What is a GFCI and why do I need them in some places?

A GFCI (Ground Fault Circuit interrupter) is a device that is designed to disconnect power to a circuit or a portion of a circuit when an imbalance of current flow is detected at a pre-determined level according to the type of GFCI device. These devices are typically available in a breaker type style and a receptacle type style.

Typically, the current is measured on two different conductors, the hot (ungrounded conductor) and neutral (grounded conductor). In other instances, the current would be measured between two different hot conductors. The purpose of all this measuring taking place is to make sure that all the current that is leaving the source is also returning to the source on the wires and not through a person or another path. (Source meaning the transformer at your home or place of business).

So the reason that these devices are required to be used to protect receptacles and other outlets is due to the location in which these points are. These locations are areas like kitchens, bathrooms, laundry areas, outdoors, garages, etc. It’s usually perceived that a GFCI would be needed if an area gets wet, but its more of the fact that these area have conductive surfaces that do or are highly likely to connect to part of the transformers we mentioned earlier. Water piping, concrete, and the earth itself are examples of non-electrical components that are inherently part of the electrical system on the structure.

So to sum it up, GFCI recognize when current is not flowing on its intended path and could be going through another path that could have a person in-line with it. Thus the GFCI would disconnect power at first notice of this problem and greatly increasing the chances of saving a life.