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NEC CODE NEC 2020

Wiring Methods (NEC 300) — NEC 2020 Edition

Free NEC 2020 practice test on general wiring methods. Covers conductors grouped together, raceway fill rules, direct burial depths, physical protection from nails and screws, and electrical continuity. 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 Wiring Methods (NEC 300) — 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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Wiring Methods (NEC 300) — NEC 2020 Edition — Question List

Question 1: Which conductors of a circuit must be installed in the same raceway, cable, trench or cord?

All of them, including the grounded conductor and EGCs
Only conductors larger than 1/0 AWG
Only the grounded and ungrounded conductors
Only the ungrounded conductors

NEC Reference: NEC 300.3(B)

Question 2: Why must all conductors of an AC circuit be grouped together in the same metal raceway?

To make pulling easier
To reduce conduit fill
To lower the voltage rating needed
To minimize induction heating of the raceway

NEC Reference: NEC 300.20(A)

Question 3: Under what condition can conductors from different circuits share the same raceway?

Insulation rating is not less than the max circuit voltage
Insulation rating is less than the max circuit voltage
The circuits share the exact same voltage
The circuits share the exact same insulation rating

NEC Reference: NEC 300.3(C)(1)

Question 4: What is the minimum cover depth generally required for a direct-buried rigid nonmetallic (PVC) conduit?

18 inch
6 inch
12 inch
24 inch

NEC Reference: NEC Table 300.5

Question 5: Direct-buried conductors and cables emerging from grade must be protected up to what height above finished grade?

18 in.
10 ft
8 ft
6 ft

NEC Reference: NEC 300.5(D)(1)

Question 6: Which type of buried conductors, when 18 inches or more below grade, generally need a warning ribbon placed in the trench above them?

Service conductors
Branch circuit conductors
Feeder circuit conductors
None require a ribbon

NEC Reference: NEC 300.5(D)(3)

Question 7: When may a raceway be used as the means of support for other raceways or cables?

When the raceway or support means is identified for that purpose
Never, under any condition
Always, if the raceway is metal
Whenever the other cables are low voltage

NEC Reference: NEC 300.11(C)

Question 8: What does 300.10 require of metal raceways, cable armor and other metal enclosures for conductors?

They must have a separate wire EGC in every case
They must be insulated from each other at every box
They must be metallically joined into a continuous electrical conductor
They need bonding only at the service

NEC Reference: NEC 300.10

Question 9: A raceway passes from a heated room into a walk-in freezer. What does 300.7(A) require?

Use only nonmetallic raceway
Seal the raceway to prevent warm air from circulating to the cold section
Increase the conductor size one step
Install an expansion joint at the wall

NEC Reference: NEC 300.7(A)

Question 10: Where cables or raceways run parallel to framing members, the nearest outside surface must generally be at least how far from the nearest edge, unless protected by a steel plate?

1 inch
1 1/4 inches
1 1/2 inches
2 inches

NEC Reference: NEC 300.4(D)

Question 11: A cable is run through a bored hole in a wood framing member. Per NEC 300.4(A)(1), the hole must generally be located at least how far from the nearest edge, or protected by a steel plate?

1 1/4 inches
1/2 inch
2 1/2 inches
3 inches

NEC Reference: NEC 300.4(A)(1)

Question 12: Direct-buried service conductors, not encased in concrete and not under a building, generally require what minimum burial depth per NEC Table 300.5, absent any special exceptions?

24 inches
6 inches
12 inches
36 inches

NEC Reference: NEC Table 300.5

Question 13: A raceway passes through a fire-rated wall. What does 300.21 require at the penetration?

Leave a clearance gap around the raceway
Wrap the raceway with insulation tape
Nothing, if the raceway is metal
Firestop it with an approved method that keeps the fire rating

NEC Reference: NEC 300.21

Question 14: May a properly installed rigid metal conduit system serve as the equipment grounding conductor?

Only for circuits over 100 A
Yes, it is listed as an EGC type in 250.118
Only if it is under 6 ft long
No, a wire EGC is always required

NEC Reference: NEC 250.118

Question 15: Where multiple systems of different voltages are installed in a building, what must be done to help identify the different systems' conductors?

Identify each system distinctly, such as by color
Nothing -- mixing is fine with no marking
Use the same color for everything
Remove all labels

NEC Reference: NEC 210.5(C)

Question 16: Are wiring methods generally permitted to be installed inside ducts used to transport dust, loose stock, or flammable vapors?

No, this is generally prohibited
Yes, always permitted freely
Only for PVC wiring
Only in residential buildings

NEC Reference: NEC 300.22(A)

Question 17: Between which points must metal raceways be mechanically continuous?

Between cabinets, boxes, fittings and other enclosures or outlets
Only at the service
Only every 10 ft
Only underground

NEC Reference: NEC 300.12

Question 18: How must raceways, cable assemblies, boxes and fittings be installed?

Supported only by the conductors inside them
Supported by ceiling grid wires used for the ceiling
Securely fastened in place
Laid loose above the ceiling

NEC Reference: NEC 300.11(A)

Question 19: Which wiring may be installed in an elevator hoistway?

Only wiring used directly in connection with the elevator
Any building branch circuit
Only fire alarm wiring
Any feeder passing through the building

NEC Reference: NEC 620.37(A)

Question 20: NM cable passes through a factory- or field-punched hole in a metal stud. What protection is required?

