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Fuses and Circuit Breakers

When a fuse blows or a circuit breaker trips, your first reaction might be to curse the darkness-or the equipment. But don't blame the messenger. That fuse or circuit breaker might have spared you or your equipment from a dangerous electrical fire.

All fuses and circuit breakers serve the same purpose-to protect electrical wiring from overheating and catching fire. They do this by breaking the flow of electricity if too much power passes through the circuit, as can happen if there are too many appliances on one circuit, or if an appliance draws too much power.

A fuse can warn you only once: when the fuse overheats it burns out and must be replaced. A circuit breaker, on the other hand, is resettable: when the heat builds up it trips a switch that breaks the circuit. To restore the flow of electricity you simply reset the switch. (But always check to determine the cause of the problem.)

Older homes tend to have fuse boxes; newer homes and upgraded electrical systems use circuit breakers. Either device will protect your wiring if used properly.

General tips

Know where your circuit breaker panel or fuse box is located, and maintain a clear path to it.
Keep the cover of the fuse box or breaker panel closed to protect children and to keep dust and dirt out.
Periodically check fuses to ensure that they are screwed in tightly. A loose fuse could overheat.
Contact an electrician if you experience any of the following signs of trouble: circuit breakers that open or fuses that blow repeatedly for no apparent reason; lights that flicker or fade; a warm outlet or switch plate; or rust, discoloration or overheating in the fuse box.

Changing a fuse

Note: The following tips apply to plug fuses (the kind with a screw base), such as the S-type fuse. To install or replace the cartridge-type fuses that protect some electrical systems or large appliances, contact a qualified repair person.

When buying fuses, look for the CSA mark. This shows that the fuse complies with recognized safety standards. (See the marks.)
Before changing a fuse, unplug all appliances on the overloaded circuit and turn off the main switch.
Take a flashlight when you change a fuse. Never use a candle for light or change a fuse in the dark.
Stand on a dry rug, rubber mat, heavy cardboard or other non-conductive surface. Never change a fuse while standing on a wet floor.
Always use the proper size and type of fuse for the circuit. For example:
Use a 15-amp "P" fuse for lights, small appliances, water heaters, baseboard heaters and other general purposes.
Use a time-delay "D" fuse for large motorized appliances, such as refrigerators, freezers, clothes dryers, furnaces, and window air conditioners. These fuses are designed to withstand a temporary surge in power when the appliance is turned on. Never use a "D" fuse for a general purpose circuit.
Never substitute a higher amp fuse or replace the fuse with a coin or other metal object. You may restore power, but you will eliminate the protection a fuse is designed to give. The result could be an electrical fire.
Screw fuses tightly in place by hand. And while you're at it, check to ensure that there are no other loose fuses in the box.
If there is flooding or water damage in your home, discard all fuses and circuit breakers that have been submerged.

Resetting a circuit breaker

When a circuit breaker trips off, find the trouble and eliminate it before resetting the breaker.
To reset the breaker, push the handle all the way OFF and then ON.

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