A tripped breaker is often just a one-time annoyance, but it can indicate potentially dangerous problems with your home's electrical system. Older homes in particular were not designed to handle today's increasing electrical demand. Overloaded circuits are one cause of the more than 40,000 residential fires attributed to electrical systems every year in the United States.

Electrical service enters your house at a main electrical panel and then is split into branch circuits serving different parts of the house. One breaker (or fuse in older homes) covers each of the branch circuits, which usually have one 120-volt wire, one neutral wire and one ground wire. A few circuits supply 240 volts to high-demand appliances such as electric ranges and dryers.

Each circuit can only handle a specified total wattage of electrical devices drawing power at one time. Most residential circuits are divided into 15- or 20-amp branch circuits, which can carry up to about 1,900 watts without tripping. Many appliances, particularly those that create heat such as hair dryers and portable heaters, can draw as much as 1,800 watts.

When electricity flows through a wire, the wire heats up because of its resistance to the flow of electric current. Circuit breakers interrupt the current when too much load is placed on the circuit. This keeps the wire from getting too hot and possibly starting a fire. In addition to simply having too much plugged into one circuit, causes of circuit breaker trips include faulty appliances; worn cords or defective plugs; and starting electrical motors, which require more power to start than to operate.

If an appliance repeatedly trips a circuit breaker, unplug it and repair or replace it. Look for damaged wires and plugs. If you find damage, avoid contact with the damaged wires or plugs. If you find yourself using extension cords or plug adaptors to plug multiple devices into the same outlet, consider having an electrician install more outlets on new or different branch circuits.

If circuit breakers trip frequently, you should have your electrical system checked by a licensed electrician. There may be a wiring problem that the electrician can fix, or you may need to add additional circuits to handle your electrical demands.

What to Do When a Circuit Breaker Trips

Start by turning off all wall switches on the circuit and unplugging lights and appliances. Then reset the circuit breaker. To reset the breaker, you must switch it all the way off, then on again. You should hear a click. Troubleshooting a circuit-breaker problem is much easier if you've already labeled each breaker with labels such as "kitchen," "dryer" and "den." Also, remember to keep your circuit breaker box easily accessible.

If the breaker trips immediately, there may be a short circuit in an outlet or switch. If the breaker doesn't trip, turn on each switch on the circuit one at a time. If turning on a switch causes the breaker to trip, there may be a short circuit in a fixture or outlet controlled by the switch.

Next, try plugging in and turning on the appliances that were connected to the circuit. If the breaker trips when you plug in the appliance, the problem may be in the cord or plug, while if it trips when you turn on the device, the appliance may be defective.

If the circuit breaker stays on, the problem was probably an overload, and you should remove some of the electrical devices on that circuit.

If the circuit breaker trips repeatedly, call a licensed electrician.