Practice Test Geeks(E2) E2 Commercial Electrical Inspector Practice Test
← All E2 Flashcard Decks

Sizing and Protection of Motor Circuits Flashcards

7 cards from real E2 practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Sizing and Protection of Motor Circuits flashcards as text

  1. Per NEC 430.24, the minimum feeder conductor ampacity for a group of motors equals the sum of all motor FLA values plus an additional percentage of which motor's FLA?

    Answer: 25% of the largest motor's FLA

    NEC 430.24 requires feeder ampacity equal to 125% of the largest motor's FLA plus 100% of all other motors' FLA, effectively adding 25% of the largest motor.

  2. A motor feeder supplies three motors with table FLA values of 40A, 25A, and 15A. What is the minimum feeder conductor ampacity per NEC 430.24?

    Answer: 90A

    Feeder ampacity = (1.25 × 40A) + 25A + 15A = 50A + 25A + 15A = 90A per NEC 430.24.

  3. Per NEC 430.62(A), the feeder overcurrent protective device for a group of motors shall not exceed the rating of:

    Answer: The largest permitted branch-circuit device for the biggest motor, plus the FLA of all other motors

    NEC 430.62(A) limits the feeder overcurrent device to the maximum permitted branch-circuit protective device rating for the largest motor plus the FLA of all other motors.

  4. Per NEC 430.122(A), when a motor is supplied through an adjustable speed drive (VFD), the branch circuit conductors must have an ampacity of at least:

    Answer: 125% of the rated input current of the drive

    NEC 430.122(A) requires branch circuit conductors supplying an adjustable speed drive to be sized at 125% of the drive's rated input current, not the motor's FLA alone.

  5. For hermetic refrigerant motor-compressors used in air-conditioning and refrigerating equipment, which NEC article governs motor circuit sizing instead of the standard Article 430 tables?

    Answer: Article 440

    Article 440 governs air-conditioning and refrigerating equipment including hermetic refrigerant motor-compressors, which have unique sizing rules distinct from general Article 430 provisions.

  6. Per NEC 430.53(A), motors of what maximum horsepower rating or less may be connected to a general-purpose branch circuit without individual overcurrent protection, when the circuit is protected at not more than 20 amperes?

    Answer: 1 HP

    NEC 430.53(A) permits motors of 1 HP or less to be connected to a general-purpose branch circuit without individual motor branch-circuit protection when specified conditions are met.

  7. Per NEC 430.53(D), when several motors are connected to a single branch circuit, the branch-circuit short-circuit protective device rating shall not exceed the maximum permitted value for:

    Answer: The motor requiring the smallest maximum protective device rating

    NEC 430.53(D) requires the branch-circuit protective device to not exceed the maximum permitted rating for the most restrictively protected motor in the group.