E2 Services, Feeders, Branch Circuits 2 — Questions and Answers
Question 1: What is the minimum ampacity required for a service entrance conductor supplying a single commercial occupancy with a calculated load of 175 amperes?
- 150 amperes
- 175 amperes (Correct answer)
- 200 amperes
- 225 amperes
Correct answer: 175 amperes
Service conductors must have an ampacity not less than the calculated load per NEC 230.42.
Question 2: Per NEC Article 230, how many sets of service entrance conductors are permitted to supply a single building from a single service drop?
- Only one set is always required
- Up to six sets under specific conditions (Correct answer)
- No more than two sets
- Unlimited sets with POCO approval
Correct answer: Up to six sets under specific conditions
NEC 230.40 permits up to six sets of service entrance conductors from a single service drop or lateral under defined conditions.
Question 3: A commercial feeder supplies a panelboard with a total computed load of 92 amperes. What is the minimum conductor ampacity allowed?
- 90 amperes
- 92 amperes (Correct answer)
- 100 amperes
- 110 amperes
Correct answer: 92 amperes
Feeder conductors must have an ampacity not less than the load they supply per NEC 215.2(A).
Question 4: What NEC section governs the minimum size of branch circuit conductors for general lighting loads?
- NEC 210.19 (Correct answer)
- NEC 215.2
- NEC 230.42
- NEC 310.15
Correct answer: NEC 210.19
NEC 210.19 specifies the minimum ampacity and size of branch circuit conductors.
Question 5: A 120/240V, single-phase service for a commercial building requires a grounded (neutral) conductor. Per NEC 230.42, the neutral must have an ampacity of at least:
- The full unbalanced load (Correct answer)
- Half the line conductor ampacity
- The same ampacity as the largest ungrounded conductor
- 70% of the phase conductor ampacity
Correct answer: The full unbalanced load
The grounded service conductor must be sized to carry the maximum unbalanced load per NEC 220.61.
Question 6: Which wiring method is NOT permitted for service entrance conductors installed inside a building?
- Rigid metal conduit (RMC)
- Open wiring on insulators through a dry area (Correct answer)
- Electrical metallic tubing (EMT)
- Type SE cable in a dry location
Correct answer: Open wiring on insulators through a dry area
Open wiring is not a recognized wiring method for service entrance conductors inside a building under NEC 230.43.
Question 7: For a 208Y/120V, 3-phase, 4-wire feeder with a computed load of 115 amperes per phase, what is the minimum ampacity for each ungrounded feeder conductor?
- 100 amperes
- 110 amperes
- 115 amperes (Correct answer)
- 125 amperes
Correct answer: 115 amperes
Feeder conductor ampacity must not be less than the computed load on each conductor per NEC 215.2.
E2 Services, Feeders, Branch Circuits 2
What is the minimum ampacity required for a service entrance conductor supplying a single commercial occupancy with a calculated load of 175 amperes?