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Notice: |
NEC is a registered
trademark of the National Fire Protection Association, Inc.
All NEC references by Electrical Helper are interpretations of the NEC
by the Electrical Helper staff and are not NEC statements. The official
position of the NEC requires that the NEC be referred to in its
entirety. |
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Sizing Alternating Current Grounding
Electrode Conductors
Table 250.66 |
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Grounding Electrode Conductor for Alternating Current Systems
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Size of Largest Ungrounded Service Entrance Conductor or
Equivalent Area for Parallel Conductors (AWG/kcmil)
(Note 3) |
Size of Grounding Electrode Conductor (AWG/kcmil) |
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Copper |
Aluminum or Copper Clad Aluminum |
Copper |
Aluminum or Copper Clad Aluminum
(Note 4) |
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2 or smaller |
1/0 or smaller |
8 |
6 |
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1 or 1/0 |
2/0 or 3/0 |
6 |
4 |
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2/0 or 3/0 |
4/0 or 250 |
4 |
2 |
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Over 3/0 through 350 |
Over 250 through 500 |
2 |
1/0 |
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Over 350 through 600 |
Over 500 through 900 |
1/0 |
3/0 |
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Over 600 through 1100 |
Over 900 through 1750 |
2/0 |
4/0 |
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Over 1100 |
Over 1750 |
3/0 |
250 |
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Fig. 8-89 Table 250.66 Grounding Electrode Conductor for
Alternating Current Systems |
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Note 1: Where multiple sets of service
entrance conductors are used as permitted in Section 230.40
Exception #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. |
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Note 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 servied. |
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Note 3: This table also applies to the
derived conductors of separately derived systems. |
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Note 4: See installation restrictions in
250.64(A) for aluminum or copper-clad aluminum conductors. |
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