Arc Fault

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jap

Senior Member
Occupation
Electrician
I helped a friend of mine locate an Arc Fault problem last night.
Arc fault to the Master Bed and Bath tripped and shut off all of the lights.
When I got there I tried to reset the breaker but it would trip immediately.
I took the hot and the neutral off and the breaker held.
I left it on, and touched the neutral to the breaker neutral terminal and it tripped.
I thought that it was interesting that it tripped even though the hot was not hooked up,so I reset the breaker but left the hot disconnected.
went down the line seperating the neutrals in the switch boxes until it cleared.
Found a socket in the Vanity Light where the neutral was touching the metal housing, repaired it and it solved the problem.
I dont do residential work but I just found it interesting that I could troubleshoot the problem without ever having to connect the hot to the breaker.
 

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
I helped a friend of mine locate an Arc Fault problem last night.
Arc fault to the Master Bed and Bath tripped and shut off all of the lights.
When I got there I tried to reset the breaker but it would trip immediately.
I took the hot and the neutral off and the breaker held.
I left it on, and touched the neutral to the breaker neutral terminal and it tripped.
I thought that it was interesting that it tripped even though the hot was not hooked up,so I reset the breaker but left the hot disconnected.
went down the line seperating the neutrals in the switch boxes until it cleared.
Found a socket in the Vanity Light where the neutral was touching the metal housing, repaired it and it solved the problem.
I dont do residential work but I just found it interesting that I could troubleshoot the problem without ever having to connect the hot to the breaker.

You didn't disconnect the hot, you disconnected the load. Power was still supplied to the breaker by virtue of the clip on the breaker to the buss. The breakers must be AFCI / GFCI combos, correct? If so, it was the GFCI circuitry that detected current on the neutral and none on the load, thus causing the trip.
 

jap

Senior Member
Occupation
Electrician
Although i believe it was just a combo arc fault breaker, didnt look that close but it was a Sq. D Homeline with a Blue Test button.It was only feeding the Lighting Circuit not any receptacles.
 

jap

Senior Member
Occupation
Electrician
I'll have to go by and see if it was a combo AFCI / GFI or not.
 

jap

Senior Member
Occupation
Electrician
How would it detect current on the neutral if the load was disconnected?
from the circuitry inside of the breaker?
 

klineelectric

Member
Location
FL
Occupation
electrical contractor
the neutral in the circuit detected a ground from the light fixture.
Arc-fault and gfci breakers seperate the neutral and ground and trip if they are connected........ as opposed to a standard circuit and breaker where the ground and neutral are connected at the main service.
 

brian john

Senior Member
Location
Leesburg, VA
Rather than randomly turning on CB's that have tripped, why not investigate trouble shoot and test. Much safer way to investigate tripped CB's
 

brantmacga

Señor Member
Location
Georgia
Occupation
Former Child
sqd blue buttons are not combo's, and all of them were recalled 2-3 years ago. it should've been replaced w/ a green button cb. sqd combo's have white buttons.

and combo does not refer to afci/gfci; it references the breaker being able to sense series and parallel arcs.


agree with brian this was not the smartest way to troubleshoot the circuit.
 

jap

Senior Member
Occupation
Electrician
This is an Arc Fault Breaker only,not a GFI.
The "Combo" means it detects series or parrallel faults,not GFI/AFCI combo.
My question is, if the load was not connected to the breaker, although the breaker was on,then what did the arc fault use to trip itself when the neutral was touched to the neutral terminal on the breaker ? If it does sense the current on the neutral to ground, then the only current it could have had on it would have been from the circuitry inside the breaker, not the Load, since the load was disconnected.

I did a lot more testing than what I had mentioned previously, there was just too much to type.

I dont randomly do anything, and feel the same as you about people who do.
 

al hildenbrand

Senior Member
Location
Minnesota
Occupation
Electrical Contractor, Electrical Consultant, Electrical Engineer
My question is, if the load was not connected to the breaker, although the breaker was on,then what did the arc fault use to trip itself when the neutral was touched to the neutral terminal on the breaker ? If it does sense the current on the neutral to ground, then the only current it could have had on it would have been from the circuitry inside the breaker, not the Load, since the load was disconnected.
You can do this same "trip" with a simple GFCI breaker or GFI receptacle. Try shorting a piece of neutral to ground on the downstream side of the GFI, when the downstream hot is disconnected from the load side of the GFI.

It'll trip every time.

Even though the load (downstream side) is not energized, the circuitry of the AFCI (in your case) is providing the current to the load neutral when a return path through the equipment grounding conductor (EGC) happens. In a normal correct installation, the AFCI protected neutral should never "see" a return path through the EGC.

A GFCI uses a simple exciter circuit, that has zero current in a correct installation, to impress a current that will exceed 5 milliamps and trip the GFCI trigger.

The manufacturer's of AFCIs are so tight with their technical info that we can't point to a specific AFCI circuit diagram and say, this is the exciter. . . but the idea is similar.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
This is an Arc Fault Breaker only,not a GFI.
The "Combo" means it detects series or parrallel faults,not GFI/AFCI combo.
My question is, if the load was not connected to the breaker, although the breaker was on,then what did the arc fault use to trip itself when the neutral was touched to the neutral terminal on the breaker ? If it does sense the current on the neutral to ground, then the only current it could have had on it would have been from the circuitry inside the breaker, not the Load, since the load was disconnected.

I did a lot more testing than what I had mentioned previously, there was just too much to type.

