AFCI
Definition
Arc-fault circuit interrupter. A device that detects the high-frequency signature of arcing current and opens the circuit. Required by the National Electrical Code in sleeping rooms and other areas in new US construction since various code cycles from 1999 onward.
- Full form
- Arc-fault circuit interrupter
- Detects
- High-frequency arcing signature
- Governing code
- US National Electrical Code
- Required since
- Various code cycles from 1999 onward
Common questions
How does an AFCI differ from a standard breaker or a GFCI?+
A standard breaker trips on overcurrent and a GFCI trips on ground-fault leakage, while an AFCI analyses the current waveform for the erratic high-frequency pattern of arcing, a fault type the other two devices do not reliably catch.
Why does AFCI presence or absence matter to a fire investigator?+
Its trip data or absence at the panel can help establish whether an arc-fault condition existed on a circuit before the fire, supporting or ruling out arcing as the ignition source.
Related terms
- Alloying
- Incorporation of a foreign metal (steel, zinc, aluminium) into a copper arc bead. The arc's intense temperature fuses adjacent metals together. The...
- Arc Fault
- An unintended electrical discharge across a gap or through degraded insulation that releases energy as heat and light. Arc faults are classified...
- Notching
- A V-shaped or crescent-shaped indentation in copper at an arc site, caused by localised material ejection during the arc event. Notching on...
- Primary Arc
- An arc that preceded and caused the fire. Its markers on copper conductors appear before any fire damage has reached that location.
- Secondary Arc
- Arc damage created after a fire was already burning, caused by the fire melting insulation and shorting conductors. These markers are consequences...