What is an AFCI Circuit Breaker?


An Arc Fault Circuit Interrupters (AFCIs) is required by the National Electrical Code for certain electrical circuits in your home.  In the US, arc faults are one of the leading causes for residential electrical fires. It is estimated that each year in the United States over 40,000 fires are caused by home electrical wiring. These electrical fires result in over 350 deaths  and over 1,400 injuries each year.

AFCIs are devices that are designed to protect against fires that are caused by arcing faults in the home electrical wiring. While conventional circuit breakers only respond to overloads and short circuits, they do not protect against arcing that produces erratic and reduced current. The AFCI circuit monitors current and identifies changes between normal and unwanted arcing conditions. Once an arcing condition is detected the AFCI opens it’s internal contacts and de-energizes the circuit, thus reducing the potential for a fire to occur in the home.

AFCIs are required by the NEC® to be a listed product. This means that they must be evaluated by a nationally recognized testing laboratory to the standard for AFCIs (UL 1699). There are three different types of AFCIs for the home that can be installed.

Branch/Feeder Breaker AFCI

This is a device intended to be installed at the source of a branch circuit or feeder, such as the panel board. The branch/feeder AFCI is able to detect arcing faults that may occur line-to-line, line-to-neutral and line-to-ground.  A common application in older homes is shared neutral circuits, a two-pole AFCI can be used to handle this type of circuit.

Combination Breaker AFCI

In addition to the protection that is provided by the Branch/Feeder AFCI, the Combination AFCI tailors for arc detection down to 5 amperes. This AFCI arc detection is beneficial to find lower level arcing in power supply cords and branch circuits. Combination AFCI protection is required by the NEC® as of January 1, 2020.

Breaker AFCI and GFCI (Ground Fault Circuit Interrupter) Protection

An AFCI can be used with GFCI protection in order to provide both arcing fault protection as well as 5mA ground fault (people) protection.  A simple way to achieve both types of protection is to use an AFCI circuit breaker and a GFCI receptacle. AFCIs are able to incorporate 5MA GFCI protection into the same package. This method for the AFCI breaker and GFCI on the same circuit can be useful where the circuit design needs both types of protection or where the installer wants to have both types of protection in their home.

Despite both being able to be used there is a major difference between the function of an AFCI compared to a GFCI (Ground Fault Circuit Interrupter). The main use of the GFCI is to protect people from fatal electric shock that could occur if parts of an electrical appliance or tool become energized due to a ground fault. Whereas the function of the AFCI is to protect the branch circuit wiring from arcing faults that may cause an electrical fire.
AFCI and GFCI circuits can work together and are a great complement for the most complete protection on a circuit.

You are able to have AFCIs installed even if your state doesn’t require them. It is a good idea to request AFCI protection on all 15 and 20A branch circuits in order to protect the entire home from electrical arcing ignition.
AFCIs are available through electrical distributors and many home centers and hardware stores across the nation. The only requirement is that the AFCI breaker needs directly hot and neutral wires on the circuit you are going to protect.