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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.
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