Service Equipment Grounding Table

Table 250.66 Grounding Electrode Conductor for Alternating-Current System
Size of Largest Ungrounded Service-Entrance Conductor or Equivalent Area for Parrell Conductors^a (AWG/kcmil)		Size of Grounding Electrode Conductor (AWG/kcmil)
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
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 separately derived ac systems. bSee installation restrictions in Section 250-64(A).

Table 250.66 Grounding Electrode Conductor for Alternating-Current System
Size of Largest Ungrounded Service-Entrance Conductor or Equivalent Area for Parrell Conductors^a (AWG/kcmil)		Size of Grounding Electrode Conductor (AWG/kcmil)
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
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 separately derived ac systems. bSee installation restrictions in Section 250-64(A).