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#169114 - 09/25/07 06:36 PM AFCI on a furnace  
George Little  Offline
Joined: Jan 2004
Posts: 1,489
Michigan USA
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

#169118 - 09/25/07 07:36 PM Re: AFCI on a furnace [Re: George Little]  
renosteinke  Offline
Cat Servant
Joined: Jan 2005
Posts: 5,316
Blue Collar Country
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!

#169120 - 09/25/07 07:40 PM Re: AFCI on a furnace [Re: renosteinke]  
gfretwell  Offline

Joined: Jul 2004
Posts: 9,142
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

#169121 - 09/25/07 07:44 PM Re: AFCI on a furnace [Re: gfretwell]  
George Little  Offline
Joined: Jan 2004
Posts: 1,489
Michigan USA
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

#169122 - 09/25/07 07:48 PM Re: AFCI on a furnace [Re: George Little]  
George Little  Offline
Joined: Jan 2004
Posts: 1,489
Michigan USA
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

#169127 - 09/25/07 10:18 PM Re: AFCI on a furnace [Re: George Little]  
ArkySparky2B  Offline
Junior Member
Joined: Mar 2007
Posts: 6
Jonesboro Arkansas
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.

#169128 - 09/26/07 12:23 AM Re: AFCI on a furnace [Re: ArkySparky2B]  
gfretwell  Offline

Joined: Jul 2004
Posts: 9,142
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

#169129 - 09/26/07 04:37 AM Re: AFCI on a furnace [Re: gfretwell]  
iwire  Offline
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
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

#169132 - 09/26/07 06:54 AM Re: AFCI on a furnace [Re: iwire]  
Elec N Spec  Offline
Joined: Jul 2006
Posts: 33
Rochester Hills, MI USA
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.

#169135 - 09/26/07 08:53 AM Re: AFCI on a furnace [Re: Elec N Spec]  
sparkyinak  Offline
Joined: Jul 2007
Posts: 1,328
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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