Arc Fault Vs Ground Fault. - Electrical - DIY Chatroom Home Improvement Forum


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Old 11-05-2011, 02:03 PM   #1
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Arc Fault vs Ground Fault.


Is there a difference between Arc Fault and Ground Fault? I assume there is.

Installed 4 Arc Fault breakers (20A Square D) on my basement outlet circuits. Per the instructions, we press the test button on the breaker and it tests good. Later we have one tripping and realize that we have accidentally shared a common from another circuit in a 3 way light switch. The imbalance eventually caused the AFB to trip as it should have per the instructions. We pull that common and we're back in business.

I call the inspector for my final inspection. He takes his little GFI outlet tester out of his pocket, puts it in an outlet, presses the test button and the circuit fails to trip. He fails me.

The builder of the home used a GFI outlet as the first outlet in the original basement circuit in order to get around the requirement to use an AFB. That circuit tests when using the GFI outlet tester ie the GFI outlet trips. I used our GFI tester on another GFI outlet and it trips. The tester seems good and it's one of two testers and outlets that test exactly the same way.

Are you supposed to use a GFI outlet tester to test an Arc Fault Breaker?
Are you required to?
Is the current required to trip an AFB different than that required to trip a GFI oulet? It seems to me it is.

I want to speak to the AFB manufacturer as well as the GFI outlet tester manufacturer in order to see if their uses are interchangeable but of course, it's Saturday.

Can someone shed some light on this for me?

Thanks!

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Last edited by JetFuelBurner; 11-05-2011 at 02:05 PM. Reason: clarification...
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Old 11-05-2011, 03:04 PM   #2
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Arc Fault vs Ground Fault.


Yes, there is a difference. AFCI's look for an "arcing" condition. GFCI's look for a current imbalance between the neutral and hot.

Finished or unfinished basement? It does matter by code. Unfinished require GFCI's.

Usually, in an area that requires GFCI's, you don't need to put in AFCI's - yet.

Ex: bathroom and kitchen are exempted for now.

2008 NEC AFCI requirements: All 120-volt, single-phase, 15- and 20-ampere branch circuits supplying outlets installed in dwelling unit family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sun rooms, recreation rooms, closets, hallways , or similar rooms or areas shall be protected by a listed arc-fault circuit interrupter, combination-type installed to provide protection of the branch circuit.

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Old 11-05-2011, 03:20 PM   #3
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Arc Fault vs Ground Fault.


GFI protection is entirely different than AFCI protection.

AFCI has a Class B GFI component that trips at 30 mA. Class A GFI protection for life safety trips at 5mA. The tester used by the inspector is used to trip Class A GFI devices. An inspector that fails you when they don't know how to properly test should be failed, not you. UL states the only recognized method to test either AFCI or GFI protection is the built-in test buttons.

You builder should also learn that GFI protection will not substitute for AFCI protection.
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Answers based on the National Electrical Code. Local amendments may apply. Check with your local building officials.
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Old 11-05-2011, 03:36 PM   #4
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Arc Fault vs Ground Fault.


Sorry. Yes. Finished basement...it is now anyway!

Inspector is using what appears to be a GFCI tester in an outlet who's circuit is protected by an AFCI breaker.

Builder used a GFCI oulet on the unfinished basement. We have now finished it and all circuits are now on AFCI. The bathroom and the existing circuit from when the basement was unfinished just have an additional GFCI outlet.

Home was built in 2006 so the new AFCI law was not in effect yet.

I've been doing my homework on Google this afternoon.

From what I can tell, the inspector is improperly testing the AFCI circuit with a GFCI outlet tester.

Hopefully, this will save my Father-in-Law a 6 hour one way drive!
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