UL 508A - Branch Circuit Currents

FLA and FLC as stated in UL508A

Last edit: 20/03/2023

Each motor has two current values:

  • FLA: "Full-Load Ampere", is the rated current of the motor, written as nameplate data and indicated in the NEC with the name "Nameplate FLC".
  • FLC: "Full-Load motor-running Current", is a value of current chosen from table 50.1 of UL 508A. Given the motor power expressed in HP, the FLC represents the maximum current that can be absorbed by the motor in the worst case.

Each component of the branch circuit (conductors, fuses, circuit breakers, etc.), except for overload relays, must be sized focusing on the FLC; the reason is that, once the motor power is fixed in HP, the FLC represents the highest current that the motor rated at that power can absorb. Therefore, if the motor is replaced by another motor of equal power, it is not necessary to replace the other elements of the branch circuit due to a possible higher current absorbed by the load.

The overload relay, as its tripping characteristic is adjustable, must be sized focusing on the FLA .