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Prevent Home Electrical Fires

Construction How-To, Electrical, Safety November 15, 2002 Sonia



Electrical problems are the cause of more than 40,000 home fires in the United States each year. On average, these fires claim close to 350 lives, injure 1,400 and result in $700 million in damages according to the U.S. Consumer Product Safety Commission. Arc faults, or electric arcs, are one of the main culprits. Arc faults can be caused by broken wires, deteriorated insulation or even by driving a nail into a wire. A plasma flame that can reach temperatures as high as 9,000 degrees Fahrenheit characterizes these arcs. An arcing fault can go undetected by standard, present-day residential circuit breakers and fuses, which are designed to detect short circuits that can cause an electricity surge.

Arc Fault Circuit Interrupters (AFCIs) are designed to provide better protection from arc fault fires. Typical household fuses and circuits do not respond to early arcing and sparking conditions in home wiring. By the time a fuse or circuit breaker opens a circuit to defuse these conditions, a fire may already have begun. Several years ago, a Consumer Product Safety Commission study identified arc fault detection as a promising new technology. Since then, CPSC electrical engineers have tested the new AFCIs on the market and found these products to be effective in protecting homes from certain faulty wiring conditions. AFCIs are already recognized for their effectiveness in preventing fires. The most recent edition of the National Electrical Code, the widely-adopted model code for electrical wiring, requires AFCIs for bedroom circuits in new residential construction. Future editions of the code will most likely expand coverage. The bedroom circuit code was adopted because many home fire fatalities occur when residents are trapped in bedrooms. You may want to consider adding AFCI protection for either new or older existing homes. Older homes with ordinary circuit breakers may especially benefit from the added protection against the arcing faults that can occur in older wiring systems.

AFCI Applications Branch circuit AFCIs may be circuit-breaker type, or may be separate units in their own enclosure, mounted near the panel board. A branch feeder is installed in the panel board at the origin of the branch circuit. These protect the branch circuit wiring, feeder wiring and also provide some limited protection to branch extension wiring, such as cord sets or power supply cords. Outlet circuit AFCIs are installed at the branch circuit outlet box and provide protection for cord sets and power-supply cords that are plugged into the outlet box. Combination devices comply with the requirements for both branch/feeder and outlet circuits and, and they provide protection for downstream branch circuit wiring as well as cord sets and power- supply cords. Outlet/branch circuit units are installed at the first outlet in a branch circuit. They provide protection to downstream branch wiring, cord sets and power-supply cords as well as upstream branch circuit wiring. Portable units plug into a receptacle outlet. These units provide protection to connected cord sets and power-supply cords. Damaged or overheated supply cords often cause fires, and these simple units can be a lifesaver. Corded AFCIs are often part of a power-supply cord and are designed to plug into a receptacle to provide protection to the power cord.

A similar device is the Leakage-Current Detection and Interruption device (LCDI). This is provided in a cord set or power supply cord and senses the current flowing through the cord. It interrupts the circuit at a preset current leakage level. It’s important to understand that none of the above devices are the same as Ground Fault Circuit Interrupters (GFCIs). GFCIs are designed to provide protection against electrical shock. Combination devices that include both AFCI and GFCI protection in one unit will be available soon. As an example of what is available, FIRE-GUARD AFCI circuit breakers, from Eaton/Cutler-Hammer, can be applied to all residential, commercial and industrial 15 and 20 ampere, 120/240V AC applications. They must use a loadcenter approved for use with Cutler-Hammer type CH or BR circuit breakers. FIRE-GUARD AFCIs are available in both single-pole and two-pole types. They can also be used in conjunction with a downstream GFCI device, such as a receptacle or ground-fault relay. Siemens manufactures a branch/feeder arc fault circuit interrupter that incorporates all of the features of a thermal magnetic circuit breaker, overload and short circuit protection, with arc fault protection. Siemens AFCIs employ electronic circuitry to continuously monitor the circuit and determine the unique characteristics of arcing faults. When there is an instance of arc fault the AFCI opens the circuit and stops the flow of electricity in a fraction of a second. Some connected loads, such as motors and dimmer switches, have inherent arcing as a normal mode of operation, but the Siemens AFCI is designed to distinguish these arcing faults from hazardous faults.

For more information on AFCIs contact an electrical supply store, an electrician or the manufacturer of circuit breakers already installed in your home. Sometimes these components can be replaced with AFCIs in the existing electrical panel box. Unless you have experience with electrical work, have a qualified electrician install AFCIs; do not attempt to do this job yourself. The installation sometimes involves working within electrical panel boxes that can be electrically live, even if the main circuit breaker is turned off. If you are qualified to do the job, it’s relatively simple. Determine the breaker that is to be replaced. If the circuit is not identified on the panel board, one method of determining the correct circuit is to plug a radio into the circuit, then turn off breakers until the radio stops. Do this for each room where AFCIs are desired. Turn off the power with the main circuit breaker, which is located at the top center of the main panel. Remember, power is still coming into the panel at the main breaker. Remove the old breaker by grasping the end where the branch wires are connected and pulling outward from the buss. Loosen the screws holding the branch wires in the old breaker, and pull the wires out. Install the branch wires into the appropriate screw holes of the AFCI circuit breaker, and tighten the screws. Position the new breaker into the buss slot with the screw terminal end facing outward from the center of the buss. Press the inside edge in place, then push the breaker toward the center of the panel buss, and press in to engage it in place. Fasten the panel neutral or pigtail to the panel neutral or load center. Finally, turn on the main breaker and close the panel door. AFCIs branch feed or circuit breaker replacement units cost about $25 to $35. Regardless the age of your home, you can provide greater electrical fire protection with the use of these new home products. They’re very economical insurance.


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