CH 2

Grounding Electrode Conductor (GEC) - Standardized Parallel Rules

NEC 2020 • 2023 COMPLIANT

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Sizing for service grounding electrodes, water pipes, and structural steel connections.

Service Conductor Size (Cu)	Service Conductor Size (Al/Cu-Clad Al)	GEC Size (Cu)	GEC Size (Al/Cu-Clad Al)
2 or smaller	1/0 or smaller	8	6
1 or 1/0	2/0 or 3/0	6	4
2/0 or 3/0	4/0 or 250 kcmil	4	2
Over 3/0 through 350 kcmil	Over 250 through 500 kcmil	2	1/0
Over 350 through 600 kcmil	Over 500 through 900 kcmil	1/0	3/0
Over 600 through 1100 kcmil	Over 900 through 1750 kcmil	2/0	4/0
Over 1100 kcmil	Over 1750 kcmil	3/0	250 kcmil

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Related NEC Tables

Table 250.122: Equipment Grounding (EGC)Table 250.102(C)(1): Bonding Jumper Sizing

Important Notes

1.2. Where there are no service-entrance conductors, the grounding electrode conductor size shall be determined by the equivalent size of the largest service-entrance conductor required for the load to be served.

Professional Usage Disclaimer

This data is provided for informational purposes only. Always verify with the latest edition of the National Electrical Code (NFPA 70) and consult with a licensed electrical professional or AHJ (Authority Having Jurisdiction) before performing any electrical work. Zing² is a reference tool, not a substitute for qualified engineering.

Professional Field Notes & Gotchas

▸GEC vs EGC: This table is ONLY for service entrance and grounding electrodes. Do NOT use this for branch circuits or subpanels (use 250.122 instead).
▸Sole Connection Rule: If the GEC is the sole connection to a ground rod, pipe, or plate, it is not required to be larger than #6 Copper or #4 Aluminum.
▸Concrete-Encased Electrode (Ufer): If the GEC is the sole connection to a concrete-encased electrode, it is not required to be larger than #4 Copper.
▸Protection: GECs #6 and larger are generally considered protected from physical damage, but smaller wires usually require armor or conduit.

NEC 2023 vs 2026: What changed?

NEC 2023 vs 2026: The 2026 code introduced standardized parallel rules to clear up confusion when multiple sets of service conductors are utilized. Sizing remains consistent with the previous cycle but with reinforced focus on sum-of-area math.

Technical FAQs

What size GEC for 4/0 Aluminum service?

For a 4/0 Aluminum service entrance conductor, NEC Table 250.66 requires a #4 Copper or #2 Aluminum grounding electrode conductor.

Does a 200A service always need a #2 Copper ground?

Not necessarily. If you use 2/0 Copper for hots, you need #4 Copper GEC. If you use 4/0 Aluminum for hots, you still use Table 250.66 based on that size.

Can I use Aluminum for a Ufer ground?

Per NEC 250.64(A), Aluminum grounding conductors cannot be used where in direct contact with masonry or earth. Copper is highly recommended for concrete-encased electrodes.