AFCI trouble

[jerrygar]

I need some help on what the problem may be:

New construction, completed and ready to call for final. One (of 4) afci breakers trips whenever anything on its circuit is activated. Put in a regular breaker, it holds. Tried a different afci, it trips.

Now for the complication: There is a sub-panel downstairs. Connect an electric tool to the outside gfi receptacle and turn it on. The above mentioned afci breaker trips. The others hold.

Help!

 

[kbsparky]

Sounds like the neutral conductor is NOT connected to the breaker ... OR the circuit has a redundant connection to another neutral in a multi-gang switch box.

Either way, the breaker will hold under no load, but will immediately trip once anything is turned on.

 

[macmikeman]

Jerry, Kb probably has it right, but one more thing. I got a whole batch of bad combo ones from one of the supply houses in Mapunapuna one day. Changing out the suspect afci was just leading me down a crazy path until I finally figured out the problem was the whole batch, not the wiring......
Makes me wonder if they were counterfeit breakers.

 

[Pierre C Belarge]

AFCI circuit breakers have GFP protection as part of the protection scheme.
The GFP protection is generally set to shunt the circuit at 30 miliamp or more, each manufacturer may be a little different.

The GFP shunt will not operate when the breaker is turned on, it will need a load on the circuit. The load most likely has a neutral to equipment ground connection somewhere in the circuit.

Turn each item on individually. You should be able to come close to locating it, and then find it as you fine tune the trouble shooting.

 

[gndrod]

AFCI circuit breakers have GFP protection as part of the protection scheme.
The GFP protection is generally set to shunt the circuit at 30 miliamp or more, each manufacturer may be a little different.

The GFP shunt will not operate when the breaker is turned on, it will need a load on the circuit. The load most likely has a neutral to equipment ground connection somewhere in the circuit.

Turn each item on individually. You should be able to come close to locating it, and then find it as you fine tune the trouble shooting.

Good stuff Pierre, I agree with the different mfr ranges. The leakage detection can make the trip factor difference between 30 ma to 50 ma ranges in brands. rbj

 

[gndrod]

I need some help on what the problem may be:



Now for the complication: There is a sub-panel downstairs. Connect an electric tool to the outside gfi receptacle and turn it on. The above mentioned afci breaker trips. The others hold.

Help!

Jerry,

Am I reading this correctly? The GFCI holds while on one BC in the basement subpanel and the AFCI trips on another different BC in the same subpanel? rbj

 

[M. D.]

I'm taking a required code class and a guy there said that an AFCI was tripping in a panel and the cause was a bad connection to the bus of another non AFCI breaker ,.. Not sure how that works,.. But if one AFCI can protect the all the circuits on a given phase ,. Why do we need to install so many?
The guys running the class did not have much to say either way on the possibility .
Anyway that was his story,...

 

[chris1971]

I had a problem with a AFCI breaker. It would hold under no load and trip when I plugged something in. I ended up opening up all the receptacles and I found the ground wire touching the neutral terminal on the receptacle. Once I removed this condition then, the breaker operated properly. Hope that might help you?

 

[ELA]

Here is an explanation for why a load on a totally different circuit can trip the GFP part of the AFCI.

I was testing AFCIs a while back and I found that it was tripping when I had a low resistance connection between the ground and the neutral wire but NO LOAD on the AFCI circuit. At first it appeared as though the breaker had the Neutral-Ground detection of newer GFCIs (where it can detect the downstream neutral-ground short without having a load)
When I read more about the AFCI it did not state anywhere that it had that special capability. I then realized that this AFCI would trip due to the fact that I had an upstream load (light) that I was unaware of. When I turned the upstream light off then the AFCI would no longer trip.

This diagram attempts to show thew concept and how the rise in the neutral voltage due the upstream load causes a neutral ->ground current to flow in the AFCI and it trips.

http://i268.photobucket.com/albums/jj22/transorb/AFCIupstream.jpg

 

[gndrod]

Here is an explanation for why a load on a totally different circuit can trip the GFP part of the AFCI.

I was testing AFCIs a while back and I found that it was tripping when I had a low resistance connection between the ground and the neutral wire but NO LOAD on the AFCI circuit. At first it appeared as though the breaker had the Neutral-Ground detection of newer GFCIs (where it can detect the downstream neutral-ground short without having a load)
When I read more about the AFCI it did not state anywhere that it had that special capability. I then realized that this AFCI would trip due to the fact that I had an upstream load (light) that I was unaware of. When I turned the upstream light off then the AFCI would no longer trip.

This diagram attempts to show thew concept and how the rise in the neutral voltage due the upstream load causes a neutral ->ground current to flow in the AFCI and it trips.

http://i268.photobucket.com/albums/jj22/transorb/AFCIupstream.jpg

Hi ELA,
From the diagram, describes parallel connected on the same BC compared to the different BC's load-no load interaction interpretation (mine) of the OP's statement. The QO115CAFCI is specifically Sq D, with diagram indicating tripping at 40ma that is off from the 50 ma trip threshold given from personal discussion with the manufacturer. According to Sq D, both L-N and L-G start at 50 ma whereas Line and Neutral initiate at 5 A available at the fault. I suspect there is additional parallel conductor imbalance between the light and AFCI loads involved. (WAG) rbj

 

[gndrod]

correction

correction

Hi ELA,
According to Sq D, both N-G and L-G start at 50 ma whereas Line and Neutral initiate at 5 A available at the fault. I suspect there is additional parallel conductor imbalance between the light and AFCI loads involved. (WAG) rbj

Pardon me...Typing and reading w/o glasses are a challenge. N-G (not L-N) and L-G are 50ma.

 

[ELA]

gndrod,
My 40 ma was an approximation. I have read values between 30 -50ma for GFP portion of the device. The exact number is not what is important in this discussion.

My diagram shows a load upstream on the same circuit because that was my test circuit. The concept is the same whether it be the same circuit or another circuit. What is important is that an upstream load can cause this issue.
A sub-panel condition would aggravate this situation.

 

[ohmhead]

Well not to say i have a solution to your problem but AFCI breaker protection is not as great as one may think it detects a leak between two conductors meaning a wave shape in the 60 cycle carrier wave so any old drill or motor or fan on that circuit and not in real good condition could trip it but i think the one post about miss wiring the neutrals is a real good point .

And a bad connection is good point to check funny thing it detects a spark or a minor spark between conductors or conductor but it has to be on for a length of time to trip kinda monitor the circuit so its not made to trip on motors and such devices when you plug it in but they do due to calibration .

I also think theres good ones and bad ones made today and as there new devices coming out to us they will find out in ten years that they may work find today but will it work when needed .

Bad brushes in motor