Why you can't run NM (Romex) to an outside condensing unit

[jar546]

Simply put, NM cable is not allowed in wet locations and even in conduit outside, it is not allowed. This is nothing new, it has been the code requirement for a very long time. This is how we get there.

NEC Article 334 covers NM cable. Type NM, NMS & NMC are part of this. None of them are allowed in damp or wet locations except NMC which is allowed in damp locations (but NOT wet) - 334.12(B)(4). Good luck finding NM-C cable anywhere. Now we need to define a wet location. If you go to Article 100, Locations-Wet, it states "...unprotected locations exposed to weather." and the NEC handbook further states that "both the inside of a raceway in a wet location and a raceway installed underground are considered wet location."

Furthermore, NEC 300.(5)(B) states that "the interior of enclosures or raceways installed underground shall be considered a wet location."

Lastly, to drive the point home with one more code section, NEC 300.9, states that "Where raceways are installed in wet locations abovegrade, the interior of these raceways shall be considered to be a wet location."


The photo below is a code violation under NEC article 334.

 

[Norcal]

Agreed, if they had used UF cable it would have been fine, any conduit outdoors or underground is a wet location so NM is out. Reminds me of a few homes in the cheap subdivisions built down the street from me, PVC conduit to the kitchen island, then either pull NM or skinned out NM cable inside it, but I judge a building by the electrical equipment & every one of the 5 subdivisions used "Zinsco II" panels (Eaton BR).