I dont randomly do anything, and feel the same as you about people who do.
If I have this correct you had the breaker neutral connected to the panel netural and when you touched the load neutral to the breaker load terminal the breaker tripped.
Is this breaker in the same panel as the main bonding jumper? If so, I don't know why the breaker tripped. If it is in a sub panel, you created a parallel path for the grounded condcutor current and the 30 to 50 mA ground fault trip circuit in the AFCI might very well see enough current to trip.
 

LEO2854

Esteemed Member
Location
Ma
I helped a friend of mine locate an Arc Fault problem last night.
Arc fault to the Master Bed and Bath tripped and shut off all of the lights.
When I got there I tried to reset the breaker but it would trip immediately.
I took the hot and the neutral off and the breaker held.
I left it on, and touched the neutral to the breaker neutral terminal and it tripped.
I thought that it was interesting that it tripped even though the hot was not hooked up,so I reset the breaker but left the hot disconnected.
went down the line seperating the neutrals in the switch boxes until it cleared.
Found a socket in the Vanity Light where the neutral was touching the metal housing, repaired it and it solved the problem.
I dont do residential work but I just found it interesting that I could troubleshoot the problem without ever having to connect the hot to the breaker.

click this link there is a lot info here.http://www.nachi.org/forum/f19/afcis-explained-mike-holt-and-eaton-engineer-13375/
 

jap

Senior Member
Occupation
Electrician
Thanks Al that pretty well explained it, and yes Don,this AFCI Breaker had the Neutral Pigtail terminated to the neutral bar and was in the Main Panel in the garage.
I cant recall exactly how it was wired, but almost sure the Ground and Neutral were seperate at this panel , since there was a Main 200 amp Disconnect outside.

Previous replyers were concerned about randomly resetting a tripped arc fault, but, without the load being connected and the AFCI tripping do to the Neutral current being produced by the circuitry inside of the Arc Fault, I would think that this current would be very minute.

It was just interesting that the Arc Fault sensed the neutral to ground connection due to the current produced from the integral circuitry and not just the " Current Out" "Current Return" of the Load.

Very smart devices.
 

ELA

Senior Member
Occupation
Electrical Test Engineer
We had discussed this situation a while back and here is what I found relating to this issue:

http://forums.mikeholt.com/showpost.php?p=924581&postcount=11

To clarify the comment at the bottom , "Can AFCIs be used in a sub-panel ? ".
I know that they can.

What I should have said was if they are located in a sub-panel you are more likely to experience their tripping on a downstream Neu-Gnd short if it existed. (even without a load)
 

al hildenbrand

Senior Member
Location
Minnesota
Occupation
Electrical Contractor, Electrical Consultant, Electrical Engineer
As noted here, the new "MOD 3" GE AFCI has no GFCI component, as stated by advertising text. Note that, in Dennis Alwon's posted diagram, two single pole AFCIs are used on a multiwire circuit, and one of the AFCIs is not connected to the load (multiwire) neutral . . . very curious.

Now, whether the MOD 3 GE AFCI is insensitive to load side neutral to EGC contacts (ground faults) is not clear based on anything that I am aware of that GE has published.

I bring this up to underscore how ridiculous the manufacturer control of AFCI technical information is.

IMO, each of the manufacturers of AFCIs has a unique hardware solution to the UL AFCI requirements, and that the manufacturers are upgrading their hardware solutions as they react to the field performance of the previous versions. The result, for those of us troubleshooting real world installations, is a need treat the AFCI as a mystery black box, or is to memorize the reported behavior of the many versions of AFCI.

I hope a homogeneous, and published, standard can be arrived at sometime before I die, . . . but it is a dim hope.
 

jap

Senior Member
Occupation
Electrician
hang in there.


By the way, I would never hook up (2) 1p Arc Faults on a MWBC with a shared neutral as indicated on that diagram, but thats just me.
To me it puts too much responsibility on the Handle tye and is also relying on Pete to trip Paul.

Thanks,
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
hang in there.


By the way, I would never hook up (2) 1p Arc Faults on a MWBC with a shared neutral as indicated on that diagram, but thats just me.
To me it puts too much responsibility on the Handle tye and is also relying on Pete to trip Paul.

Thanks,
I don't understand. There is no requirement for a common trip when using a MWBC. The requirement is for a means of simultaneous disconnect. There is no issue with a handle tie providing the simultaneous means of disconnect as that is its intended purpose. It is not intended to provide a common trip.
 

jap

Senior Member
Occupation
Electrician
At first glance I was under the impression that if there was a fault on B phase or a neutral to ground connection,and the Neutral was connected to the A phase Arc Fault breaker, the A phase breaker would trip and in turn trip the B Phase Arc Fault.(There is no way that that could be the case).

I wasnt sure how the B Phase Breaker would trip since there was no return neutral attached to it.

Will an arc fault activate if there is a problem regardless of wether there is a neutral return path connected to it or not ? if so, it would clear a lot of things up for me.

I would just never use (2) 1p Arc faults with a handle tye on a multiwire branch circuit.
Although it seems by the literature that it would be fine,and I'm sure a lot do,I dont like the way the neutral of the shared circuits only land on one of the breakers.
I would install (2) Arc faults with (2) Seperate romexes, But thats just me.
 

jap

Senior Member
Occupation
Electrician
I guess I'm too caught up on my interpretation of the GFI "What goes out must come back" and be equal amounts or I'm going to trip scenario.

which it seems on an Arc Fault Breaker this is not necessarily the case.
 
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