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NEC Motor FLA Calculator (Tables 430.248 & 430.250)

Lookup full-load currents (FLC) for 1-phase and 3-phase electric motors per NEC Tables 430.248 and 430.250. Sizes 125% branch conductors (430.22) and maximum overcurrent protection (430.52).

⚡ NEC 2023 Code Basis & Electrical Safety Disclaimer

Based on NEC 2023 (same as 2020 & 2017 Article 430). Estimates for planning only — electrical installations must comply with local code editions and be performed/verified by a licensed electrician. Not a substitute for engineered design or an AHJ ruling.

⚙️ Motor Branch Circuit Schematic
Motor Branch Circuit SchematicDiagram showing breaker box, branch conductors, motor starter overload, and motor terminal box.

Motor Circuit Sizing Results

NEC Full-Load Current (FLC / FLA)
15.2 A
NEC Table 430.250 Lookup
Min Conductor Ampacity (125%)
19.0 A
NEC 430.22 Continuous Duty
Recommended Copper Conductor
14 AWG Cu
75°C Terminals (THHN/THWN)
Max Circuit Breaker / OCPD
40 A Breaker
250% FLC (NEC 430.52 & 240.6)

Worked Example: 5 HP 3-Phase 230V Motor Circuit Sizing

Consider sizing the branch circuit for a 5 HP 3-phase 230V squirrel-cage induction motor:

  • Step 1 (Table FLC Lookup): Per NEC 430.6(A)(1), look up 5 HP at 230V in Table 430.250 $\rightarrow$ 15.2 Amperes FLC (do NOT use nameplate FLA).
  • Step 2 (Branch Conductors): Per NEC 430.22, min conductor ampacity = 15.2 A × 1.25 = 19.0 A. Selected copper wire = 14 AWG Cu (rated 20 A at 75°C).
  • Step 3 (Short-Circuit Protection): Per NEC 430.52(C)(1), max inverse-time breaker rating = 15.2 A × 2.50 = 38.0 A.
  • Step 4 (Next Standard Size): Under Exception 1, 38.0 A rounds up to the next standard rating in NEC 240.6(A) $\rightarrow$ 40 Ampere Breaker.

Engineering Code & Reference Citations

  • NFPA 70 / NEC Table 430.248: Full-Load Currents in Amperes, Single-Phase Alternating-Current Motors. nfpa.org
  • NFPA 70 / NEC Table 430.250: Full-Load Current, Three-Phase Alternating-Current Motors. nfpa.org
  • NFPA 70 / NEC Section 430.22 & 430.52: Single Motor Branch-Circuit Conductor & Rating of Protective Devices. nfpa.org

Frequently Asked Questions (FAQ)

What is the NEC FLA for a 5 HP 3-phase 230V motor?

Per NEC Table 430.250, a 5 HP 3-phase 230V motor has a full-load current (FLC) of 15.2 Amperes. The minimum conductor ampacity is 19.0 A (15.2 × 1.25), and maximum inverse-time breaker size is 40 A.

What is the NEC FLA for a 10 HP 3-phase 460V motor?

Per NEC Table 430.250, a 10 HP 3-phase 460V motor has a full-load current (FLC) of 14 Amperes.

Why must NEC table FLA be used instead of motor nameplate FLA for circuit sizing?

NEC 430.6(A)(1) mandates using NEC Table 430.248 or 430.250 values for sizing branch conductors, switches, and overcurrent protection to ensure safe replacement with standard-efficiency motors. Nameplate FLA is used only for motor overload protection.

How is minimum motor branch-circuit conductor ampacity calculated?

Under NEC 430.22, conductors supplying a single continuous-duty motor must have an ampacity of not less than 125% of the motor full-load current (FLC × 1.25).

How is the maximum inverse-time circuit breaker sized for a motor?

Per NEC 430.52(C)(1), an inverse-time circuit breaker is sized up to 250% of the motor FLC. Under Exception 1, if 250% does not equal a standard breaker rating, the next higher standard rating in NEC 240.6(A) is permitted.

What is the full-load current for a 1 HP 115V single-phase motor?

Per NEC Table 430.248, a 1 HP 115V single-phase motor has a full-load current of 16 Amperes.

What is the FLA for a 50 HP 3-phase 460V motor?

Per NEC Table 430.250, a 50 HP 3-phase 460V motor has a full-load current of 65 Amperes.

What multiplier applies to dual-element time-delay fuses for motor protection?

Per NEC Table 430.52, dual-element time-delay fuses are permitted up to 175% of the motor FLC (rounded up to the next standard rating if necessary).

How does 208V motor FLA compare to 230V FLA?

Because power is voltage times current, lower voltage requires higher current. For example, a 5 HP 3-phase motor draws 16.7 A at 208V versus 15.2 A at 230V.

What is the difference between FLC and FLA in the NEC?

In the NEC, Full-Load Current (FLC) refers to the values published in Tables 430.248/430.250, whereas Full-Load Amps (FLA) typically refers to the nameplate current stamped on the motor.

What standard fuse/breaker sizes exist in NEC 240.6(A)?

Standard ratings per NEC 240.6(A) include 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 125, 150, 175, 200, 225, 250, 300, 350, 400, 450, 500, 600 Amperes.

Are NEC 430 motor FLA values identical across NEC 2017, 2020, and 2023?

Yes. The full-load current values in NEC Tables 430.248 and 430.250 have remained unchanged across the 2017, 2020, and 2023 editions of NFPA 70.