Most of us are familiar with the circuit breakers located in our home's electrical panel. But do you know how they work and what their limitations are? Have you heard about the newest generation of electric devices that provide an increased level of protection from electric shock or fire?
The ground fault circuit interrupter (GFCI), and the arc fault circuit interrupter (AFCI) represent the latest electric technology designed to save lives and protect property. The GFCI provides protection against electric shock and electrocution. The AFCI saves lives and property by significantly reducing the likelihood of a fire in the home started by faulty wiring connections, cords, appliances and other hazards. The widespread installation of AFCI's and GFCI's could save hundreds of lives and billions of dollars in property damage in our country every year. Here is a basic explanation of how these devices work.
Circuit Breakers and Fuses
Circuit breakers and fuses are basic electric safety devices and are absolutely necessary to protect the wiring in our homes from being overloaded. Whenever a circuit or electric wire has too much current flowing through it these devices cut the flow of electricity until the problem is fixed. A fuse, just a thin wire enclosed in a casing, is exposed to the same current flow as the hot wire in a circuit. If the current flow is too high, the thin fuse wire will heat up and vaporize. This cuts off the power before house wiring is damaged and a fire is started. A fuse will work only one time and must be replaced.
A circuit breaker operates like a fuse, when current rises to unsafe levels it trips and stops the flow, however it can be used over and over. In addition to operating because of the higher temperature created by overcurrent, it contains an electromagnet that will trip the breaker due to the extra magnetic force caused by unsafe current flow.
Circuit breakers and fuses will not operate fast enough to prevent electric shock or electrocution in the event of an accident. Circuit breakers and fuses also may not trip during arcing faults because the current flow may be low enough to keep them from tripping early enough to prevent a fire.
The Ground Fault Circuit Interrupter - A Lifesaver
GFCI's protect against potentially deadly shock when they detect even miniscule, but potentially dangerous "ground faults" or leaks of electric current from the circuit. A GFCI monitors the amount of current flowing from hot to neutral. If there is any imbalance, it trips the circuit. It is able to sense a mismatch as small as 4 or 5 milliamps, and it can react as quickly as one-thirtieth of a second. For example, if a person were holding a hairdryer and dipped it into a sink full of water, electric current would flow from the hair dryer through the person. A GFCI would react to the ground fault or leak fast enough to prevent a potentially fatal accident. GFCI's can be installed as wall outlets, as circuit breakers, and can come installed on outdoor extension cords and cords of certain appliances.
The Arc Fault Circuit Interrupter - Saving Lives and Property
AFCI's are the latest development in electrical safety technology for the home. They work to prevent fires by detecting arcs caused by low current electric faults. Overcurrent devices like circuit breakers may not always detect these arc faults. Arc faults can take anywhere from seconds to years to develop, may be sustained at 120 volts, and are generally hidden from view. Some common examples of what can cause an arc fault include: improperly installed or loose connections inside wall outlets and switches, damaged or deteriorated insulation on wiring, wiring punctured by nails or staples, undersized extension cords where insulation covering has become brittle from age and overloading, and damaged appliance cords and plugs.
The AFCI contains a microprocessor that recognizes the unique current and voltage characteristics of arc faults and cuts off the power until the cause of the arc fault is eliminated. On January 1st, 2002 the National Electric Code required all circuits feeding bedrooms in new construction to have arc fault protection.
You may want to consider adding arc fault breakers to your existing home. Older homes may benefit from the added detection of arcing that can occur in aging wiring systems. Some AFCI breakers come with GFCI protection as well. AFCI circuit breakers retail at about $150, so they are not inexpensive, but they can provide peace of mind.