arc fault ghost

[ohm]

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

I hate it when problems just clear up. They usually come back to haunt me.

 

[ELA]

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.

I am still learning about AFCI's also. I have recently been performing extensive testing on one brand of AFCI in order to learn more.
It is true that one of the requirements for detcting an arc is high freq noise in the 10K -100Khz band.

I do not agree with what you said as far as , "Noisy power to the AFCI is just as important as noise downstream".

That would depend upon how the AFCI measures the high freq. noise levels, whether voltage sensing or current sensing. If current based then the noise current must be conducted through the AFCI sensing core (as it is with a downstream arcing load). This noise current must also have a higher energy level when compared to a normal radio frequency emission level.

 

[ohm]

I am still learning about AFCI's also. I have recently been performing extensive testing on one brand of AFCI in order to learn more.
It is true that one of the requirements for detcting an arc is high freq noise in the 10K -100Khz band.

I do not agree with what you said as far as , "Noisy power to the AFCI is just as important as noise downstream".

That would depend upon how the AFCI measures the high freq. noise levels, whether voltage sensing or current sensing. If current based then the noise current must be conducted through the AFCI sensing core (as it is with a downstream arcing load). This noise current must also have a higher energy level when compared to a normal radio frequency emission level.

ELA I'm no expert but the following Siemens article

http://www2.sea.siemens.com/NR/rdon...BCF53/0/IEEE_Holm_Conference_Final_061107.pdf

mentions current generated broadband noise from 10 Hz to 1GHz. This seems like a good article but other presentations I've attended are pretty tight-lipped.

The failure I saw was when an arching stab on a main breaker caused a downstream AFCI (GE series unit) to trip.

If you've got some findings from your work I (and many others) would love to hear them. Thanks.

 

[ELA]

The failure I saw was when an arching stab on a main breaker caused a downstream AFCI (GE series unit) to trip.

If you've got some findings from your work I (and many others) would love to hear them. Thanks.

Ohm,
I am no expert either. If the upstream feeder has a loose connection then the current through the AFCI can be pulsing at a high rate and could cause a trip.

If that is what you meant when you said , "Noisy power to the AFCI is just as important as noise downstream" , then I agree.

It is important to qualify that the "noisy power" is being created by a loose connection (or arc). Noisy power can come from many sources other than an arc.

I have been doing investigations over a long period when I can find the time. I will start a new thread and share the information once I complete my testing.

 

[jumper]

I hate it when problems just clear up. They usually come back to haunt me.

amen to that. imho its true 99% of the time and i still worry about the other 1%, because i believe its only a matter of time. problems dont "just clear up", they just stay hidden longer.

 

[CopperTone]

if a vacuum is plugged in under load it will cause an arc while the plug is being inserted into the receptacle. This will trip the arc fault.

I tell people all the time to make sure the piece of equipment switch is off then plug it in then turn it on. This I have seen happen a lot. I have seen it happen with lamps, alarm clocks, dehumidifiers, etc

 

[ohm]

if a vacuum is plugged in under load it will cause an arc while the plug is being inserted into the receptacle. This will trip the arc fault.

I tell people all the time to make sure the piece of equipment switch is off then plug it in then turn it on. This I have seen happen a lot. I have seen it happen with lamps, alarm clocks, dehumidifiers, etc

Switching a user off , especially a heavy load, prior to plugging it in, is always a good idea to save the connection but I've not seen it trip an AFCI yet.

When the series AFCI first came out we tried & tried to get a trip in the class I was teaching, to no avail.

We also tried to get a trip by driving a staple into a piece of romex. After much effort we could get a trip on an AFCI but the 20A standard breaker held. I was getting worried and the class was getting frustrated.

Maybe the combo does better.

 

[ELA]

Switching a user off , especially a heavy load, prior to plugging it in, is always a good idea to save the connection but I've not seen it trip an AFCI yet.

