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NEC CODE NEC 2023

Motor Circuit Calculations 1 (NEC 430) — NEC 2023 Edition

Free NEC 2023 practice test on motor circuit calculations. Covers branch-circuit conductor sizing (430.22), full-load current tables (430.248/430.250), overload protection (430.32), snap switch disconnects (430.109), and live-part guarding. Simple English, full explanations.

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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).

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This Motor Circuit Calculations 1 (NEC 430) — NEC 2023 Edition has 30 questions with detailed answers and NEC references. Take the full test, review every wrong answer, and look up the NEC article it references before moving on.

Tip: Use the NEC index (back of the book) — find answers by keyword, not by article number.

Topics covered: NEC articles 100, 210, 220, 240, 250, 300, 310, 430, and special occupancies.
Passing score: Aim for 80%+ on NEC code tests before exam day.
Questions: 30 multiple-choice, one correct answer each

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Motor Circuit Calculations 1 (NEC 430) — NEC 2023 Edition — Question List

Question 1: For a single-phase motor used in continuous-duty service, what is the minimum ampacity required for the branch-circuit conductors?

Not less than 125% of motor FLC
Not less than 115% of motor FLC
Not more than 100% of motor FLC
Not less than 250% of motor FLC

NEC Reference: NEC 430.22(A)

Question 2: A single-phase continuous-duty motor has a full-load current (FLC) of 20 amperes. What minimum branch-circuit conductor ampacity is required?

25 amperes
21.5 amperes
22 amperes
22.5 amperes

NEC Reference: NEC 430.22(A)

Question 3: A 40-ampere single-phase continuous-duty motor needs branch-circuit conductors sized at 125% of FLC. Using THW copper conductors at 75 C, what size is needed?

8 AWG THW
6 AWG THW
12 AWG THW
14 AWG THW

NEC Reference: NEC 430.22(A) / Table 310.16

Question 4: Per NEC Table 430.248, what is the listed full-load current (FLC) of a 5 HP, 230-volt single-phase AC motor?

28 amperes
40 amperes
44 amperes
32 amperes

NEC Reference: NEC Table 430.248

Question 5: A 2 HP, 230-volt single-phase continuous-duty motor has a marked service factor of 1.1 and a full-load current of 12 amperes. What overload protection rating should be used?

12 amperes
10 amperes
14 amperes
8 amperes

NEC Reference: NEC 430.32(A)(1)

Question 6: A 50 HP, 460-volt three-phase motor is supplied by branch-circuit conductors sized at 125% of FLC. Per NEC Table 430.250, what is the required conductor ampacity?

81.25 amperes
65 amperes
52 amperes
100 amperes

NEC Reference: NEC Table 430.250

Question 7: A 15 HP and a 5 HP motor, both 230-volt, are supplied by the same feeder. Per NEC 430.24, what minimum feeder conductor ampacity is required?

67.7 amperes
57.5 amperes
52.5 amperes
15.2 amperes

NEC Reference: NEC 430.24

Question 8: A 20-ampere AC general-use snap switch is used to disconnect a small motor. What is the maximum motor full-load current permitted for this switch?

16 amperes
20 amperes
15 amperes
17 amperes

NEC Reference: NEC 430.109(C)(2)

Question 9: Exposed live parts of motors and controllers operating at or above what voltage must be guarded against accidental contact?

75 volts
50 volts
120 volts
240 volts

NEC Reference: NEC 430.232

Question 10: Per NEC Table 430.250, what is the full-load current of a 10 HP, 230-volt three-phase motor?

28 amperes
42 amperes
14 amperes
56 amperes

NEC Reference: NEC Table 430.250

Question 11: For sizing motor branch-circuit conductors and short-circuit protection, which current value should be used?

The NEC table full-load current value
The nameplate current, always
A rough estimate
The breaker rating

NEC Reference: NEC 430.6(A)(1)

Question 12: Per NEC Table 430.52, what is the maximum rating, as a percent of motor FLC, for an inverse-time circuit breaker used as motor branch-circuit short-circuit and ground-fault protection (most common motor types)?

250%
125%
400%
700%

NEC Reference: NEC Table 430.52

Question 13: Per NEC Table 430.52, what is the maximum rating, as a percent of motor FLC, for a time-delay (dual-element) fuse used as motor branch-circuit protection?

175%
300%
125%
600%

NEC Reference: NEC Table 430.52

Question 14: A continuous-duty motor with no marked service factor (or a service factor less than 1.15) needs overload protection sized at what percent of FLC?

