WHAT IS A GROUND FAULT CIRCUIT INTERRUPTER?
These special electrical devices (GFCI’s) shut the power off to a circuit when as little as .005 amp is leaking. Under normal circumstances, the current flowing through a circuit is the same at any point. That is, if there is a 5 amp flowing through the white wire coming back.
If there is a flaw in the system, some electricity may be flowing to a dangerous spot, but there may not be enough flowing to blow a fuse or trip a breaker. For example, if the electrical insulation in an appliance is defective, there may be a small current leaking to the case of the appliance.
Under normal circumstances, this would be detected. However, this can become very dangerous if a person (particularly one who is not well insulated with rubber gloves/shoes) touches the case. A potentially fatal electrical current can flow through the person to ground. This creates an electrical shock hazard.
A GFCI prevents this from happening by comparing the electricity going out through the black wire against that coming in through the white wire. If the difference is more than .005 amp, the system will shut off.
Sometimes it is difficult to know how many electrical components in a house are protected by a GFCI. It is possible to have several electrical outlets all protected by one GFCI.
WHERE ARE GFCI’S NEEDED?
These devices may be incorporated into a circuit breaker, or into an electrical outlet. Most codes require their use on outdoor outlets and bathroom outlets. They do make sense wherever water and electricity may be brought close together. For example, GFCI’s are also required on swimming pool and whirlpool electrical systems.