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Old 05-20-2010, 11:59 AM   #1
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AFCI breaker won't reset. Help me troubleshoot.


Today I was operating a carpet cleaner in my sunroom. (WOW is it gross how dirty carpets get). The Carpet Doctor draws 11 Amps. At the same time I had a ceiling fan running on high, a Plasma screen tv on standby (off, but not really off, right), one light fixture. I had to park the carpet cleaner while it was on for @ 20 seconds and it bogged down. Then the AFCI breaker blew (BTW 20 Amp AFCI circuit that I ran and was inspected and permitted).

I removed almost all the loads (the ceiling fan is only operated by remote - so I can't take it off high). The breaker will reset but then after 2-5 seconds it snaps off.

Because it was quick and easy I pulled the three receptacles that were in use at the time to look for something suspicious. Nothing obvious was wrong. Where should I look next?

Help! Thanks!
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Old 05-20-2010, 12:26 PM   #2
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Originally Posted by Leah Frances View Post
The breaker will reset but then after 2-5 seconds it snaps off.
Yes, Ma'am, I will try.

If you disconnect the #12 wire from the AFCI output and it still trips I think it is almost certainly defective.

Watch for arc-flash and shock danger. Work deliberately and carefully.

Maybe the manuf. has a trip curve posted somewhere for this breaker. One of the inputs to this curve would be arc duration [?] and the other is current vs. time. For a regular breaker a two second trip time might mean a 3x overcurrent; 60A.

Maybe there is a running motor somewhere on this circuit, the brushes of which are failing. Ceiling fans don't have brushes, I think.

Last edited by Yoyizit; 05-20-2010 at 12:32 PM.
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Old 05-20-2010, 12:35 PM   #3
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I've hear lots of complaints on other board about AFI's failing, it's possible yours just did. The simplest timeswise - but expensive - is to pull your existing AFI breaker and put in a new one. I'll bet that fixes it.
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Old 05-20-2010, 12:56 PM   #4
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If you disconnect the wire from the breaker, and it still trips, then the AFCI has gone bad and will need replaced.

If it doesn't trip with the wire disconnected, than probably a loose connection somewhere in the circuit started to burn under the load from the carpet cleaner, and the AFCI is doing it's job. If a loose connection started to burn, it'd probably be arcing now under any load at all.

If the AFCI only trips with the wire attached, I'd check all the splices and connections through the whole circuit before trying to reset it anymore.
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Old 05-20-2010, 01:12 PM   #5
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If you have another AFCI try swapping the wires/breakers

If the 2nd AFCI trips its something in the wiring



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Old 05-20-2010, 01:37 PM   #6
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Ok, thanks for the suggestions. Here's what I'm going to try:

1. disconnect the #12 wire from the AFCI output and it still trips I think it is almost certainly defective. What exactly am I disconnecting? The hot/black?
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Old 05-20-2010, 02:14 PM   #7
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Quote:
Originally Posted by Leah Frances View Post
Ok, thanks for the suggestions. Here's what I'm going to try:

1. disconnect the #12 wire from the AFCI output and it still trips I think it is almost certainly defective. What exactly am I disconnecting? The hot/black?
Yes, that's the AFCI 'output', under the screw terminal.
There won't be voltage on that disconnected black wire unless you've got some really knotty problems. One day at a time.

Since arcs throw off electromagnetic energy at all frequencies and since house wiring acts as an antenna I'm wondering if an arc on another circuit anywhere in the house can trip this AFCI.

Last edited by Yoyizit; 05-20-2010 at 02:31 PM.
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Old 05-20-2010, 02:45 PM   #8
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Yes, that's the AFCI 'output', under the screw terminal.Roger - I will give this a try.
There won't be voltage on that disconnected black wire unless you've got some really knotty problems. Hope not, since I ran the circuit. One day at a time.

