Grounding & Bonding
EGC and GEC sizing tables, grounding electrode types, and requirements.
3 reference items · 3 sections
Equipment Grounding Conductors (EGC)
Minimum EGC Size by OCPD Rating
NEC 250.122 EGC Size Calculator
Equipment Grounding Conductor Sizing
| OCPD Rating (A) | Copper EGC | Aluminum EGC |
|---|---|---|
| 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 |
| 1000 | 2/0 AWG | 4/0 AWG |
| 1200 | 3/0 AWG | 250 kcmil |
| 1600 | 4/0 AWG | 350 kcmil |
| 2000 | 250 kcmil | 400 kcmil |
| 2500 | 350 kcmil | 600 kcmil |
| 3000 | 400 kcmil | 600 kcmil |
| 4000 | 500 kcmil | 750 kcmil |
| 5000 | 700 kcmil | 1200 kcmil |
| 6000 | 800 kcmil | 1200 kcmil |
1.EGC must not be smaller than values shown
2.Size based on rating of overcurrent device ahead of equipment
3.Where circuit conductors are increased in size for voltage drop, EGC must be proportionally increased
The EGC provides a low-impedance path for fault current to trip the OCPD. It does NOT carry current during normal operation.
Grounding Electrode Conductors (GEC)
GEC Sizing Based on Service Conductor
NEC 250.66
Grounding Electrode Conductor Sizing
| Service Conductor (Cu) | Service Conductor (Al) | GEC Copper | GEC Aluminum |
|---|---|---|---|
| 2 AWG or smaller | 1/0 AWG or smaller | 8 AWG | 6 AWG |
| 1 AWG or 1/0 AWG | 2/0 AWG or 3/0 AWG | 6 AWG | 4 AWG |
| 2/0 AWG or 3/0 AWG | 4/0 AWG or 250 kcmil | 4 AWG | 2 AWG |
| Over 3/0 thru 350 kcmil | Over 250 thru 500 kcmil | 2 AWG | 1/0 AWG |
| Over 350 thru 600 kcmil | Over 500 thru 900 kcmil | 1/0 AWG | 3/0 AWG |
| Over 600 thru 1100 kcmil | Over 900 thru 1750 kcmil | 2/0 AWG | 4/0 AWG |
| Over 1100 kcmil | Over 1750 kcmil | 3/0 AWG | 250 kcmil |
1.GEC connects the service equipment grounding bus to the grounding electrode system
2.For parallel service conductors, use the equivalent area of a single conductor
The GEC to a ground rod or pipe electrode need not be larger than 6 AWG copper or 4 AWG aluminum. The GEC to a concrete-encased electrode (Ufer ground) need not be larger than 4 AWG copper.
Grounding Electrode System
Grounding Electrode Types
NEC 250.52
Grounding Electrode Types & Requirements
| Electrode Type | NEC Section | Requirement |
|---|---|---|
| Metal water pipe | 250.52(A)(1) | ≥10 ft in contact with earth; must be supplemented |
| Metal building frame | 250.52(A)(2) | Effectively grounded |
| Concrete-encased (Ufer) | 250.52(A)(3) | ≥20 ft of ½" rebar or 4 AWG bare Cu in footing |
| Ground ring | 250.52(A)(4) | ≥20 ft of 2 AWG bare Cu, ≥30" deep |
| Ground rod/pipe | 250.52(A)(5) | ≥8 ft long, ≥⅝" diameter (rod) |
| Other listed electrodes | 250.52(A)(6) | Per manufacturer listing |
| Plate electrode | 250.52(A)(7) | ≥2 sq ft exposed to soil, ≥30" deep |
1.If available, metal water pipe and building frame MUST be used
2.Single ground rod must achieve ≤25Ω; if not, install a second rod
A supplemental electrode is required when using a metal water pipe electrode. Two ground rods spaced ≥6 ft apart are accepted without resistance testing per 250.53(A)(2).
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