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NEC 2020 Code Questions Practice Test 9

Free NEC 2020 practice test with 30 questions covering garage and accessory building GFCI protection, underground raceway sealing, transformer secondary conductor tap rules, grounding electrode conductor protection, and raceway condensation sealing. NEC 2020 references included.

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This NEC 2020 Code Questions Practice Test 9 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: Mixed-format test — questions jump between topics just like the real exam. Don't spend more than 90 seconds on any one question.

Topics covered: All NEC chapters — branch circuits, grounding, conductors, wiring methods, motors, and more.
Passing score: Aim for 80%+ consistently before scheduling your exam.
Questions: 30 multiple-choice, one correct answer each

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NEC 2020 Code Questions Practice Test 9 — Question List

Question 1: What is the required size of a neutral conductor for a dwelling unit with a calculated load of 220 A. The unbalanced load is 120 A and service disconnect rating is 250A.

1 AWG
2 AWG
3 AWG
4 AWG

NEC Reference: NEC 310.15(B)(16)

Question 2: If a service is fed by three parallel sets of 400 kcmil conductors, what is the required conductor size for GEC?

3/0 AWG
2/0 AWG
2 AWG
4 AWG

NEC Reference: NEC 250.166

Question 3: A 400 breaker protects a set of 450 kcmil feeder conductors. A feeder fed from 450 kcmil feeder that supply disconnects with 25 A over current device. What is the minimum size conductor for these tap?

8 AWG
6 AWG
4 AWG
16 AWG

NEC Reference: NEC 310.15(B)(16)

Question 4: What size service entrance conductors are required for 250 A continuous three phase load if the terminals are at ambient temperature of 70 C?

3/0 AWG
250 kcmil
400 kcmil
2/0 AWG

NEC Reference: NEC 312.5

Question 5: Under which of the following condition the on-site generator is not considered as separately derived system?

When the generator does not have neutral conductor
When the generator is placed near the feeder service conductor panel board
Generator having transfer witch that switches the neutral conductor also
When generator neutral conductor is solidly interconnected service supply system neutral conductor

NEC Reference: NEC 250.30

Question 6: When the circuits are protected by a over current device rating of 1000 A, what size bonding jumper is required for each metal raceway?

1/0 AWG
2/0 AWG
3/0 AWG
4 AWG

NEC Reference: NEC 250.122

Question 7: When five conductors each with an ampacity of 25 A bundled through NM cable, what is the adjusted ampacity of each cable.

25 amperes
20 amperes
30 amperes
22.5 amperes

NEC Reference: NEC 310.15(B)(3)(a)

Question 8: A 40 KVA , 480 V three phase transformer has a primary over current protection device is rated at 75 A. What is the size of primary conductor that can be used?

2 AWG
4 AWG
3 AWG
1 AWG

NEC Reference: NEC 310.15(B)(16)

Question 9: How many number of 500 kcmil THWN conductors that can be installed in a 4 in. * 4 in. wireway?

4 conductors
5 conductors
6 conductors
7 conductors

NEC Reference: NEC 376.22(A)

Question 10: What size service entrance conductors are required for 250 A continuous three phase load if the terminals are at ambient temperature of 70 C?

3/0 AWG
250 kcmil
400 kcmil
2/0 AWG

NEC Reference: NEC 312.5

Question 11: 125 volt, 15 and 20 ampere receptacles installed in a dwelling unit garage require:

GFCI protection
AFCI protection only
No protection is required
A dedicated 50 ampere circuit

NEC Reference: NEC 210.8(A)(2)

Question 12: Underground raceways entering a building from an underground distribution system must be sealed with an approved compound to prevent:

Moisture or gases from entering the building
Rodents from chewing the raceway only
It has no protective purpose
Sunlight exposure

NEC Reference: NEC 300.5(G)

Question 13: Under the 10-foot transformer secondary conductor rule, the secondary conductors must have an ampacity of not less than what fraction of the transformer secondary current rating?

