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#9630 - 05/07/02 03:40 PM AFCI's Tripping upon Ground Fault Test  
C.Urch  Offline
Member
Joined: May 2001
Posts: 36
Kill Devil Hills, NC USA
Got the power turned on to my first home under the new code requiring AFCI protection for bedrooms. Out of curiosity, I pushed the ground fault test button on my GFI plug tester while plugged into a bedroom plug and the breaker tripped! I thought these things were not suppose to trip with a ground fault test? Anyone else had this problem? Also, one of our inspectors here is under the impression that AFCI circuits cannot leave the room they are intended to protect; that is to say that you cannot wire a bedroom bath combination of AFCI. He is saying that every bedroom must have it's own AFCI breaker and it cannot feed the master bath in that bedroom or an adjacent bedroom. Am I missing something in the new code? How would one go about interconnecting smoke detectors if the circuit is not allowed to leave the bedroom? Any ideas???


Work Gear for Electricians and the Trades

#9631 - 05/07/02 04:00 PM Re: AFCI's Tripping upon Ground Fault Test  
CTwireman  Offline
Member
Joined: Feb 2002
Posts: 840
Connecticut, USA
I believe that AFCI's have GFI protection built into them as well.


Peter

#9632 - 05/07/02 04:37 PM Re: AFCI's Tripping upon Ground Fault Test  
resqcapt19  Offline
Member
Joined: Nov 2000
Posts: 2,148
IL
There is no limit on what the AFCI circuit serves. The code only requires that any branch circuit feeding bedroom outlets have AFCI protection. As far as the GFCI tester tripping the AFCI, I don't know. The ground fault function that is built into (and that really provides much of the protection) the AFCI is not a Class A GFCI. It is a GFP that trips at about 30 mA of ground fault current. The GFCI tester should only have a ground fault current of less then 10 mA. GFCIs are required to trip at 4 to 6 mA.
Don(resqcapt19)


Don(resqcapt19)

#9633 - 05/07/02 08:35 PM Re: AFCI's Tripping upon Ground Fault Test  
Fred  Offline
Member
Joined: Apr 2001
Posts: 449
Straughn, IN 47387
Last fall I bought the first AFCI breakers my supply house sold. I installed one in my shop feeding a single Hubbell CR-20 duplex receptacle. I plugged everything I could find into this outlet to try to trip the breaker with no success. My Ideal GFI plug-in tester was the only thing that tripped it other than a direct line to neutral short or a line to EG short. I posted my results on several of the forums at the time but got little response. I installed 3 of these in a new custom home this spring. The inspector made sure to see if they were in the panel but said he had no way of testing them. They haven't spontaneously tripped yet and I don't believe they will. I just hope they function as a standard 20A over-current device should if the need arises.


#9634 - 05/07/02 08:54 PM Re: AFCI's Tripping upon Ground Fault Test  
N.O.Minded  Offline
Member
Joined: Jan 2002
Posts: 10
Pensacola,FL-USA
The AHJ in my area are requiring the AFCI to feed bedrooms and are requiring our smokes (of course) to be on one of the Bdrm circuits. I adimately agree with Don that the code only requires Bdrms to be AFCI protected and does not limit the use of these new products to "protect only the Bdrms" as long as the load does not exceed the Max. allowed for the device. I am however, curious about the GFI tester tripping these devices. Perhaps (hopefully) a faulty tester.
Andrew
Also, shouldn't the smokes be on their own circuit? I know that it is not cost effective, however my understanding of these new devices leads me to believe that "what if" little suzie Q were supposed to be sleeping in her bed but instead she was playing with her toys and just happened to short one of the recepts in her room tripping the breaker. The lights are already out so she doesn't give it a second thought. BTW the batteries in the smokes went bad last summer and the smokes started chirping so jo-blo took them out without replacing them. So right about now it's 12:00 AM and everyone is asleep in the house including Grandma who fell asleep and forgot about the food she was cooking on the stove!! If the smokes are on little suzies bdrm circuit what will happen?

