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AFCIs vs. GFCIs

AFCIs should not be confused with ground fault circuit interrupters or GFCIs. The popular GFCI
devices are designed to provide protection from the serious consequences of electric shock.

While both AFCIs and GFCIs are important safety devices, they have different functions. AFCIs
are intended to address fire hazards; GFCIs address shock hazards. 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.

How the AFCI Works

Conventional circuit breakers only respond to overloads and short circuits; so they do not
protect against arcing conditions that produce erratic current flow. An AFCI is selective so that
normal arcs do not cause it to trip. The AFCI circuitry continuously monitors current flow
through the AFCI.

AFCIs use unique current sensing circuitry to discriminate between normal and unwanted
arcing conditions. Once an unwanted arcing condition is detected, the control circuitry in the
AFCI trips the internal contacts, thus de-energizing the circuit and reducing the potential for a
fire to occur. An AFCI should not trip during normal arcing conditions, which can occur when a
switch is opened or a plug is pulled from a receptacle.

Presently, AFCIs are designed into conventional circuit breakers combining traditional overload
and short-circuit protection with arc fault protection. AFCI circuit breakers (AFCIs) have a test
button and look similar to ground fault circuit interrupter (GFCI) circuit breakers.

It is important to note that AFCIs are designed to mitigate the effects of arcing faults but
cannot eliminate them completely. In some cases, the initial arc may cause ignition prior to
detection and circuit interruption by the AFCI. The AFCI circuit breaker serves a dual purpose –
not only will it shut off electricity in the event of an “arcing fault”, but it will also trip when a
short circuit or an overload occurs. The AFCI circuit breaker provides protection for the branch
circuit wiring and limited protection for power cords and extension cords. Single-pole, 15- and
20- ampere AFCI circuit breakers are presently available.

Should You Install AFCIs?

Currently AFCIs are required in new construction on circuits serving bedrooms. You may want
to consider adding AFCI protection for both new and existing homes. Older homes with
ordinary circuit breakers especially may benefit from the added protection against the arcing
faults that can occur in aging wiring systems.

Be sure to have a qualified electrician install AFCIs; do not attempt this work yourself. The
installation involves working within electrical panel boxes that are usually electrically live, even
with the main circuit breakers turned off.

Testing your AFCIs

AFCIs should be tested after installation to make sure they are working properly and
protecting the circuit. Subsequently, AFCIs should be tested once a month to make sure
they are working properly and providing protection from fires initiated by arcing faults.
A test button is located on the front of the device. The user should follow the instructions
accompanying the device. If the device does not trip when tested, the AFCI is defective
and should be replaced.