CEA Wiring Methods and Materials 4 — Questions and Answers
Question 1: When conductors of different systems share the same raceway, they must all be insulated for the:
- Lowest voltage present
- Average voltage of all systems
- Highest voltage present (Correct answer)
- Voltage of the largest conductor
Correct answer: Highest voltage present
NEC 300.3(C)(1) requires all conductors sharing a raceway to be insulated for the highest voltage present in that raceway.
Question 2: What is the color code for the high-leg (wild leg) conductor in a 4-wire, 3-phase delta system?
- White
- Orange (Correct answer)
- Red
- Blue
Correct answer: Orange
NEC 230.56 and 408.3(F) require the high-leg conductor in a 3-phase delta system to be identified with orange color.
Question 3: Electrical metallic tubing (EMT) is NOT permitted to be used in which condition?
- Exposed runs in dry commercial locations
- Concealed runs in concrete
- Subject to severe physical damage (Correct answer)
- Fished in walls of existing buildings
Correct answer: Subject to severe physical damage
NEC 358.12 prohibits EMT where it will be subject to severe physical damage due to its thin-wall construction.
Question 4: Type MC cable used for wiring in an accessible ceiling plenum space used for environmental air must be which type?
- Any listed MC cable
- MC cable with a PVC outer jacket only
- MC cable listed for use in cable trays
- MC cable with a smooth or corrugated aluminum sheath or listed plenum cable (Correct answer)
Correct answer: MC cable with a smooth or corrugated aluminum sheath or listed plenum cable
NEC 330.10(A)(11) and 300.22 require cables in air-handling plenums to be plenum-rated or have a metallic sheath that limits flame and smoke spread.
Question 5: A 2-inch rigid metal conduit (RMC) must have a support within what distance of each box, cabinet, or conduit fitting?
- 1 foot
- 2 feet
- 3 feet (Correct answer)
- 5 feet
Correct answer: 3 feet
NEC 344.30(B)(1) requires RMC to be supported within 3 feet of each outlet box, junction box, device box, cabinet, conduit body, or other conduit termination.
Question 6: Which statement about aluminum conductors smaller than No. 8 AWG is correct under the NEC?
- They are permitted for all general wiring
- They are not permitted for branch circuit wiring (Correct answer)
- They may be used only in conduit
- They require special copper-clad fittings
Correct answer: They are not permitted for branch circuit wiring
NEC 310.106(B) prohibits solid aluminum conductors smaller than No. 8 AWG for branch circuit wiring due to connection failure risks.
Question 7: When pulling wire through conduit, the maximum pulling tension for copper conductors is based on a stress of:
- 0.008 lb/circular mil (Correct answer)
- 0.008 lb/AWG number
- 0.008 psi per foot of conduit
- 0.008 amps per circular mil
Correct answer: 0.008 lb/circular mil
Industry practice limits conductor pulling tension to 0.008 lb per circular mil of cross-sectional area to avoid stretching or damaging copper conductors.
CEA Wiring Methods and Materials 4
When conductors of different systems share the same raceway, they must all be insulated for the: