GFCI Electrical Outlets

We hear talk about safe electrical outlets that will trip the circuit breaker if there is a short circuit in the appliance we have plugged into it. Ok, what is a ground fault circuit interrupter (GFCI) outlet and how does it work. There are two types of GFCI used in houses, a GFCI circuit breaker that is installed in the electrical panel and the GFCI outlet where the circuit interrupter is built into the outlet. GFCI outlets are used more often that GFCI circuit breakers because the outlets are much less expensive than the GFCI circuit breakers.

A GFCI outlet protects people from electrical shock if there is a short circuit. It is much

different than a fuse. The function of a fuse is to protect a house from an electrical fire. A basic 110 volt electrical circuit consists of three wires; a black wire called the hot or load (sometime it is a red wire), a white wire that is the neutral, and a ground wire that is either plain bare copper or green. If the hot wire were to accidentally touch the neutral wire for some reason an incredible amount of current will flow through the circuit and start heating it up like one of the coils in a toaster. The fuse, or circuit breaker, heats up faster than the wire and the fuse burns out or the circuit breaker trips to the off position before the wire can start a fire. Short circuits can be caused by a variety of reasons such as a mouse chews through the wire insulation, a nail is driven through the wire while hanging a picture, or the vacuum cleaner sucks up a lamp cord and cuts it.

A GFCI outlet works in a more subtle way. When you look at a normal 120-volt outlet there are two vertical slots and a round hole centered below them. The left slot is slightly larger than the right. The left slot is called "neutral," the right slot is called "hot" and the hole below them is called "ground." If an appliance is working properly, all electricity that the appliances uses will flow from hot through the appliance and back to neutral. A GFCI monitors the amount of current flowing from hot to neutral. If there is an imbalance, or difference between them the GFCI outlet trips the circuit at the outlet. It is able to sense a mismatch as small as 4 - 5 milliamps, and it can react as quickly as 1/13 of a second.

For illustration purposes, say you are outside with your power saw and it is raining. You are standing on the ground, and since the saw is wet there is a path from the hot wire inside the saw through you to ground. If electricity flows from hot to ground through you, it could be fatal. The GFCI senses the current flowing through you because not all of the current is flowing from hot to neutral as it expects. Some of it is flowing through you to ground. As soon as the GFCI senses that, it trips the circuit and cuts off the electricity. The amount of current flowing through you to ground is very small, 5 milliamps, which you will not feel.

GFCI Electrical Outlets

GFCI Electrical Outlets