Q. Must metal siding and metal framing members be grounded?
A. The NEC doesn’t specifically require metal siding or metal framing members to be bonded (not grounded) to an effective ground-fault current path [250.4(A)(4)]. However, exposed structural metal that forms a metal building frame must be bonded to one of the following (effective ground-fault path) [250.104(C)]:
• Service equipment enclosure
• Grounded neutral service conductor
• Grounding electrode conductor sized in accordance with Table 250.66
• One of the electrodes of the grounding electrode system
The bonding jumper for structural metal is sized to the conductors that supply the building or structure, in accordance with Table 250.66. In addition, the bonding jumper must be:
• Copper, where within 18 inches of earth [250.64(A)]
• Securely fastened and not exposed to physical damage [250.64(B)]
• Installed without a splice or joint, unless spliced by compression connectors or by the exothermic welding process [250.64(C)]
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