Ground Fault Circuit Interrupters Explained

When does a ground fault occur?

What is a GFCI Receptacle?

A ground fault occurs whenever electricity escapes the confines of the wiring in a light fixture, appliance, or power tool and takes an alternative unintended path to the ground. When that alternative path is through water or a human, the results can be fatal.

Did you Know That...

About 200 people in the United States die from ground faults each year. This number accounts for two-thirds of all electrocutions that occur in homes every year.

How to eliminate ground fault accidents?


In order to eliminate the possibility of these ground fault accidents, Charles Dalziel, an electrical engineering professor at the University of California, invented the ground-fault circuit interrupter (GFCI) in 1961.

A Ground Fault Circuit Interrupter, better known as a GFCI or GFI, works by measuring the electrical current leaving the hot side of a power source and comparing it to the current of the returning neutral side. If the currents are unequal, this means that a part of the current has been misguided down an alternative path. This is where the GFCI comes in and works its magic.

Shop all GFCI Outlets

How does a ground fault circuit interrupter work?

The GFCI detects that the current is flowing along the wrong path and immediately shuts off the power. As they are able to sense a current imbalance as small as 4 or 5 milli-amps, GFCI receptacles can also react as fast as one-thirtieth of a second. Although they are primarily designed to prevent electric shock, they can also prevent some fires. 

Picture this!

It is a rainy day and you are working outside with a power saw. You are standing on the ground and the power saw is inevitably becoming wet from the rain, creating a path from the hot wire inside the saw through you to the ground. If the electricity in use flows through you from the hot wire to the ground, the possible resulting electrical shock could be fatal. However, if you have a GFCI receptacle, the current’s failure to flow from hot to neutral would be detected and the electricity would be immediately shut off to prevent the flow from flowing through you and thus avoid the deadly ground fault.

What are the different types of GFCI receptacles?

The GFCI Receptacle is very similar to a common wall receptacle, also known as an outlet. There are several different types, all of which ensure a specific type of extra protection against ground faults. Learn about the difference between a GFCI receptacle & a GFI outlet. 

Basic GFCI

Basic GFCI
The basic GFCI receptacles set the starting point for GFCI ground fault circuit interrupter outlets. They provide the basic protection needed for exposed outlets. It simply does its job by monitoring the current flowing through a circuit and interrupting this current if it differs by as little as .006 amperes from the returning current. Although it does not have specific special features, it still offers great protection against ground faults.

Tamper-Resistant GFCI

Tamper Resistant GFCI
Tamper-Resistant GFCI receptacles have spring-loaded shutters that only open when a proper two or three bladed plug is inserted into the socket. They can also be easily identified with the marking TR imprinted on the outlet. They are designed to prevent foreign objects (such as keys, hairpins, or nails) from entering into the electrical socket. *Please Note* All 15- and 20-amp, 125 volt residential GFCI receptacles must be of the classified Tamper-Resistant GFCI.

Weather-Resistant GFCI

Weather resistant gfci
Weather-Resistant GFCI outlets provide an additional level of protection in damp environments. Built with more durable housing and corrosion-resistant metal components, Weather-Resistant GFCIs resist both UV light and extreme temperatures. Therefore, these are ideal for protecting outdoor electrical devices.

Tamper-Resistant/Weather-Resistant GFCI

Tamper Resistant/Weather Resistant GFCI
Tamper-Resistant/Weather-Resistant types combine the characteristics of both the tamper resistant and weather-resistant GFCI receptacles. With the protective features of the tamper resistant type, in which it prevents foreign objects from entering into the socket, and the additional protection that the weather-resistant type offers in wet environments, this combination GFCI provides the ultimate protection of all the GFCI models.

Blank Face GFCI

Blank Face GFCI
Since GFCI protection is required near pools, spas, and hot tubs, Blank Face GFCI are specially designed for these applications. The Blank Face includes lockout action that blocks the reset button if GFCI protection has been compromised. This reduces the possibility of users believing that their reset GFCI is providing protection when it is not.

