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  • 🧰 Code Tables You Need to Know – GEC Sizing (NEC Table 250.66)

🧰 Code Tables You Need to Know – GEC Sizing (NEC Table 250.66)

The critical NEC tables that every journeyman should master.

Author

Chris Martinez
August 01, 2025

⚡ Grounding Electrode Conductor (GEC) Size Chart

Largest Ungrounded Service-Entrance Conductor or Equivalent Area for Parallel Conductors (Copper)

Minimum GEC Copper Size

Minimum GEC Aluminum or Copper-Clad Size

2 AWG or smaller

8 AWG

6 AWG

Over 2 AWG – 1/0 AWG

6 AWG

4 AWG

Over 1/0 AWG – 3/0 AWG

4 AWG

2 AWG

Over 3/0 AWG – 350 kcmil

2 AWG

1/0 AWG

Over 350 kcmil – 600 kcmil

1/0 AWG

3/0 AWG

Over 600 kcmil – 1100 kcmil

2/0 AWG

4/0 AWG

Over 1100 kcmil

3/0 AWG

250 kcmil

🛑 Exceptions (VERY IMPORTANT):

  • Rod, pipe, or plate electrodes: GEC is not required to be larger than 6 AWG copper or 4 AWG aluminum, regardless of service size.

  • Concrete-encased electrode (ufer ground): GEC is not required to be larger than 4 AWG copper.

📝 Quick Field Example:

If your service conductors are 2/0 AWG copper, your minimum GEC is:

  • Copper GEC: 2 AWG

  • Aluminum GEC: 1/0 AWG