Arc-fault Circuit Interrupters and Why They're Needed

Arc faults in a home are one of the leading causes of household fires.

What is an arc?

When an electric current crosses an air gap from an energized component to a grounded component, it produces a glowing plasma discharge known as an arc. For example, a bolt of lightning is a very large, powerful arc that crosses an atmospheric gap from an electrically charged cloud to the ground or another cloud. Just as lightning can cause fires, arcs produced by domestic wiring are capable of producing high levels of heat that can ignite their surroundings and lead to structure fires.

Plasma Arc

What is an AFCI?

An arc-fault circuit interrupter is a circuit breaker designed to prevent fires by detecting non-working electrical arcs and disconnecting power before the arc starts a fire. The AFCI distinguishes between a working arc that may occur in the brushes of a vacuum sweeper, light switch, or other household devices, and a non-working arc that can occur in a lamp cord that has a broken conductor in the cord from overuse, for instance.

AFCIs resemble GFCIs in that they both have test buttons, though it is important to distinguish between the two. GFCIs are designed to protect against electrical shock, while AFCIs are primarily designed to protect against fire.

AFCI's vs GFCI's

Arc-fault circuit interrupters, or AFCIs, provide protection against arcing in fixed wiring, appliance cords, and extension cords. The U.S. Consumer Protection Safety Commission (CPSC) and the National Association of State Fire Marshals (NASFM) have called AFCIs the "most promising fire-protection technology since the advent of the smoke detector."

AFCI Breakers

How does it work?

Conventional circuit breakers respond to overloads and short circuits.  They do not protect against arcing conditions that produce erratic current. Like circuit breakers, AFCIs protect against short circuits and overloads, but also protect against arcs by electronically identifying the unique current and voltage characteristics of arc faults, and de-energizing the circuits when arc faults occur.

What does this have to do with home inspections?

Home inspections search out issues from structural and roofing, to electrical, plumbing, HVAC, and appliance problems. AFCIs and GFCIs are just a small part of what we look for during an inspection that the average person would never know existed. Give me a call to see how I can help make your current home safer, or to give you the information you need before closing on a new home.

*Some text and images used with permission from www.nachi.org