PART IV. GROUNDING (BONDING) OF ENCLOSURE, RACEWAY, AND SERVICE CABLE
250.86 Other Enclosures.
Metal raceways and enclosures containing electrical conductors that operate at over 50V [250.112(I)] must be grounded (bonded) to an effective ground-fault current path [250.4(A)(5)].
Metal raceways and metal enclosures containing circuit conductors from electrical supply sources that operate at 50V or less aren't required to be grounded [250.86]. For example, metal boxes used with power-limited fire alarm circuits operating at 50V or less aren't required to be grounded.Exception 2: Short sections of metal raceways used for the support or physical protection of cables aren't required to be grounded (bonded) to an effective ground-fault current path. Figure 250.123
NM cable on a wall of an unfinished basement installed, in a listed metal raceway, must be grounded to an effective ground-fault current path [334.15(C)].Exception 3: Metal elbows having 18 in. or more of earth cover aren't required to be grounded (bonded) to an effective ground-fault current path. Figure 250.124
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