I would appreciate any guidance on this matter... I am going to be doing a project where as I have to wire 5 smoke detectors together (2 in a front common hall, 2 in a rear common hall, one in the basement). The walls are concrete.
Therefore, I was going to use either wire mold or emt as a raceway, and strip the sheathing off the romex at the locations where it will be inside the raceway. At either end I would have only about 1 inch of sheating entering the raceways. If I use emt, I would have a transition at either end to secure the romex. If I use wire mold, I would essentially do the same thing. Thus the raceway is simply that, a raceway and the 'cable' of romex is reduced to four conductors (hot, neutral, ground and red wire is signal wire) in a raceway.
I am being told by a wiring inspector that this is a code violation because the wires are not THHN.
Where does it state than romex wires are not THHN, and this method cannot be used?