arc fault ghost

[billdozier]

Hey guys he showed up in alabama today. had a custom we were finishing up punch list. simple untill we started troubleshooting one closet light in a bedroom. Thats where he showed up. Tried changing breakers still there. broke apart plugs switches the whole nine. still there. Got into attic pulled out staples still there. Decided to run 12-2 from panel to origin of switch cleared put in switch leg jumper cleared put in plug jumpers cleared ok put original homerun back and remake joints everything clears we didnt do anything but bust joints and pull plugs and now it works I hate arcfault breakers. The one thing I found odd was after we had busted the homerun loose it would hold untill we turned on a breaker on the opposite phase then it would trip. What would cause this tripping. There were loads on the other breakers. Watch out for the ghost hes a tricky charectar

 

[charlietuna]

Sounds to me there is a mixed up splice on a neutral.........

 

[raider1]

Sounds like to me there is a connection between the neutrals of the two circuits. This will cause an imbalance in the current on the neutral wires and the GFPE part of the AFCI breaker is tripping.

Just a thought.

Chris

 

[electricalperson]

the ideal suretest circuit analyzer will test for shared neutrals and will trip the GFCI if theres one.

that tool and a megger is a good thing to troubleshoot afci's with. just dont megger an afci breaker

 

[billdozier]

heres the thing we cleared it and never found any shared neutrals. nothing we put the plugs and switches back in how we pulled them out and everything cleared. What gives? It had to be the ghost

 

[quogueelectric]

I for one do not believe in ghosts. If it is tripping an adjascent breaker ther is a miswire between them.

 

[iwire]

heres the thing we cleared it and never found any shared neutrals. nothing we put the plugs and switches back in how we pulled them out and everything cleared. What gives? It had to be the ghost

It could have been as simple as a bare ground wire hitting the neutral terminal on a receptacle before you pulled it out.

 

[billdozier]

we checked all of the grounds before we pulled the plugs out thinking that had to be it nope course not we didnt change any wiring just pulled some plugs out. I hate arcfaults and dread adoption of 08 in my area. They trip for no reason and fix themselfs sorry cow but thats a ghost or gremlin

 

[Fulthrotl]

heres the thing we cleared it and never found any shared neutrals. nothing we put the plugs and switches back in how we pulled them out and everything cleared. What gives? It had to be the ghost

just a thought.... but if i had nuisance tripping, and swapped afci's and
it didn't clear, my next shot would be to slam in a regualar breaker,
heat it up, and go looking for a faulted neutral before i removed anything.

shut off everything but the offending circuit, and go looking with a
shurtest. it'll show a neutral fault within fifteen feet or so of the
device you are plugged into, (upstream, that is) so you can test each
one until you get a reading, then rip stuff apart....so if the first device
is within 15' of the panel, the panel will show up as a fault, but you can
just go device to device until it lights up, and then start there and
go backwards.

 

[ohm]

Hey guys he showed up in alabama today. had a custom we were finishing up punch list. simple untill we started troubleshooting one closet light in a bedroom. Thats where he showed up. Tried changing breakers still there. broke apart plugs switches the whole nine. still there. Got into attic pulled out staples still there. Decided to run 12-2 from panel to origin of switch cleared put in switch leg jumper cleared put in plug jumpers cleared ok put original homerun back and remake joints everything clears we didnt do anything but bust joints and pull plugs and now it works I hate arcfault breakers. The one thing I found odd was after we had busted the homerun loose it would hold untill we turned on a breaker on the opposite phase then it would trip. What would cause this tripping. There were loads on the other breakers. Watch out for the ghost hes a tricky charectar

Wow talk about a coincidence, I've got the same problem in Birmingham. I'ts even in a bedroom closet! AFCI #2 and #3 trip if the closet light switch is closed. Since I ran the circuits in the same conduit to a JB in the attic (remodel) I dread a trip into the attic.

