CEA Wiring Methods and Materials 5 — Questions and Answers
Question 1: Surface metal raceways installed in dry locations are required to be listed and may NOT be used in which location?
- Unfinished basements
- Hoistways (Correct answer)
- Office buildings
- Finished walls of dwellings
Correct answer: Hoistways
NEC 386.12 prohibits surface metal raceways in hoistways and locations subject to severe physical damage, among other restricted areas.
Question 2: When conductors are installed in parallel, each set of parallel conductors must:
- Be of the same length and same material only
- Use the same conduit system
- Be the same length, same conductor material, same AWG, and same type of insulation (Correct answer)
- Have the same overcurrent device
Correct answer: Be the same length, same conductor material, same AWG, and same type of insulation
NEC 310.10(H) requires parallel conductors to be the same length, material, circular mil area, insulation type, and termination method to ensure equal current sharing.
Question 3: Conduit fill for three or more conductors in a conduit is limited to what percentage of the conduit's interior cross-sectional area?
- 25%
- 31%
- 40% (Correct answer)
- 53%
Correct answer: 40%
NEC Chapter 9 Table 1 limits conduit fill to 40% for three or more conductors, balancing wire-pulling ease and heat dissipation.
Question 4: What wiring method uses a factory assembly of one or more insulated conductors under an overall nonmetallic sheath, approved for direct burial?
- Type NM-B
- Type UF (Correct answer)
- Type SE
- Type AC
Correct answer: Type UF
Type UF (Underground Feeder) cable is specifically listed for direct burial and wet locations, unlike NM-B which is for dry indoor use only.
Question 5: A grounding conductor is required in flexible metal conduit (FMC) when the FMC exceeds what length?
- 3 feet
- 4 feet
- 6 feet (Correct answer)
- 8 feet
Correct answer: 6 feet
NEC 348.60 permits FMC to serve as an equipment grounding conductor only when 6 feet or less in length and meeting other conditions; beyond 6 feet a separate EGC is required.
Question 6: When installing cable trays in an industrial establishment, which cable type is NOT listed for use in cable tray systems?
- Type TC (tray cable)
- Type MC cable
- Type NM-B cable (Correct answer)
- Type XHHW conductors
Correct answer: Type NM-B cable
Type NM-B (nonmetallic sheathed cable) is not listed for use in cable trays; NEC 392.10 specifies which cables and conductors are approved for tray installations.
Question 7: A reducer bushing used when reducing conduit size at a pull box must be approved and installed so that conductors are protected from:
- Voltage drop across the fitting
- Abrasion at the conduit opening (Correct answer)
- Overheating at the junction point
- Magnetic induction from ferrous metal
Correct answer: Abrasion at the conduit opening
NEC 300.16 requires fittings at conduit openings to protect conductors from abrasion caused by the sharp edges of conduit ends.
CEA Wiring Methods and Materials 5
Surface metal raceways installed in dry locations are required to be listed and may NOT be used in which location?