E2 Wiring Methods and Materials 2 — Questions and Answers
Question 1: What is the maximum number of 90-degree bends permitted in a single run of EMT between pull points?
- Two 90-degree bends
- Three 90-degree bends
- Four 90-degree bends (Correct answer)
- Five 90-degree bends
Correct answer: Four 90-degree bends
NEC 358.26 limits EMT to a maximum of four quarter bends (360 degrees total) between pull points.
Question 2: Which wiring method is specifically listed for use in concrete encasement?
- Electrical Metallic Tubing (EMT)
- Intermediate Metal Conduit (IMC)
- Rigid Metal Conduit (RMC) (Correct answer)
- Flexible Metal Conduit (FMC)
Correct answer: Rigid Metal Conduit (RMC)
RMC (Rigid Metal Conduit) is permitted for direct burial and encasement in concrete per NEC 344.10.
Question 3: Under NEC Article 330, Metal-Clad (MC) cable installed exposed in a commercial building must be supported at intervals not exceeding:
- 18 inches
- 3 feet
- 6 feet (Correct answer)
- 10 feet
Correct answer: 6 feet
NEC 330.30 requires MC cable to be secured and supported at intervals not exceeding 6 feet.
Question 4: When installing liquidtight flexible metal conduit (LFMC) in lengths exceeding 6 feet, the installer must:
- Use a separate equipment grounding conductor inside (Correct answer)
- Install expansion fittings every 6 feet
- Increase conduit trade size by one
- Replace with rigid conduit
Correct answer: Use a separate equipment grounding conductor inside
Per NEC 350.60, LFMC in lengths over 6 feet is not permitted to serve as the sole equipment grounding path — a separate EGC is required.
Question 5: What is the minimum cover requirement for RMC installed directly in a concrete slab on grade?
- 0 inches — no cover required (Correct answer)
- 1 inch
- 2 inches
- 3 inches
Correct answer: 0 inches — no cover required
NEC Table 300.5 requires no additional cover for RMC encased in concrete above grade.
Question 6: A commercial inspector finds Schedule 40 PVC conduit installed in a machinery area subject to physical damage. This installation is:
- Acceptable if conduit is painted
- Acceptable with warning labels
- A code violation — Schedule 80 or RMC required (Correct answer)
- Acceptable below 6 feet only
Correct answer: A code violation — Schedule 80 or RMC required
NEC 352.12(A) prohibits Schedule 40 PVC where subject to physical damage; Schedule 80 or a metal raceway must be used.
Question 7: The NEC requires that all conductors of the same circuit, including the EGC, must be contained within the same raceway primarily to:
- Simplify color coding
- Reduce voltage drop
- Prevent inductive heating of metallic raceways (Correct answer)
- Meet minimum fill requirements
Correct answer: Prevent inductive heating of metallic raceways
NEC 300.3(B) requires all circuit conductors to be in the same raceway to prevent inductive heating caused by unbalanced magnetic fields in metal enclosures.
E2 Wiring Methods and Materials 2
What is the maximum number of 90-degree bends permitted in a single run of EMT between pull points?