as required in 334.30) if the EMT sleeve is longer than 12"? Is the EMT sleeve itself considered as "securing and supporting" the NM, provided the EMT is itself properly secured?
I understand that the NM must be secured with 12" of the entry to the sleeve, I'm asking about the other end, where the NM passes into the box. I'm asking about the general case of cable entering a typical junction box, I know there is a special rule for entering an electrical panel thru a sleeve.
- Is there a requirement to clamp the NM if it enters the box thru a sleeve? I can see how this could be done with an interior clamp integral to the box (e.g., an old style metal gangable device box), but a typical knockout clamp couldn't be used because the EMT adapter would preclude that.
It feels like if there is no clamp as the NM comes in, then we've really already transitioned to conduit wiring, which means we really don't have a sleeve anymore, it's now conduit.
- Would using a NM/EMT transition fitting when the NM first enters the EMT sleeve (more than 12" away from the box) make any difference at all? Are these fittings ever required, and if so, for what? You can't just strip the sheath from NM and go into conduit wiring with them, because the conductors in NM aren't suitable for conduit wiring as they aren't intended for pulling, wet environments, etc as THHN or XHHW would be. So what the heck are these NM/EMT fittings used for?
So thanks for any insights you can offer, I've seen a lot of really thoughtful responses from the folks that hang out here.