Section 250.122/Equipment Grounding Conductor Sizing
NEC 250.122 and Table 250.122 establish equipment grounding conductor sizing based on the overcurrent device rating, with a proportional upsizing requirement.
Equipment grounding conductors must be sized not smaller than shown in Table 250.122 based on the overcurrent device rating. Where circuit conductors are adjusted in size for voltage drop or other reasons, the equipment grounding conductor must be proportionally adjusted upward using the same ratio.
Why this section exists
The equipment grounding conductor must carry fault current long enough for the overcurrent device to clear the fault. If the EGC is too small, it can overheat and lose continuity before the breaker trips, leaving equipment enclosures energized. The proportional upsizing requirement ensures that the EGC maintains the same relative impedance when circuit conductors are increased.
What plan reviewers look for
Plan reviewers cross-reference every circuit's EGC size against Table 250.122 and the overcurrent device rating. They check for proportional upsizing when circuit conductors have been increased beyond the minimum required, which is common on long feeder runs designed for voltage drop.
Common violations
Related NEC requirements
Section 250.119 covers EGC identification. Section 250.118 lists permitted EGC types (wire, conduit, cable tray, etc.). Section 250.4 provides the general grounding requirements. Table 250.66 covers grounding electrode conductor sizing (different from EGC sizing).