Master Electrician Exam (NEC)Overcurrent ProtectionMedium
A commercial office space is being renovated, and new 120V, 20-ampere general-purpose receptacle branch circuits are being installed. The circuits will supply computer workstations and lighting. Which of the following conditions mandates the use of an Arc-Fault Circuit Interrupter (AFCI) for these circuits?
- AThe area is designated as an office space in a commercial occupancy.
- BThe circuits are supplied by a 480Y/277V panelboard.
- CThe circuits are located in a dwelling unit's sleeping area.
- DThe circuits are installed in a metal raceway system.
Show answer & explanationAnswer & explanation
Correct answer: C. The circuits are located in a dwelling unit's sleeping area.
AFCI protection is primarily mandated by NEC 210.12 for dwelling units in specific locations, including sleeping areas. Commercial office spaces generally do not require AFCI protection unless specified by local codes or specific circumstances, which are not mentioned here.
Why the other options are wrong
- A. Commercial office spaces are not typically required to have AFCI protection under the NEC, unlike dwelling units.
- B. The supply voltage (480Y/277V) is irrelevant to AFCI requirements for 120V circuits; AFCI applies to 120V branch circuits.
- D. The type of raceway does not generally dictate AFCI requirements.
AFCI Requirements (NEC)
Arc-Fault Circuit Interrupters (AFCIs) are primarily required by NEC 210.12 for 120-volt, single-phase, 15- and 20-ampere branch circuits supplying outlets or devices in specific dwelling unit locations.
- NEC 210.12 governs AFCI.
- Applies to 15A and 20A, 120V circuits.
- Required in dwelling unit bedrooms, family rooms, etc.
Memory trick: AFCI 'arcs' 'fire' 'homes' from danger.