1. What is an arc fault?
When referring to electricity, an arc occurs when an electric current "jumps" a gap from one medium to another. This transfer could be intentional - as is with an arc welder - or unintentional, as is when a tree falls on a power line.

An arc fault is an unintentional "jumping" of an electric current over an unplanned path. With temperatures exceeding 10,000°F, these arcs can easily ignite surrounding materials, such as wood framing or insulation.

2. What causes an arc fault?
Typical causes of an arc fault are:
• Damaged wires
• Receptacle leakage
• Worn electrical insulation
• Wet connectors or conduit
• Loose electrical connections
• Shorted wires
• Wires or cords in contact with vibrating metal
• Overheated or stressed electrical cords or wires
• Misapplied/damaged appliances

3. How does an AFCI work?
Unlike a standard circuit breaker that detects overloads and short circuits, an AFCI utilizes advanced electronic technology to "sense" different arcing conditions. In essence, the AFCI monitors the circuit and distinguishes between "normal" and "dangerous" arcing conditions. Some equipment in the home, such as vacuum cleaners and furnace motors, naturally create arcs. These arcs fall under normal arcing conditions.

Dangerous arcs, however, occur for the numerous reasons listed above. These arcs are recognized by the AFCI and stopped before any damage can occur.

4. Why should I install AFCIs in my home?
According to the Unites States Fire Administration (USFA), an estimated 67,800 home fires, with over 2,800 casualties and a billion dollars in damages, occur each year due to electrical fires. The US Department of Housing and Urban Development (HUD) promotes AFCIs as one of the many devices that can be used to help prevent burns and fire related injuries. In addition, it cites a 1999 CPSC Report recommending the use of AFCIs to "prohibit or reduce potential electrical fires from happening".

An AFCI can be a homeowner's first line of defense against these tragedies. Smoke alarms and fire extinguishers work after a fire has already started. An AFCI may stop the fire before it starts.

5. Are there different types of AFCIs?
AFCIs are intended to mitigate the effects of arcing faults by functioning to de-energize the circuit when an arc fault is detected. AFCIs are required by the NEC to be a listed product. This means that they must pass an evaluation by a nationally recognized testing laboratory to make sure they are up to AFCI standards (UL 1699). NEC 210.12 establishes the requirement to use AFCIs for branch circuits in locations as specified in this NEC rule.

Branch/Feeder AFCI
A device intended to be installed at the origin of a branch circuit or feeder, such as at a panel board. The branch/feeder AFCI provides for detection of arcing faults that occur line-to-line, line-to-neutral, or line-to-ground. These are called parallel arcs because they cross a gap on two parallel lines. To be able to handle shared neutral circuits (a common application in older homes), a two-pole AFCI can be used.

Combination AFCI
In addition to detecting parallel arcs, a combination AFCI detects series arcs. A series arc occurs when the current jumps a gap that lies within a single wire, rather than jumping a gap between two separate wires. This AFCI can detect low voltage arc faults down to 5 amperes. Combination AFCI protection is required by the NEC as of January 1, 2008.

AFCI and GFCI Protection
An AFCI can be used in conjunction with GFCI protection to provide both arcing fault protection as well as 5mA ground fault (user) protection. A common way to provide both types of protection is to use an AFCI circuit breaker and a GFCI receptacle. AFCIs can also incorporate 5mA GFCI protection into the same package. This solution for AFCI and GFCI on the same circuit can be useful where the circuit design requires both types of protection or where the installer (or user) wants to have both types of protection.

6. What is the difference between AFCI and ground fault circuit interrupter (GFCI)?
There is a major difference between the functioning of an AFCI and a GFCI (ground fault circuit interrupter). The function of the GFCI is to protect people from the deadly effects of electric shock that could occur if parts of an electrical appliance or tool become energized due to a ground fault. The function of the AFCI is to protect the branch circuit wiring from dangerous arcing faults that could initiate an electrical fire.

AFCI and GFCI technologies can co-exist with each other and are a great complement for the most complete protection that can be provided on a circuit.

7. Where in the home are combination AFCIs required by the National Electrical Code (NEC)?
The 2008 NEC requires combination AFCIs on circuits for all dwelling unit family rooms, dining rooms, living rooms, libraries, dens, bedrooms, sun rooms, recreation rooms, hallways, closets, finished basements, or other rooms of that nature. Whether in new construction or retrofit, NEMA supports the maximum electrical protection level available to reduce the chance of an electrical fire.

8. Can I have AFCIs installed even if my state or municipality doesn't require them?
Absolutely. Do you only place locks on the front door of the house? Just like placing locks on all external doors and windows for security reason, it is logical to request AFCI protection on all 15 and 20A branch circuits, not just those in the bedroom, to protect the entire home from an electrical arcing ignition hazard.

AFCIs are available through electrical distributors and in many home centers and hardware stores nationally. The only major physical requirement is that the AFCI requires directly wired hot and neutral wires on the circuit you're going to protect.

9. What is the price of new safety technology worth?
When ground fault circuit interrupters (GFCIs) were introduced in the 1970s, similar discussions took place regarding the cost/benefit to the consumer, homebuilder and others. GFCIs have been a standard requirement in homes for over 30 years, with additional locations and circuits being added over time as well. GFCI also has a statistical track record over time as to the reduction of electrocutions. On an annualized basis, in 1983, there were almost 900 electrocutions total per year with approximately 400 being consumer product related. Ten years later, the total was reduced to 650 annually and slightly over 200 consumer product electrocutions annually.

With over 20 years of history, statistically based analysis of GFCIs was built on a solid foundation of data. AFCIs are new and have only been installed in new construction on bedroom circuits for a few years. As with all products, given time, they too will be able to provide a solid statistical base of measure.

Some have argued that it should be shown how many times an AFCI has "prevented" a fire from occurring. Of course, this is not a feasible request. The AFCI disconnects the power when an arc fault occurs, therefore no incidence of fire or arc is reported to authorities. The same can be true when a smoke alarm alerts the homeowner and the small smoking event is extinguished without incident. Is that statistic reported to the Federal Government or local fire department? Of course not. Safety prevention is just that - a prevention. The only statistics that are reported are those that have resulted in a fire or a response of a fire department. Many safety protection actions go unreported.