nuisance afci tripping

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captainkevin

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Missouri
We are doing lots of residential loft projects. We are having trouble with afci tripping when there is 120v smoke detector on the circuit. Are these units so sensitive that if the smoke detectors are sensing low battery and chirp that the little resistance at the chirp could be tripping the unit. I can not find any limitations on down stream devices for these breakers but I am beginning to wonder. Any help would be appreciated
 
Re: nuisance afci tripping

Contact the manufacturer of both the smoke alarms and the breaker to see if others have reported the same issue. I currently use Firex brand smoke alarms and Siemens AFCI breakers, and have not had a problem.
 
Re: nuisance afci tripping

I use Siemens AFCI's, and Kidde smoke detectors, without a problem (along those lines.)

If you are rock solid--absolutely 100% in no doubt that the problem is related to your smokes, I'd change brands and see if it changes. On hearing your problem though, I'd point the finger of blame at the AFCI. What brand devices do you use?
 
Re: nuisance afci tripping

First, assure that there isn't a grounding conductor touching the neutral to rule that out.
I suggest that all the loads be removed from the branch circuit in question. Then remove the line and neutral conductors from the AFCI and the EGC from the ground bar. Check the resistance between the neutral and EGC which should show open. If not the EGC is touching the neutral in the circuit. This often happen when pushing a duplex outlet back into the box where the bar EGC bends such that it contacts the neutral screw of the outlet.
If you rule that out then you can go after the installed devices in an attempt to isolate the problem, reinstalling each one at a time until the problem child is located.
 
Re: nuisance afci tripping

did you try searching these forums? I found several discussions that might apply.

here's one, if I can do the link right:

http://www.mikeholt.com/codeforum/ultimatebb.php?ubb=get_topic;f=11;t=005351#000002

if that doesn't work, just go to "search" and search all forums for "afci". the thread I tried to post was titled "smoke detectors".

as for your question about sensitivity & the chirping: I'm not sure, but I would suspect not the chirp, as much as the circuit elements that switch the supply from AC to battery back-up. Just a hunch, so don't quote me.
 
Re: nuisance afci tripping

I have had many problems with Siemens AFCI breakers false tripping. But the problems have been:
1. Shared neutral
2. bootleg neutral (hot from AFCI circuit neutral from another circuit)
3. Ground to neutral fault.
4. paddle fan controls. (click type)
5. vacuum cleaners.
6. florescent light's.
7. plug in surge suppressor strips. (When a motor load on the AFCI circuit is switched)

But I have never had a smoke detector cause one to trip? ( and we use several brands)
 
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