Published June 28, 2026
The equipment grounding conductor — the ground wire — is one of the most misunderstood parts of an electrical circuit. Many people assume it needs to match the current-carrying conductors in size, or that it only matters for safety inspections. Here's what the NEC actually requires and why it matters.
The equipment grounding conductor (EGC) provides a low-impedance path back to the source in the event of a ground fault. When a hot conductor contacts metal equipment, the EGC allows enough current to flow to trip the overcurrent protective device (OCPD) quickly — clearing the fault and preventing electrocution or fire. Without a properly sized EGC, the fault current path has too much impedance, the breaker may not trip fast enough, and energized metal stays dangerous.
Per NEC Table 250.122, the minimum EGC size is based on the rating of the overcurrent protective device protecting the circuit — not the size of the conductors you pulled. This is a common point of confusion. A 20A circuit requires a minimum 12 AWG copper EGC regardless of whether you pulled 12 AWG or upsized to 10 AWG for voltage drop.
Some common minimum copper EGC sizes from Table 250.122:
There is one important exception: NEC 250.122(B). If you increased your circuit conductors beyond the minimum required size for ampacity — for example, to compensate for voltage drop on a long run — you must proportionally increase the EGC as well. The adjustment is based on the ratio of the actual conductor area to the required conductor area.
For example, if a 60A circuit normally requires 6 AWG conductors but you pulled 4 AWG to reduce voltage drop, your EGC must be proportionally larger than the 10 AWG minimum from Table 250.122.
Aluminum can be used for equipment grounding conductors, but the required sizes are larger than copper. Table 250.122 provides separate columns for copper and aluminum. In most commercial and residential work, copper EGCs are standard — aluminum is more common in larger feeder applications.
Sizing the ground wire correctly isn't just a code formality — it's what ensures a fault clears fast enough to protect people and equipment. Use Table 250.122, size it to the OCPD, and upsize proportionally if your conductors are larger than required.
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