Electrical – Running NM-B in PVC SCH 40 Conduit from Outdoor Breaker Panel


For space-saving reasons, I have outdoor breaker panels, and most of my branch circuits are wired through the attic down to individual outlets. Currently, the wires run through the wall from the breaker panel into the attic, but it is getting difficult to pull any more wires through.

My service wires actually enter from under the panel, and there is a ~2" entry at the top of the panel. What I would like to do is run my branch circuits through 2" SCH 40 PVC conduit up from the breaker panel on the outside of the building, and have one 90° bend to go through the wall and into the attic. The total length of the conduit run would be less than 10' and none of it is underground.

I would like to know if I can run NM-B (Romex) through this conduit from the breaker box legally. For one of the panels, this will consist of a maximum 12 individual 12/2 cables. For the other panel, this will consist of a maximum 4 10/3 and 2 12/3 cables.

I believe the conduit is appropriately large enough for the number of conductors, but I've seen other answers regarding running NM-B through conduit where conduit length is a concern.

Best Answer

NM-B cannot be in conduit that's outdoors. Outdoor conduit is considered a wet/damp location, and NM-B is not allowed in wet/damp locations. Aside from that, you'd have to do conduit fill calculations, to make sure the conduit is large enough.

This other answer might be helpful.