2.2 Grounding Electrode Conductor Sizing
Size GEC conductors using NEC Table 250.66 and apply statutory ceiling limits for ground rods, concrete-encased electrodes, and ground rings.
Key Blueprint Takeaways
- Table 250.66 sizes GEC based on the largest service-entrance ungrounded conductor.
- Ground rod connections never require larger than 6 AWG copper (NEC 250.66(A)).
- Concrete-encased Ufer ground connections never require larger than 4 AWG copper (NEC 250.66(B)).
Grounding connects the electrical system to the earth, stabilizing voltages during lightning strikes, line surges, and unintentional contact with higher-voltage lines.
The Grounding Electrode Conductor (GEC) links the grounded service conductor and main bonding jumper to earth electrodes. Table 250.66 governs sizing, with specific relief exemptions for ground rods and concrete-encased footings.
An electrical service entrance has 500 kcmil copper service-entrance phase conductors. What is the minimum size copper Grounding Electrode Conductor (GEC) required to connect to a concrete-encased electrode (Ufer ground) under Table 250.66?