I get good megger readings except for .05 meg between the hot and neutral on ckt #2 so I must have miswired at the JB or skinned a wire.

Bill, if I don't post again soon...how about checking for me in the attic.

 

[ohm]

Wow talk about a coincidence, I've got the same problem in Birmingham. I'ts even in a bedroom closet! AFCI #2 and #3 trip if the closet light switch is closed. Since I ran the circuits in the same conduit to a JB in the attic (remodel) I dread a trip into the attic.

I get good megger readings except for .05 meg between the hot and neutral on ckt #2 so I must have miswired at the JB or skinned a wire.

Bill, if I don't post again soon...how about checking for me in the attic.

Bill, climbed into the attic today (about 2 ft clearence) and guess what I did? I had two AFCI ckts. in one JB and fed the hot from one AFCI using the neutral from the other...just like everyone guessed. When I turned on the closet light both AFCI's tripped. Have you killed your ghost yet? These talks help!

 

[rt66electric]

must have load on to test

must have load on to test

I spent 8 hours or more locating a "screwed wire". Remember you must have a load on the offending circuit. I used a -light bulb in a temphead and a male cordcap setup- to plug into recepts(its the first and cheapest thing I found out of the truck). If there is no other loads on the circuit, a load from another circuit will cause an AF to trip. Isolate the problem circuit by loading each circuit individually and testing with all other AF's off. Electricity will run from the neutral side of a load (lightbulb) on one circuit and allllll-thee-way-around the house through the neutal and busbars and find the spot where the ground and neutral are touching, causing a infinitesimally(itty-bitty) small arc that is detected by the AF. The resistanace at the faultpoint is less than traveling all-the-way to the EGC. Don't get fooled and chase down the wrong circuit. Start in the middle of the faulty run, pulling recepts and such and work your way to the problem, it is Probably a neutral touching a ground. After several "inspection holes" cut in the drywall (wishing I had one of those durn see-snakes) I found a screw that went through 2romex cables hitting both neutrals and both grounds. (troubleshooting was confusing because I had TWO faults, one before and one after the recept) I was unable to put a load on the damaged curcuit to because it was the 1st recept from the panel, But a load on a nearby circuit would give me the testload needed to trip the AF. Charged the H0/GC for my time.

 

[billdozier]

ohm glad you found your neutrals shared sorry you had to get in an attic to do it. Mine cleared after we pulled on wires and traced everything out. Never found a reason for the initial trip. Cleaners plugged in vacum and it tripped. Another guy from the shop went reset the breaker put electric drill on circuit and it wouldnt trip. Thats why I think it was a ghost

 

[ELA]

I spent 8 hours or more locating a "screwed wire". Remember you must have a load on the offending circuit.

If there is no other loads on the circuit, a load from another circuit will cause an AF to trip.


Electricity will run from the neutral side of a load (lightbulb) on one circuit and allllll-thee-way-around the house through the neutal and busbars and find the spot where the ground and neutral are touching, causing a infinitesimally(itty-bitty) small arc that is detected by the AF.


The resistanace at the faultpoint is less than traveling all-the-way to the EGC.

.

Interesting information and troubleshooting, thanks.
I am not sure I agree with the part about an "itty-bitty arc" being detected though.

It is my understanding that AFCI's will not detect an arc of less than 5 amps.
I think it is likely most "ghost" trips are due to the GFI portion of the AFCI which trips at 30 -50 ma.

It is interesting, and can be easily replicated , that the GFI portion of the AFCI can trip even without an intended load downstream of the AFCI.
As long as there is a neutral to ground connection downstream of the AFCI
++ sufficient current flow in other unprotected circuits.


As you pointed out current from another circuit can use this AFCI's downstream neutral-ground fault as a parallel path resulting in a GFI trip.

I really think the manufacturers should be required to provide an indicator to show if the AFCI tripped due to a ground fault or an ARC.

