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NEC CODE NEC 2023

Motor Circuit Calculations-2 (NEC 430)

Free Online NEC Code Questions : Motor Circuit Calculations (NEC 430)

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Yes — free, no signup required. Each question links to the relevant NEC article so you can study the code directly.

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).

How to Use This Practice Test

This Motor Circuit Calculations-2 (NEC 430) has 10 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: 10 multiple-choice, one correct answer each

10

Questions

15 min

Time

70%

Pass

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Motor Circuit Calculations-2 (NEC 430) — Question List

Question 1: A 5 HP single phase motor is connected to a 240 volts power supply. What is the minimum size branch circuit conductors required for this motor?

No 8 THWN
No 6 THWN
No 4 THWN
No 10 THWN

NEC Reference: NEC 430.248

Question 2: A 4 hp 230 V single phase motor has a service factor of 1.15 and name plate current rating of 25 A. What size dual element fuse can be used to protect the motor from overloads, short circuit and ground faults?

25 A
30 A
28 A
35 A

NEC Reference: NEC 430.32(A)(1)

Question 3: What size branch circuit conductor that can be used for a 5 HP, 230 volts three phase motor with terminals rated at 75<sup>0</sup> C?

14 AWG
12 AWG
10 AWG
8 AWG

NEC Reference: NEC 430.250

Question 4: What size inverse time circuit breaker is required for a 10HP, 230 volts three phase motor operated at 75<sup>0</sup>C?

70A
56 A
40A
30 A

NEC Reference: NEC 430.250

Question 5: The following motors are fed from a single phase motor. What size feeder protection is required for the motors? <ol> <li>10 HP, 230 volts three phase motor</li> <li>15 HP, 230 volts three phase motor.</li> </ol>

175 A
105 A
125 A
200 A

NEC Reference: NEC 430.250

Question 6: What size feeder conductor can be used for the following motors operating at 75<sup>0</sup> C? <ol> <li>15 HP , 460 V Three phase motor</li> <li>10 HP, 460 V Three phase motor</li> </ol>

8 AWG
6 AWG
10 AWG
12 AWG

NEC Reference: NEC 430.250

Question 7: Which of the following motor is highest rated motor?

3 HP, 208 volts Three phase
10 HP, 230 volts Three phase
10 HP, 460 volts Three Phase
3 HP , 115 volts Single phase

NEC Reference: NEC 10.6

Question 8: What is the size of the branch circuit conductor that can supply 3 HP 115 volts single phase motor with terminals operating at 60<sup>0 </sup>C?

8 AWG
10 AWG
12 AWG
14 AWG

NEC Reference: NEC 430.248

Question 9: A 5 HP Three phase motor with a name plate FLA of 25 A is used for intermittent duty and rated for 5 minute service. What size branch circuit conductor can be used for the motor when the terminals are rated at 75 <sup>0</sup>C?

12 AWG
8 AWG
10 AWG
14 AWG

NEC Reference: NEC 430.22(E)

Question 10: Motor branch circuit protection devices can also protect the motor against overloads.

True
False

NEC Reference: NEC 430.51

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.

EXAM CARD NEC CODE

Questions10

Time limit15 min

Pass score70%

Code editionNEC 2023

DifficultyIntermediate

Last reviewedJun 2026

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Source: NEC 2026 (NFPA 70)