I brought this up a few times(see previous topics).
I use ENT with insulated ground instead of NM. Heres why--
680-12 requires disconnect.
680-25(d) requires panelboards and DISCONNECTS to have an insulated ground.
680-25(c) requires motors have an insulated ground, with permission for interior of single family dwellings to use NM (a chapter 3 wiring method).
680-25(d) does not include the permission for single family dwellings. Therefore, NM not allowed.
I have seen many NM installations. Apparently it's often accepted.
