GFCI (Ground Fault Circuit Interrupter) outlets are receptacles that are designed to prevent lethal shock.
How do they work?
Outlets (receptacles) have three wires. Two of the wires conduct electrical current, the other is an equipment grounding wire. The first wire, usually black or red, brings the electricity to the outlet. This wire is usually referred to as the "hot" wire. The second wire returns the electricity to the electrical panel and ultimately the ground (earth), therefore it is technically the "grounded conductor", but it is commonly referred to as the "neutral" wire. The grounded conductor should always be white. If you touch the "hot" ungrounded wire and you're in contact with the ground you’ll complete the circuit and you’ll get a shock. The technical name for this event is a ”ground fault”, because current is getting back to the ground in a way that it shouldn’t - it’s using your body.
To prevent lethal shock through ground faults, special outlets called Ground Fault Circuit Interrupters, or GFCIs, are required in homes. GFCIs constantly monitor the amount of electricity flowing through it. If a GFCI device detects a ground fault, it will shut off, or “interrupt” current within a fraction of a second. It won’t be fast enough to prevent a painful shock, but it’s enough to keep you from getting killed.
GFCI devices were first required near swimming pools in 1971. Today they’re required in areas where lethal shocks are most likely to happen, usually in areas that are wet and have good contact with the earth. These areas include the exterior, garages, kitchens, bathrooms, unfinished basements, crawl spaces, and outlets within 6′ of laundry sinks, utility sinks, and wet bar sinks, among other places.
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