Why are GFCI outlets so important?
Why are GFCI outlets so important?
When I was growing up, GFCI outlets didn’t exist. Why are they now required in kitchens, bathrooms, and other damp locations?
How Electricity Works
Household electrical circuits for 120 volts have two conductors: a “hot” wire and a “neutral” wire. You can think of the “hot” wire as the source of the electrical energy, and the “neutral” wire as the wire that returns the electricity to the electric company or the generator. A light bulb (or an electric motor, or a toaster) connected to the hot and the neutral wires completes the path for the electricity to flow so that the light bulb can use the electricity to provide the power to light up the bulb. There is electrical insulation around the wires and the switches and the light bulb itself (the glass of the bulb is an electrical insulator for the wires inside) to make sure the electricity goes only where it is supposed to go.
I become the Conductor
Many things conduct electricity. Copper wires are good conductors of electricity. But tap water, metal plumbing pipes, and the human body also conduct electricity. If I touch a hair dryer with one hand, and the lavatory handle with their other hand, then it is possible that the water can touch an electrical wire inside the dryer, and the electricity can flow from the “hot” wire in the dryer, through the water, through me, through the plumbing pipes, and through the ground itself back to the electric company or the generator. I’m providing the path for the electricity. I’ll feel a very unpleasant tingling or jolt. I can be burned by the electrical shock, and worst case I could die. This situation is called a “ground fault.”
The GFCI outlet stops the electricity flow through me
GFCI stands for “Ground Fault Circuit Interrupter”. A GFCI outlet detects that the electricity between the “hot” wire and the “neutral” wire are not balanced, and so the GFCI will “trip” and cut off the electricity. This prevents me from being injured if I become the accidental connection between the hot wire and the ground.
Use GFCIs near water
GFCI outlets should be used in places where water is likely to be present: kitchens, bathrooms, laundry rooms, unfinished basements, and outside areas.
One outlet may protect other outlets
One GFCI outlet can be used to protect other outlets as well, depending on how the outlets are wired together. One GFCI outlet in a kitchen often protects other outlets in the kitchen. One GFCI outlet in a bathroom often protects other outlets in the same room or even in other bathrooms. GFCI circuit breakers, installed in the main electrical panel or a distribution panel, can also fill the same purpose.
What about the ground wire?
Modern electrical wiring in a home includes a ground wire as well as the hot wire and the neutral wire. This ground wire, like a GFCI outlet, is there to provide protection against electricity flowing in the wrong place. If the hot wire in an appliance accidentally touches the metal casing of the appliance (with no electrical insulation in between), then the metal casing becomes electrified. If I touch the metal I could get shocked. By adding a ground wire that is connected to the metal casing, the electricity from the hot wire will flow through the metal casing, through the ground wire, and back to the electric company or generator. The electrical current in this situation will be much larger than the appliance normally uses, and the circuit breaker (or fuse) at the main panel or distribution panel will trip, cutting off the electricity to the appliance. This protects me from getting shocked – it turns off the electricity to the appliance before I ever touch the dangerous electrified metal casing.
The ground wire is also helpful for sensitive electronic equipment – it provides a path to ground independent of the neutral wire, so that all the equipment is at the same electrical potential as each other.
GFCI outlets can protect when there is no ground wire
Older houses often do not have ground wires on at least some of their outlets. These outlets can be made safe for humans by installing a GFCI outlet (or circuit breaker). Even though no ground wire is present, the GFCI outlet will protect the person. In this arrangement, the outlet should be marked “no equipment ground” to show that though the outlet is safe for humans, it may not do what is needed for some equipment.
Three prong outlet on two wire cable
Sometimes homeowners will install a three-prong outlet in an older home where no ground wire is present. This should never be done because it provides a false sense of security. Instead, install a GFCI outlet. In homes with metal conduit and metal electrical boxes, the metal conduit and the box acts as the ground wire, no separate ground wire is needed.
Bootleg grounds
Sometimes a homeowner will do an even more dangerous thing. They will connect both the ground screw of the outlet and the neutral screw of the outlet to the same neutral wire. Some people call this a “bootleg ground”. In this case, some of the electricity to run the appliance could be flowing through the metal casing of the appliance. A person could be shocked by touching the appliance. Again, install a GFCI outlet instead.
Use GFCIs for safety
Bottom line: for your own safety and the safety of your family, make sure that outlets in the kitchen, bathroom, laundry room, garage, outside, or any damp area are GFCI protected!
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