Figure 4-6. The grounded (neutral) conductor is used to carry normal neutral current or ground fault current

DOE-HDBK-1092-98

NEC Section 250-23 (b)

OSHA Section 29 CFR 1910.304 (f) (4)

Figure 4-6. The grounded (neutral) conductor is used to carry normal neutral current or ground fault current

in case a ground fault should develop on one of the ungrounded (hot) phase conductors.

Step 1:

Service exceeding 1100 kcmil--NEC Table 250-94 2400 kcmil x 0.125 = 300

kcmil

Answer:

The grounded conductor is required to be at least a #300 kcmil, THWN copper

conductor.

This method is used where the service entrance conductors are over 1100-kcmil copper or

1750-kcmil aluminum. NEC Table 250-94 cannot be used for sizing the grounded conductor. The

grounded conductor is required to be not less than 12 1/2% of the cross-sectional area of the largest

phase conductor.

Note: NEC Table 250-94 is used only if the service conductors are rated less than 1100 kcmil for

copper or 1750 kcmil for aluminum.

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