What wire size is needed to ground a 300 amp service panel in USA?

Answer 1

#2 AWG copper to water main #6 AWG copper to ground rod

Answer 2

Notes:

1. Where multiple sets of service-entrance 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.

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.

1

This table also applies to the derived conductors of separately derived

ac systems.

2

See installation restrictions in Section 250-64(a).

Answer 3

"There are very specific calculations required here. Several variables have to be determined. You don't even say whether you have single phase power or three phase.

Do yourself a favor. Be safe AND legal. Pay a few bucks to have an electrical engineer do the calcs for the electrical service entrance conductor sizing."

This is not an answer...it's a waffle.

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A service of 300 amp is an in between size. What the code states is that the next size of ground conductor must be used.

For a 400 amp service a #3 bare copper conductor is to be used for a 300 amp service.

Answer 4

The Proper ground wire is determined based on the size of the main feeder wires.

400Amp single phase dwelling service wire is 400 MCM copper or 600 AL (NEC 310.15(B)(6) Then ground wire is either #1/O Copper or # 3/O Al (NEC 250.66)

For other services see NEC 310.16 for the proper wire size then refer to 250.66 for ground size

Answer 5

According to 2008 NEC, the min size of the wire is 3 AWG copper or 1 AWG aluminuim.

Answer 6

250 kcmil in copper or 400 kcmil in aluminum.