Equipment & SystemsQuestion 249 of 521
When sizing branch-circuit conductors and short-circuit/ground-fault protection for a standard motor, which current value does the NEC require you to use?
a.The full-load current from Tables 430.247 through 430.250
b.The nameplate full-load amperes
c.The locked-rotor current
d.The service-factor amperes
Explanation
NEC 430.6(A)(1) requires the table FLC values (430.247-430.250) for conductor and branch-circuit protection sizing. The nameplate FLA is used only for overload (running) protection, while locked-rotor and service-factor amps serve other purposes.
Law Reference: 2023 NEC §430.6Practice all 521 questions free — no signup required.
Related questions on this topic
- Using the same 20 HP, 460 V motor (FLC 27 A), what is the maximum dual-element (time-delay) fuse permitted by Table 430.52 for branch-circuit short-circuit and ground-fault protection?
- A 5 HP, 230 V, three-phase motor has an FLC of 15.2 A. What is the maximum nontime-delay fuse permitted by Table 430.52 for branch-circuit protection?
- For the same 5 HP, 230 V motor (FLC 15.2 A), what is the maximum instantaneous-trip circuit breaker setting permitted by Table 430.52?
- Which motor current rating is used to select the running overload (overcurrent) protection device?
- A motor nameplate reads 28 A full-load, service factor 1.0, temperature rise not marked. What is the maximum overload rating under NEC 430.32(A)(1)?
- A feeder supplies two three-phase, 460 V motors: 20 HP (FLC 27 A) and 10 HP (FLC 14 A). Per NEC 430.24, what minimum feeder conductor ampacity is required?
Last reviewed: · editorial process
PrepPass Editorial Team · Verified against California CSLB C-10 Electrical Trade Examination · How we review