GFCIEver seen an outlet that has a reset button on it and wondered what was going on there? You’re looking at a ground-fault circuit interrupter and it’s there to protect people from being electrically shocked.

Remind you of a fuse? They’re somewhat similar, but not exactly. The main purpose of a fuse is to protect a larger electrical system (like a home) from undergoing a dangerous fault that sets off an electrical fire. A fuse uses a small wire to carry current so that if the current exceeds a certain amperage that surpasses the amperage for which the system was built and begins to heat the wire past a particular point, the wire will melt and the overheating circuit will break before any electrical fires can happen. That’s very helpful, because mundane household activities like vacuuming and hanging pictures can damage a circuit in such a way that huge amounts of current being to flow in places that aren’t built to withstand it, and that means the wires holding that current will start to heat up like the wires in your toaster. The fuse heats up faster than the wire and burns out before the wire can start a fire.

So that’s the point of the fuse, but a GFCI (which stands for ground-fault circuit interrupter) is slightly different. It’s more subtle and is built right into the standard American 120-volt outlet, which if you remember, has two vertical slots and then a round hole centered below them. The slightly larger left slot is called “neutral” and the slightly smaller right slot is called “hot” and the hole in the bottom center is called the “ground”. A properly functioning appliance will cause electricity to flow from the hot slot to the neutral slot.

The ground-fault circuit interruptor monitors the amount of current flowing from hot to neutral for imbalance and trips the circuit if something isn’t going the way it should be. It’s able to sense an imbalance as small as one between 4 to 5 milliamps and reacts within one-thirtieth of a second.

GFCI worksThis makes using appliances much safer. Say you’re using your power drill on a cold, wet day and you are standing on the wet ground outside your house. The drill is a little wet, making it possible for there to be a path from the hot wire inside the drill through you to ground. You don’t want the electricity to flow from the hot to ground through you because that could really mess you up; luckily the GFCI can sense the current flowing through you because not all of the current is flowing from hot to neutral, as would be expected. Once it senses that a second circuit is causing there to be less electricity flowing to neutral than expected, it trips the circuit and cuts off the electricity.

So say this happens while you’re using your hair dryer or something and you identify the unsafe aspect of what you were doing and fix it; how do you go back to using that outlet? Just reset it with the other button, it will reconnect the circuit and make it possible for you to use appliances plugged into that outlet again.

Leave a Reply