A wrap of electrical tape
A steel plate on both sides
A listed bushing or grommet covering all metal edges
Nothing, if the hole is deburred

NEC Reference: NEC 300.4(B)(1)

Question 21: Why must conductors in vertical raceways be supported at the intervals of Table 300.19(A)?

To reduce induction heating
To keep their weight from damaging insulation and terminations
To allow fewer pull boxes
To improve voltage drop

NEC Reference: NEC 300.19(A)

Question 22: Conductor splices and taps must generally be made where?

Within an accessible box or approved enclosure
Buried directly in the wall with no box
Inside a wall cavity with no access
Anywhere, with no restriction

NEC Reference: NEC 300.15

Question 23: A raceway is installed in a wet location above grade. How is the interior of the raceway treated?

As a hazardous location
As a damp location
As a dry location
As a wet location

NEC Reference: NEC 300.9

Question 24: For 3 or more conductors in a raceway, what is the maximum fill percentage generally permitted, per NEC Chapter 9, Table 1?

NEC Reference: NEC Chapter 9, Table 1

Question 25: A long run of PVC conduit needs an expansion fitting when the expected length change from temperature is more than what?

1/4 inch
2 inches
6 inches
1 foot

NEC Reference: NEC 352.44

Question 26: A cable is laid in a notch cut in a wood stud. What protection is required?

A steel plate at least 1/16 in. thick covering the notch
Nothing, if the notch is 1 in. deep
A plastic nail plate of any thickness
Insulating tape over the cable

NEC Reference: NEC 300.4(A)(2)

Question 27: Exposed NM cable is subject to physical damage. How must it be protected?

No protection is needed indoors
With a layer of insulating tape
With a fire-retardant coating
In RMC, IMC, EMT, Schedule 80 PVC, RTRC-XW or other approved means

NEC Reference: NEC 334.15(B)

Question 28: Raceways entering a building from an underground distribution system must generally be sealed to prevent what?

Moisture or gases entering the building
Nothing -- sealing is unnecessary
Only insects
Only sunlight

NEC Reference: NEC 300.5(G)

Question 29: Insulated conductors must be suitable for which conditions of the installation?

Only the voltage
Only the color code
The voltage, temperature and location (dry, damp, wet, sunlight, corrosive)
Only the conductor material

NEC Reference: NEC 310.10

Question 30: Who has the responsibility to approve equipment and materials, and to grant special permission, under the NEC?

The electrical contractor
The authority having jurisdiction (AHJ)
The building owner
The equipment manufacturer

NEC Reference: NEC 90.4

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.

Wiring Methods (NEC 300) — NEC 2020 Edition

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Wiring Methods (NEC 300) — NEC 2020 Edition — Question List

Question 1: Which conductors of a circuit must be installed in the same raceway, cable, trench or cord?

Question 2: Why must all conductors of an AC circuit be grouped together in the same metal raceway?

Question 3: Under what condition can conductors from different circuits share the same raceway?

Question 4: What is the minimum cover depth generally required for a direct-buried rigid nonmetallic (PVC) conduit?

Question 5: Direct-buried conductors and cables emerging from grade must be protected up to what height above finished grade?

Question 6: Which type of buried conductors, when 18 inches or more below grade, generally need a warning ribbon placed in the trench above them?

Question 7: When may a raceway be used as the means of support for other raceways or cables?

Question 8: What does 300.10 require of metal raceways, cable armor and other metal enclosures for conductors?

Question 9: A raceway passes from a heated room into a walk-in freezer. What does 300.7(A) require?

Question 10: Where cables or raceways run parallel to framing members, the nearest outside surface must generally be at least how far from the nearest edge, unless protected by a steel plate?

Question 11: A cable is run through a bored hole in a wood framing member. Per NEC 300.4(A)(1), the hole must generally be located at least how far from the nearest edge, or protected by a steel plate?

Question 12: Direct-buried service conductors, not encased in concrete and not under a building, generally require what minimum burial depth per NEC Table 300.5, absent any special exceptions?

Question 13: A raceway passes through a fire-rated wall. What does 300.21 require at the penetration?

Question 14: May a properly installed rigid metal conduit system serve as the equipment grounding conductor?

Question 15: Where multiple systems of different voltages are installed in a building, what must be done to help identify the different systems' conductors?

Question 16: Are wiring methods generally permitted to be installed inside ducts used to transport dust, loose stock, or flammable vapors?

Question 17: Between which points must metal raceways be mechanically continuous?

Question 18: How must raceways, cable assemblies, boxes and fittings be installed?

Question 19: Which wiring may be installed in an elevator hoistway?

Question 20: NM cable passes through a factory- or field-punched hole in a metal stud. What protection is required?

Question 21: Why must conductors in vertical raceways be supported at the intervals of Table 300.19(A)?

Question 22: Conductor splices and taps must generally be made where?

Question 23: A raceway is installed in a wet location above grade. How is the interior of the raceway treated?

Question 24: For 3 or more conductors in a raceway, what is the maximum fill percentage generally permitted, per NEC Chapter 9, Table 1?

Question 25: A long run of PVC conduit needs an expansion fitting when the expected length change from temperature is more than what?

Question 26: A cable is laid in a notch cut in a wood stud. What protection is required?

Question 27: Exposed NM cable is subject to physical damage. How must it be protected?

Question 28: Raceways entering a building from an underground distribution system must generally be sealed to prevent what?

Question 29: Insulated conductors must be suitable for which conditions of the installation?

Question 30: Who has the responsibility to approve equipment and materials, and to grant special permission, under the NEC?

Key NEC References for This Test

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