What is an AFCI? (Arc-Fault Circuit Interrupter)

By Scott Bowers,

Starting January 1, 2002, The National Electrical Code , Section 210-12, required that all branch circuits supplying 125V, single phase, 15 and 20 ampere outlets installed in dwelling unit bedrooms be protected by an arc-fault Circuit interrupter. Eventually there were more areas that were required, but the NEC selected to require them on bedroom circuits first because a CPSC study showed many home fire deaths were related to bedroom circuits.

The AFCI (Arc Fault Circuit Interrupter) breaker, will shut off a circuit in a fraction of a second if arcing develops. The current inside of an arc is not always high enough to trip a regular breaker. You must have noticed a cut or worn piece of a cord or a loose connection in a junction box or receptacle arcing and burnt without tripping the regular breaker. As you can guess this is a major cause of fires in a dwelling.

There is a difference between AFCIs and GFCIs. AFCIs are intended to reduce the likelihood of fire caused by electrical arcing faults; whereas, GFCIs are personnel protection intended to reduce the likelihood of electric shock hazard. Don’t misunderstand, GFCIs are still needed and save a lot of lives.
Combination devices that include both AFCI and GFCI protection in one unit will become available soon. AFCIs can be installed in any 15 or 20 ampere branch circuit in homes today and are currently available as circuit breakers with built-in AFCI features. In the near future, other types of devices with AFCI protection will be available.

Main Street Electric Company are proud users of Eaton products. Watch Erik Drost at Eaton’s Power Systems Experience Center in Pittsburgh, Pennsylvania where he discussed Arc Fault Circuit Interrupter (AFCI) technology and how it helps keep your home safe.

How an AFCI works and why every home should have them installed.

If a GFCI receptacle is installed on the load side of an AFCI it is possible for both the AFCI and the GFCI to trip on a fault if the current exceeds the limit for both devices. It is also possible for the AFCI to trip and the GFCI to not trip since the two devices could race each other. However, in no case is safety compromised.

At first the cost for AFCI was high. End-users pai between $20 and $50 for each AFCI. The cost is expected to dropped as much more are ordered.

Code Section 210-12

(a) Definition: An arc-fault circuit interrupter is a device intended to provide protection from the effects of arc faults by recognizing characteristics unique to arcing and by functioning to de-energize the circuit when an arc fault is detected.

(b) Dwelling Unit Bedrooms. All branch circuits that supply 125-volt, single-phase, 15- and 20-ampere receptacle outlets installed in dwelling unit bedrooms shall be protected by an arc-fault circuit interrupter(s). This requirement shall become effective November 1, 2002.

There are a lot of homes that have been wired with aluminum wiring and it would not be financially possible to rewire the entire house or service.

There are a few things you can do to make sure that the wiring is not becoming a problem:

  • You should be on the lookout for devices or lighting going on and off.
  • Breakers or outlets overheating. Have the main panel checked for corrosion or loose connections.
  • When adding copper devices or wire to aluminum, make sure this work is done by someone who knows the proper procedure for this type of wiring.
  • A little preventative maintenance can go a long way in preventing future safety hazards.

Read more about the “AFCI Debate” in another one of our blog posts here.