GFCI stands for Ground Fault Circuit Interrupter while AFCI stands for Arc Fault Circuit Interrupter. Ground faults pose a high risk of electrical shock, and arc faults can easily start a fire, which makes GFCI and AFCI receptacles critical to safety. Given their protective characteristics, the National Electrical Code NFPA 70 made both types of outlets mandatory for residential applications.
In terms of external appearance, these special sockets are characterized by TEST and RESET buttons on their surface. With the TEST button you can check whether the protection mechanism is working correctly, and the RESET button is used to reestablish the protection after it has tripped in response to a fault. Unlike regular circuit breakers, which are primarily intended to protect wiring and equipment, GFCIs and AFCIs are intended to protect building occupants.
This article provides an overview of GFCIs, AFCIs, and their applications. However, it is intended to be informative and not to be used in place of the NEC when specifying an actual installation.
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How GFCI and AFCI outlets work
GFCI and AFCI outlets respond to disturbances in electrical current, turning off when dangerous conditions are detected. These protection devices are characterized by a much faster response than circuit breakers and fuses.
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OUTPUT TYPE |
OPERATION |
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GFCI |
Under normal conditions, when there is no earth fault, the current is equal in the energized conductor and the neutral conductor. A GFCI measures the difference between both currents – any non-zero value indicates a current leak and the GFCI trips. GFCIs have an extremely fast response and can disconnect the power supply in just 1/40th of a second (25 milliseconds). The RESET button appears when a GFCI trips and can be pressed to reestablish the connection after correcting the fault. |
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AFCI |
An AFCI responds to the current distortions that characterize dangerous electrical arcs, especially those capable of starting a fire. In other words, AFCIs can detect changes in waveform and disconnect the power supply accordingly. Some electrical arcs occur normally and are not dangerous, and two examples are sparks when flipping a switch or unplugging a plug. AFCIs are designed not to trip when these brief electrical arcs occur. |
When should a GFCI outlet be used?
In general, the NEC requires GFCIs in damp or wet locations to protect occupants from electrical shock. The following are some of the most critical applications:
- Bathrooms
- Kitchens
- Laundry
- Spa and pool areas, including underwater pool lights
- Crawlspaces below ground level and unfinished areas
- External locations, garages and outbuildings
GFCIs are available as receptacles and circuit breakers. A GFCI circuit breaker protects the entire circuit, while a GFCI receptacle protects loads connected to itself and any other receptacles connected downstream on the same circuit. In other words, if you have many receptacles on the same circuit and the first one connected is a GFCI, they will all be protected.
When should an AFCI outlet be used?
Because AFCIs contribute to fire protection, the NEC requires their use in all single-phase branch circuits rated at 15 amps and 20 amps. Previously, AFCI protection was only required for certain areas, such as bedrooms, dining rooms and living rooms, but newer versions of the electrical code have changed the requirement to include the entire dwelling unit. Another difference is that the previous requirement was only for receptacles, but AFCI protection now extends to all circuits that meet the conditions set forth in the NEC.
Because AFCI protection is now required for the entire dwelling unit, AFCI breakers in the main electrical panel are typically more effective than individual outlets. If you have an older property and want to update your AFCI protection to meet the latest versions of the NEC, a professional assessment is highly recommended.
How to Test GFCI and AFCI Outlets
GFCI and AFCI outlets are designed for simple testing thanks to their characteristic TEST and RESET buttons. The testing procedure is very simple:
- Press the RESET button if the device is disarmed or new.
- Plug a lamp into the socket and make sure it is turned on.
- When you press the TEST button, the lamp should go out. If the bulb stays on, there is a problem and you should contact a qualified electrician to have the GFCI or AFCI checked.
- When pressing the RESET button, the lamp should light up again.
It is highly recommended to test your GFCIs and AFCIs at regular intervals, for example once a month. Note that some are located in areas of your home that are not used frequently, such as guest rooms and outbuildings – make sure these are tested too.
Conclusion
GFCIs and AFCIs make your home safer by reducing the risk of electrical shock and helping to prevent fires. However, this only applies if your electrical installation meets the NEC requirements in the first place. Installations in older buildings, such as pre-war apartments, are more likely to have electrical safety issues since they were built under less stringent electrical codes.
If you want to improve the electrical safety of your property, the first step is a professional assessment of your current installation. There has been a notable reduction in the number of victims due to electrocution and fire since GFCIs and AFCIs became mandatory by electrical codes.
