Excel Electrical Services

AFCI Testing

Many electrical contractors, electrician, journeyman electrician and apprentices have problems finding the cause for an Arc Fault Circuit Breaker (AFCI) tripping.  The following is a simple reference guide to help speed up the process of elimination in your search for the short.  These operations are not for the DIY novice home owner and should be conducted only by a certified electrician or under the supervision of a qualified electrician.

If you are troubleshooting a branch circuit that is terminated at the panel with an AFCI try the following:

  • Switch the AFCI breaker to the off position.

  • Remove the wires from the breaker.

  • Place the neutral (most cases white wire) under the neutral bus bar (look for similar wires)

  • Energize the circuit by installing the ungrounded conductor (usually black or red) under the lug screw of a de-energized non AFCI circuit breaker.

  • Turn that circuit breaker to the on position.

  • If the circuit breaker trips to the off position then search for a dead short in the branch circuit.

  • If the circuit breaker holds in the on position then try reinstalling the wires under a new AFCI breaker.

  • If the new AFCI breaker holds and there is a load on the circuit then you have found the problem and made the necessary repair.

  • If the new AFCI breaker trips to the off position then there is an Arc in the system and requires further investigation.

  • Unplug all equipment attached to the AFCI circuit and turn all light switches off

  • Open all junction boxes outlets and switches LOOKING FOR a grounded and grounding conductor or conductors (the neutral wire (usually white) and the ground (usually green or bare copper) in contact with each other.

  • If you find contact with the neutral and ground wire separate them and try reenergizing the AFCI circuit.

  • If the breaker holds in the on position then place a load on the circuit by turning on the light switches one at a time.

  • If the AFCI holds then return to the panel and turn the AFCI to the off position and put back all of the outlets and switches.

  • If the AFCI trips to the off position check all of the neutral connections in each box under each wire nut and or crimp.

  • Most AFCI problems occur in the light fixtures due to poor crimps at the factory or poor termination by the electrician at the time of installation.

  • The AFCI breaker will trip if a neutral wire in nicked in a way that it is close to breaking in two, if the neutrals are close enough to a metal box or grounded parts, bad switches that crackle or pop when turned to the on position, a loose light bulb in a socket, and any other similar occurrences you can think of.

  • Combo AFCI breakers work the same except that an Arc acting as a dead short but not enough resistance to trip a normal breaker will trip an AFCI breaker.  This usually occurs where the cord connects to an outlet or when you have bad equipment connected to a circuit.

If you understand how GFCI's work then you can trouble shoot the AFCI circuit problem.  If you exercise the order of these steps while comparing the results and using your previous experience you will master troubleshooting AFCI breakers.

By David Weber, Big City Electric