AFCI Vs GFCI - Electrical - DIY Chatroom Home Improvement Forum

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Old 10-05-2009, 06:37 AM   #1
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Can someone please explain the difference and the appropriate application for an AFCI and GFCI.


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Old 10-05-2009, 07:37 AM   #2
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gfi is used in wet areas: baths, kitchens exterior and garage. They protect against ground faults. AFCI is used in bedrooms to protect against arc faults.


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Old 10-05-2009, 07:58 AM   #3
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I'll try to expand a little.
GFCI's are designed to protect people from electrical shocks. It's detecting current on the hot and neutral, and in normal conditions, it will be the same. In abnormal conditions, a "ground fault" this current will not be the same and the GFI will trip. I believe it's greater than or equal to 5ma. The GFI doesn't know where this fault is occurring so it assumes that the leakage is a person. An equipment ground is not required for a GFCI to work.

AFCI's are designed to detect an arc in the circuit to prevent fires. I believe it uses some sort of AM or FM frequency detection to detect an "arc"

Applications for GFCI's are mostly required where water, electricity, and personnel are likely to be mixed (kitchens, bathrooms, outside, garages, etc)

AFCI applications under 05 code were just required for bedroom "outlets" (lighting and receptacles) 08 code expanded this to almost include, pretty much, where a GFCI wasn't required.

That's the best I can do. Hope it helps some.
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Old 10-05-2009, 11:12 AM   #4
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A GFCI is sort of like a bank teller. It counts the amount of electricity going out on one wire, then makes sure the same amount of electricity returns on the other wire. If less electricity is returning on the other wire, it sounds the alarm and shuts off the electricity.

This would be the case if you were being shocked - some of the electricity would flow through your body rather then returning through the other wire. The GFCI detects this and shuts off the electricity before you can even notice you are being shocked! And this is what is happening sometimes when someone thinks they have a faulty GFCI. It keeps tripping - they keep resetting it. Actually they have a faulty appliance and they are being shocked, then it is shutting off the electricity as it is designed to do. (Fix or replace the appliance.)

You can get a GFCI outlet or a GFCI breaker.

As to an AFCI, if you have ever plugged in something and the sparks flew. Or had an extension cord and set something heavy on it and sparks flew... That is the situation an AFCI is designed to detect. Sparks or arcing. It will shut off the power if it detects this sparking. And of course sparks flying around can cause a fire, so these prevent fires.

There are different types of AFCI. One is called a "combination AFCI". This provides more protection from several different types of sparking. It is NOT a GFCI as some people think. ONLY an AFCI with additional protection.

To my knowledge, you can only get an AFCI breaker (not an outlet).

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