Home Wiring Short Circuits

Problem: Power to a circuit is cut off by a fuse or circuit breaker in the main panel.

Background: If a fuse is blown, the fuse window will appear discolored and the metal strip running across the inside of the window will be bro ken. This indicates a short circuit caused by either 2 bare wires touching, or by a hot wire grounding out to a metal object somewhere in the circuit. Circuits protected by cartridge fuses will give no visible indication that a short circuit has taken place. Tripped circuits protected by circuit breakers can be identified when the handle of the circuit breaker is in the “tripped” or “off” position.

What to do: If the circuit power cuts off and no fuse appears to be blown. The method for identifying the cause of a short circuit is the same for fuses or circuit breakers. Disconnect all lights and appliances on the circuit with the blown fuse or tripped circuit breaker. Then replace the blown fuse or turn on the tripped circuit breaker. If the fuse blows or the circuit breaker trips with all appliances unplugged from the circuit, the short is in the circuit wiring itself and the wiring must be repaired or replaced. If the circuit is good, reconnect each light and appliance on that circuit, one at a time.

Special advice: Use extreme caution when reconnecting lights and appliances. Do not connect suspiciously frayed cords to outlets. When you turn on the faulty light or appliance, the fuse will blow or the breaker will trip again. Carefully check appliances for bare cords, broken light sockets, or damaged plugs before replugging.

Helpful hint: If one particular fuse blows several times, shut off all wall switches and appliances on that circuit, and remove all line cords from the sockets. Remove the fuse and screw a 100-watt light bulb into the fuse receptacle. If the bulb lights with all appliances unplugged from the circuit, a short exists within the circuit. If it doesn’t light, connect each of the appliances, lamps, and line cords one at a time. If the bulb lights at the fuse panel and the appliance fails to work, you’ve located the short. Remove the bulb from the panel before disconnecting the faulty appliance.

Home Wiring Inadequate

Problem: Excess demand on electrical system, which shows up as blown fuses, tripped circuit breakers, dim or flickering lights, or appliances that operate at only partial capacity.

Background: Electrical requirements for the average home have- almost tripled since 1955. In 1940, for example, the average home used 30 electrical appliances while today’s home uses about 80. The electrical systems of about 90% of homes in the United States are not designed to accommodate the number of appliances currently avail able. Many homes over 20 years old require complete rewiring, and even a number of newer homes need either rewiring or expanded wiring systems (including new circuits) to handle major appliances.

What to do: If your home’s wiring system has any of the symptoms listed below, the individual circuits may be overloaded or the wiring of these circuits may be inadequate.

Blown fuses or tripped circuit breakers: When fuses blow and circuit breakers trip frequently, it indicates an overloaded circuit, or that the power drain from appliances is greater than the circuit can handle. Short circuiting in appliances or wiring could also be the problem.
Lights dim or flicker: This problem can be caused by having too many appliances on one circuit, or by putting too large of a power drain on the circuit when specific appliances are turned on. (It may also be caused by electrical storms or by voltage drops at the power plant.)
Appliances with heating coils warm up slowly: Inadequate wiring may be indicated by electric space heaters and hot plates that are slow to warm up, and by similar appliances that re quire high power and seem to be operating on decreased power.
Television picture shrinks: If the image on your TV is smaller than the picture tube area, the circuit could be overloaded with too many appliances or extension cords. If it occurs only occasionally, it is probably caused by the heavy current drain of appliances that are started up on the same circuit.
Air conditioners work at less than full capacity: The heavy power needs of air-conditioner compressors can require more line voltage than circuits provide. With large air-conditioning units, separate circuits may be needed.
Special advice: When in doubt about any electrical wiring problem, consult an electrician. Always use caution when working with electricity. Before proceeding with any electrical work, make sure the main disconnect on the service entrance panel is in the “off” position, or pull the main fuses if the panel is the cartridge fuse type. When working on individual receptacles or light switches, also turn off the circuit breaker for the circuit you will be working on, and test the receptacle with a test light before handling bare wires.

Helpful hint: Never stand on a wet or damp floor when working at the service panel. Wear rubber gloves and stand on a rubber mat for added safety.

Circuit Wiring Overloads

Problem: Power to a circuit is cut off because of either temporary overloads or constant over loads.

Overloaded electrical power strip

Background: Most circuit failures are caused by overloads. Electricity in home wiring flows under pres sure, much like water moves under pressure in a plumbing system. The electrical pressure is known as volt age. The flow of electricity is called amperage. Wire of a specific size may have too great a resistance to handle the current required of it. If a fuse blows and the window remains clear, an overloaded circuit is most likely the cause. Cartridge-type fuses will give no visible indication of an overloaded circuit. Circuit breakers will be in the “tripped” or “off” position.

What to do: If a circuit fails repeatedly, there may be a short in it or there may be too many heavy appliances on that circuit. If removing some of the appliances from the circuit does not eliminate the overload, an individual circuit must be added for the appliance with the heaviest current drain. Fused circuits can be corrected to handle temporary overloads by using a time delay fuse of either 15 or 20 amperage. This type of fuse will handle temporary power drains from the start-up of appliance motors. Many electric motors need nearly three times the normal line current for initial starting. Circuit breakers are designed to automatically handle temporary overloads.

Special advice: To check loads on a specific circuit, total the number of watts used for appliances and lights on that circuit at the same time. Appliance wattage rates are usually on the nameplate at the back of an appliance, or on the motor. After adding up the total, divide the sum by 120 volts to calculate the amperages. For example, if the total exceeds 1,800 watts for a circuit with a 15-amperage fuse, or exceeds 2,400 watts for a circuit with a 20-amperage fuse, the circuit is overloaded. One or more appliances may be plugged into another circuit to avoid an over load, as long as new overloads are not created. If overloads remain, call an electrician to add an additional circuit.

Helpful hint: When calculating circuit loads, you may find appliance plates give amperages rather than watts. To convert into watts, multi ply amperages by voltage (120 or 240). If horsepower is given on motors, multiply horsepower by 746 to find wafts.