250.66: Grounding Electrode Conductor (GEC)

Sizing Grounding Electrode Conductors for Alternating-Current Systems.

Source: NEC 2020

The Math Shortcut

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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

Related NEC Tables

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

Professional Usage

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.

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