Thread: AFCI versus GFCI

Does anyone have a simple, non-technical explanation of why Arc Fault Circuit devices are needed and why GFCI's can't be used in their place?

Everytime a client asks me why there are AFCI over current protection devices in the panel, their eyes tend to glass over about the time I explain about measuring variances in phases.

I'm pretty sure that "one works and one doesn't always work" is not an acceptable answer.

Jeff Beck
Foresight Home Inspection LLC

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AFCI and GFCI have different purposes. AFCI primarily protects the building wiring from fire. GFCI protects people from electrocution. We use GFCI's where those dangers are greatest and AFCI where those dangers are greatest. Maybe someday as the technology develops there will be both types of protection everywhere in the house, but for now this devices are about as safe as technology can make it and still be affordable.

Try that on for size. Of course we can get more technical but you asked for simple.

If you want simpler, just tell them to press the test buttons and see if the power goes off and then reset it. That would make them more informed than most of the folks.

Short write-up on "combination" (series+parallel) AFCIs with some good graphics here:

http://ecatalog.squared.com/pubs/Cir...0760HO0602.pdf

There are some AFCI/GFCI breakers available, here's the page for Cutler-Hammer products:

http://www.google.com/url?sa=t&ct=re...3e6b0CO0TDTLtw

Originally Posted by Jeff Beck

Does anyone have a simple, non-technical explanation of why Arc Fault Circuit devices are needed and why GFCI's can't be used in their place?

Originally Posted by Jim Luttrall

AFCI and GFCI have different purposes. AFCI primarily protects the building wiring from fire. GFCI protects people from electrocution. We use GFCI's where those dangers are greatest and AFCI where those dangers are greatest. Maybe someday as the technology develops there will be both types of protection everywhere in the house, but for now this devices are about as safe as technology can make it and still be affordable.

Jim's answer was great.

Originally Posted by Jeff Beck

Everytime a client asks me why there are AFCI over current protection devices in the panel, their eyes tend to glass over about the time I explain about measuring variances in phases.

My eyes just glassed over too , AFCI do not measure variances in phases, they monitor the circuit for waveforms associated with arcs ... but explaining that also causes layman's (and many non-layman's) eyes to glaze over and roll back into their sockets.

I include the following UL laboratories info in my report:

Arc Fault Circuit Interrupters (AFCIs)

AFCI's involve a technology that detects arcing-faults in electrical circuits that could cause fires. By recognizing characteristics unique to arcing and functioning to de-energize the circuit when an arc-fault is detected, AFCI's further reduce the risk of fire beyond the scope of conventional fuses and circuit breakers.

Effective January 1, 2002, NFPA 70, The National Electrical Code (NEC), Section 210-12, requires that all branch circuits supplying 125V, single phase, 15- and 20-ampere outlets installed in dwelling unit bedrooms be protected by an arc-fault Circuit interrupter. Additional information is available at UL | Arc Fault Circuit Interrupters (AFCIs)

I usually just use some analogies:

AFCI = prevents the child with the paper clips from getting shocked

GFCI = Prevents you from being shocked when standing at sink with hand in water and electric mixer falls in

Yes those are gross simplifications but people get it without glazing over,

//Rick

Originally Posted by Rick Bunzel

AFCI = prevents the child with the paper clips from getting shocked

AFCIs do not provide shock protection. They are designed to detect arcing in wiring system and attached appliances to prevent fires.

Originally Posted by Rick Bunzel

I usually just use some analogies:

AFCI = prevents the child with the paper clips from getting shocked

As Michael said, AFCI does not prevent shock, it just help reduce fires caused by arcing.

GFCI = Prevents you from being shocked when standing at sink with hand in water and electric mixer falls in

A GFCI may help 'reduce' the shock to a less serious level, but any shock combined with water is not good, but it does not 'prevent' shocks.

I just say if they are there or not and if they tested properly dung the inspection. The more information you provide the more libel you will be when a problem occurs and someone dies.

C&P'ing other folks stuff is not a good idea. You need to believe and know what you put in a report.

I explain that AFCI'c stop the electrical fires that occur in the walls.

GFCI's prevent the husband from getting zapped when the wife throws the toaster in the tub.

I have been told that AFCI's are now recommended for all wiring over 50 years old by some old wiring experts. Heard it an ASHI conference on historic houses.


Annie-Laurie

Annie says,

GFCI's prevent the husband from getting zapped when the wife throws the toaster in the tub.

I say she better hope the cord was long enough for the toaster to reach the tub or we have some real issues then.

Originally Posted by Annie-Laurie Hunter

I explain that AFCI'c stop the electrical fires that occur in the walls.

GFCI's prevent the husband from getting zapped when the wife throws the toaster in the tub.

They don't "prevent" or "stop" anything.

They "help" "prevent" fires and "reduce" the zapping - but you will still get zapped, you just won't die from it (if it is working properly, that is).

I know some of what I post is 'only about words', but 'words' make or break what you are saying and what is taken as you are meaning. Here are two examples: 1) The dog bit the man.; 2) The man bit the dog. *SAME* "words" - but completely different meanings.

Originally Posted by Jerry Peck

I know some of what I post is 'only about words', but 'words' make or break what you are saying and what is taken as you are meaning. Here are two examples: 1) The dog bit the man.; 2) The man bit the dog. *SAME* "words" - but completely different meanings.

If the "dog" in number 1 is a canine that answers to the name of "Fido", and the "dog" in number 2 is in a bun slathered in mustard, I don't see a problem with either one. I agree with Jerry and want to add that context is also important.

Back to the original question:

Does anyone have a simple, non-technical explanation of why Arc Fault Circuit devices are needed and why GFCI's can't be used in their place?

AFCI reduces the risk of fire
GFCI reduces the risk of electrocution

There will probably be a day within most of our lifetimes when combo type AFCI/GFCI breakers are required on most of the 15A and 20A branch circuits in the home.

A fairly simple explanation would be:

A GFCI protects against an unintentional path between a power source and a grounding source by measuring the difference in current between the neutral and "hot" wire which should be zero under normal conditions, but increases if the current is flowing through a ground source and trips within a fraction of a second. The grounding source can be water from various sources or the unintentional contact with an electrical source to persons or other equipment. The power is shut down to prevent an electrocution in case the conductor carrying the current to the ground source happens to be flesh.

An AFCI detects a spark present somewhere in the circuit. This could be due to loose wiring, outlets, switches, nails dviven through walls into wires, etc. The power is shut down to prevent a fire due to the arcing that is present somewhere.

Having super technical info about any system is good... just read your audience. Yuppie buying a posh new condo probably doesn't understand or care.... all he needs to know is that it can cut off power. If nothing else, get it stuck in his mind where it can be reset and where the 'afci info sticker is' - usually on the panel.

The retired engineer/scietific type will love the technical story. After learning the technical info getting into this profession the best thing you can do is learn when to use it.