TN LLE Wiring Methods and Installation — Questions and Answers
Question 1: According to NEC Table 300.5, what is the minimum burial depth for Type UF cable used for a 120/240V residential branch circuit?
- 6 inches
- 12 inches (Correct answer)
- 18 inches
- 24 inches
Correct answer: 12 inches
NEC Table 300.5 requires Type UF cable to be buried a minimum of 12 inches deep for residential branch circuits.
Question 2: Under NEC 300.4(A)(1), where cables pass through bored holes in wood framing, the edge of the hole must be at least how far from the nearest edge of the wood member (or a steel protective plate must be installed)?
- 1 inch
- 1-1/4 inches (Correct answer)
- 1-1/2 inches
- 2 inches
Correct answer: 1-1/4 inches
NEC 300.4(A)(1) requires the edge of bored holes to be at least 1-1/4 inches from the nearest edge of the wood member to protect cables from nails and screws.
Question 3: According to NEC 334.30, Type NM cable must be secured within how many inches of every cabinet, box, or fitting it enters?
- 6 inches
- 8 inches
- 12 inches (Correct answer)
- 18 inches
Correct answer: 12 inches
NEC 334.30 requires NM cable to be secured within 12 inches of every cabinet, box, or fitting.
Question 4: According to NEC 334.30, what is the maximum interval for securing and supporting Type NM cable in exposed locations?
- 2.5 feet
- 3 feet
- 4.5 feet (Correct answer)
- 6 feet
Correct answer: 4.5 feet
NEC 334.30 requires NM cable to be secured and supported at intervals not exceeding 4.5 feet in exposed locations.
Question 5: Which of the following wiring methods is NOT permitted in wet locations?
- Rigid Metal Conduit (RMC)
- Intermediate Metal Conduit (IMC)
- Type NM cable (Correct answer)
- Liquidtight Flexible Metal Conduit (LFMC)
Correct answer: Type NM cable
Type NM cable is prohibited in wet or damp locations per NEC 334.12; RMC, IMC, and LFMC are all listed for use in wet locations.
Question 6: Under NEC 300.22(C), wiring installed in a plenum ceiling space used for air handling must:
- Use only plenum-rated cables or wiring enclosed in metal conduit (Correct answer)
- Use any cable type since it is above the ceiling tile
- Be installed only in armored cable (AC)
- Be installed in rigid nonmetallic conduit
Correct answer: Use only plenum-rated cables or wiring enclosed in metal conduit
NEC 300.22(C) requires that wiring in air-handling plenums use listed plenum-rated cables or be installed in metal conduit to limit smoke spread.
Question 7: What does NEC 300.15 require at each point where conductors are spliced or terminated?
- Conductors must be soldered at all splice points
- A box, conduit body, or fitting must be installed at each splice or termination point (Correct answer)
- Splices must only be made at the panelboard
- Wire nuts are not permitted for permanent splices
Correct answer: A box, conduit body, or fitting must be installed at each splice or termination point
NEC 300.15 requires a box, conduit body, or fitting to be installed at each point where conductors are spliced or terminated.
Question 8: Type SE (Service Entrance) cable used for branch circuit or feeder wiring inside a building is governed by which NEC article?
- NEC Article 330
- NEC Article 334
- NEC Article 338 (Correct answer)
- NEC Article 340
Correct answer: NEC Article 338
Type SE cable — including its use for interior branch circuit and feeder wiring — is covered under NEC Article 338, Service Entrance Cable.
Question 9: According to NEC Table 300.5, what is the minimum direct burial depth for Rigid Metal Conduit (RMC) installed underground (not encased in concrete)?
- 0 inches
- 6 inches (Correct answer)
- 12 inches
- 24 inches
Correct answer: 6 inches
NEC Table 300.5 requires RMC installed as direct burial to have a minimum cover of 6 inches.
Question 10: Per NEC 300.5(G), conduits or raceways that enter a building from underground must:
- Be sealed or plugged to prevent moisture or gases from entering the structure (Correct answer)
- Terminate in a NEMA 4 enclosure at the point of entry
- Use only RMC for the final 5 feet before building entry
- Be equipped with a drain fitting at the lowest point of the conduit run
Correct answer: Be sealed or plugged to prevent moisture or gases from entering the structure
NEC 300.5(G) requires underground conduits entering a building to be sealed or plugged to prevent moisture or gases from traveling through the conduit into the building.
Question 11: According to NEC 314.28(A)(1), the minimum dimension of a pull box used for straight pulls must be at least:
- 4 times the trade diameter of the largest conduit entering the box
- 6 times the trade diameter of the largest conduit entering the box
- 8 times the trade diameter of the largest conduit entering the box (Correct answer)
- 10 times the trade diameter of the largest conduit entering the box
Correct answer: 8 times the trade diameter of the largest conduit entering the box
NEC 314.28(A)(1) requires that for straight pulls the minimum box dimension must be at least 8 times the trade size of the largest raceway entering the box.
Question 12: Per NEC 358.26, what is the maximum total degrees of bends permitted in a single run of EMT between pull points?
- 180 degrees
- 270 degrees
- 360 degrees (Correct answer)
- 450 degrees
Correct answer: 360 degrees
NEC 358.26 limits bends in any EMT run between pull points to not more than 360 degrees total, equivalent to four 90-degree bends.
Question 13: According to NEC 334.12, Type NM cable is prohibited from being installed in which of the following locations?
- Interior walls of single-family dwellings
- Attic spaces above insulation
- Embedded in poured concrete or masonry (Correct answer)
- Accessible crawl spaces of one-family homes
Correct answer: Embedded in poured concrete or masonry
NEC 334.12(1) prohibits Type NM cable from being embedded in poured concrete, aggregate, or masonry because the jacket is not rated for such conditions.
Question 14: NEC 300.3(B) requires that all conductors of the same circuit — including the grounded conductor and equipment grounding conductor — must be:
- Installed in separate raceways to minimize heat buildup
- The same AWG size throughout the entire circuit
- Contained within the same raceway, cable, or run together as a group (Correct answer)
- Color-coded using only black, white, and green throughout
Correct answer: Contained within the same raceway, cable, or run together as a group
NEC 300.3(B) requires all conductors of the same circuit to be contained within the same cable or raceway to prevent inductive heating in metal enclosures.
