Circuit Interrupter Makes Itself a Welcome Intrusion

A ground-fault circuit interrupter installed in household branch circuits could prevent many of the more than 200 electrocutions and thousands of electric shocks and burns that occur in homes each year, according to the U.S. Consumer Product Safety Commission.

This, of course, assumes that the device has been properly installed.

The GFCI is an electrical circuit built into a device such as a circuit breaker or an outlet receptacle. It is designed to protect people from severe or fatal electric shocks.

It does this by switching off the power to the device in about one-fortieth of a second. This is fast enough to prevent injury to anyone in good health.

The GFCI is activated when the circuit senses an imbalance in the electrical current between the hot and neutral line, which is as small as 5 milliamperes (five-thousandths of an ampere). At 50 milliamperes, it takes only 3 1/2 seconds for a person’s pulse to stop.

An imbalance in the electrical current occurs when there is an unintentional electrical path between the current and a grounded surface. This is referred to as a ground fault. Without a GFCI, if a person provides the path to ground, he/she could be severely shocked, burned or electrocuted.

A GFCI outlet receptacle cannot do the job if it is not properly installed. With a regular duplex outlet receptacle, there are two terminals for the hot wire and two terminals for the neutral wire. It doesn’t matter which hot terminal you connect the hot wire to. The same holds true for the neutral wire. It’s a different story, however, with a GFCI receptacle.

Markings on the back of GFCI outlets indicate “line” and “load.” The wires from the circuit breaker or fuse panel box must be connected to their respective line terminal screws. If instead they are connected to the load terminals, the GFCI outlet will not provide protection against a shock hazard.

Manufacturers recommend that GFCIs be checked once a month.