Previous Motor Circuit Calculations 2 (NEC 430) — NEC 2023 Edition Next Motor Circuit Calculations 3 (NEC 430/440) — NEC 2023 Edition

NEC CODE NEC 2020

Motor Circuit Calculations 3 (NEC 430/440) — NEC 2020 Edition

Free NEC 2020 practice test on motor and motor-compressor circuit calculations. Covers hermetic refrigerant motor-compressor branch-circuit and short-circuit protection (Article 440), controllers, and disconnecting means (Article 430). Simple English, full explanations.

TOPICS COVERED

NEC Practice Tests

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 45 min for 30 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).

How to Use This Practice Test

This Motor Circuit Calculations 3 (NEC 430/440) — NEC 2020 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

Questions

45 min

Time

70%

Pass

Timer starts immediately. Progress is auto-saved.

Motor Circuit Calculations 3 (NEC 430/440) — NEC 2020 Edition — Question List

Question 1: What is the maximum rating, as a percent of motor-compressor rated-load current, for the short-circuit and ground-fault protective device of a single motor-compressor?

225 %
175 %
200 %
150 %

NEC Reference: NEC 440.22(A)

Question 2: Per the exception in NEC 440.22(A), what is the minimum ampere rating allowed for a motor-compressor short-circuit and ground-fault protective device, even if the calculated value is lower?

10 A
15 A
20 A
25 A

NEC Reference: NEC 440.22(A) Exception

Question 3: What size branch-circuit conductor is required for an 18-ampere motor-compressor connected to a 240-volt circuit, with terminals rated at 75 C?

12 AWG
10 AWG
14 AWG
8 AWG

NEC Reference: NEC 440.32 / Table 310.16

Question 4: What size branch-circuit protection is required for a 20-ampere motor-compressor connected to a 240-volt circuit?

35 A
40 A
45 A
50 A

NEC Reference: NEC 440.22(A)

Question 5: What size branch-circuit conductor is suitable for a 5 HP, 208-volt three-phase motor, with terminals rated 75 C?

12 AWG
10 AWG
8 AWG
14 AWG

NEC Reference: NEC Table 430.250 / Table 310.16

Question 6: A single-pole, general-use snap switch is only permitted to control (start and stop) a stationary motor rated up to what horsepower?

1/2 HP
1/4 HP
3/4 HP
1 HP

NEC Reference: NEC 430.83(C)

Question 7: The branch-circuit overcurrent device of a stationary motor rated below what horsepower may also serve as the motor's controller?

5 HP
3 HP
1 HP
1/8 HP

NEC Reference: NEC 430.81(A)

Question 8: A disconnecting means for motor circuits over 1000 volts must be capable of being locked in which position?

Closed position
Open position
On position
Both open and closed

NEC Reference: NEC 430.109

Question 9: Overload protection is generally required for a motor rated above what horsepower?

1/8 HP
1/4 HP
1/2 HP
1 HP

NEC Reference: NEC 430.32(A)

Question 10: A motor disconnecting means located "within sight" of the motor must be visible and not more than what distance away?

25 feet
50 feet
70 feet
90 feet

NEC Reference: NEC Article 100

Question 11: For a hermetic refrigerant motor-compressor, overload protection is generally based on which current value?

The rated-load or branch-circuit selection current
A random guess
The building service size
The compressor's weight

NEC Reference: NEC 440.52

Question 12: Per NEC 440.12(A), a disconnecting means for a hermetic motor-compressor is generally sized based on what percent of the compressor rated-load current, if not horsepower-rated?

115%
125%
100%
175%

NEC Reference: NEC 440.12(A)

Question 13: A cord-and-plug-connected room air conditioner rated 250 volts or less generally must not draw more than what percent of the branch-circuit rating?

80%
100%
125%
50%

NEC Reference: NEC 440.62(B)

Question 14: Per NEC 440.4(A), hermetic refrigerant motor-compressor equipment must be marked with which of the following, in addition to other data?

Rated-load current
The installer's name
Nothing is required
Only the paint color

NEC Reference: NEC 440.4(A)

Question 15: A motor controller (other than certain inverse-time breakers) must generally 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 16: A manually resettable overload relay that could restart a motor unexpectedly, creating a hazard, must generally be reset from where?

