Section 215.2/Feeder Conductor Sizing
NEC 215.2 establishes minimum feeder conductor sizing requirements including the 125 percent continuous load factor that frequently affects commercial electrical designs.
Feeder conductors must have an ampacity not less than the load served. Where a feeder supplies continuous loads or any combination of continuous and noncontinuous loads, the conductor ampacity must be not less than the noncontinuous load plus 125 percent of the continuous load. The feeder size must also meet the minimum required by the load calculation methods in Article 220.
Why this section exists
Feeders carry the aggregate load from multiple branch circuits and are critical links in the electrical distribution system. Conductors carrying continuous loads (expected to run for 3 hours or more) generate more sustained heat. The 125 percent multiplier provides a thermal safety margin and matches the overcurrent device listing requirements for continuous operation.
What plan reviewers look for
Plan reviewers check feeder conductor sizes on the riser diagram and panel schedules against the load calculations. They verify that the 125 percent continuous load factor is applied to lighting and other continuous loads. They also check for voltage drop documentation on long feeder runs.
Common violations
Related NEC requirements
Article 220 covers load calculation methods. Section 210.19 covers branch circuit conductor sizing with the same 125% continuous load requirement. Section 240.4 covers overcurrent protection. Table 310.16 provides conductor ampacity values.