115%
125%
100%
150%

NEC Reference: NEC 430.32(A)(1)

Question 15: The NEC defines "within sight" for a motor disconnecting means as visible and not more than what distance away?

50 feet
25 feet
100 feet
10 feet

NEC Reference: NEC Article 100

Question 16: Per NEC 430.110(A), a motor disconnecting means for a motor rated 100 HP or less must generally have an ampere rating of at least what percent of the motor FLC?

115%
125%
100%
80%

NEC Reference: NEC 430.110(A)

Question 17: Per NEC 430.83, a motor controller (other than certain inverse-time breakers) must have a horsepower rating not lower than what?

The horsepower rating of the motor
Half the motor horsepower
Any rating at all
Twice the motor horsepower, always

NEC Reference: NEC 430.83

Question 18: Per NEC 430.7, what information must generally appear on a motor nameplate?

Rated voltage, current, frequency, and horsepower
Nothing is required
Only the manufacturer color
Only the purchase date

NEC Reference: NEC 430.7

Question 19: Can a dual-element (time-delay) fuse serve as both branch-circuit short-circuit protection AND running overload protection for a motor?

Yes, if properly sized
No, never
Only for three-phase motors
Only for motors under 1 HP

NEC Reference: NEC 430.32 / 430.52

Question 20: Per NEC 430.14(A), a motor must generally be located or protected so that what condition is avoided?

Inadequate ventilation and blocked maintenance access
Too much airflow
Being too close to a wall outlet
Nothing -- location never matters

NEC Reference: NEC 430.14(A)

Question 21: Exposed non-current-carrying metal parts of motor frames must generally be what, per NEC 430.144?

Grounded
Painted
Left ungrounded always
Insulated from ground

NEC Reference: NEC 430.144

Question 22: Per NEC Table 430.250, what is the full-load current of a 25 HP, 460-volt three-phase motor?

34 amperes
68 amperes
17 amperes
54 amperes

NEC Reference: NEC Table 430.250

Question 23: A continuous-duty motor has a marked service factor of 1.15 and a full-load current of 20 amperes. What overload protection rating is permitted?

25 amperes
23 amperes
20 amperes
30 amperes

NEC Reference: NEC 430.32(A)(1)

Question 24: Does NEC Article 430 require motor circuit conductors to use a specific special color, different from general branch-circuit conductor rules?

No special motor-only color rule exists
Yes, all motor conductors must be orange
Yes, all motor conductors must be white
Yes, all motor conductors must be bare

NEC Reference: NEC Article 430

Question 25: For a multispeed motor, branch-circuit conductors between the controller and the motor must be sized based on which full-load current value?

The highest full-load current among the speeds
The lowest full-load current among the speeds
The average of all speeds
Only the nameplate horsepower

NEC Reference: NEC 430.22(B)

Question 26: For a wound-rotor motor used for other than short-time, intermittent, periodic, or varying duty, secondary conductors between the controller and resistor must be sized at not less than what percent of the motor secondary full-load current?

125%
100%
250%
80%

NEC Reference: NEC 430.23(A)

Question 27: What is the main purpose of the motor branch-circuit short-circuit and ground-fault protective device, as distinct from the overload device?

Clear short circuits and ground faults quickly
Protect against slow overheating only
Turn the motor on and off daily
Nothing -- it has no real purpose

NEC Reference: NEC Article 430 Part IV

Question 28: Per NEC Table 430.248, what is the full-load current of a 1 HP, 115-volt single-phase motor?

16 amperes
8 amperes
24 amperes
32 amperes

NEC Reference: NEC Table 430.248

Question 29: Can a motor be allowed to restart automatically after tripping on overload, if unattended restarting could result in a hazard?

Only if it will not create a hazard
Always automatically, with no restriction
Never under any circumstance
Only on weekends

NEC Reference: NEC 430.43

Question 30: Can the motor controller disconnecting means also serve as the required motor disconnecting means, if it meets the requirements of 430.109?

Yes, if it meets 430.109 requirements
No, two separate devices are always required
Only for motors under 1 HP
Only for three-phase motors

NEC Reference: NEC 430.111

Key NEC References for This Test

Article	What It Covers
Ch. 1–4	General rules — apply to all installations
Ch. 5–7	Special rules — override Ch. 1–4 where they conflict
Ch. 8	Communications — completely independent of Ch. 1–7
Ch. 9	Tables — referenced by articles, not standalone enforceable rules
Art. 210.12	AFCI — major expansion in NEC 2026
Art. 230.67	Surge protection at service equipment — new NEC 2026

Study Tip: Learn the NEC index — use keywords, not article numbers. Practice finding 5 different topics in under 2 minutes each.

