Tables > Grounding > Alternating Current > Electrode conductor

	Size Of Largest Service-Entrance Conductor Or Equivalent Area For Parallel Conductors Size Of Grounding Electrode Conductor Copper Aluminum Or Copper-Clad Aluminum Copper *Aluminum Or Copper-Clad Aluminum 2 or smaller 1/0 or smaller 8 6 1 or 1/0 2/0 or 3/0 6 4 2/0 or 3/0 4/0 or 250 kcmil 4 2 Over 3/0 thru 350 kcmil Over 250 kcmil thru 500 kcmil 2 1/0 Over 350 kcmil thru 600 kcmil Over 500 kcmil thru 900 kcmil 1/0 3/0 Over 600 kcmil thru 1100 kcmil Over 900 kcmil thru 1750 kcmil 2/0 4/0 Over 1100 kcmil Over 1750 kcmil 3/0 250 kcmil
Where multiple sets of service conductors are used as permitted in Section 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. 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. 1This table also applies to the derived conductors of separately derived ac systems. 2See installation restrictions in Section 250-64(a). FPN: See Section 250-24(b) for size of ac system conductor brought to service equipment. Reprinted with permission from NFPA 70-1999, the National Electrical Code®, Copyright 1998, National Fire Protection Association, Quincy, MA 02269. This reprinted material is not the referenced subject which is represented only by the Standard in its entirety.
See also Calculations Solving for Conductor Area in Three-wire Three-Phase Circuits Solving for Conductor Area in Two-wire Single-Phase Circuits Guides Conductor sizing and ampacities for insulated conductors rated 0-2000 Volts in raceway, cable, or direct buried Determining maximum conductor length to limit voltage drop Tables Wire conductor properties Definitions Electromagnetic Induction Conductor