 

[ohm]

I spent 8 hours or more locating a "screwed wire". Remember you must have a load on the offending circuit. I used a -light bulb in a temphead and a male cordcap setup- to plug into recepts(its the first and cheapest thing I found out of the truck). If there is no other loads on the circuit, a load from another circuit will cause an AF to trip. Isolate the problem circuit by loading each circuit individually and testing with all other AF's off. Electricity will run from the neutral side of a load (lightbulb) on one circuit and allllll-thee-way-around the house through the neutal and busbars and find the spot where the ground and neutral are touching, causing a infinitesimally(itty-bitty) small arc that is detected by the AF. The resistanace at the faultpoint is less than traveling all-the-way to the EGC. Don't get fooled and chase down the wrong circuit. Start in the middle of the faulty run, pulling recepts and such and work your way to the problem, it is Probably a neutral touching a ground. After several "inspection holes" cut in the drywall (wishing I had one of those durn see-snakes) I found a screw that went through 2romex cables hitting both neutrals and both grounds. (troubleshooting was confusing because I had TWO faults, one before and one after the recept) I was unable to put a load on the damaged curcuit to because it was the 1st recept from the panel, But a load on a nearby circuit would give me the testload needed to trip the AF. Charged the H0/GC for my time.

I told a guy about the method the Navy taught to troubleshoot a circuit. They said start in the middle (just as you said). He called it the "binary method". Don't check every receptacle but skip half of them every time and it should speed things up. And yes, load down the circuit. Sometimes I use a 1/2" hole hawg, so I can listen to results, even from another room.

Yesterday I found a loose screw on a receptacle running about 200 deg. that way. It was feeding another room and only working if the load was small. The wire and receptacle were all charred and even the cover and wall were darkened. The house didn't have AFCI's and was well on it's was to being toast.

 

[jayrad1122]

Siemen's Afci's do..

Siemen's Afci's do..

I really think the manufacturers should be required to provide an indicator to show if the AFCI tripped due to a ground fault or an ARC.

The Siemens Combination AFCI has leds that tell if it tripped because of an overcurrent, arc fault, or arc fault to ground. I have not installed one yet to see how it works, but this info is out of the brochure I have.

 

[Full Spool]

It could have been as simple as a bare ground wire hitting the neutral terminal on a receptacle before you pulled it out.

That would be my guess, I have had the similar problem before.

 

[ohm]

Interesting information and troubleshooting, thanks.
I am not sure I agree with the part about an "itty-bitty arc" being detected though.

It is my understanding that AFCI's will not detect an arc of less than 5 amps.
I think it is likely most "ghost" trips are due to the GFI portion of the AFCI which trips at 30 -50 ma.

It is interesting, and can be easily replicated , that the GFI portion of the AFCI can trip even without an intended load downstream of the AFCI.
As long as there is a neutral to ground connection downstream of the AFCI
++ sufficient current flow in other unprotected circuits.

As you pointed out current from another circuit can use this AFCI's downstream neutral-ground fault as a parallel path resulting in a GFI trip.

I really think the manufacturers should be required to provide an indicator to show if the AFCI tripped due to a ground fault or an ARC.

I'm still learning about AFCI's. I had one trip because of a problem upstream not downstream. An IEEE paper by an AFCI mfg. said the wideband noise generated by an arc was one condition of their trip strategy. Noisy power to the AFCI is just as important as noise downstream. It can easily be heard by an AM radio tuned off a station.

 

[ohm]

That would be my guess, I have had the similar problem before.

That's why I use stranded green THHN to pigtail my receptacles in a crowded box.

 

[CopperTone]

we're been on the 08 since jan. 08 - I hope I am not jinxing myself but we use arc faults every day and never have problems with them. Well only once but it turned out to be a screw through the wire - it was our own fault.
Been using them on the 05 in bedrooms as well with no problems.

I hate explaining the extra cost to customers all the time - I make more money with mark up and all - but it's always the same why why why questions - same with TR receptacles but they are a cheaper sell.