Yes, you are correct in your understanding of the general application of FLA and FLC. You've also hit upon an important point regarding situations where FLA is higher than the Table FLC.Here's the breakdown of what to do when the motor's nameplate FLA is higher than the FLC listed in the tables in Article 430 of the NEC

You MUST use the motor's nameplate FLA for all calculations.

Here's why: Nameplate Trumps Table

The motor's nameplate FLA represents the actual current that the specific motor is designed to draw under full load conditions. The NEC explicitly states that nameplate values should be used when available and when they are greater than the table values.

NEC 430.6(A)(1) General Motor Applications. "...The values given in Table 430.247, Table 430.248, Table 430.249, and Table 430.250 shall be used to determine the ampacity of conductors or ampere ratings of switches, branch-circuit short-circuit and ground-fault protection, instead of the actual current rating marked on the motor nameplate. Where the motor nameplate current rating is used with adjustable trip circuit breakers according to 430.52(C)(1), the actual current rating marked on the motor nameplate shall be used."

Safety and Protection

Undersizing conductors or overcurrent protection based on an artificially low FLC value would create a dangerous situation. The motor would draw more current than the circuit is designed to handle, potentially leading to overheating, insulation failure, and fire.

Overload Protection

This is sized based on the motor's FLA.

Conductor Sizing

Conductor ampacity must be at least 125% of the motor's

nameplate FLA (NEC 430.22).

Branch Circuit Protection (Short-circuit and Ground-fault protection)

The maximum size of the breaker or fuses is based on the motor's

nameplate FLA, using the percentages specified in NEC 430.52.

In Summary

If the motor's nameplate FLA exceeds the FLC value found in the NEC tables, disregard the table value and

always use the motor's nameplate FLA for calculating conductor ampacity and sizing the branch circuit overcurrent protection. This ensures that the circuit is appropriately sized to handle the motor's actual operating current and provides adequate protection against overloads and short circuits.

Example

Let's say you have a 10 HP, 460V motor. Table 430.250 lists the FLC as 14 amps. However, the motor's nameplate FLA is 16 amps.

Conductor Sizing

16 amps 1.25 = 20 amps minimum conductor ampacity.

Overcurrent Protection:* Use 16 amps to calculate the maximum size of the breaker or fuses, based on the type of protection and percentages listed in NEC 430.52. Flag for review