|Table 250.66 Grounding Electrode Conductor
for Alternating-Current System
|Size of Largest Ungrounded
or Equivalent Area for
|Size of Grounding
|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 1100||Over 1750||3/0||250|
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).