Arc-Fault Circuit Interrupters: Protecting Property and Reducing Fire Risk


Are you reading a home inspection report and finding out your home does not have AFCI protection? How big of a deal is this and how much is it going to cost to repair? Read on for more information:


What are Arc-Fault Circuit Interrupters or AFCIs?

AFCIs are devices that monitor the current running through a pair of wires and shut the circuit off if certain circumstances are met, such as signs of electrical arcing.

Arcing is just what it sounds like: electricity “arcing” or jumping from one surface to another, and arcing creates a lot of heat. What we call “welding” is actually controlling the electrical arcing between two pieces of metal, where the electrical arc generates so much heat it fuses the metals together. Electrical arcing can be caused conditions such as two loose wires that were bonded together by a wire nut or a loose connection slowly failing over time, giving just enough space for the electrical wires to arc. Another common condition that is used as an example of arcing is a homeowner hammering a nail into their walls and accidently hitting two electrical wires. Both conditions can cause arcing, which can cause a fire.

AFCI devices montior the current flowing through both the “hot” (often black, ungrounded conductor) and “neutral” or “common” (often white, grounded conductor) and distinguish between small / mild arcs, such as those that occur when you turn on a light switch, and more serious arcs, such as when you put a nail through a pair of wires while hanging a heavy shelf. When the AFCI device senses this arcing, it immediately shuts the circuit off, de-energizing the hot wire. When correctly sensing a dangerous arc and shutting off the circuit, the AFCI does its job and potentially stops a fire from occuring. Not only that, but you won’t be able to energize the circuit again until the arc is corrected, necessitating an electrician to correct the problem that was created. In short, AFCIs can save property and thus lives.


What is the difference between an Arc-Fault Circuit Interrupter and a Ground-Fault Circuit Interrupter?

GFCIs have been around and required in bathrooms since the early 1970’s and nowadays are required basically anywhere that water could be present. GFCIs and AFCIs utilize similar technology, but you can think of a GFCI as a more sensitive AFCI. GFCIs are typically rated to shut of a circuit if sensing a fluctuation of more than 5 miliAmps (5 thousandths of an Amp), whereas an AFCI is rated to shut off a circuit at about 30 miliAmps (30 thousandths of an Amp). For a quick reference, a single (1) Amp can stop a human heart, so these devices monitor fluctuations in current that are extremely small. You can think of GFCIs as protecting people and AFCIs as protecting property (from shock and fire).


Where are Arc-Fault Circuit Interrupters (AFCIs) required in a home?

electrical panel with inadequate AFCI protection

A few AFCI breakers are present at this 2005 electrical subpanel, but not enough as required by 2020 standards.

AFCIs where first required in 2001 to be connected to the bedroom receptacles in a home. From that point forward they gradually became required in more and more places, with them required at most residential electrical outlets starting in 2014 and pretty much every electrical outlet that isn’t already protected by a GFCI device in 2020. At time of writing, when inspecting a home in the San Antonio area, I am required to report the absence of AFCI protection at all living space circuits (this includes lights and receptacles / plugs) of a home unless they are protected by a GFCI already, even though a home may have been built before AFCI devices even existed.

AFCI devices are almost always circuit breakers located at either the main electrical panel or the subpanel, depending on how your particular home is wired. In the South Texas areas including San Antonio, we typically have an exterior electrical cabinet called the “main” and a smaller electrical cabinet inside the home called a “subpanel”; the subpanel contains the circuits that energize the lights and receptacles throughout the house and this is where we will typically find the AFCI breakers.


My home does not have Arc-Fault Circuit Interrupter (AFCI) protection and I want to install it. What will it take and how much will this cost?

I can’t answer this question and nobody can unless they are a licensed electrician from your local area who is quoting you a price. Some conditions to consider that may affect the price:

1) If your home’s electrical subpanel / main panel is very old, you should consider updating it to a modern panel with modern circuit breakers. It is at this time that an electrician can install AFCI circuit breakers to protect the circuits were AFCI protection is required. This is the costliest method of installing AFCI protection, but if your home’s electrical system is very out of date, replacing the electrical panels can be the most practial means of improving its safety.

2) If your home’s electrical panels are performing adequately, don’t require replacement but are more than about 25 years old, installing AFCI breakers may not be possible due to the design of the panel or space at the panel. Plenty of electrical panels installed in the 80’s and 90’s are performing just fine and don’t require any replacement, but you can’t actually fit a modern AFCI breaker in the box. In a situation like this, it may be practical to have an electrician install AFCI receptacles where necessary to protect as many circuits as practical. AFCI receptacles look very similar to the GFCI receptacles that you are used to seeing in bathrooms and wet locations, with a light and push-button-reset when tripped. These devices are individually pricy but installing them locally where required is probably cheaper than replacing a functioning electrical panel.

3) If your home was built after 2001, you probably could hire an electrician to change out the basic non-AFCI/GFCI electrical breakers at the panels for the correct AFCI circuit breakers where necessary; you should already have some in place so the electrician just needs to find the breakers, de-energize the panel and change them out as required. This would, typically, take no more than a day’s labor. Keep in mind, the price of these circuit breakers can be relatively high.



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