Ground Conductor Sizing: NEC Table 250.122 for EGC and Table 250.66 for GEC
A contractor wiring a 400 A service for a new industrial building sized the grounding electrode conductor at 3 AWG copper because he used NEC Table 250.122, the same table he relies on for equipment grounding conductors on branch circuits. The engineer caught the error before inspection: for a 400 A service with 600 kcmil copper ungrounded conductors, Table 250.66 requires a 2/0 copper grounding electrode conductor. The 3 AWG would have carried normal current without complaint, but it would not...
2026-09-17
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