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NEC CODE NEC 2020

Equipment for General Use (NEC 400/402/408/424/440/480) — NEC 2020 Edition

Free NEC 2020 practice test on general-use equipment rules: flexible cords, fixture wires, panelboards, air-conditioning branch circuits, transformer vaults, fixed electric space heating, and storage batteries. 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).

How to Use This Practice Test

This Equipment for General Use (NEC 400/402/408/424/440/480) — 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

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Equipment for General Use (NEC 400/402/408/424/440/480) — NEC 2020 Edition — Question List

Question 1: What is the minimum approved wire size generally permitted for a fixture wire?

18 AWG
16 AWG
12 AWG
10 AWG

NEC Reference: NEC 402.6

Question 2: Per NEC 408.36(C), a dust-tight circuit breaker must not be installed on which equipment?

Panel boards
Junction boxes
Enclosures
Boxes

NEC Reference: NEC 408.36(C)

Question 3: A 20-ampere branch circuit supplies only one 120-volt cord-and-plug window air conditioner. What is the maximum full-load current rating permitted for that unit?

16 amperes
20 amperes
10 amperes
18 amperes

NEC Reference: NEC 440.62(B)

Question 4: A transformer vault doorway protected by an automatic sprinkler or water-spray system must generally have a minimum fire rating of how much?

1 hour
3 hours
1/2 hour
2 hours

NEC Reference: NEC 450.43

Question 5: When ground-fault protection is provided for impedance heating elements, what is the maximum transformer secondary voltage generally permitted?

80 volts
30 volts
65 volts
50 volts

NEC Reference: NEC Article 426/427

Question 6: Fixed outdoor electric deicing and snow-melting equipment is generally classified as what type of load?

Continuous load
Non-continuous load
Heavy load
Not relevant for service conductor calculations

NEC Reference: NEC 426.4

Question 7: What is the allowable ampacity of a 10 AWG fixture wire, per NEC Table 402.5?

28 amperes
23 amperes
17 amperes
30 amperes

NEC Reference: NEC Table 402.5

Question 8: What is the nominal voltage of a lead-acid battery cell, per NEC 480.2?

2 volts
1.2 volts
1.7 volts
2.2 volts

NEC Reference: NEC 480.2

Question 9: A 300-volt motor disconnecting means must generally be rated how, relative to the motor full-load current?

Not less than 115% of motor full load current
At least 125% of motor full load current
Not greater than 120% of motor full load current
A flat 150 amperes

NEC Reference: NEC 430.110

Question 10: Which of the following is NOT a standard rating for a branch circuit supplying fixed electric space heaters in a dwelling unit?

40 amperes
30 amperes
20 amperes
25 amperes

NEC Reference: NEC 424.3

Question 11: A flexible cord generally cannot be used as a substitute for what?

The fixed wiring of a structure
A portable lamp cord
An extension cord
A tool cord

NEC Reference: NEC 400.12

Question 12: What is the allowable ampacity of a 14 AWG fixture wire, per NEC Table 402.5?

35 amperes
25 amperes
30 amperes
40 amperes

NEC Reference: NEC Table 402.5

Question 13: What is the nominal voltage of an alkali (nickel-cadmium type) cell, per NEC 480.2?

1.2 volts
2 volts
3.6 volts
1.5 volts

NEC Reference: NEC 480.2

Question 14: What is the general NEC definition of a "continuous load"?

Maximum current expected to continue for 3 hours or more
Any load running more than 10 minutes
Any load over 50 amperes
Only loads running 24 hours a day

NEC Reference: NEC Article 100

Question 15: True or false: panelboards must generally be of dead-front construction, meaning no live parts are exposed on the front.

True
False
Only for panelboards over 400A
Only in dwelling units

NEC Reference: NEC 408.38

Question 16: Fixed outdoor electric deicing and snow-melting equipment generally requires what type of protection, per NEC Article 426?