Intentional manual action only
It resets itself automatically, always
A random timer
It never needs resetting

NEC Reference: NEC 430.43

Question 17: If the motor disconnecting means is not within sight of the controller location, what does NEC 430.102(B) generally require?

The disconnect must be lockable in the open position
Nothing extra is required
A sign is enough, no lock needed
The controller must be moved instead

NEC Reference: NEC 430.102(B)

Question 18: Tap conductors supplying an individual motor from a branch circuit generally must have an ampacity of not less than what fraction of the branch-circuit conductor ampacity, when very short?

One-third the branch-circuit conductor ampacity
Exactly the same size, always
One-tenth the branch-circuit conductor ampacity
No tap is ever permitted

NEC Reference: NEC 430.28

Question 19: For air-conditioning or refrigerating equipment with multiple motors and loads on a single nameplate, what value is generally used to size the equipment's branch-circuit protection?

The nameplate maximum overcurrent protection rating
A random guess
Always 15 amperes
The building main breaker size

NEC Reference: NEC 440.22(B)

Question 20: What is the "branch-circuit selection current" for a hermetic refrigerant motor-compressor?

A nameplate value used for sizing when larger than rated-load current
A random constant
Always equal to the branch breaker size
The compressor's weight in pounds

NEC Reference: NEC Article 440

Question 21: Can a single motor be supplied from a feeder that also supplies other loads, without a separate feeder just for that motor?

Yes, if properly sized
No, every motor needs a dedicated feeder
Only for motors under 1 HP
Only for single-phase motors

NEC Reference: NEC 430.24 / 430.63

Question 22: Exposed non-current-carrying metal parts of a motor-compressor unit must generally be what, similar to standard motor frames?

Grounded
Insulated from ground
Painted only
Left ungrounded

NEC Reference: NEC 440.61

Question 23: For air-conditioning or refrigeration equipment, the disconnecting means must generally be readily accessible and located within sight of what?

The equipment it serves
A neighboring building
Nowhere specific
Only the main panel, regardless of distance

NEC Reference: NEC 440.14

Question 24: On HVAC equipment nameplates, what do the abbreviations MCA and MOCP generally stand for?

Minimum circuit ampacity and maximum overcurrent protection
Motor control assembly and motor overcurrent panel
Nothing standard -- they vary by installer
Maximum current allowed and minimum operating cost

NEC Reference: NEC Article 440

Question 25: Can the same disconnecting means serve both the required motor disconnect and a required equipment disconnect for air-conditioning/refrigeration equipment, when they are the same device?

Yes, if it meets both articles' requirements
No, two separate devices are always required
Only for motors under 1 HP
Only for single-phase equipment

NEC Reference: NEC 440.14 / 430.109

Question 26: Can a thermal protector built into a hermetic motor-compressor serve as the required overload protection?

Yes, if suitable for the application
No, a separate device is always required
Only for motors over 50 HP
Only for three-phase compressors

NEC Reference: NEC 440.52(A)(1)

Question 27: Under NEC 440.22(A), when the calculated motor-compressor short-circuit protective device rating does not correspond to a standard fuse or breaker size, what should be done?

Use the next higher standard rating, within the cap
Leave the equipment unprotected
Always round down, no matter what
Double the value automatically

NEC Reference: NEC 440.22(A)

Question 28: When two or more motor-compressors, or a motor-compressor plus other loads, are supplied by a single branch circuit, how is the branch-circuit conductor generally sized?

125% of the largest, plus the sum of the rest
100% of all loads added together, no multiplier
Only the largest single load, ignoring the rest
A flat 20 amperes regardless of load

NEC Reference: NEC 440.33

Question 29: Is it good practice, though not always mandatory, to locate the motor disconnecting means near the controller?

Yes, for convenience and safety
No, they must always be in separate buildings
It is against code to place them near each other
It makes no practical difference

NEC Reference: NEC 430.102

Question 30: When a motor overload relay is in a different ambient temperature than the motor itself, what type of overload relay should generally be selected?

An ambient-compensated overload relay
Any relay at all, it does not matter
A relay with no thermal sensing
A relay sized for double the FLC

NEC Reference: NEC 430.32(C)

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 3 (NEC 430/440) — NEC 2020 Edition

How this test works

Frequently Asked Questions

How to Use This Practice Test

Student Reviews

Leave a Review

Key NEC References for This Test

Motor Circuit Calculations 3 (NEC 430/440) — NEC 2020 Edition

How this test works

Frequently Asked Questions

Is this Motor Circuit Calculations 3 (NEC 430/440) — NEC 2020 Edition free?

