Quick Hits

EPISODE 15 — Installing and Sizing the Grounding Electrode Conductor (270.64, 270.66)

Slide 1 — Hook "How the grounding electrode conductor gets physically installed, protected, and sized — one of the most test-relevant sections in Part III."

Slide 2 — 270.64 Installation basics

• Aluminum/copper-clad aluminum GECs: can't be used in corrosive conditions or direct concrete contact (without proper covering); can't terminate within 18" of earth outdoors.

• 6 AWG+ copper/aluminum, NOT exposed to damage: can run exposed along the building surface, no extra protection needed.

• 6 AWG+ EXPOSED to damage, or ANYTHING smaller than 6 AWG: must be protected in RMC, IMC, Schedule 80 PVC, RTRC-XW, EMT, or cable armor.

• Generally has to be ONE continuous length — no splices — except for specific listed compression connectors, exothermic welds, busbar sections, or certain structural/piping connections.

Slide 3 — 270.66 Sizing (Table 270.66)

• Sized based on the largest ungrounded service/feeder conductor — bigger ungrounded conductors need a bigger GEC (standard ratio table, same structure you've seen in lower-voltage articles).

• Exceptions cap the size when connecting ONLY to certain electrode types: rod/pipe/plate-only connections max out at 6 AWG copper (4 AWG aluminum); concrete-encased-only connections max out at 4 AWG copper; ground-ring-only connections match the ring conductor's own size.

Slide 4 — Quiz + CTA Q: "A grounding electrode conductor connecting ONLY to a concrete-encased electrode (with no other electrode types) is capped at what maximum required size?" A) 6 AWG copper B) 4 AWG copper C) 2 AWG copper D) 1/0 AWG copper

✅ Answer: B — 270.66(B): 4 AWG copper wire cap for concrete-encased-electrode-only connections.

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