Ground-fault protection of equipment (GFPE)
No protection is required
Only a fuse, no GFCI/GFPE
Only a disconnect switch

NEC Reference: NEC 426.28

Question 17: Storage battery installations that can produce hydrogen gas generally require what, per NEC Article 480?

Ventilation to prevent hydrogen gas accumulation
No special provisions are ever needed
A fire sprinkler only
A dedicated 20A receptacle only

NEC Reference: NEC Article 480

Question 18: What is the general purpose of a fire-rated door on a transformer vault, per NEC 450.43?

To contain fire and limit its spread
To keep out sunlight
To reduce noise only
It has no fire-related purpose

NEC Reference: NEC 450.43

Question 19: When MORE than one cord-and-plug room air conditioner is supplied by the same branch circuit, what total percentage of the branch-circuit rating generally applies, per NEC 440.62(A)?

Up to 100%, under 440.62(A) conditions
Always exactly 80%, same as a single unit
Always exactly 50%
This is never permitted

NEC Reference: NEC 440.62(A)

Question 20: Because fixed outdoor deicing and snow-melting equipment is treated as a continuous load, its branch-circuit conductors are generally sized at not less than what percentage of the load current?

125%
100%
80%
150%

NEC Reference: NEC 426.4

Question 21: Fixed electric space-heating cable sets and heating panels are generally required to be marked with what information?

Rating in volts and watts (or volts and amperes)
No marking is ever required
Only the installer's name
Only the installation date

NEC Reference: NEC 424.35

Question 22: The allowable ampacity of a fixture wire, listed in NEC Table 402.5, depends primarily on its conductor size and what other characteristic?

The insulation temperature rating
The wire's color
The manufacturer only
Nothing else matters

NEC Reference: NEC Table 402.5

Question 23: Per the NEC informational note in 480.2, what is roughly the nominal voltage of a lithium-ion (Li-ion) cell?

About 3.6-3.8 volts
2 volts
1.2 volts
12 volts

NEC Reference: NEC 480.2

Question 24: A 300-volt motor has a full-load current of 50 amperes. What is the minimum ampere rating generally required for its disconnecting means?

57.5 amperes
50 amperes
60 amperes
75 amperes

NEC Reference: NEC 430.110

Question 25: Equipment intended for use in dusty locations is generally listed and marked for what type of service?

"Dust-tight" or for the classified location
No marking is ever required
Only a serial number
Only a UL sticker with no wording

NEC Reference: NEC 100 / 500 series

Question 26: If a transformer vault doorway is NOT protected by an automatic sprinkler or water-spray system, its fire rating generally must be what, compared to the reduced 1-hour rating that applies when such protection IS present?

Higher (typically 3 hours)
The same 1-hour rating
No fire rating is ever required
Exactly half an hour

NEC Reference: NEC 450.43

Question 27: True or false: without GFCI/ground-fault protection, impedance heating systems generally have a lower maximum transformer secondary voltage limit than the 80-volt limit permitted when such protection IS provided.

True
False
Voltage limits do not depend on GFCI protection
GFCI protection is never used with impedance heating

NEC Reference: NEC Article 426/427

Question 28: True or false: flexible cords generally must not contain splices or taps, unless listed for that purpose.

True
False
Only for indoor cords
Only for cords under 6 feet

NEC Reference: NEC 400.9

Question 29: For motor disconnecting means rated 600 volts or less, the NEC generally bases the minimum ampere rating on what value?

The motor full-load current
The service panel rating
The building square footage
The feeder conductor size only

NEC Reference: NEC 430.110

Question 30: A thermostat that controls a fixed electric space-heating unit and also serves as the disconnecting means must generally do what to all ungrounded conductors?

Open (disconnect) all ungrounded conductors
Open only the neutral conductor
Nothing -- it does not need to disconnect
Only reduce voltage, not disconnect

NEC Reference: NEC 424.20

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.

