NMC-B cable has a voltage rating of 600V.
The rated voltage for a cable is the voltage for which a cable is designed and defines the electrical testing requirements.
The rated voltage is expressed as the ratio of two values, U0/U, where U0 is the effective value (root mean square or r.m.s.) of the voltage between any insulated conductor and the “ground” (metal covering of the cable or surrounding medium). U is the effective value (r.m.s.) between any two-phase conductors of a multi-conductor cable or system of single conductor cables.
In an alternating current (AC) system, the rated voltage of a cable should be at least equal to the nominal voltage given by the U0/U value. In direct current (DC) system, the rated voltage of the system should be no higher than 1.5 times that of the nominal voltage of the cable.
Read NFPA's electrical safety tips to learn how to protect your family and home from electrical fires.