CEA Wiring Methods and Materials 3 — Questions and Answers
Question 1: Intermediate metal conduit (IMC) has walls that are thinner than rigid metal conduit (RMC). Which statement about IMC is correct?
- IMC cannot be threaded
- IMC uses the same fittings as RMC
- IMC is approved for all the same applications as RMC (Correct answer)
- IMC requires special couplings not interchangeable with RMC
Correct answer: IMC is approved for all the same applications as RMC
NEC 342 lists IMC as suitable for all environments where RMC is permitted, including concrete encasement and direct burial.
Question 2: What is the required minimum burial depth for rigid metal conduit (RMC) installed under a residential driveway?
- 6 inches
- 12 inches (Correct answer)
- 18 inches
- 24 inches
Correct answer: 12 inches
NEC Table 300.5 requires RMC and IMC to be buried at least 6 inches under residential driveways.
Question 3: Type UF cable installed as a direct-buried feeder to an outbuilding must be buried at least how deep under a one-family dwelling's yard?
- 6 inches
- 12 inches
- 18 inches (Correct answer)
- 24 inches
Correct answer: 18 inches
NEC Table 300.5 requires direct-buried Type UF cable to be at least 24 inches deep, reduced to 18 inches under a dwelling's yard in some applications; the standard general requirement is 24 inches.
Question 4: Which fitting must be used where electrical metallic tubing (EMT) enters a box to protect conductors from the sharp edge of the tubing?
- Locknut
- Bushing
- Connector with insulating throat or separate bushing (Correct answer)
- Set-screw coupling
Correct answer: Connector with insulating throat or separate bushing
NEC 358.46 requires fittings that protect conductors at EMT terminations, typically connectors with an insulating throat.
Question 5: Non-metallic sheathed cable (NM-B) is permitted to be installed in which of the following locations?
- Wet or damp locations
- Embedded in masonry
- Dry locations in wood-frame residential structures (Correct answer)
- Commercial kitchens
Correct answer: Dry locations in wood-frame residential structures
NM-B cable is restricted to dry locations and is most commonly used in wood-frame, one- and two-family dwellings per NEC 334.10.
Question 6: When installing service-entrance (SE) cable above a roof with a slope of less than 4 inches in 12 inches, the cable must maintain at least how much clearance above the roof?
- 6 inches
- 8 inches
- 18 inches (Correct answer)
- 36 inches
Correct answer: 18 inches
NEC 230.24(A) requires SE conductors to maintain 18 inches clearance over flat or low-slope roofs, with exceptions for steep-slope roofs.
Question 7: Liquidtight flexible metal conduit (LFMC) is required when used in outdoor wet locations primarily because it:
- Provides a higher ampacity than LFNC
- Has a PVC jacket that prevents moisture ingress (Correct answer)
- Is rated for higher voltage than standard FMC
- Can be buried without further protection
Correct answer: Has a PVC jacket that prevents moisture ingress
LFMC's outer PVC jacket seals out moisture and liquids, making it suitable for wet and outdoor locations unlike plain FMC.
CEA Wiring Methods and Materials 3
Intermediate metal conduit (IMC) has walls that are thinner than rigid metal conduit (RMC).
Which statement about IMC is correct?