NM cable is a bundle of individual conducting wires wrapped in a plastic vinyl outer sheathing.
Normally the cables carry 10-, 12-, or 14-gauge conducting wires for individual house circuits.
The sheathing on NM cable does offer some protection against incidental physical damage.
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Sheathing on Romex is made of tough polyvinyl chloride (PVC) thermoplastic.
The sheathing on both 14 and 12 AWG wire is 19 mils thick.
Still, no matter how strong the NM sheathing is, it is not meant for exposed applications.
Similarly, NM attached to the face of concrete walls is susceptible to damage and thus is not allowed.
Such wiring is well protected against physical damage.
The electrical conduit is designed for use with specific types of individual conductor wires.
How Many Wires Per Conduit?
This is a subject of some debate among electricians.
Some pros argue that NM cable inside conduit may be susceptible to heat build-up and is therefore not allowed.
Others take a more lenient view.
It is not good practice to put Romex in conduit.
Individually coated bundled wires are contained within the sheathing.
It’s generally best to run only separate THHN wires inside the conduit.
An exposed wire can cause a fire.
National Electric Code of Minnesota.
