GFCI vs AFCI Devices

Ground fault circuit interrupters and arc fault circuit interrupters sound as though they’re very similar, but their functions and purposes are very different.

The primary purpose of ground fault circuit interrupters is to protect people from electrical shock. Arc fault circuit interrupters are intended to limit the possibility of an electrical fire caused by an arc. The way each device functions is also very different.

GFCI Devices

Ground fault devices compare the current in the ungrounded (black) and grounded (white) conductors. If there is a difference over 5 milliamperes (5ma) between the conductors, the device shuts off power. The difference is caused by current leaking out of the circuit to ground, a ground fault. The fault must be removed before the GFCI will reset.

The electrical circuitry is simple for GFCI devices. The two conductors are passed through a coil of wire (a toroid). The difference in current induces voltage in the toroid, which activates a trip mechanism. This circuit design is universal for the GFCI devices; all manufacturers’ GFCI devices trip this way.

Ground fault circuitry can be built into receptacles or circuit breakers. GFCI devices can become defective, which is why they have always had test and reset buttons on the face of the receptacles and test buttons on the breakers. Since around 2016, GFCI receptacles have had self-test circuitry built into them. These newer receptacles test themselves every 3 seconds and shut off if they fail the self-test. Circuit breakers do not have the self-test feature built into them and must be tested manually per the manufacturer’s instructions, usually monthly. GFCI receptacles now provide better protection than the breakers.

GFCI devices could become defective and still provide power. Unless someone used the test buttons or a GFCI tester, the defective device would remain in service. Newer devices should not provide power when they are defective. They should not reset when the reset button is pushed—whether after the test button is pushed, a fault is induced by a tester, or a fault is detected by the receptacle self-test. The GFCI will also not reset if there is no power to the device. Indicator lights on newer devices will show if a device is tripped and also may indicate if it has power.

AFCI Devices

Arc devices have much more sophisticated circuitry. The arc detection circuitry has been developed over the last 20 years and is complex. The earliest devices would only detect series arcs, or arcs that were directly in the circuit. The next step was to detect parallel arcs—arcs that occurred between the ungrounded and grounded conductors. Now all AFCI devices in residential construction are required to detect both series and parallel arcs.

The circuitry is required to distinguish between arcs that occur in normal operation of some devices, especially in motors like fans and vacuum cleaners, and arcs that occur as faults and need to have the power shut down. The different manufacturers have all developed proprietary circuitry to achieve these results. The earliest series type AFCI devices were very likely to have nuisance trip problems.

There are AFCI breakers and AFCI receptacles. The breakers are just about universal in new construction. I have never seen an AFCI receptacle installed in a new house.

Since AFCI devices are protecting against arcing, if an AFCI receptacle is installed, the circuit feeding the receptacle isn’t protected by the device. Code requires the conductors feeding an AFCI receptacle be protected by flexible or solid metal conduit.

Since the breakers protect the wire right from the panel, no protection is necessary for the conductors. It is much easier to install an AFCI breaker than to install a protected feeder to an AFCI receptacle. If a circuit is extended or a receptacle replaced, some jurisdictions may require anything added to an existing building to be up to current standards, and an AFCI receptacle may need to be installed.

Required Locations

Ground fault receptacle protection is required where the possibility of an electrical shock to people is high, such as near water or in electrically conductive areas. Bathrooms, kitchen counters, within 6 feet of any sink, garages, unfinished basements, laundry rooms, and all exterior locations. Receptacles near any body of water, such as tubs, whirlpools, spas, pools, and saunas, need GFCI protection usually within 6 feet. Some locations like pools and pool equipment may have additional requirements.

The electrical code began requiring GFCI protection in the mid-’70s and has expanded through the years. The adoption of GFCI requirements is fairly uniform through most jurisdictions, though the time frame for adoption varies.

In my inspection and reporting, I recommend GFCI protection in all areas according to the most current standards. I do not excuse missing GFCI protection as “grandfathered” or “not required when the house was built.” I note it all in my reports and strongly recommend upgrading it to current standards. If someone is injured or worse from an electrical shock in a house you inspected, no one is going to want to hear “it was grandfathered in.” GFCI devices can also be used on older wiring with no third grounding conductor. This upgrade will provide shock protection for people on ungrounded circuits, but it does not provide grounding protection for equipment that requires a grounding conductor.

The requirements for AFCI protection can vary widely by jurisdiction. To properly report on AFCI protection, an inspector needs to be familiar with the requirements in the location of the inspection. Some areas may have different requirements between different localities such as town, county, or state. The initial AFCI requirements were for bedroom receptacles beginning about 2003. In 2006 this was expanded to everything in a bedroom—including lights, ceiling fans, and smoke detectors.

Some jurisdictions have limited AFCI requirements to the bedrooms. The current code requires AFCI protection in residences for all 15 and 20 amp 120 volt circuits that supply all outlets (this includes receptacles, switches, lights, appliances, and smoke detectors) in all habitable spaces—including closets, hallways, laundry rooms, and finished basements. Attics, unfinished basements, garages, and exterior areas are areas where AFCI protection isn’t required. Protection is now required in most of the house. While it certainly isn’t wrong to recommend upgrading to current standards, the standards of the inspection location should be referenced rather than the overall standard if protection of all habitable spaces isn’t required.

Reviewing the GFCI and AFCI requirements shows areas of overlap where both types of protection are necessary. Combination AFCI/ GFCI breakers are now readily available to meet these conditions.

Testing Procedures

ASHI and most state standards require an inspector to test the GFCI protection in a home. It is best practice to test receptacles with both a GFCI tester and by pushing the test button. Don’t forget to reset all tripped devices. Yes, it may take quite a while to find the GFCI receptacle behind the refrigerator or the storage in the garage or basement. If you are not able to test all the GFCI devices (i.e. exterior receptacles after the house is locked up), note that in your report. If you can’t find a GFCI to reset it, be sure the current owner of the property is advised of the situation so they can remedy it.

All GFCI devices should be accessible to reset, not behind a refrigerator or on the garage ceiling. If you can’t find it, your client may not be able to find it either. GFCI receptacles are now available with audible alarms that sound when the device trips. These are annoying when doing an inspection but can alert someone to a tripped device especially in an important location like a sump pump or freezer.

The presence or absence of AFCI devices is required to be noted in your report. AFCI devices should not be tested unless a home is unoccupied and empty. If a home is occupied, tripping an AFCI breaker may shut off equipment or devices that may lose programming or be critical to life safety (i.e. respirators). In an empty home, push the AFCI test buttons and check that the required protected areas are indeed turned off.

Since AFCI circuitry is proprietary, a device manufactured to test one manufacturer’s device may destroy another manufacturer’s circuitry. If you have purchased an AFCI device tester, throw it away.

Combination AFCI/GFCI breakers can and should be tested, as it is assumed that any device on GFCI circuits can be turned off and on with the testing. Circuit breakers usually will be marked on their face with the type of protection they are intended to provide.

Understanding the operation and reasons for GFCI and AFCI protection is important for you and most especially your clients. They are the ones who may suffer the consequences of inadequate or defective GFCI and AFCI protection. Upgrading an older home to current standards generally would not be a prohibitively expensive proposition.