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
NEC CODE
NEC 2023
Motor Circuit Calculations-2 (NEC 430)
Free Online NEC Code Questions : Motor Circuit Calculations (NEC 430)
TOPICS COVERED
NEC Questions
How this test works
Read each question carefully
Look for absolute words like always / never — they often distinguish the right answer.
Manage your time
You have 15 min for 10 questions. Skip tough ones and come back.
Progress is auto-saved
Your answers are saved locally — a page refresh won't lose your work.
Review your answers
After submitting you'll see every explanation and your NEC references.
Frequently Asked Questions
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).
10
Questions
15 min
Time
70%
Pass
Timer starts immediately. Progress is auto-saved.
0
Correct0
Wrong0s
TimeMotor Circuit Calculations-2 (NEC 430) — Question List
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
Student Reviews
No reviews yet — be the first to share your experience!
Leave a Review