NEC Tables · Motors

Table 430.52 — motor short-circuit protection

What percentage of FLC your breaker or fuse may be — by motor and device type.

Free · NEC 2023 · Updated
800 % of FLC
Single-phase motors · Instantaneous-TripBreaker
maximum rating per Table 430.52(C)(1)
Exam trapThese percentages protect against short circuits only — they are far above FLC on purpose. Overload protection is separate (430.32). Confusing the two layers is how this article fails people.

Motor branch-circuit protection is sized as a percentage of table FLC: 250% for inverse-time breakers on most AC motors, 175% for dual-element fuses. When the math lands between standard sizes, 430.52(C)(1) Exception 1 lets you round up to the next standard rating in 240.6(A).

Type of MotorPercentage of Full-Load Current
Type of MotorNontimeDelayFuse1Dual Element(Time-Delay)Fuse1Instantaneous-TripBreakerInverseTimeBreaker2
Single-phase motors300175800250
AC polyphase motors other than wound-rotor300175800250
Squirrel cage — other than Design B energy-efficient — and Design B premium efficiency300175800250
Design B energy-efficient and Design B premium efficiency3001751100250
Synchronous3300175800250
Wound-rotor150150800150
DC (constant voltage)150150250150
Notes that change the answer — 430.52(C)(1)

Note: See 430.54 for certain exceptions to the values specified.

1The values in the Nontime Delay Fuse column apply to time-delay Class CC fuses.

2The values given in the last column also cover the ratings of nonadjustable inverse time types of circuit breakers that can be modified as in 430.52(C)(1)(a) and (C)(1)(b).

3Synchronous motors of the low-torque, low-speed type (usually 450 rpm or lower), such as those used to drive reciprocating compressors, pumps, and so forth, that start unloaded, do not require a fuse rating or circuit-breaker setting in excess of 200 percent of full-load current.

Values derived from the 2023 National Electrical Code for exam study. Verify installations against the adopted code and local amendments.

Race your codebook — 3 lookups on this table

Q1

A 30 hp motor is fed through a listed VFD. The drive is listed and marked "Suitable for Output Motor Conductor Protection," and the installer wants to size the branch-circuit short-circuit and ground-fault protective device using the drive's rated input current instead of the motor's full-load current. Which section allows this alternative sizing method and specifies the table to use?

  1. A 430.131
  2. B 430.122(B)
  3. C 430.130(A)
  4. D 430.124(A)
Show answer & explanation

Correct: C — 430.130(A)

430.130(A)(1) permits sizing the branch-circuit short-circuit and ground-fault protective device from Table 430.52(C)(1) using the power conversion equipment's rated input current when it is listed and marked "Suitable for Output Motor Conductor Protection." 430.122(B) covers output conductor sizing, not protective device sizing, so it doesn't answer this ask.

Q2

An electrician is installing a drive-fed single motor circuit. The drive manufacturer's instructions list a maximum allowable rating for the branch-circuit short-circuit and ground-fault protective device that is lower than what Table 430.52(C)(1) would otherwise permit for that motor's full-load current. Which section governs whether the installer must stay at or below the manufacturer's marked maximum rather than the table value?

  1. A 430.130(A)
  2. B 430.126(A)
  3. C 430.132
  4. D 430.128
Show answer & explanation

Correct: A — 430.130(A)

430.130(A)(2) requires that manufacturer-stipulated or equipment-marked maximum protective device ratings not be exceeded, even if 430.130(A)(1) would otherwise permit a higher value. 430.128 addresses the disconnecting means, not protective device ratings, so it doesn't apply here.

Q3

An electrician is sizing the branch-circuit overcurrent device for a monorail hoist motor and needs the specific fuse or inverse-time circuit breaker rating table referenced for cranes and hoists. Which section directs the installer to Table 430.52(C)(1) for this purpose?

  1. A 610.42(A)
  2. B 610.53
  3. C 610.42
  4. D 610.43(D)
Show answer & explanation

Correct: A — 610.42(A)

610.42(A) explicitly requires branch-circuit fuses or inverse-time breakers for crane, hoist, and monorail hoist motors to be rated per Table 430.52(C)(1). 610.42 is only the general heading requiring branch-circuit protection without giving the table reference, 610.43(D) covers overload protection for hoists rather than short-circuit/ground-fault sizing, and 610.53 addresses overcurrent protection for control transformers/resistors, not motor branch circuits.

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