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.