I would venture to say that most people nowadays have heard of GFCI's, but how many of you know what an AFCI is?. A large majority of our homes now have these outlets (or breakers). But do you know how they work? Do you know where these outlets are required to be? Check your house after reading this article and I bet you have a few to install!
What is a GFCI?
A ground-fault circuit interrupter, or GFCI, is a device used in electrical wiring to disconnect a circuit when unbalanced current is detected between an energized conductor and a neutral return conductor. Electricity follows the least resistant path to ground.
How does it work?
Let's use a lamp as an example. In layman's terms, so we can all understand, electricity comes out of one "slot" of the outlet, through the cord, and into the light bulb socket. The light illuminates and the electricity keeps flowing back down the cord and into the other "slot" of the outlet to a grounded busbar in your electrical panel. Now lets say the lamp was wired up wrong or the socket was cracked and you touch it. Instead of the electricity following the cord back to the outlet (to ground), it can enter your body (because you are grounded) and you can be shocked. A GFCI outlet will detect that the amount of current (amps) it sent out to the light is not the same as the amount coming back to the outlet (because it entered your body instead of travelling back to the outlet) and it will "trip" or shut off the power in less than 1/10th of a second to save your life. If there wasn't a GFCI outlet, the current will keep flowing possibly allowing your body to remain energized, which can result in severe injury or even death.
GFCIs are designed to provide protection in such a situation, unlike standard circuit breakers, which guard against overloads and short circuits.
It is estimated that about 300 deaths by electrocution occur every year, so the use of GFCIs has been adopted in new construction, and recommended as an upgrade in older homes, in order to reduce the possibility of injury or fatality from electric shock.
What outlets require GFCI protection?
According to the 2018 IRC (International Residential Code)
What is an AFCI?
Arc-fault circuit interrupters, (AFCIs) are special types of electrical receptacles (outlets) and circuit breakers designed to detect and respond quickly to potentially dangerous electrical arcs in home branch wiring.
How do they work?
AFCI's work by monitoring the electrical waveform and rapidly opening (interrupting) the circuit they serve if they detect changes in the wave pattern that are characteristic of a dangerous arc. They also must be able to distinguish safe, normal arcs, such as those created when a switch is turned on or a plug is pulled from a receptacle, from arcs that can cause fires. An AFCI can detect, recognize, and respond to very small changes in wave pattern.
What is an arc?
When an electric current crosses an air gap from an energized component to a grounded component, it produces a spark known as an arc. For example, a bolt of lightening is a very large, powerful arc that crosses an atmospheric gap from an electrically charged cloud to the ground or another cloud. Just as lightning can cause fires, arcs produced by wiring in our homes are capable of producing high levels of heat that can ignite their surroundings and lead to fires.
According to statistics from the National Fire Protection Agency for the year 2005, electrical fires damaged approximately 20,900 homes, killed 500 people, and cost $862 million in property damage. Although short-circuits and overloads account for many of these fires, arcs are responsible for the majority and are undetectable by traditional (non-AFCI) circuit breakers.
Where are arcs likely to happen?
Arcs can form where wires are improperly installed or when insulation (the coating around the wires) becomes damaged. In older homes, wire insulation tends to become brittle and prone to cracking and chipping. Damaged insulation exposes the current-carrying bare wire increasing the chances that an arc may occur.
Situations in which arcs may be created:
Where are AFCI's required?
According to the 2018 IRC code, all 120 volt, 15 and 20 amp outlets should be protected by AFCI's in the following areas:
AFCI's vs. GFCI's
So now we all should know the difference between GFCI's and AFCI's. GFCIs detect ground faults, which occur when current leaks from a hot (ungrounded) conductor to a grounded object as a result of a short-circuit. This situation can be hazardous when a person unintentionally becomes the current’s path to the ground. GFCIs function by constantly monitoring the current flow between hot and neutral (grounding) conductors, and activate when they sense a difference of 5 milliamps or more. Thus, GFCIs are intended to prevent personal injury due to electric shock, while AFCIs prevent personal injury and property damage due to structure fires.
So there you have it. You have your work cut out for you. Protecting your family and your home is the number one priority we all should have. Both of these items will significantly reduce your risk of severe injury, death, and the loss of your home due to a fire.
My name is Chris Dallaglio and I'm the owner of Total Eclipse Inspections LLC. I'm a licensed Home Inspector, Radon Measurement Professional, U.S. Dept of Energy Home Energy Score Assessor, part-time blogger.