NEC Branch Circuit Requirements 2 — Questions and Answers
Question 1: What is the maximum overcurrent protection allowed on a 14 AWG copper branch circuit conductor?
- 15 amperes (Correct answer)
- 20 amperes
- 25 amperes
- 30 amperes
Correct answer: 15 amperes
Per NEC 240.4(D), 14 AWG copper is limited to 15-ampere overcurrent protection.
Question 2: A 20-ampere branch circuit supplying receptacles requires conductors of at least which size copper?
- 14 AWG
- 12 AWG (Correct answer)
- 10 AWG
- 8 AWG
Correct answer: 12 AWG
A 20-amp circuit requires 12 AWG copper conductors per NEC 240.4(D).
Question 3: On a multi-outlet branch circuit, the rating of any single cord-and-plug-connected utilization equipment must not exceed what percentage of the branch-circuit rating?
- 50%
- 70%
- 80% (Correct answer)
- 100%
Correct answer: 80%
NEC 210.23(A)(1) limits a single plug-connected load to 80% of the branch-circuit rating.
Question 4: What is the maximum rating of a branch circuit permitted to supply standard 15-ampere receptacles when more than one receptacle is on the circuit?
- 15 amperes
- 20 amperes (Correct answer)
- 30 amperes
- 40 amperes
Correct answer: 20 amperes
Per NEC Table 210.21(B)(3), 15-amp receptacles may be used on a 20-amp circuit with multiple outlets.
Question 5: Branch circuits rated 30 amperes are permitted to supply which type of load in a dwelling unit?
- General-use receptacles
- Fixed appliances and equipment only (Correct answer)
- Lighting outlets only
- Any 15-amp receptacle
Correct answer: Fixed appliances and equipment only
NEC 210.23(B) limits 30-amp circuits to fixed equipment, not general-use receptacles in dwellings.
Question 6: Conductors of a branch circuit must have an ampacity not less than the maximum load to be served and not less than what for continuous loads?
- 100% of the continuous load
- 115% of the continuous load
- 125% of the continuous load (Correct answer)
- 150% of the continuous load
Correct answer: 125% of the continuous load
NEC 210.19(A) requires branch-circuit conductors to be sized at 125% of continuous load.
Question 7: What is the minimum branch-circuit conductor size permitted for a 40-ampere branch circuit using copper?
- 10 AWG
- 8 AWG (Correct answer)
- 6 AWG
- 4 AWG
Correct answer: 8 AWG
A 40-amp branch circuit requires 8 AWG copper conductors per the ampacity tables.
NEC Branch Circuit Requirements 2
What is the maximum overcurrent protection allowed on a 14 AWG copper branch circuit conductor?