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#50098 03/23/05 06:54 PM
Joined: Aug 2003
Posts: 1,374
Ryan_J Offline OP
From UL:

Recently, there have been a number of questions from the field about the response of arc fault circuit interrupter (AFCI) circuit breakers to commercially available AFCI indicators. AFCI indicators operate by producing a waveform similar to an arc fault. However, because they cannot produce an actual arc fault, an AFCI indicator may not trip every available AFCI.

Therefore, if an AFCI indicator plugged into a receptacle protected by an AFCI does not trip the AFCI, it does not mean that the AFCI protecting the circuit is defective and needs to be replaced. When this situation occurs, you should push the "Test" button provided as an integral part of the AFCI itself. If the integral test button does not trip the AFCI circuit breaker, it should be replaced.

To notify users of this product limitation, Underwriters Laboratories Inc. requires AFCI indicators to be marked or be provided with instruction manuals that state the following or equivalent:


CAUTION: AFCIs recognize characteristics unique to arcing, and AFCI indicators produce characteristics that mimic some forms of arcing. Because of this the indicator may give a false indication that the AFCI is not functioning properly. If this occurs, recheck the operation of the AFCI using the test and reset buttons. The AFCI button test function will demonstrate proper operation.


For more information on AFCI indicators, contact Steve Brown in Melville, N.Y., by phone at +1-631-271-6200, ext. 22420; or by e-mail at If you find a defective AFCI, please alert the product's manufacturer and UL through UL's AHJ Product Report Form available online at

Ryan Jackson,
Salt Lake City
#50099 03/23/05 07:06 PM
Joined: Jan 2002
Posts: 1,457
This is a hot button issue with me. [Linked Image]

#50100 03/23/05 08:00 PM
Joined: Sep 2001
Posts: 806
So how exactly does the built-in test button on an AFCI breaker work? Since it cannot create an arc fault, one would have to ASSume that it simply tests the trip mechanism "downstream" of the software "black box" that supposedly does the waveform analysis and arc detection. In other words, it CANNOT check the actual operation of the complete device, unlike the test feature on a GFCI, which actually creates a differential current between hot and neutral. Has anyone taken one of these things apart to see what is actually going on inside? I have only seen the block diagrams and descriptions from manufacurer websites and such. I haven't come across a defective unit to dissect, and they are too expensive to sacrifice a "working" one.

If the built-in test function doesn't do a thorough test, and neither can an external tester, I guess that the public has to take the functionality of these things "on faith"? Smells like the makings of a lawsuit down the road, when a fire starts on an AFCI "protected" circuit....

#50101 03/23/05 09:59 PM
Joined: May 2002
Posts: 68
Smells like the makings of a lawsuit down the road, when a fire starts on an AFCI "protected" circuit....
No the fire investgator will just rule it as an regular electrical fire and they will be off the hook. [Linked Image]

Be Fair, Be Safe
Just don't be Fairly Safe

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