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NEC CODE NEC 2023

Motor circuit calculations (NEC 400)

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The National Electrical Code (NFPA 70) is the benchmark standard for safe electrical installation in the US. It is updated every 3 years by the NFPA.

Study the edition adopted by your state. As of 2025, most states use the 2020 or 2023 NEC. These tests are written to the 2023 edition.

The most tested articles are 100 (Definitions), 200–250 (Wiring & Grounding), 300–314 (Wiring Methods), 400–411 (Conductors), 430 (Motors), and 700–701 (Emergency Systems).

9

Questions

14 min

Time

70%

Pass

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Motor circuit calculations (NEC 400) — Question List

Question 1: What is the ampacity of a conductor that supplies a single phase motor used in continuous duty applications?

not less than 115 % of motor FLC
not less than 125 % of motor FLC
less than 115 % of motor FLC
less than 125 % of motor FLC

NEC Reference: NEC 430.6

Question 2: A Single phase continuous duty motor has a full load current (FLC) of 20 amperes. Which of the following is the ampacity of conductor that should used to supply the power to the motor.

25 amperes
21.5 amperes
22 amperes
22.5 amperes

Question 3: Which of the following type of conductor is used to supply a 40 ampere single phase motor used for continuous duty applications?

No 8 THW
No 6 THW
No 12 THW
No 14 THW

NEC Reference: NEC 310.16

Question 4: Which of the following is the allowed full load current (FLC) of a 5 HP, 230 volts single phase AC motor?

28 Amperes
40 amperes
44 amperes
32 amperes

NEC Reference: NEC 430.248

Question 5: Which of the following is the overload protection rating of a 2 HP 230 volts single phase motor used in continuous duty applications. The service factor of a motor is 1.1.

12 amperes
10 amperes
14 amperes
8 amperes

NEC Reference: NEC 430.248

Question 6: A 50 HP 460 volts three phase AC motor is supplied with THWN conductors. Which is of the following is the size of the branch circuit conductors?

81.25 amperes
74.75 amperes
70 amperes
85 amperes

NEC Reference: NEC 430.250

Question 7: Two motors 15HP and 5 HP motors are operated at 230 volts and connected to a single feeder. Which of the following is the size of feeder conductor?

67.7 A
57.5 A
52.5
15.2

NEC Reference: NEC 430.250

Question 8: If a 20 ampere ac snap switch is used to disconnect a 1.5 Hp motor what must be the maximum full load current of a motor?

16 Amperes
20 Amperes
15 Amperes
17 Amperes

NEC Reference: NEC 430.109(c)(2)

Question 9: If the motors operate at or over ........... volts , the live parts of the motor must be guarded.

75
50
120
240

NEC Reference: NEC 430.232

EXAM CARD NEC CODE

Questions9

Time limit14 min

Pass score70%

Code editionNEC 2023

DifficultyIntermediate

Timer starts immediately. Progress is auto-saved.