Many Devices Protect From Electrical Shock and Fire

By James Dulley

January 21, 2009 5 min read

Dear Pat: My children are getting old enough to use small electrical appliances. Can you tell me about the various types of fuses and circuit breakers for their protection and mine? — Jennifer H.

Dear Jennifer: People often think of protection from being shocked, and some devices do this, but house fires are also a serious problem. House fires caused by electrical problems are particularly bad because they often start inside a wall. Especially at night, a fire can spread far before it is detected.

The most common protective electrical items in most homes are circuit breakers and fuses. They are found in the home's main electrical panel, which provides electricity to the entire house. Circuit breakers and fuses are designed to shut off the electric current when it exceeds a predetermined level. This often is either 15 or 20 amperes, or amps.

To help understand this, we can compare flowing electricity to flowing water. An amp is the actual amount of electricity flowing through a wire just as gallons per minute are the actual amount of water flowing through a pipe. A bigger water pipe can handle more water and a bigger electrical wire can handle more amps.

Electrical voltage is the force pushing the amps through a wire just as water pressure pushes water through a pipe. If you increase the water pressure, more water flows through the pipe. If you increase the voltage, more amps of electricity flow through the wire.

Certain size electric wires are required by municipal building and safety codes to handle certain numbers of amps. If you plug in too many appliances, the total amps required to run those appliances can be too great for the wire. When that happens, the wire can get so hot it starts a fire or shorts out through the insulation.

Both circuit breakers and fuses stop the flow of electricity through a wire before the excess flow gets dangerously high for the wiring. Of the two devices, circuit breakers are most convenient. Once you unplug the excessive appliances, you can flip the breaker switch to restore the flow of electricity.

Unlike circuit breakers, when a fuse blows it must be replaced before electrical flow can be restored. Even though less convenient and seldom installed in new homes, fuses still provide the most reliable and precise protection. That is why many expensive and sensitive electronic devices are equipped with fuses instead of circuit breakers.

The most modern circuit breakers are called arc fault circuit interrupters, or AFCIs. Even though the electric current does not get too high, arcing has a particular signature and an AFCI interrupts, or shuts off, the flow of electricity when arcing occurs.

A ground fault circuit interrupter, or GFCI, is similar to a circuit breaker in that it can be reset. But GFCIs are designed to protect against electric shock. If the insulation on a wire breaks or gets shorted to ground, the electric current skyrockets and the circuit breaker or fuse shuts it off.

A GFCI will detect a slight short circuit or ground and shut off the electricity. This slight short circuit is generally not enough to cause the electric current to spike and trip a circuit breaker. If the current from this slight short circuit pass through the nerves to your heart, it can be fatal.

GFCIs should be installed on all outdoor circuits, or circuits located near sources of moisture, such as bathrooms and garages. For example, if you are using a hair dryer with a slight short and your arm is touching a damp fixture in the bathroom, some electricity could flow through your body. A CFGI is designed to turn off the flow of electricity before you can be shocked fatally.

Send your questions to Here's How, 6906 Royalgreen Dr., Cincinnati, OH 45244 or visit To find out more about Pat Logan and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at

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