Hint: A close call indeed
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Whew! That was a really close call. The roofer almost drove that screw right through the electrical metallic tubing (EMT). Fortunately, it only nicked the side of it.
This is what can happen when repairs are made to metal-corrugated sheet roof decking. This is also why Sec. 300.4(E) requires cables, raceways and boxes installed under these types of roof decks, to be spaced down from the deck at least 1½ in. from the lowest portion of the roof decking. An exception allows rigid metal conduit (RMC) and intermediate metal conduit (IMC) to be installed closer since the heavier walls of those conduits are less likely to be penetrated by roofing screws. Section 410.10(F) requires the same 1½ in. separation for luminaires installed under this type of roof decking. I’ve personally seen many SER feeder cables, branch circuit metal-clad (MC) cables and even MC cables used for fire alarm circuits that have gotten damaged by these screws during roofing repairs where the wiring methods were installed too close to the roof. Presently, Sec. 300.4(E) does not apply to fire alarm circuits since Art. 760 and particularly Sec. 760.3 makes no reference to Sec. 300.4(E). However, that may change in the 2020 Edition of the NEC. But until it becomes official, I would still heed the spacing requirements of Sec. 300.4(E).