The combined computed load of the circuits supplied
Zero — no ampacity requirement applies
Twice the primary conductor ampacity
It is not permitted under any conditions

NEC Reference: NEC 240.21(C)(2)

Question 14: The grounded conductor of a grounded system must be routed to each service disconnecting means and:

Bonded to the service disconnecting means
Left disconnected at the service
Run only to the meter socket
Omitted entirely for safety

NEC Reference: NEC 250.24(C)

Question 15: Where exposed, a grounding electrode conductor or its enclosure must be securely fastened to the surface on which it is carried, and must be protected if exposed to:

Physical damage
Sunlight only
Low temperature only
It never requires protection

NEC Reference: NEC 250.64(B)

Question 16: Where a raceway is exposed to different temperatures on each end, such as passing from an air-conditioned space to the outdoors, it must be sealed to prevent the circulation of:

Warm air to a colder section
Electrons through the raceway
Sound between rooms
It has no purpose

NEC Reference: NEC 300.7(A)

Question 17: Where conductors of different insulation temperature ratings are used in the same circuit, the allowable ampacity of the circuit must be based on:

The lowest temperature-rated conductor in the circuit
The highest temperature-rated conductor
The average of all conductor ratings
Whichever conductor is longest

NEC Reference: NEC 310.14(A)(3)

Question 18: Conductors entering an outlet, device, or junction box must be protected from:

Abrasion
Nothing, no protection is required
Voltage drop only
Sunlight only

NEC Reference: NEC 314.17

Question 19: Type MC cable must generally be supported and secured at intervals not exceeding:

4.5 feet
6 feet
10 feet
15 feet

NEC Reference: NEC 330.30

Question 20: Per NEC Table 352.30, rigid PVC conduit of trade size 1 must be supported at intervals not exceeding:

3 feet
5 feet
8 feet
10 feet

NEC Reference: NEC 352.30

Question 21: A solid-state (electronic) general-use switch used to control permanently connected loads must be marked to indicate:

The type of load(s) it is suitable for
The installer's name
No marking is ever required
Only the manufacturer's logo

NEC Reference: NEC 404.22

Question 22: Receptacles installed in a new branch circuit must be of the:

Grounding type
Non-grounding type
Either type, at the installer's discretion
No receptacle type is specified

NEC Reference: NEC 406.4(A)

Question 23: All luminaires installed under the NEC must be:

Listed
Homemade only
Exempt from listing
Approved verbally by the inspector only, no listing needed

NEC Reference: NEC 410.6

Question 24: A fixed storage-type water heater with a capacity of 450 liters (120 gallons) or less is considered, for branch-circuit sizing purposes, to be:

A continuous load
A non-continuous load, always
Exempt from branch-circuit sizing rules
A momentary load only

NEC Reference: NEC 422.13

Question 25: Fixed outdoor electric de-icing and snow-melting equipment must be protected by:

Ground-fault protection of equipment (GFPE)
No protection at all
A simple fuse only, no GFPE
AFCI protection only

NEC Reference: NEC 426.28

Question 26: For a motor used in a torque application or with an adjustable-speed drive, conductor and overload sizing is generally based on:

The nameplate-rated current
A random assumed value
It is never permitted to size these motors
The service panel rating only

NEC Reference: NEC 430.6(A)(2)

Question 27: A single-phase, cord-and-plug-connected room air conditioner must be provided with a factory-installed leakage-current protection device as part of:

The attachment plug or supply cord
The service panel only
No such device is required
A separate wall switch only

NEC Reference: NEC 440.65

Question 28: A generator installed in a hazardous (classified) location must be:

Suitable for the location in which it is installed
It does not matter what location it is installed in
Generators are prohibited in every building
Painted a specific color only

NEC Reference: NEC 445.10

Question 29: Overcurrent protection for a transformer is intended to open the circuit before the transformer temperature exceeds:

Its insulation system's safe operating temperature
Room temperature, always
There is no temperature concern for transformers
32 degrees F only

NEC Reference: NEC 450.8

Question 30: A single motor-compressor has a rated-load current of 18 amperes. What is the minimum required branch-circuit conductor ampacity?

