Gfci breaker versus afci breaker

[keith ouellette]

I bought a gfci breaker to add a exterior outlet 40ft from my shop. When I was looking for it I saw an afci breaker. Could someone tell me the differance and which one is better to use?

[Bob Hoffmann]

From Wikipedia:

An arc fault circuit interrupter (AFCI) is a circuit breaker (http://en.wikipedia.org/wiki/Circuit_breaker) designed to prevent fires (http://en.wikipedia.org/wiki/Fire) by detecting non-working electrical (http://en.wikipedia.org/wiki/Electricity) arcs (http://en.wikipedia.org/wiki/Spark) and disconnect power before the arc starts a fire (http://en.wikipedia.org/wiki/Fire). The AFCI should distinguish between a working arc that may occur in the brushes of a vacuum sweeper, light switch, or other household devices and a non-working arc that can occur, for instance, in a lamp cord that has a broken conductor in the cord from overuse. Arc faults in a home is one of the leading causes for household fires.
AFCIs resemble a GFCI/RCD (Ground-Fault Circuit Interrupt/Residual-Current Device) (http://en.wikipedia.org/wiki/Residual-current_device) in that they both have a test button, though it is important to distinguish between the two. GFCIs are designed to protect against electrical shock, while AFCIs are primarily designed to protect against fire.

[Greg Peterson]

GFCI will prevent electrocution. AFCI will prevent fire due to compromised wiring.

GFCI is required in any environment that is outside or on a concrete floor.

AFCI is used primarily on bedroom circuits (I believe AFCI's are code for bedrooms in new construction).

[keith ouellette]

thanx. Are there any gfci 240v. If it is required in a room with concrete floors than most shops would need them at a 240v rating or is that not a concern? I thought gfci was only needed outside or in bathrooms.

[Chris Friesen]

GFCI is required in any environment that is outside or on a concrete floor.

This may vary by region. Up here in Canada garage outlets are not required to be gfci-protected.

[Greg Peterson]

Good point Chris. GFCI and AFCI is code out here.

[Tom Veatch]

A "ground fault" breaker, as I understand it, compares the current in the "hot" wire to the current in the "neutral" wire. If they differ by more than some miniscule amount, the breaker assumes the difference is flowing to ground through a fault - like some poor guy's body - and breaks the circuit.


AFCI is used primarily on bedroom circuits (I believe AFCI's are code for bedrooms in new construction).

How does an "arc fault" breaker tell the difference between a "working" arc and a "non-working" arc(assuming it can be explained in terms a layman can understand) and why would that be more desirable for bedroom circuits than some other circuit?

[Dave MacArthur]

Caveat: everything below is paraphrased to give you the general IDEA, so you know what to read/search for in the code. My inspector agreed with this in Phoenix. Yours may not.

Kieth, GFCI is required ouside and in garages in the US at "grade level". Basically, think this: anyplace you could POSSIBLY create a puddle say washing your car, and plug in an extension cord and electrocute yourself... probably requires a GFCI. HOWEVER, there are numerous "exceptions"--most boil down to something similar to "if the plug is already permanently used, or wierd, or hard to reach, and you just WOULDN"T plug in a weedeater or leafblower to an extension cord and go stand in a puddle...". My paraphrasing. Anyways, dedidicated single outlets for such things as freezers/refrig in garage are excepted, plugs near ceiling, special receptable styles, hardwired machines, and virtually all 240 v plugs, CAN fall under an exception.

I just wired 10 circuits into my garage with a sub panel, lighting, 20A 110V outlets, and 20-30 A 220V circuits. Basically the only circuits I had to GFCI protect were the 110V receptacle circuits in the shop. AND I DID THIS WITH A GFCI receptacle instead of a circuit breaker! Vastly cheaper (8$ vs. $60), same effectiveness, easier to notice/reset.

Here's my standard link to the best info I found in a lot of research on wiring a garage:
http://www.sawmillcreek.org/showpost.php?p=601780&postcount=5

[Greg Peterson]

All of my outlets are protected by placing a GFCI outlet as the first outlet in the series. I do have one GFCI breaker that feeds a sump pump located outside. I could have placed a GFCI outlet at the sump pump location, but I prefer that the entire circuit be protected rather than anything plugged into the outlet. The pump also required a separate circuit so I couldn't just daisy chain it to a GFCI outlet in the garage.

As for how a AFCI works, I couldn't tell you. As for why it's code for bedrooms, my understanding is that the AFCI would help prevent a fire in a bedroom wall while someone was sleeping in the room.

[Chris Kalkowski]

AFCI is used primarily on bedroom circuits (I believe AFCI's are code for bedrooms in new construction).


This can vary too. I just bought a new construction house and it is just GFCI.

[Bill Brady]

AFCI breakers were just required in the 2005 code. AFCI receptacles were required in earlier codes but they were not widely manufactured. This device is the required because a manufacturer made a pitch to the code comittee and the bought into it. There is talk of requiring AFCI breakers throughout new home construction in the future.

GFCI breakers or receptacles were expanded for todays usage about 12 years ago.

[Paul Simmel]

>>> How does an "arc fault" breaker tell the difference between a "working" arc and a "non-working" arc(assuming it can be explained in terms a layman can understand) and why would that be more desirable for bedroom circuits than some other circuit? Here it is in my words… As stated, a GFCI monitors (compares) the draw and the return amperage on a particular circuit. This is totally different than a regular breaker in that a regular breaker monitors a surge on the hot lead only. A GFCI will save one’s life because at the “instant” of electrocution, the draw/return are at variance… hence a tripped GFCI. An AFCI will trip if shorted (working arc) like a regular breaker would. A “non-working” arc, is, well… a not-quite-short (an arc) that is not enough to trip a regular breaker. That means Fire. An AFCI will not protect against electrocution as would a GFCI.