This guide covers the application of NEC Table 430.250, which is used to determine the Full-Load Current (FLC) for three-phase alternating-current motors. This FLC value is critical for correctly sizing conductors, overcurrent protection, and motor control equipment.
📘 Table Purpose and Scope
NEC Table 430.250 provides standardized FLC values for motors running at usual speeds and with normal torque characteristics.
- Voltage Ranges: The listed currents are for rated motor voltages but are also permitted for use within the system voltage ranges of 110 to 120 volts and 220 to 240 volts.
- Application: The FLC found in this table must be used to determine the size of conductors and the rating of overcurrent protection devices, as mandated by NEC 430.6(A)(1), regardless of the actual measured current on the motor nameplate.
📊 NEC Table 430.250: Full-Load Currents (Three-Phase)
| Horsepower | 115 Volts | 200 Volts | 208 Volts | 230 Volts | 460 Volts | 575 Volts | 2300 Volts |
| 1/2 | 4.4 | 2.5 | 2.4 | 2.2 | 1.1 | 0.9 | – |
| 3/4 | 6.4 | 3.7 | 3.5 | 3.2 | 1.6 | 1.3 | – |
| 1 | 8.4 | 4.8 | 4.6 | 4.2 | 2.1 | 1.7 | – |
| 1-1/2 | 12 | 6.9 | 6.6 | 6.0 | 3.0 | 2.1 | – |
| 2 | 13.6 | 7.8 | 7.5 | 6.8 | 3.4 | 2.7 | – |
| 3 | – | 11 | 10.6 | 9.6 | 4.8 | 3.9 | – |
| 5 | – | 17.5 | 16.7 | 15.2 | 7.6 | 6.1 | – |
| 7-1/2 | – | 25.3 | 24.2 | 22 | 11 | 9 | – |
| 10 | – | 32.2 | 30.8 | 28 | 14 | 11 | – |
| 15 | – | 48.3 | 46.2 | 42 | 21 | 17 | – |
| 20 | – | 62.1 | 59.4 | 54 | 27 | 22 | – |
| 25 | – | 78.2 | 74.8 | 68 | 34 | 27 | – |
| 30 | – | 92 | 88 | 80 | 40 | 32 | – |
| 40 | – | 120 | 114 | 104 | 52 | 41 | – |
| 50 | – | 150 | 143 | 130 | 65 | 52 | – |
| 60 | – | 177 | 169 | 154 | 77 | 62 | 16 |
| 75 | – | 221 | 211 | 192 | 96 | 77 | 20 |
| 100 | – | 285 | 273 | 248 | 124 | 99 | 26 |
| 125 | – | 359 | 343 | 312 | 156 | 125 | 31 |
| 150 | – | 414 | 396 | 360 | 180 | 144 | 37 |
| 200 | – | 552 | 528 | 480 | 240 | 192 | 49 |
| 250 | – | – | – | 602 | 302 | 242 | 60 |
| 300 | – | – | – | 723 | 361 | 289 | 72 |
| 350 | – | – | – | 834 | 414 | 336 | 83 |
| 400 | – | – | – | – | 477 | 382 | 96 |
| 450 | – | – | – | – | 512 | 410 | 103 |
| 500 | – | – | – | – | 579 | 463 | 116 |
💡 Application of FLC for Conductor Sizing
The FLC value found in Table 430.250 is used to determine the minimum size of the conductors supplying the motor.
Continuous Duty Motors (NEC 430.22(A)):
For a single motor used in a continuous duty application, the conductors must have an ampacity of not less than 125% of the motor’s FLC rating:
Minimum Conductor Ampacity = FLC (Table 430.250) x 1.25
This 125% increase accounts for the heat generated by continuous operation.
Example:
For a 10 HP motor operating at 460 Volts:
- Find FLC from Table 430.250: 14 Amperes.
- Calculate Minimum Ampacity: 14 A x 1.25 = 17.5 Amperes.
- You would then select a conductor size from NEC Table 310.16 that has an ampacity of at least 17.5 Amperes.
Note on Nameplate vs. Table:
Per NEC 430.6(A)(1), the FLC determined from this table must be used for sizing conductors and calculating the overcurrent protection rating, even if the FLC listed on the motor’s nameplate is different.
