NEC 210.19 Conductors–Minimum Ampacity and Size

Branch Circuits Not More Than 600 Volts

NOTE: See 310.15 for ampacity ratings of conductors. See Part II of Article 430 for minimum rating of motor branch-circuit conductors. See 310.15(A)(3) for temperature limitation of conductors.
NOTE: Conductors for branch circuits as defined in Article 100, sized to prevent voltage drop exceeding 3 percent at the farthest outlet of power, heating, and lighting loads, or combinations of such loads, and where the maximum total voltage drop on both feeders and branch circuits to the farthest outlet does not exceed 5 percent, provide reasonable efficiency of operation.

General. Branch-circuit conductors shall have an ampacity not less than the maximum load to be served. Conductors shall be sized to carry not less than the larger of 210.19(A)(1)(a) or (b).

For branch circuits not more than 600 volts, conductors shall have an ampacity not less than the maximum load to be served. Conductors shall be sized to carry not less than the larger of (a) or (b).

The conductor ampacity may require other correction or adjustment factors applicable to the conductor installation.

a. Where a branch circuit supplies continuous loads or any combination of continuous and noncontinuous loads, the minimum branch-circuit conductor size shall have an allowable ampacity not less than the noncontinuous load plus 125% of the continuous load.
b. The minimum branch-circuit conductor size shall have an allowable ampacity not less than the maximum load to be served after the application of any adjustment or correction factors.

Exception: If the assembly, including the overcurrent devices protecting branch
circuit(s), is listed for operation at 100% of its rating, the allowable ampacity of the branch-circuit conductors shall be permitted to be not less than the sum of the continuous load plus the noncontinuous load.

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