Equipment for General Use (NEC 400/402/408/424/440/480) — NEC 2020 Edition

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Key NEC References for This Test

Equipment for General Use (NEC 400/402/408/424/440/480) — NEC 2020 Edition

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Frequently Asked Questions

Is this Equipment for General Use (NEC 400/402/408/424/440/480) — NEC 2020 Edition free?

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How to Use This Practice Test

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Equipment for General Use (NEC 400/402/408/424/440/480) — NEC 2020 Edition — Question List

Question 1: What is the minimum approved wire size generally permitted for a fixture wire?

Question 2: Per NEC 408.36(C), a dust-tight circuit breaker must not be installed on which equipment?

Question 3: A 20-ampere branch circuit supplies only one 120-volt cord-and-plug window air conditioner. What is the maximum full-load current rating permitted for that unit?

Question 4: A transformer vault doorway protected by an automatic sprinkler or water-spray system must generally have a minimum fire rating of how much?

Question 5: When ground-fault protection is provided for impedance heating elements, what is the maximum transformer secondary voltage generally permitted?

Question 6: Fixed outdoor electric deicing and snow-melting equipment is generally classified as what type of load?

Question 7: What is the allowable ampacity of a 10 AWG fixture wire, per NEC Table 402.5?

Question 8: What is the nominal voltage of a lead-acid battery cell, per NEC 480.2?

Question 9: A 300-volt motor disconnecting means must generally be rated how, relative to the motor full-load current?

Question 10: Which of the following is NOT a standard rating for a branch circuit supplying fixed electric space heaters in a dwelling unit?

Question 11: A flexible cord generally cannot be used as a substitute for what?

Question 12: What is the allowable ampacity of a 14 AWG fixture wire, per NEC Table 402.5?

Question 13: What is the nominal voltage of an alkali (nickel-cadmium type) cell, per NEC 480.2?

Question 14: What is the general NEC definition of a "continuous load"?

Question 15: True or false: panelboards must generally be of dead-front construction, meaning no live parts are exposed on the front.

Question 16: Fixed outdoor electric deicing and snow-melting equipment generally requires what type of protection, per NEC Article 426?

Question 17: Storage battery installations that can produce hydrogen gas generally require what, per NEC Article 480?

Question 18: What is the general purpose of a fire-rated door on a transformer vault, per NEC 450.43?

Question 19: When MORE than one cord-and-plug room air conditioner is supplied by the same branch circuit, what total percentage of the branch-circuit rating generally applies, per NEC 440.62(A)?

Question 20: Because fixed outdoor deicing and snow-melting equipment is treated as a continuous load, its branch-circuit conductors are generally sized at not less than what percentage of the load current?

Question 21: Fixed electric space-heating cable sets and heating panels are generally required to be marked with what information?

Question 22: The allowable ampacity of a fixture wire, listed in NEC Table 402.5, depends primarily on its conductor size and what other characteristic?

Question 23: Per the NEC informational note in 480.2, what is roughly the nominal voltage of a lithium-ion (Li-ion) cell?

Question 24: A 300-volt motor has a full-load current of 50 amperes. What is the minimum ampere rating generally required for its disconnecting means?

Question 25: Equipment intended for use in dusty locations is generally listed and marked for what type of service?

Question 26: If a transformer vault doorway is NOT protected by an automatic sprinkler or water-spray system, its fire rating generally must be what, compared to the reduced 1-hour rating that applies when such protection IS present?

Question 27: True or false: without GFCI/ground-fault protection, impedance heating systems generally have a lower maximum transformer secondary voltage limit than the 80-volt limit permitted when such protection IS provided.

Question 28: True or false: flexible cords generally must not contain splices or taps, unless listed for that purpose.

Question 29: For motor disconnecting means rated 600 volts or less, the NEC generally bases the minimum ampere rating on what value?

Question 30: A thermostat that controls a fixed electric space-heating unit and also serves as the disconnecting means must generally do what to all ungrounded conductors?

Key NEC References for This Test

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