Section 210.3/Branch Circuit Rating Classification
NEC 210.3 defines how branch circuit ratings are determined by the overcurrent device, establishing the basis for conductor sizing and outlet device ratings.
Branch circuits are classified by the rating of the overcurrent device protecting the circuit. The rating determines the minimum conductor size, the outlet device ratings, and the maximum load permitted on the circuit.
Why this section exists
The branch circuit rating ties together three critical design elements: the overcurrent device, the conductor, and the outlets. All three must be coordinated so that the circuit operates safely under normal and overload conditions. By defining the circuit rating as the overcurrent device rating, the NEC provides a single reference point that controls all other sizing decisions on the circuit.
What plan reviewers look for
Plan reviewers verify that the breaker size shown on the panel schedule is consistent with the conductor size and outlet device ratings for every branch circuit. A 20-amp breaker must have at least 12 AWG conductors and 20-amp rated receptacles (or 15-amp receptacles on a multi-outlet 20-amp circuit per 210.21(B)). Mismatches between these three elements are among the most common panel schedule errors.
Common violations
Related NEC requirements
Section 210.19 establishes minimum conductor sizing for branch circuits.Section 240.4 requires conductors to be protected in accordance with their ampacity. Section 210.21 covers outlet device ratings relative to the branch circuit rating.