Section 430.6/Determination of Motor Full-Load Current
NEC 430.6 requires motor branch circuit conductors and overcurrent protection to be based on the full-load current from NEC Tables 430.247 through 430.250, not the motor nameplate current.
Motor branch circuit conductor sizing, overcurrent protection sizing, and disconnect sizing must be based on the full-load current (FLC) values from the applicable NEC table: Table 430.247 for DC motors, Table 430.248 for single-phase AC motors, Table 430.249 for two-phase AC motors, or Table 430.250 for three-phase AC motors. The motor nameplate ampere rating must NOT be used for these calculations. The nameplate current is used only for determining the motor overload protection per Section 430.32. This distinction exists because the table values represent a statistical average for motors of a given horsepower and voltage, while individual motor nameplate currents vary by manufacturer and efficiency. Using the table FLC ensures conductors and overcurrent devices are sized for any motor of the specified horsepower, regardless of manufacturer.
Why this section exists
A motor replacement during the building's life may have a different nameplate current than the original motor. If conductors and overcurrent devices were sized based on the original nameplate, the replacement motor could exceed the conductor ampacity or trip the overcurrent device during normal operation. The table-based approach ensures the branch circuit infrastructure can serve any motor of the specified horsepower. The overload protection (430.32) does use the nameplate because its purpose is to protect that specific motor's windings from sustained overload, and it is expected to be adjusted when a motor is replaced.
What plan reviewers look for
Plan reviewers check the panel schedule and feeder schedule for motor circuit sizing. They verify that the conductor size matches 125% of the table FLC (per Section 430.22 and 430.52) and not 125% of the nameplate current. They check the motor schedule for horsepower, voltage, and phase, and cross-reference against the correct FLC table. For motor-compressor circuits (air conditioners), they verify that Article 440 is applied instead of Article 430, since motor-compressors use the nameplate RLA or BCSC rather than FLC tables.