← Electrical Systems Studio
🌍

Ground Conductor Sizing

NEC 250.122 (EGC) · NEC 250.66 (GEC)

When to use: Use whenever installing branch circuits, feeders, or service entrance equipment. NEC Article 250 covers two distinct grounding conductors:

EGC (Equipment Grounding Conductor): Runs in the same raceway as circuit conductors. Sized per NEC Table 250.122 based on the overcurrent protective device rating. Provides a fault return path.

GEC (Grounding Electrode Conductor): Connects the neutral/service to earth (ground rod, building steel, etc.). Sized per NEC Table 250.66 based on the largest service conductor.

Parameters
NEC Table 250.122 — EGC (excerpt)
OCPD (A)
Copper
Aluminum
15
#14 AWG
#12 AWG
20
#12 AWG
#10 AWG
30
#10 AWG
#8 AWG
40
#10 AWG
#8 AWG
60
#10 AWG
#8 AWG
100
#8 AWG
#6 AWG
200
#6 AWG
#4 AWG
300
#4 AWG
#2 AWG
400
#3 AWG
#1 AWG
500
#2 AWG
#1/0 AWG
600
#1 AWG
#2/0 AWG
800
#1/0 AWG
#3/0 AWG
Equipment Grounding Conductor (EGC)
#6 AWG
Copper · 200A OCPD · NEC 250.122
Grounding Electrode Conductor (GEC)
#2 AWG
Copper · Service: 4/0–350 kcmil · NEC 250.66
Key Distinctions
EGC = fault return path in the circuit raceway
GEC = connects neutral to earth at service entrance
EGC sized by OCPD rating (Table 250.122)
GEC sized by service conductor size (Table 250.66)
GEC maximum: #2 AWG Cu or 1/0 Al (for concrete-encased electrode)
Both must be continuous and properly terminated