NEC Wiring Methods & Materials 2 — Questions and Answers
Question 1: What is the minimum burial depth for Type UF cable supplying a 120V outdoor receptacle not exceeding 20A?
- 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 at least 12 inches deep for 120V circuits rated 20A or less.
Question 2: Which wiring method is permitted in a Class I, Division 1 hazardous location?
- Type NM cable
- Threaded rigid metal conduit (RMC) (Correct answer)
- Type MC cable without an interlocked armor
- Type AC cable
Correct answer: Threaded rigid metal conduit (RMC)
NEC 501.10(A) requires threaded rigid metal conduit (RMC) or threaded steel intermediate metal conduit (IMC) in Class I, Division 1 locations.
Question 3: When installing EMT, what is the maximum distance from a box or fitting that a support must be placed?
- 2 feet
- 3 feet (Correct answer)
- 5 feet
- 10 feet
Correct answer: 3 feet
NEC 358.30(A) requires EMT to be secured within 3 feet of every outlet box, junction box, cabinet, or fitting.
Question 4: What color is the equipment grounding conductor insulation typically required to be?
- White or gray
- Green or bare (Correct answer)
- Black
- Red
Correct answer: Green or bare
NEC 250.119 requires equipment grounding conductors to be identified by green insulation, green with one or more yellow stripes, or bare copper.
Question 5: What is the maximum number of quarter bends (360 degrees total) permitted in a single run of conduit between pull points?
- Two 90-degree bends
- Three 90-degree bends
- 360 degrees total (Correct answer)
- Four 90-degree bends
Correct answer: 360 degrees total
NEC 358.26 (for EMT) and similar sections for other conduit types limit bends to 360 degrees total between pull points.
Question 6: Which of the following is NOT an acceptable use of flexible metal conduit (FMC)?
- Connection to vibrating equipment
- In wet locations (Correct answer)
- Final connection to motors
- Where flexibility is required after installation
Correct answer: In wet locations
NEC 348.12(2) prohibits FMC in wet locations unless a corrosion-resistant FMC listed for the purpose is used.
Question 7: For conductors installed in conduit, what is the fill percentage limit when there are three or more conductors?
- 40%
- 53%
- 31% (Correct answer)
- 60%
Correct answer: 31%
NEC Chapter 9, Table 1 limits conduit fill to 40% for two conductors and 31% for three or more conductors.
NEC Wiring Methods & Materials 2
What is the minimum burial depth for Type UF cable supplying a 120V outdoor receptacle not exceeding 20A?