Motor Circuit Calculations 1 (NEC 430) — NEC 2023 Edition

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Motor Circuit Calculations 1 (NEC 430) — NEC 2023 Edition

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Motor Circuit Calculations 1 (NEC 430) — NEC 2023 Edition — Question List

Question 1: For a single-phase motor used in continuous-duty service, what is the minimum ampacity required for the branch-circuit conductors?

Question 2: A single-phase continuous-duty motor has a full-load current (FLC) of 20 amperes. What minimum branch-circuit conductor ampacity is required?

Question 3: A 40-ampere single-phase continuous-duty motor needs branch-circuit conductors sized at 125% of FLC. Using THW copper conductors at 75 C, what size is needed?

Question 4: Per NEC Table 430.248, what is the listed full-load current (FLC) of a 5 HP, 230-volt single-phase AC motor?

Question 5: A 2 HP, 230-volt single-phase continuous-duty motor has a marked service factor of 1.1 and a full-load current of 12 amperes. What overload protection rating should be used?

Question 6: A 50 HP, 460-volt three-phase motor is supplied by branch-circuit conductors sized at 125% of FLC. Per NEC Table 430.250, what is the required conductor ampacity?

Question 7: A 15 HP and a 5 HP motor, both 230-volt, are supplied by the same feeder. Per NEC 430.24, what minimum feeder conductor ampacity is required?

Question 8: A 20-ampere AC general-use snap switch is used to disconnect a small motor. What is the maximum motor full-load current permitted for this switch?

Question 9: Exposed live parts of motors and controllers operating at or above what voltage must be guarded against accidental contact?

Question 10: Per NEC Table 430.250, what is the full-load current of a 10 HP, 230-volt three-phase motor?

Question 11: For sizing motor branch-circuit conductors and short-circuit protection, which current value should be used?

Question 12: Per NEC Table 430.52, what is the maximum rating, as a percent of motor FLC, for an inverse-time circuit breaker used as motor branch-circuit short-circuit and ground-fault protection (most common motor types)?

Question 13: Per NEC Table 430.52, what is the maximum rating, as a percent of motor FLC, for a time-delay (dual-element) fuse used as motor branch-circuit protection?

Question 14: A continuous-duty motor with no marked service factor (or a service factor less than 1.15) needs overload protection sized at what percent of FLC?

Question 15: The NEC defines "within sight" for a motor disconnecting means as visible and not more than what distance away?

Question 16: Per NEC 430.110(A), a motor disconnecting means for a motor rated 100 HP or less must generally have an ampere rating of at least what percent of the motor FLC?

Question 17: Per NEC 430.83, a motor controller (other than certain inverse-time breakers) must have a horsepower rating not lower than what?

Question 18: Per NEC 430.7, what information must generally appear on a motor nameplate?

Question 19: Can a dual-element (time-delay) fuse serve as both branch-circuit short-circuit protection AND running overload protection for a motor?

Question 20: Per NEC 430.14(A), a motor must generally be located or protected so that what condition is avoided?

Question 21: Exposed non-current-carrying metal parts of motor frames must generally be what, per NEC 430.144?

Question 22: Per NEC Table 430.250, what is the full-load current of a 25 HP, 460-volt three-phase motor?

Question 23: A continuous-duty motor has a marked service factor of 1.15 and a full-load current of 20 amperes. What overload protection rating is permitted?

Question 24: Does NEC Article 430 require motor circuit conductors to use a specific special color, different from general branch-circuit conductor rules?

Question 25: For a multispeed motor, branch-circuit conductors between the controller and the motor must be sized based on which full-load current value?

Question 26: For a wound-rotor motor used for other than short-time, intermittent, periodic, or varying duty, secondary conductors between the controller and resistor must be sized at not less than what percent of the motor secondary full-load current?

Question 27: What is the main purpose of the motor branch-circuit short-circuit and ground-fault protective device, as distinct from the overload device?

Question 28: Per NEC Table 430.248, what is the full-load current of a 1 HP, 115-volt single-phase motor?

Question 29: Can a motor be allowed to restart automatically after tripping on overload, if unattended restarting could result in a hazard?

Question 30: Can the motor controller disconnecting means also serve as the required motor disconnecting means, if it meets the requirements of 430.109?

Key NEC References for This Test

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