How it works & the NEC rules behind it
The National Electrical Code mandates two distinct types of personnel and property protection devices that operate on different principles:
- GFCI (Ground-Fault Circuit-Interrupter — §210.8): Protects humans from lethal electric shock and electrocution by sensing imbalances between hot and neutral currents as low as 4 to 6 milliamperes (mA) within milliseconds.
- AFCI (Arc-Fault Circuit-Interrupter — §210.12): Protects structures from electrical fires by detecting dangerous electrical arcing (sparking from frayed cords, punctured Romex, loose wire terminals) that standard thermal-magnetic breakers ignore.
- Dual-Function (DFCI / AFCI+GFCI): Combines both arc-fault and ground-fault protection in a single circuit breaker or receptacle device.