IEC Wiring Methods and Materials 3 — Questions and Answers
Question 1: Which of the following wiring methods is permitted for use in wet locations as a standalone installation (without additional enclosure)?
- Type NM cable
- Liquidtight flexible metal conduit (LFMC) (Correct answer)
- Type AC cable
- Type SE cable
Correct answer: Liquidtight flexible metal conduit (LFMC)
Liquidtight flexible metal conduit (LFMC) is listed for use in wet locations per NEC 350.10.
Question 2: How many 90-degree bends are permitted between pull points in a conduit run?
- Two 90-degree bends (180 degrees total)
- Three 90-degree bends (270 degrees total)
- Four 90-degree bends (360 degrees total) (Correct answer)
- There is no limit
Correct answer: Four 90-degree bends (360 degrees total)
NEC 358.26, 344.26, and related articles limit total bends between pull points to 360 degrees (four 90-degree bends).
Question 3: Type TC (Tray Cable) is most commonly installed in which environment?
- Concealed in walls of residential buildings
- Open cable tray systems in industrial facilities (Correct answer)
- Underground direct burial
- Inside metallic conduit only
Correct answer: Open cable tray systems in industrial facilities
Type TC cable is specifically designed and listed for use in cable tray systems, per NEC Article 336.
Question 4: When installing EMT in a corrosive environment, which protection method is required?
- No additional protection is needed; EMT is inherently corrosion-resistant
- The EMT must be painted with an approved corrosion-resistant coating
- A different wiring method suitable for corrosive conditions must be used or the EMT must be listed for the environment (Correct answer)
- The EMT must be wrapped in PVC tape
Correct answer: A different wiring method suitable for corrosive conditions must be used or the EMT must be listed for the environment
NEC 358.10(B) states that EMT shall not be used where subject to severe corrosive influences unless protected by a corrosion-resistant material or a different method is used.
Question 5: What is the minimum size trade-size conduit permitted to contain conductors used in wiring methods requiring conduit?
- 1/2 inch (Correct answer)
- 3/4 inch
- 1/4 inch
- 3/8 inch
Correct answer: 1/2 inch
The minimum permitted trade size for conduit is 1/2 inch per NEC 358.20, 344.20, and similar articles for most conduit types.
Question 6: When NM cable passes through a floor, what protection is required?
- No protection is needed if the cable is secured
- The cable must be enclosed in rigid metal conduit for the entire floor thickness
- The cable must be protected by a minimum 6-inch guard from the floor and a bushing at the top (Correct answer)
- The cable must be placed inside PVC conduit for at least 12 inches above the floor
Correct answer: The cable must be protected by a minimum 6-inch guard from the floor and a bushing at the top
NEC 334.15(C) requires NM cable passing through a floor to be enclosed in rigid metal conduit, IMC, Schedule 80 PVC, or equivalent protection for at least 6 inches above the floor, with a bushing at the top.
Question 7: Which statement is correct regarding the use of flexible metal conduit (FMC) as an equipment grounding conductor?
- FMC always serves as an adequate equipment grounding conductor regardless of size or length
- FMC listed at 3/8-inch trade size and not exceeding 6 feet may serve as the EGC under certain conditions (Correct answer)
- FMC is never permitted to serve as an EGC; a separate green wire is always required
- FMC may serve as the EGC only if it is 1-inch trade size or larger
Correct answer: FMC listed at 3/8-inch trade size and not exceeding 6 feet may serve as the EGC under certain conditions
NEC 250.118(5) permits FMC to serve as an EGC when the trade size is 3/8 to 1-1/4 inches and the length does not exceed 6 feet, among other conditions.
IEC Wiring Methods and Materials 3
Which of the following wiring methods is permitted for use in wet locations as a standalone installation (without additional enclosure)?