[This message has been edited by N.O.Minded (edited 05-07-2002).]


#9635 - 05/07/02 11:17 PM Re: AFCI's Tripping upon Ground Fault Test  
Bill Addiss  Offline
Member
Joined: Oct 2000
Posts: 3,878
NY, USA
I have recently put in 2 AFCIs and they both tripped with my Ideal GFCI tester too. I didn't think about anything being wrong though. The ones I had were Murray brand.

Bill


#9636 - 05/08/02 08:44 PM Re: AFCI's Tripping upon Ground Fault Test  
Electricmanscott  Offline
Member
Joined: Jan 2002
Posts: 1,457
Holden, MA USA
NO Minded, wow that is some theory. All that was left out was the second shooter on the grassy knoll. Seriously though I beleive the thinking is that if the smokes are on their own circuit and the circuit trips for whatever reason, or Grandma is making cookies for little Suzie and sets of the smoke detectors, she then turns of the circuit because of the noise, forgets to turn it back on. It would be more likely to be turned back on if something else was turned off like lighting or receptacles which would be more obvious than the smoke detectors alone.


#9637 - 05/08/02 10:35 PM Re: AFCI's Tripping upon Ground Fault Test  
caselec  Offline
Member
Joined: Apr 2002
Posts: 558
San Jose, CA
Some of the city's I work in have required the smoke detectors to be on their own circuit and I have always been against it. I agree with Electricmanscott that if they are tied on with lights or receptacles it is not very likely that this circuit will be turned off for very long. If they are on their own circuit the only way to know that the circuit is off would be to look for the little LED light in the detectors. How many home owners look to see if the light is on in their smoke detector? As to the comment about the batteries being removed, if the batteries are low OR removed the detector will beep until a good battery is installed.


Curt Swartz

#9638 - 05/09/02 08:46 AM Re: AFCI's Tripping upon Ground Fault Test  
Brendan Foley  Offline
Member
Joined: Dec 2001
Posts: 35
Cleveland, TN
All commercially available AFCI's also have equipment level GFI protection inherent in the design. This would explain why the GFI tester trips the breaker. I am not familiar with the specs of these testers, but our sensitivity level, is 30 mA.

The code does not limit AFCI protection to the bedroom, that is merely the minimum standard. I agree with Don that there is no limit to which circuits can have AFCI protection. I have them throughout my home on every 15 and 20 amp 125v circuit.

Tying in the smokes to a lighting circuit makes sense as a trip indication. However if the only thing that is on the circuit is the smokes, you would probably be less likely to have an event that would cause a trip as long as all of the connections are good, and the insulation integrity of the circuit is good.

The AFCI's will trip on overloads and short circuits just like standard circuit breakers. However, there is added protection for arcing faults and ground faults.

The proper way to test the breaker is to push the test button. I cannot speak to the other manufacturers' designs, but our AFCI test button puts a simulated arc current wave form into the custom integrated circuit, thus tripping the breaker. If upon pushing the test button, the breaker does not trip, then the breaker should be replaced.

Brendan Foley
Eaton | Cutler-Hammer


#9639 - 05/09/02 05:55 PM Re: AFCI's Tripping upon Ground Fault Test  
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
Hmm, I can see both sides of the argument for smoke detectors on their own circuit or combined with lights.

I suppose the ultimate system to get the best of both worlds would be an individual circuit for the detectors fed from a C/B with an integral alarm contact which sounds a separate buzzer if it trips, a little like the alarm fuses used in telephone exchanges.
That's probably getting carried away for residential though.

Brendan,
How did Cutler-Hammer come up with 30mA as the trip threshold for integral ground-fault protection in your AFCIs? Is is just coincidence that 30mA happens to be the standard ground-fault threshold for GFI in Europe now, or were your breakers designed with IEC specifications in mind as well as UL/ANSI?


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