This was posted on a DIY site. I don't see how Article 312 would apply to a sleeve for NM-B running to a surface mounted device ie switch or receptacle. Your thoughts?
We commonly 'sleeve' romex NM-B cable from a suface mounted wall box ...and it extends up into a joist space...and does not penetrate any of the structure.This saves us from installing a splice box up there!
The conduit is generally a straight piece and extends up into the joist space,and MUST have a protective bushing on that far end.
A complete conduit system is defined as one with enclosures etc at each end.
A 24" short nipple between two enclosures ,and no longer than 24" is permotted to be filled at 60% of its area...as it is apart of a complete system.
This would require a trade size conduit of no less than 3/4" for a 12-2G NM-B cable.
Your installation is not a complete system...and the 1/2" conduit is fine,[I prefer 3/4" for this ] if between 18" and not longer than 10ft..and if it is also secured at the far end...if the NM-B was installed without trauma...a bushing is installed and the opening sealed as per 312-5.c.d...and the cable is stapled within 12" of the exit point in that joist space...
I have always used a bushing and properly secured the cable, but don't see the purpose of the raceway seal. I don't know how the moderator thinks that this Article would apply as this is not entering a cabinet, cutout or meter socket.