A commercial building has one 120/240-volt, 3-phase, 4-wire AC service. The largest ungrounded service-entrance conductor is 1 AWG copper. All service-entrance conductors are installed as a single set, not in parallel. The electrode connection uses the general AC grounding-electrode-conductor sizing table, with no electrode-specific reduction. What is the minimum copper grounding electrode conductor size under the 2026 NEC?

Where to look it up

https://www.dli.mn.gov/sites/default/files/pdf/eli_inspection_checklist-2026NEC.pdf ; https://fasttraxsystem.com/grounding-vs-bonding/

Why A is correct

A, 6 AWG copper. The government's 2026 NEC grounding-electrode-conductor chart pairs 1 AWG copper service-entrance conductors with 6 AWG copper grounding electrode conductors. Use the largest ungrounded service conductor and the selected electrode-conductor material; voltage, phase count, neutral size and a downstream equipment grounding conductor do not substitute for those inputs. The service voltage and number of phases alone do not establish an 8 AWG minimum. Smaller table choices are insufficient; larger choices may be usable but are not the minimum. The stated single-set and general-table conditions exclude parallel-conductor aggregation and electrode-specific reductions. Sources: Minnesota DLI, 2026 NEC residential inspection checklist, page 9, grounding-electrode-conductor chart: https://www.dli.mn.gov/sites/default/files/pdf/eli_inspection_checklist-2026NEC.pdf ; Paul Abernathy, original 2026 Article 250 technical review, distinction between GEC and EGC/bonding-jumper sizing: https://fasttraxsystem.com/grounding-vs-bonding/