When the series AFCI first came out we tried & tried to get a trip in the class I was teaching, to no avail.

We also tried to get a trip by driving a staple into a piece of romex. After much effort we could get a trip on an AFCI but the 20A standard breaker held. I was getting worried and the class was getting frustrated.

Maybe the combo does better.

Ohm,
I have had similar results at purposely trying to get a combination arc fault to nuisance trip. I think that - just like the GFCI they have gotten better at nuisance trip immunity as they mature. Perhaps some manufacturers are better than others as far as immunity to false trip?

It sounds like your class should be interesting for your students.
Do you have or have you tried using an Ideal Sure Test Circuit Analyzer as part of your work or class?
I know those devices cannot officially be used to identify an AFCI device as faulty but they seem like they could be a good tool in debugging and demonstrations?

 

[ohm]

Ohm,
I have had similar results at purposely trying to get a combination arc fault to nuisance trip. I think that - just like the GFCI they have gotten better at nuisance trip immunity as they mature. Perhaps some manufacturers are better than others as far as immunity to false trip?

It sounds like your class should be interesting for your students.
Do you have or have you tried using an Ideal Sure Test Circuit Analyzer as part of your work or class?
I know those devices cannot officially be used to identify an AFCI device as faulty but they seem like they could be a good tool in debugging and demonstrations?

I haven't taught in a few years and haven't used a sure test yet but I'm inches away from getting one. $280 is about the best price I've found and another $100 for case,leads etc.

I've gotten by with digital multimeters, meggers, earth testers large loads and wiggies so far but from what I'm reading the sure test seems like a time saver...what say you?

 

[ELA]

SureTest ?

SureTest ?

I have not used the Ideal Suretest products and that is why I asked if you had. I know there are others on this forum that have used them and seem to feel they were of value.

I do not regularly troubleshoot AFCI circuits and I cannot offer any direct experience as to their value. I would be interested in hearing from those who do own them in terms of their value in the troubleshooting process.

 

[Fulthrotl]

I have not used the Ideal Suretest products and that is why I asked if you had. I know there are others on this forum that have used them and seem to feel they were of value.

I do not regularly troubleshoot AFCI circuits and I cannot offer any direct experience as to their value. I would be interested in hearing from those who do own them in terms of their value in the troubleshooting process.

i got one for a couple reasons.... i had a neutral fault test to pass,
and this made it easier to find the cross connect. as i posted earlier,
it'll detect a neutral / ground cross connect upstream for about 15'.

that'll let you test without loading the circuit. it's fast.

here's the other reason.... all the inspectors around here are starting to
get them. i don't call for inspection unless i know it'll pass, and if i don't
have the tool the inspector is gonna use, well, it's a crap shoot.

now, here's what i learned on here... dunno if it is out yet, but the newest
generation of suretest will tell the amount of load on a branch circuit, from
any point in the circuit.

so, if you are gonna buy one, check and see if the unit you buy has that
feature yet... mine doesn't......

it's also an excellent diagnostic tool on a number of levels. i had a 'pooter
network administrator having his undies in a wad about a power source
for his server.... i stuck the suretest on the outlet, and it comes up with
info that looks like this... it settles a lot of discussions.

first screen: all wiring correct, no cross connected neutrals / grounds

second screen: 121.2 volts rms h/n
0.1 volts rms n/g
171.3 volts h/n peak
60.0 hz frequency

third screen: voltage drop 4.4% @ 15 amps, 115.5 volts available
voltage drop 5.8% @ 20 amps, 113.9 volts available
voltage drop 3.5% @ 12 amps, 116.7 volts available

fourth screen: 480 amps bolted fault available at that point, h/n
550 amps bolted fault available at that point, h/n/g

fifth screen: .34 ohms total impedance, hot
.02 ohms total impedance, neutral
.25 ohms total impedance, ground

all of the values are from the point of connecton to the secondary winding
of the poco, or next upstream transformer.

sixth screen: gfci trips at 164 ms @ 7.4 ma

seventh screen: afci test... here is the instructions from the manual:

"AFCI breakers are prone to nuisance tripping when wired with a shared
neutral or when the neutral conductor is accidentally grounded before
the panel. The AFCI tripping occurs because it senses an imbalance
between the current going out on the hot and the current returning
on the neutral. A shared neutral between two hot conductors creates
this imbalance.