What is the NEC code book?

Which NEC edition should I study?

What articles are covered on electrician licensing exams?

How to Use This Practice Test

Student Reviews

Leave a Review

Motor Circuit Calculations 3 (NEC 430/440) — NEC 2020 Edition — Question List

Question 1: What is the maximum rating, as a percent of motor-compressor rated-load current, for the short-circuit and ground-fault protective device of a single motor-compressor?

Question 2: Per the exception in NEC 440.22(A), what is the minimum ampere rating allowed for a motor-compressor short-circuit and ground-fault protective device, even if the calculated value is lower?

Question 3: What size branch-circuit conductor is required for an 18-ampere motor-compressor connected to a 240-volt circuit, with terminals rated at 75 C?

Question 4: What size branch-circuit protection is required for a 20-ampere motor-compressor connected to a 240-volt circuit?

Question 5: What size branch-circuit conductor is suitable for a 5 HP, 208-volt three-phase motor, with terminals rated 75 C?

Question 6: A single-pole, general-use snap switch is only permitted to control (start and stop) a stationary motor rated up to what horsepower?

Question 7: The branch-circuit overcurrent device of a stationary motor rated below what horsepower may also serve as the motor's controller?

Question 8: A disconnecting means for motor circuits over 1000 volts must be capable of being locked in which position?

Question 9: Overload protection is generally required for a motor rated above what horsepower?

Question 10: A motor disconnecting means located "within sight" of the motor must be visible and not more than what distance away?

Question 11: For a hermetic refrigerant motor-compressor, overload protection is generally based on which current value?

Question 12: Per NEC 440.12(A), a disconnecting means for a hermetic motor-compressor is generally sized based on what percent of the compressor rated-load current, if not horsepower-rated?

Question 13: A cord-and-plug-connected room air conditioner rated 250 volts or less generally must not draw more than what percent of the branch-circuit rating?

Question 14: Per NEC 440.4(A), hermetic refrigerant motor-compressor equipment must be marked with which of the following, in addition to other data?

Question 15: A motor controller (other than certain inverse-time breakers) must generally have a horsepower rating not lower than what?

Question 16: A manually resettable overload relay that could restart a motor unexpectedly, creating a hazard, must generally be reset from where?

Question 17: If the motor disconnecting means is not within sight of the controller location, what does NEC 430.102(B) generally require?

Question 18: Tap conductors supplying an individual motor from a branch circuit generally must have an ampacity of not less than what fraction of the branch-circuit conductor ampacity, when very short?

Question 19: For air-conditioning or refrigerating equipment with multiple motors and loads on a single nameplate, what value is generally used to size the equipment's branch-circuit protection?

Question 20: What is the "branch-circuit selection current" for a hermetic refrigerant motor-compressor?

Question 21: Can a single motor be supplied from a feeder that also supplies other loads, without a separate feeder just for that motor?

Question 22: Exposed non-current-carrying metal parts of a motor-compressor unit must generally be what, similar to standard motor frames?

Question 23: For air-conditioning or refrigeration equipment, the disconnecting means must generally be readily accessible and located within sight of what?

Question 24: On HVAC equipment nameplates, what do the abbreviations MCA and MOCP generally stand for?

Question 25: Can the same disconnecting means serve both the required motor disconnect and a required equipment disconnect for air-conditioning/refrigeration equipment, when they are the same device?

Question 26: Can a thermal protector built into a hermetic motor-compressor serve as the required overload protection?

Question 27: Under NEC 440.22(A), when the calculated motor-compressor short-circuit protective device rating does not correspond to a standard fuse or breaker size, what should be done?

Question 28: When two or more motor-compressors, or a motor-compressor plus other loads, are supplied by a single branch circuit, how is the branch-circuit conductor generally sized?

Question 29: Is it good practice, though not always mandatory, to locate the motor disconnecting means near the controller?

Question 30: When a motor overload relay is in a different ambient temperature than the motor itself, what type of overload relay should generally be selected?

Key NEC References for This Test

Related Practice Tests