18 amperes
22.5 amperes
27 amperes
36 amperes

NEC Reference: NEC 440.32

NEC 2020 Code Questions Practice Test 9

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NEC 2020 Code Questions Practice Test 9

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Student Reviews

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NEC 2020 Code Questions Practice Test 9 — Question List

Question 1: What is the required size of a neutral conductor for a dwelling unit with a calculated load of 220 A. The unbalanced load is 120 A and service disconnect rating is 250A.

Question 2: If a service is fed by three parallel sets of 400 kcmil conductors, what is the required conductor size for GEC?

Question 3: A 400 breaker protects a set of 450 kcmil feeder conductors. A feeder fed from 450 kcmil feeder that supply disconnects with 25 A over current device. What is the minimum size conductor for these tap?

Question 4: What size service entrance conductors are required for 250 A continuous three phase load if the terminals are at ambient temperature of 70 C?

Question 5: Under which of the following condition the on-site generator is not considered as separately derived system?

Question 6: When the circuits are protected by a over current device rating of 1000 A, what size bonding jumper is required for each metal raceway?

Question 7: When five conductors each with an ampacity of 25 A bundled through NM cable, what is the adjusted ampacity of each cable.

Question 8: A 40 KVA , 480 V three phase transformer has a primary over current protection device is rated at 75 A. What is the size of primary conductor that can be used?

Question 9: How many number of 500 kcmil THWN conductors that can be installed in a 4 in. * 4 in. wireway?

Question 10: What size service entrance conductors are required for 250 A continuous three phase load if the terminals are at ambient temperature of 70 C?

Question 11: 125 volt, 15 and 20 ampere receptacles installed in a dwelling unit garage require:

Question 12: Underground raceways entering a building from an underground distribution system must be sealed with an approved compound to prevent:

Question 13: Under the 10-foot transformer secondary conductor rule, the secondary conductors must have an ampacity of not less than what fraction of the transformer secondary current rating?

Question 14: The grounded conductor of a grounded system must be routed to each service disconnecting means and:

Question 15: Where exposed, a grounding electrode conductor or its enclosure must be securely fastened to the surface on which it is carried, and must be protected if exposed to:

Question 16: Where a raceway is exposed to different temperatures on each end, such as passing from an air-conditioned space to the outdoors, it must be sealed to prevent the circulation of:

Question 17: Where conductors of different insulation temperature ratings are used in the same circuit, the allowable ampacity of the circuit must be based on:

Question 18: Conductors entering an outlet, device, or junction box must be protected from:

Question 19: Type MC cable must generally be supported and secured at intervals not exceeding:

Question 20: Per NEC Table 352.30, rigid PVC conduit of trade size 1 must be supported at intervals not exceeding:

Question 21: A solid-state (electronic) general-use switch used to control permanently connected loads must be marked to indicate:

Question 22: Receptacles installed in a new branch circuit must be of the:

Question 23: All luminaires installed under the NEC must be:

Question 24: A fixed storage-type water heater with a capacity of 450 liters (120 gallons) or less is considered, for branch-circuit sizing purposes, to be:

Question 25: Fixed outdoor electric de-icing and snow-melting equipment must be protected by:

Question 26: For a motor used in a torque application or with an adjustable-speed drive, conductor and overload sizing is generally based on:

Question 27: A single-phase, cord-and-plug-connected room air conditioner must be provided with a factory-installed leakage-current protection device as part of:

Question 28: A generator installed in a hazardous (classified) location must be:

Question 29: Overcurrent protection for a transformer is intended to open the circuit before the transformer temperature exceeds:

Question 30: A single motor-compressor has a rated-load current of 18 amperes. What is the minimum required branch-circuit conductor ampacity?

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