Circuit breakers an ally against fire
People often think of protection from being shocked, and some devices, through fuses or circuit breakers, protect against 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 even detected. The most common protective electrical items in most homes are circuit breakers and fuses in a main panel, which provides electricity to the entire house. These 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, think of an analogy with water flow. 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 the wire just as water pressure is the force pushing water through a pipe. If you increase the water pressure, more water flows through a pipe. If you increase the voltage, more amps of electricity flow through a wire.
Certain size electric wires are required by electrical codes to handle certain amounts of amps. If you plug in too many appliances, the total amps can be too great for the wire. When this happens, the wire can get very hot and start a fire or short out through the insulation. Both circuit breakers and fuses stop electric current if it gets too high for the wiring.
Circuit breakers are more convenient than fuses. Once you unplug the excessive appliances, flip the breaker switch to turn the electricity on again. When a fuse blows, you have to replace. Even though less convenient and seldom installed in new homes, fuses still provide the most reliable and precise protection. This is why many expensive sensitive electronic devices use fuses instead of circuit breakers.
The newest circuit breakers are called arc fault circuit interrupters (AFCI). Even though the electric current does not get too high, arcing has a particular signature and an AFCI shuts off the electricity.
A ground fault circuit interrupter (GFCI) is similar to a circuit breaker in that it can be reset, but it is 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 is generally not enough to cause the electric current to spike and trip a circuit breaker. If the current from this slight short circuit passes through the nerves to your heart, it can be fatal.
GFGIs should be installed on all outdoor circuits or ones around 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 may flow through your body.