Licensed Electrical Contractor Services, Feeders, and Branch Circuits 3 — Questions and Answers
Question 1: What is the minimum burial depth for a service lateral installed in rigid metal conduit (RMC) under a residential driveway?
- 6 inches
- 12 inches (Correct answer)
- 18 inches
- 24 inches
Correct answer: 12 inches
NEC Table 300.5 requires RMC installed under a residential driveway to be buried a minimum of 12 inches.
Question 2: When calculating feeder loads for a commercial occupancy with 30 or more receptacles, NEC 220.44 allows a demand factor for receptacles above 10 kVA of:
- 50% (Correct answer)
- 60%
- 75%
- 90%
Correct answer: 50%
NEC 220.44 allows a 50% demand factor on receptacle loads exceeding 10 kVA in non-dwelling occupancies.
Question 3: Service-entrance cable (Type SE) used as interior wiring must comply with the requirements of:
- Article 230 only
- Article 338 and applicable wiring method articles (Correct answer)
- Article 310 only
- Article 250
Correct answer: Article 338 and applicable wiring method articles
NEC 338.10(B) states that SE cable used as interior wiring must comply with Article 338 and the applicable portions of Article 334.
Question 4: Per NEC 230.54, service-entrance conductors in a raceway must be protected from water entering the raceway at the service head by:
- A weatherhead pointed upward
- Conductors formed in a drip loop (Correct answer)
- Sealing fittings
- A watertight junction box
Correct answer: Conductors formed in a drip loop
NEC 230.54(F) requires conductors to be arranged in a drip loop to prevent water from entering the raceway.
Question 5: The minimum size copper grounded conductor for a 400-ampere service with 500 kcmil copper ungrounded conductors is:
- 2 AWG
- 1/0 AWG (Correct answer)
- 3/0 AWG
- 250 kcmil
Correct answer: 1/0 AWG
Per NEC Table 250.102(C)(1), 500 kcmil ungrounded conductors require a minimum 1/0 AWG copper grounded (neutral) conductor.
Question 6: Which of the following is NOT a permitted wiring method for a branch circuit supplying a swimming pool pump motor?
- Rigid PVC conduit
- Liquidtight flexible nonmetallic conduit
- Type NM cable (Correct answer)
- Rigid metal conduit
Correct answer: Type NM cable
NEC 680.21(A)(1) prohibits Type NM cable for circuits supplying swimming pool pump motors.
Question 7: A branch circuit rated at 15 amperes is supplying only lighting. The maximum load permitted on this circuit is:
- 1,440 watts (Correct answer)
- 1,500 watts
- 1,725 watts
- 1,800 watts
Correct answer: 1,440 watts
At 120V × 15A × 80% = 1,440 watts, as continuous lighting loads must not exceed 80% of circuit rating.
Licensed Electrical Contractor Services, Feeders, and Branch Circuits 3
What is the minimum burial depth for a service lateral installed in rigid metal conduit (RMC) under a residential driveway?