Basic wiring practices for AFCI-protected circuits

Unlike a conventional circuit breaker, which detects overloads and short circuits, an arc fault circuit interrupter (AFCI) uses advanced electronic technology to sense different arcing conditions. This device weeds out the harmful arc characteristics from the “normal” arcs that occur during the normal operation of loads and other wiring devices. Common household items, such as a motor-driven vacuum cleaner or a furnace motor, naturally create arcs when they operate—each of which is considered a normal arc (click here to see Fig. 1).

Another example is the arc that may occur when a light switch is turned off. Dangerous arc faults, however, may result from improper installation, damaged wiring, overheated or stressed electrical cords, worn electrical insulation, wires and/or cords in contact with vibrating metal, damaged electrical appliances, and more. This type of arc condition creates high-intensity heat, which may exceed 10,000°F and result in burning particles that can easily ignite surrounding material, such as wood framing or insulation.

AFCIs are designed to recognize arc faults when they occur and automatically shut the circuit down before it becomes a fire hazard. Manufacturers of AFCIs test for hundreds of possible operating conditions, designing each AFCI to constantly discern between normal and dangerous arcs.

Due to the proven effectiveness of AFCIs, it’s important electricians follow proper wiring practices to help minimize troubleshooting efforts. The following sections highlight some of the best practices for electrical installation projects, but especially those performed on circuits that will be protected by AFCIs. Appropriate steps to successfully troubleshoot a potential wiring problem that will cause the AFCI to trip are also covered.

Other related information:

• Proper Tools and Work Practices
• Installation and Troubleshooting Tips
• AFCIs and the NEC

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