Adding Surge Protection
Occasionally your electrical service can experience sudden increases in power, known as surges. A surge almost certainly will not harm lights and appliances, but it could damage sensitive electronic equipment, such as a computer. To protect a few pieces of equipment, purchase a surge protector that simply plugs into an outlet. Or you can replace an existing receptacle with a surge-protecting receptacle. Install it as you would a normal receptacle, except that you will be connecting wires to wires rather than to screw terminals.
Adding Surge Arresters to Circuits
To protect a circuit against surges, install this device in your service panel. At the service panel, shut off the main circuit breaker, and take off the panel cover. Remove the 1/2-inch knockout that is nearest to the circuit you want to protect. Insert the surge arrester through the knockout hole, and fix it in place by tightening the nut. Wire as shown, connecting the white wire to the neutral bus bar and the black wire(s) to breakers. Before connecting, cut wires as short as possible for maximum protection.
Troubleshooting Circuit Breakers
Think of a circuit breaker as a heat-sensing switch. As the illustrations at right show, when the toggle is on, current flows through a set of contacts attached to a spring and lever. The contacts are held together by tension in the bimetal strip through which the current flows. If there is a short or an overload in the circuit, the bimetal strip heats up and bends. As it bends it releases a lever that opens the spring-loaded contact. The contact remains open until the toggle is manually reset by the homeowner.
Identify a tripped breaker. A tripped breaker will identify itself in any of the four ways shown at left. To find out whether the problem has corrected itself, reset the breaker. If the problem persists, the breaker will shut itself off again. Usually the problem is an overload, and you only need to unplug or turn off one of the circuit’s big energy users. If the circuit breaker keeps tripping even though it isn’t overloaded, suspect a short. A defective plug, cord, or socket may be the problem.
Check connections in boxes. Short circuits can occur in electrical boxes. Here, a wire has pulled loose from the switch and has shorted out against the box.
Inspect wiring. Frayed or nicked insulation will expose wire and could cause a short. Wrap damaged insulation with layers of electrical tape.
Watch for overheated fixtures. High-wattage bulbs can melt insulation. Never use bulbs with higher wattage ratings than those for which the fixture is rated.
Fuses serve the same purpose as circuit breakers, but instead of tripping as a breaker does, a fuse contains a strip of metal that melts when too much current in the circuit produces heat. When this happens, you must eliminate the short or overload and replace the blown fuse.
Understanding blown fuses - By examining a fuse you usually can tell what made it blow—an overload or a short. A short circuit usually explodes the strip, blackening the fuse window. An overload usually melts it, leaving the window clear.
Fuse options - A tamper-proof fuse is an important safety device that makes it impossible to install a fuse with a higher amperage rating than the circuit is designed for. It comes with a threaded adapter that fits permanently into the box. The adapter accepts only a fuse of the proper rating. When an electric motor on a washing machine or refrigerator starts up, it causes a momentary overload that can blow fuses unnecessarily. A time-delay fuse avoids this problem by not blowing during the surge. Only a sustained overload will blow the fuse.
Cartridge fuses - Fuses for 30- to 60-amp circuits typically are the ferrule-contact cartridge type. Knife-blade-contact fuses carry 70 amps or more. Handle both with extreme caution. Touching either with your bare hand could fatally shock you.
Removing cartridge fuses - For safety keep a plastic fuse puller with your spare fuses and use it as shown. Note, too, that the ends of a cartridge fuse get hot, so don’t touch them immediately after you’ve pulled the fuse.
Testing cartridge fuses - To see if a cartridge fuse has blown, check it with a continuity tester. Clamp or hold the clip on one end and touch the probe to the other. The bulb will light if it is not blown.