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AFCI on a furnace #169114 09/25/07 06:36 PM
Joined: Jan 2004
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George Little Offline OP
Member
I was asked if a 120v. 15a. circuit to a furnace located in a bedroom needs AFCI protection and if I'm not mistaken the answer would be yes. What say you?


George Little
2017 / 2014 NEC & Related Books and Study Guides
Re: AFCI on a furnace [Re: George Little] #169118 09/25/07 07:36 PM
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Posts: 5,316
renosteinke Offline
Cat Servant
Member
George .... I'd love to hear how this application turns out.

As written the furnace would need an AFCI. Nor does the new version allow any exceptions for appliances that use igniters for the gas flame, rather than having a pilot light.

When an igniter operates, that sure looks like a spark to me. Either the AFCI will shut down the appliance .... or I am completely misled as to just what an AFCI is supposed to do!

Re: AFCI on a furnace [Re: renosteinke] #169120 09/25/07 07:40 PM
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gfretwell Offline
Member
If you gotta put the smokes on AFCI, I sure don't see any relief for anything else. The only question would be if it was really "in" the bedroom. (the old "closet" question)


Greg Fretwell
Re: AFCI on a furnace [Re: gfretwell] #169121 09/25/07 07:44 PM
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George Little Offline OP
Member
Thanks Greg I agree. As for clarification the furnace is a horizontal furnace located above the closet and is serviced standing on a ladder located in the bedroom. I would say it is in the bedroom.


George Little
Re: AFCI on a furnace [Re: George Little] #169122 09/25/07 07:48 PM
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George Little Offline OP
Member
Reno- I don't think the spark ignition would trip the AFCI because it's supplied by a xformer but I could be wrong. The AFCI only sees arc's on the 120v. lines.???


George Little
Re: AFCI on a furnace [Re: George Little] #169127 09/25/07 10:18 PM
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Posts: 6
A
ArkySparky2B Offline
Junior Member
Is this furnace open to the room, or is it in an enclosed area, with just an access panel? If it is in an enclosed area, I would consider it technically not in the "bedroom".
Plus, as a HVAC tech, the last thing I would want to see is the furnace on an arc fault. The risk of the arc fault tripping out is too great, leaving the home without heat when it is needed the most.


It's all about herding those electrons.
Re: AFCI on a furnace [Re: ArkySparky2B] #169128 09/26/07 12:23 AM
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gfretwell Offline
Member
George, I agree this should not be tripping the AFCI. The AFCI is really looking for a series of short, high current events. (on the order of 50a or more). I can't see an igniter doing anything like that.


Greg Fretwell
Re: AFCI on a furnace [Re: gfretwell] #169129 09/26/07 04:37 AM
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iwire Offline
Moderator
If the AFCI does trip due to the igniter IMO it will be the GFP portion of a AFCI that is causing the trip. (All AFCIs have built GFP protection in the 30 ma range if I recall)

I also with Greg's point about the transformer providing some isolation.


Bob Badger
Construction & Maintenance Electrician
Massachusetts
Re: AFCI on a furnace [Re: iwire] #169132 09/26/07 06:54 AM
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Elec N Spec Offline
Member
My vote would be that it had to be AFCI protected. I agree that if a smoke alarm has to be protected a furnace should be protected as well.

Tony T.

Re: AFCI on a furnace [Re: Elec N Spec] #169135 09/26/07 08:53 AM
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Posts: 1,335
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sparkyinak Offline
Member
Iwire, I'm no expert on AFCI design however why do you thing the GFCI side of the AFCI would trip? If it is working properly, the GFCI portions measues power in/power out. If there is a difference of a few millivolts, it trips. If the igniter is grounding out then yes it would trip.

Last edited by sparkyinak; 09/26/07 08:54 AM. Reason: Do not know how to spell AFCI

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