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#13513 09/06/02 07:07 AM
Joined: Sep 2002
Posts: 131
If your going by the 2002 code, smoke detectors in bedrooms would be protected by AFCI, this does not sit right with me. In theory if someone was to unplug a lamp under load the AFCI should trip. If that were to happen the smoke detectors would not be live. We should not have to rely on the battery to save our lives. Most people don't check them anyway. I think smoke detectors should be able to be on a non AFCI circuit.

(B) Dwelling Unit Bedrooms. All branch circuits that supply 125-volt, single-phase, 15- and 20-ampere outlets installed in dwelling unit bedrooms shall be protected by an arc-fault circuit interrupter listed to provide protection of the entire branch circuit.

#13514 09/06/02 05:54 PM
Joined: Aug 2001
Posts: 7,520
In theory if someone was to unplug a lamp under load the AFCI should trip.

That would be a series arc, and one limited to a small value by the lamp. All the specifications that have been presented for AFCIs indicate that they will not trip on such a series arc.

(Uh oh.... Get ready for another rough ride! [Linked Image])

#13515 09/07/02 06:53 AM
Joined: Sep 2002
Posts: 131
So what are sucumstances to which they trip.
The local inspectors thought I had a valid point. I don't know what you mean small load from the lamp. that load would be way more than the minimum of 1 or 3 ma that I believe is rating for the AFCI

#13516 09/07/02 09:58 AM
Joined: Oct 2000
Posts: 4,086
Likes: 3

The AFCI breakers are designed to ignore the type of situation you describe, just as it would ignore the internal arc in a switch that controlled a load as it was turned on and off. It is supposed to see these as "good arcs" and not bad ones.

Aside from that, there are many that agree with your thoughts about not including the smokes on the AFCI circuit.

I'm thinking I heard that Canada does not permit it. Electric-Ed; can you confirm that?


#13517 09/07/02 11:35 AM
Joined: Aug 2001
Posts: 7,520
Apparently the AFCI is designed to trip only if it sees an arc of 75A or more over a period of several cycles, effectively limiting its usefulness to detecting parallel arcs in a 15 or 20A branch circuit.

The ground-fault protection incorporated is set at a level of 30mA, and you'll find many people on this board who are unhappy that the AFCI has been marketed on the basis that a series arc will trip the breaker when it eventually burns through the insulation and becomes a ground fault (or not, as the case may be).

This has really been a hot subject; if you do a subject header search on "AFCI" and another on "arc fault" you'll see plenty of threads.

Just to get you started, here's one of them.

[This message has been edited by pauluk (edited 09-07-2002).]

#13518 09/07/02 06:56 PM
Joined: Jul 2002
Posts: 175
Bill, you are correct.
The CEC prohibits the installation of a smoke alarm on a circuit protected by a GFCI or an AFCI.


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