Journeyman Electrician Exam (NEC)Equipment and DevicesEasy
A newly installed 20-ampere branch circuit for general-purpose receptacles in a dwelling unit must be protected by an overcurrent device. What is the maximum standard ampere rating for the overcurrent device permitted for this circuit?
- A15 amperes
- B30 amperes
- C25 amperes
- D20 amperes
Show answer & explanationAnswer & explanation
Correct answer: D. 20 amperes
NEC 240.4(D) specifies that overcurrent devices for circuits supplying receptacles rated 20 amperes or less, and that are not motor circuits, shall not exceed the ampere rating of the circuit conductors. For a 20-ampere circuit, the maximum standard overcurrent protection is 20 amperes.
Why the other options are wrong
- A. 15 amperes is for 15-ampere circuits, not 20-ampere circuits.
- B. 30 amperes is typically used for specific appliance or dedicated circuits, not general-purpose 20-ampere receptacle circuits.
- C. 25 amperes is not a standard overcurrent device rating for general-purpose dwelling unit receptacle circuits.
Branch Circuit Overcurrent Protection
The protective device (e.g., circuit breaker) that limits the current flowing through a branch circuit to prevent damage to conductors and equipment.
- Rating must not exceed conductor ampacity, with some exceptions.
- Protects against overloads and short circuits.
- Standard ratings are specified in NEC 240.6(A).
Memory trick: Circuit's shield must match its strength.