A. Redwood Kardon responds: Wherever steel studs are used to support NMC cable (the plastic-jacketed cable commonly used in residential construction), there is the potential for the framing to become energized. Metal electrical boxes or metal equipment that might be attached to steel studs must always be grounded, which effectively grounds the studs. When plastic device boxes are used, I recommend installing a bonding jumper to the steel frame. This jumper should be sized to match the highest-rated breaker that feeds the specific section of wall. In some areas, the electrical inspector may require a bonding jumper for steel boxes as well.
While the National Electric Code (NEC) does not specifically address the question of grounding a steel frame in residential construction, Section 250 of the NEC contains two citations that mention "structural metal frame of a building" as applied to large steel structures. Section 250-58a says the metal frame must not be used as the equipment...
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