What are the different types of GFCI amp availability?

Along with the various types of receptacles, there are also different GFCI amps available to choose from. Amp is used to measure electrical current, so the different amps correlate with the current that flows between the outlet and the electrical device

GFCI Amperage

15-amp GFCI: Usually found in a residential home, 15-amp outlets are configured with NEMA 5-15R Connector

20-amp GFCI: These higher-amp GFCIs are often installed in offices and commercial buildings. However, 20-amp outlets are also essential in residential homes where high-current devices, such as kitchen appliances, are used.

How to test your GFCI outlet?

Testing Your GFCI

GFCI Receptacles contain both a reset button and a test button. When an electrical current problem is detected, they can manually be reset by simply pushing the red reset button in the middle of the receptacle. Along with the reset button, there is also a test button that can be used to verify that the outlet works properly.

To test the outlet, plug in a light or some other appliance and simply press the test button. If it is working correctly, you should hear a snap sound that trips the outlet and cuts off the power, hence turning off the light or other appliance.

You can also use a voltage test to confirm that the outlet did turn off the power and works correctly. It is suggested to test your GFCI once a month to ensure that the outlet is providing full protection for your household.

The National Electric Code (NEC)

Over the years, the National Electrical Code (NEC) has expanded the requirements for GFCI to protect anyone who uses electricity. Originally, they were only required in areas where there was temporary open wiring at construction sites and in dwelling unit bathrooms.

More recently, however, the NEC has expanded the GFCI protection requirements to many other areas including fountains and swimming pools, commercial occupancies, and temporary installations. Be sure to stay up to date with the National Electrical Code (NEC) to protect lives and property from electrical hazards by checking up on the newest NEC yearly!

Frequently Asked Questions

Where should I install my GFCI?

GFCI receptacles are designed to prevent ground faults which cause electric shocks and fires due to incorrect current path flow. One of the common mistaken paths the electrical current may take is water. Therefore, they should be installed in any areas where water may be present, including: bathrooms, garages, kitchens, unfinished basements, wet bar sinks, outdoors, and laundry & utility sinks.

Why should I buy a Tamper-Resistant GFCI?

Tamper-Resistant GFCI receptacles feature a built-in safety shutter system to prevent the insertion of foreign objects (such as keys, hairpins, or nails) into the receptacle opening. This is especially convenient for homes where children may be. If a child attempts to insert something into the receptacle, the tamper-resistant outlet will detect that it is not a proper two or three bladed plug and will not allow the insertion. With this safety feature, injury from electric shock will be avoided.

Why should I buy a Weather-Resistant GFCI?

Ideal for outdoor use, weather-resistant GFCIs resist both UV light and extreme temperatures. They provide protection against the unpredictable weather, such as rain, snow, ice, moisture, and humidity, which may create ground faults.

Can I plug my refrigerator into a GFCI?

No, you should not plug your refrigerator or any other moisture-driven appliance, such as a wash machine, into a GFCI. A receptacle would detect the water from the moisture and trip up the circuit, and unnecessarily power off the appliance.

How do I identify the different GFCI receptacles just by looking at them?

GFCI receptacles are easily distinguished. The tamper-resistant type are marked with a TR right above the red reset button and the black tester button on the GFCI receptacle. The weather-resistant types are marked in the same way, but with a WR directly above the reset and tester button.

Stay Connected!

If you have any blog topics you would like to read about, leave your suggestions in the comment section below!

Be sure to keep up with our Twitter and Facebook feeds for blog updates!

Wattson Lumen
Wattson Lumen

As a Georgia-born, amped up electrical supplies enthusiast, international Popstar, and unqualified lifequard, Wattson prefers to lighten your day with humor and led lights (Just don't ask him to jump in if you're drowning).

Need Assistance?