A GFCI (ground fault circuit interrupter) is a specialized electrical outlet that monitors the flow of electricity through a circuit. They are designed to protect us from hazards like shock, electrocution, and fires. If a GFCI detects discrepancies, such as when an electrical current is leaking out of the intended path (for example, into a human body), it will immediately shut off power to prevent severe injury or death.

Now considered an essential safety feature in modern electrical systems, these outlets are typically installed in high-risk areas where moisture or water is present, such as kitchens, bathrooms, garages, basements, and outdoor patios.

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There are three types of GFCI outlets:

1. Receptacle GFCIs: the traditional type of outlet, commonly installed in areas like bathrooms and kitchens.
2. GFCI circuit breakers: installed in the electrical panel of a building, they protect an entire circuit rather than just one outlet.
3. Portable GFCIs: they can be plugged into a regular outlet to add protection for a temporary circuit.

As their name suggests, GFCI outlets are equipped with a built-in circuit interrupter that senses differences between the hot and neutral wires in an electrical circuit. Under normal conditions, the amount of electricity flowing through the hot wire should match the amount returning through the neutral wire.

Electrical faults can occur in numerous ways. When water comes into contact with a live electrical component connected to a GFCI, it acts as a conductor that allows the current to escape along an unintended path, triggering the circuit interrupter to trip.

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If there is any discrepancy in the amount of current returning through the neutral wire (even as little as a few milliamps), the GFCI outlet detects the imbalance and cuts power to the circuit almost instantly, usually within 1/40th of a second. This rapid response prevents the possibility of severe electrical shocks.

Fortunately, you can test a GFCI without dropping a hair drier into a filled bathtub. In most cases, the outlet has separate Test and Reset buttons. Pressing the Test button simulates a fault condition to ensure the outlet is functioning correctly. A working outlet is usually indicated by a tiny orange or green LED on the fixture. You can then press the Reset button to restore power after testing.

While GFCI outlets offer reliable protection compared with standard outlets, they aren't meant for every type of electrical device. Some items should never be plugged into a GFCI, as they could malfunction or trip the circuit unnecessarily, leading to power disruptions or unsafe situations. Below is a list of devices not suited for GFCIs.

1. Devices with a "high inrush" current

Appliances like refrigerators, freezers, air conditioner units, and power tools require a serious initial burst of electricity when powered on. Yes, even though refrigerators are almost always located in kitchens, the counterintuitive truth is that they can cause the GFCI to trip because of the large initial surge of current, even if there is no actual fault. This is known as "nuisance tripping," and it is aptly named. Don't risk spoiling a fridge full of foods by plugging it into a GFCI.

2. Outdoor equipment

Similarly, outdoor equipment such as electric lawnmowers or pressure washers should ideally be plugged into a dedicated outdoor outlet. While GFCIs are designed for outdoor use to reduce shock hazards, high-powered equipment can cause the GFCI to trip if it draws too much current at one time. 

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3. High-powered appliances

Appliances that use significant power, such as space heaters, microwave ovens, or vacuum cleaners, can cause a GFCI outlet to trip, especially if they are used on a circuit with high loads. These appliances could create a situation where the GFCI trips frequently (more nuisance tripping).

4. Surge protectors or power strips

Some power strips and surge protectors, particularly those with multiple plugs for high-powered devices, could cause the GFCI outlet to trip due to the combined electrical load. A sudden power surge or imbalance could cause the GFCI to trip unexpectedly, defeating the GFCI outlet's purpose and causing repeated circuit tripping.

5. Sump pumps

While the National Electrical Code (NEC) specifically mandates that new construction includes GFCIs in basements, there is another ironic exclusion among the list: sump pumps. Sump pumps are designed to prevent flooding, but if the GFCI trips and cuts off its power, your basement might end up under several inches of water.

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6. Medical equipment

Medical equipment like CPAP machines and oxygen concentrators require continuous, uninterrupted power, so we advise plugging these vital devices into conventional outlets, not GFCIs. Some medical devices have sensitive circuitry, and the GFCI may trip unnecessarily, causing a loss of power to life-sustaining equipment.

You may have noticed the common denominator among all these scenarios: any device requiring a constant power supply should be kept away from GFCIs to avoid unnecessary tripping.

GFCIs are a critical safety feature for areas in which electronics are likely to be exposed to moisture, including wet bar areas, laundry rooms, and outdoor spaces. A simple fault, such as a chafed appliance cord touching a metal pipe, or water exposure to a heating element, could result in catastrophe without a GFCI outlet in place.

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The electricians I've consulted emphasize the importance of addressing why the outlet tripped. When a GFCI trips, it means that it detects a potential ground fault or leakage of current. The device is doing its job! Ignoring the issue or resetting the outlet without inspecting the cause is a way to invite a housefire, serious injuries, or even fatal electric shocks.

GFCI is sometimes shortened to "GFI" (because it's easier on the tongue), and it can be considered one of the world's first smart home devices. These simple but effective outlets are an essential safety feature in our living spaces, workplaces, and public buildings because they can stop electrical accidents before they happen. For added safety, be aware and informed about what you plug into one.