Since arcs throw off electromagnetic energy at all frequencies and since house wiring acts as an antenna I'm wondering if an arc on another circuit anywhere in the house can trip this AFCI.Unlikely, since the wonky circuit is sitting on top of another AFCI breaker/circuit that I also ran and is working just fine.
I hate things like this.
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Old 05-20-2010, 02:50 PM   #9
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Since you mention that the tripping AFCI is directly on top of another AFCI in the panel, you might want to think about this as well:

I have heard that sometimes when AFCIs are stacked together in a panel, the heat rising from one breaker can cause problems with the one above it. I believe the AFCIs get warmer than traditional breakers, due to the electronics inside. I'm not saying this is your problem here, but it's something to think about if you can't find anything else wrong. I have heard of people arranging their panels to keep some distance between AFCI breakers, in order to keep them cooler.
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Old 05-20-2010, 04:12 PM   #10
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You need to disconnect both black and white wires from your AFI breaker for defective testing.
(do not disconnect the curly white wire from the neutral bar)

If the breaker still trips, it's bad ---> go get another one.

If the breaker holds with both wires disconnected, then re-connect the white wire first, and see if that has any effect.

Finally, re-connect the black wire, and report the results here.
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Old 05-20-2010, 06:21 PM   #11
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I have heard that sometimes when AFCIs are stacked together in a panel, the heat rising from one breaker can cause problems with the one above it.
Not only that.

Space flight latching relays that worked by themselves were causing each other to trip when crammed together.

Their magnetic shielding, if any, was not enough. It made the techs crazy until they caught on to this. Apparently the relay manuf. didn't foresee this usage.
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Old 05-20-2010, 08:51 PM   #12
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Quote:
Originally Posted by kbsparky View Post
You need to disconnect both black and white wires from your AFI breaker for defective testing.
(do not disconnect the curly white wire from the neutral bar)

If the breaker still trips, it's bad ---> go get another one.

If the breaker holds with both wires disconnected, then re-connect the white wire first, and see if that has any effect.

Finally, re-connect the black wire, and report the results here.
Sparks - thanks for the explicit advice. It's been a super long day, so tonight DH and I are watching TV in the dark - Good thing I wired another circuit to the room. I'll run the test first thing in the AM.

THANKS THANKS THANKS
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Old 05-21-2010, 12:23 PM   #13
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McSteve brings up a good point.

Unloaded or loaded, the AFCI electronics will draw power , called 'quiescent current'.
For 2w dissipation at 120v this current would be 2/120 = 17 mA. To measure this you'll probably need to remove the AFCI and use clip leads.

The tricky part is getting the manuf. to cough up a range of current values that indicate a healthy AFCI.
If you have several identical units you could get an idea of the current ranges for units that are OK.

True RMS values are more accurate here because the current waveform is not going to be a sine wave.
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Old 05-21-2010, 07:12 PM   #14
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Quote:
Originally Posted by kbsparky View Post
You need to disconnect both black and white wires from your AFI breaker for defective testing.
(do not disconnect the curly white wire from the neutral bar)

If the breaker still trips, it's bad ---> go get another one.

If the breaker holds with both wires disconnected, then re-connect the white wire first, and see if that has any effect.

Finally, re-connect the black wire, and report the results here.
Breaker passed these tests. And by that I mean it did not indicate a 'fail'. Going to Lowes in the AM to get another one and try it, just in case. I could get lucky, right. Today's craptastic misery-fest was also coupled with my lawn-guy breaking the wire on my invisible dog fence. Found out when my neighbor called to tell me she saw one of my pups running loose!
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Last edited by Leah Frances; 05-21-2010 at 07:15 PM.
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Old 05-21-2010, 07:17 PM   #15
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Check out this 8 minute video
http://www.sea.siemens.com/us/Produc...stic_Tool.aspx

Even with one of these gadgets it's probably difficult to troubleshoot.

The vacuum cleaner late in the video seems to cause the problem but the tech decides it's the fault of the lamp. I must have missed something. . .?

After watching the procedure at the end of the video, it seems to me if you just use a battery AM radio tuned between stations, and turn on and off each load with the radio held nearby, whatever makes the loudest 'pop' or crash of static is suspect.
Then repeat while moving each switch very slowly.

Last edited by Yoyizit; 05-21-2010 at 08:07 PM.
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