Given the similarity of the names of the systems, many people struggle to understand the differences between GFCI and AFCI outlets. This understandable issue also sometimes leads to the mistaken notion that these critical safety systems are interchangeable. Homeowners need to know how GFCI and AFCI outlets work, what their differences are, and where to use each.
What Are GFCI and AFCI Outlets?
GFCI stands for ground-fault circuit interrupter, and AFCI stands for arc-fault circuit interrupter. A circuit interrupter is an electrical safety system that intervenes to turn off a circuit in case there’s a fault state. However, GFCI and AFCI systems operate quite differently because of the fault states they target.
How a GFCI Works
During normal operation, an electrical outlet should have a relatively stable flow of current between the hot and neutral wires. These are the two wires that virtually every electrical device in your house connects to through the two vertical prongs on the plug.
A ground fault occurs when electricity leaks out of the circuit and tries to find its way to the ground. The classic example of this is a hair dryer plugged into an outlet near a bathroom sink. Water can come into contact with the outlet, the plug, or even the hair dryer. When this happens, the electrical current will try to find a path to the ground. That path could go through a person, leading to electrocution.
When a GFCI system detects a slight fluctuation in the current, it shuts off the electricity in that circuit. The process takes a fraction of a second. It also occurs at a fluctuation level in milliamps that’s well below what would normally stop a person’s heart.
How an AFCI Works
An arc-fault circuit interrupter monitors the waveform of the electrical current for signs of unexpected arcing. AFCIs are modern systems that use microprocessors to evaluate what’s happening in the current. Notably, AFCIs are very good at detecting the difference between a small spark due to normal operation and something dangerous. For example, an AFCI usually has no trouble letting the brushes inside a drill’s motor operate, even though this technically is a form of arcing.
Fire prevention is the main goal of an AFCI. The classic use case for an AFCI is to protect the wiring inside a living room wall. People frequently put nails and screws into living room walls, and there’s a danger each time of damaging an electrical wire. A damaged wire can sit behind the wall, heating up, creating the conditions for a fire.
AFCIs are designed to monitor for irregular waveforms. If there’s a damaged wire inside the wall somewhere along the circuit, it will make the waveform unstable. The microprocessor notices the electrical instability and cuts the circuit for safety.
Where to Use Each
GFCIs and AFCIs tend to end up connected to outlets in fairly different living spaces. This is because they protect against relatively different electrical safety problems.
Where to Use GFCIs
You will mostly see GFCIs in spaces where electricity has a high risk of coming into contact with water. One reason most people are already familiar with GFCI outlets is that they are common safety features in bathrooms and kitchens. This is particularly common near high-use countertops, such as spaces for food prep or personal care.
GFCIs are required by the National Electrical Code for all kitchen and bathroom receptacles. The NEC also requires them within 6 feet of any sink, so this includes most laundry rooms and many utility rooms. If there are outlets in a basement, the outlets need to be GFCIs. All outdoor outlets require GFCIs, too. Similarly, all outlets in a garage must have a GFCI. If your home has outlets in a crawlspace, GFCI outlets should also be present there.
Specific appliances should also connect to outlets that have GFCIs. These include dishwashers, electric ranges, wall-mounted ovens, clothes dryers, and microwaves.
Where to Use AFCIs
AFCIs belong in what are fundamentally living spaces. Family rooms, dining rooms, kitchens, and living rooms. You will also want to add an AFCI to any laundry room. The same goes for bedrooms, closets, hallways, and recreation rooms. These tend to be the places where people hang pictures and regularly plug in and unplug devices.
Dual-Function Systems
You may notice some overlap between the areas that require GFCIs and AFCIs, particularly kitchens and laundry rooms. The good news is that dual-function systems are available to provide ground- and arc-fault circuit interruption. Dual-function systems simplify compliance and wiring.
Can You Just Rely on Grounding and Circuit Breakers?
If you’re building a new house or performing certain renovations, the electrical code requires compliant GFCI and AFCI solutions. Even if your house went up before the current requirements, it is a good idea to use GFCIs and AFCIs rather than relying on just grounding and circuit breakers. Both grounds and circuit breakers address overcurrent, which is a fundamentally different problem.
The big reason you can’t depend on grounding and circuit breakers is that they aren’t built for the same purposes as GFCIs and AFCIs. Suppose there’s a damaged wire inside a wall. That damage might draw less than 5 amps. For reference, the lowest-rated circuit breaker in a typical electrical panel is 15 amps. Consequently, the damage simply won’t trip the breaker.
Now, revisit the hair dryer scenario from the GFCI section. Your home’s grounding system just doesn’t care that there’s a human inside the circuit. Even if the completed path drew away some of the power, what current would go through a person is still more than the couple of hundred milliamps needed to stop their heart.
Also, bear in mind that a GFCI doesn’t provide the overcurrent protection necessary to serve as a proper circuit breaker. The GFCI only detects when there’s a problem between the hot and neutral wires. If a 30-amp current moves stably through a 15-amp circuit with a GFCI, then the GFCI doesn’t trip. The electricity just goes down the return path like normal.
John Henry's Plumbing, Heating, Air, and Electrical serves Lincoln, NE, Omaha, and the surrounding areas. In business since 1996, our company offers upfront pricing with no hidden charges. We have a 4.8 rating across more than 5,000 Google reviews. The BBB has even named us an Integrity Award winner.
We are a family-owned and licensed business. If you have questions about your home’s electrical system, we perform inspections. Customers can also ask us to handle emergencies 24/7.
If you have concerns about GFCIs or AFCIs in your Lincoln home’s electrical system, contact John Henry's Plumbing, Heating, Air, and Electrical today.
