Commonly referred to as “Romex” cable, this type of electrical wire (Non-Metallic Sheathed Cable) may be used for both exposed and concealed work in normally dry locations at temperatures not to exceed 90°C (with ampacity limited to that for 60°C conductors), as specified in by the National Electric Code (NEC).
NM-B cable is primarily used in indoor residential wiring as branch circuits for outlets, switches, and other loads. NM-B cable may be run in air voids of masonry block or tile walls where such walls are not subject to excessive moisture or dampness.
Voltage rating for NM-B cable is 600 volts.
Type NM-B Manufacturer’s Specification Sheet.
Type NM-B Wire Composition and Sample Uses.