How a GFCI Works - The Definitive Guide

Updated: Jan 19


How do those GFCI receptacles work in your bathroom? They trip sometimes and I don't understand how they work and what they are even supposed to do. Here we will look at the basics of what a GFCI receptacle or device does and explain the difference between line and load.





What Does a GFCI do Exactly?

Well to put it into the most simplest words possible, a GFCI(Ground Fault Circuit Interrupter) monitors the amount of current flowing from hot to neutral. If there is any difference between the two points, it trips the circuit. GFCI are extremely sensitive, noticing even small differences as small as 4 or 5 milliamps. They react quite quick and can trip in as fast as one-thirtieth of a second. You more than likely will receive a small shock if unsafe conditions happen, but it wont kill you. You will live to tell the tale, as they say.


What type of Protection Does This Provide

This can be extremely useful in preventing electrical injury to people using those devices, by protecting against faulty wiring, failed appliances, and electric shock. The reason that they are commonplace in bathrooms is that a bathroom has a lot of uses for water. Someone could accidentally drop and electrical device in said water and cause a short circuit. Instead of injuring the person, it will cut power almost immediately, possibly saving a life. Did you know that it only takes 5-9 milliamps of current to make it so that you cannot let go of an object that is live. GFCIs are proven time and time again that they can save lives.


What Do GFCI Devices Look Like?

GFCI Receptacle

This is a picture of what a GFCI breaker looks like.(above)They also come in other forms such as appearing in receptacles, dead fronts(a receptacle with no outlets on the front just the test and reset buttons.) and are integrated into things like power bars, and plug in devices for vehicle block heaters.

They have many uses as these little devices save people and equipment from damage. As time goes on, we see more and more of electrical items building GFCI into them as a result. GFCIs are here to stay and have a strong future in the world that we live in


What is the Difference between Line and Load?


A GFCI outlet on the back has two sets of wiring terminals, on it. The top is labeled ‘line’ and the bottom is labelled ‘load.’ The ‘line’ section refers to the wires that are upstream from the device providing power to the outlet. The ‘load’ side refers to anything that is downstream from the GFCI outlet that provides electric shock protection to.

To hook up a GFCI outlet, connect the black and white wires that are feeding the plug on the line terminals and if there are devices that come after the GFCI plug, connect the wires up to the load side. Finally, connect the ground wire to the green screw on the GFCI plug.

To test a GFCI outlet to ensure everything was hooked up properly, on the front face of the has a test button and a reset button. By pressing the test button the GFCI will turn off and do its job. Anything downstream from the outlet will turn off as well. By pressing the reset button, the outlet will turn on again, ready for to do its job.

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