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| Table 250.66 Grounding Electrode Conductor for Alternating-Current System |
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| Size of Largest Ungrounded Service-Entrance Conductor or Equivalent Area for Parrell Conductorsa (AWG/kcmil) |
Size of Grounding Electrode Conductor (AWG/kcmil) |
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| Copper | Aluminum or Copper-Clad Aluminum |
Copper | Aluminum or Copper-Clad Aluminum |
| 2 or smaller | 1 or smaller | 8 | 6 |
| 1 or 1/0 | 2/0 or 3/0 | 6 | 4 |
| 2/0 or 3/0 | 4/0 or 250 | 4 | 2 |
| Over 3/0 through 350 |
Over 250 through 500 |
2 |
1/0 |
| Over 350 through 600 |
Over 500 through 900 |
1/0 | 3/0 |
| Over 600 through 1100 |
Over 900 through 1750 |
2/0 | 4/0 |
| Over 1100 | Over 1750 | 3/0 | 250 |
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Notes: 1. Where multiple sets of service-entrance conductors are used as permitted in 230.40, Exception No.2, the equivalent size of the largest service-entrance conductor shall be determined by the largest sum of the areas of the corresponding conductors of each set. 2. Where there are no service-entrance conductors, the grounding electrode conductor size shall be determined by the equivalent size of the largest service-entrance conductor required for the load to be served. aThis table also applies to the derived conductors of seperately derived ac systems. bSee installation restrictions in Section 250-64(A). | |||
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