The SureTest can test for these conditions by applying a small load of 300mA
between hot and neutral to simulate a normal load and ensure that the AFCI
breaker does not trip. To conduct a shared neutral test, press the AFCI
button to enter the AFCI main menu. Press the side arrow ( ) to highlight the
NEUT symbol. Then, press the AFCI button to activate the test. The TEST
icon will light brightly while the test is being conducted. The AFCI breaker
should not trip. If the breaker does trip, a shared neutral is the probable
cause.

 

[ohm]

Fulthrotl, thanks for a great run-down, you should be in sales! I'll look for the current feature you mentioned.

 

[izak]

Quote: From OHM

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


how do you terminate that stranded wire under the green screw on the receptacle without violating the listing?

most (not all) 15 and 20 amp 120/277 volt devices arent designed to terminate stranded wire under the green screw...

 

[izak]

Sorry guys... censure me if you feel necessary, but,



BILLDOZIER: In my opinion, anyone who will attribute problems with technology that he/she cannot understand to "ghosts" only shows thier extreme ignorance in regards to that matter and in my opinion, should be treated as other users/moderators on this forum treat DIY questions and statements....

Harsh? maybe. but give me a break.
we are all supposed to be Trade Professionals here.
some of you may consider me a prick for this post but I mean, in the last seven YEARS we have had PLENTY of time to learn how to use/treat this equipment. If you havent got it by now..... well.... i dont want to hear/see anymore 'GHOST' BS

 

[ELA]

so, if you are gonna buy one, check and see if the unit you buy has that
feature yet... mine doesn't......

it's also an excellent diagnostic tool on a number of levels.

fifth screen: .34 ohms total impedance, hot
.02 ohms total impedance, neutral
.25 ohms total impedance, ground

Thanks Fulthrotl,
Sounds like a nice tool to have if you need to deal with AFCI installation and troubleshooting.

I read a while back about a firmware upgrade needed to help it detect if the line impedance was too high when using the AFCI test portion of the unit.
Does your have that upgrade?

When I read that release it made sense to me that if the line impedance was too high that a true parallel arc could not be simulated since >75 amps may not be available at the point of test.

That then made me wonder. Do these devices simulate a parallel arc, series arc or both?

It seems if they simulated a series arc that then a higher impedance line could still be tested in the AFCI mode?

 

[ohm]

Quote: From OHM

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


how do you terminate that stranded wire under the green screw on the receptacle without violating the listing?

most (not all) 15 and 20 amp 120/277 volt devices arent designed to terminate stranded wire under the green screw...

Actually a check of the White Book will reveal all of those devices are rated for solid or stranded to #10 AWG. The cup at the screw screw is a good indicator.

 

[ohm]

Thanks Fulthrotl,
Sounds like a nice tool to have if you need to deal with AFCI installation and troubleshooting.

I read a while back about a firmware upgrade needed to help it detect if the line impedance was too high when using the AFCI test portion of the unit.
Does your have that upgrade?

When I read that release it made sense to me that if the line impedance was too high that a true parallel arc could not be simulated since >75 amps may not be available at the point of test.

That then made me wonder. Do these devices simulate a parallel arc, series arc or both?

It seems if they simulated a series arc that then a higher impedance line could still be tested in the AFCI mode?

I believe the 75A is peak not RMS so it could be available in all but the most extreme situations.

 

[ELA]

I believe the 75A is peak not RMS so it could be available in all but the most extreme situations.

Why would you say that?
You read 75 amps in all publications I have seen. I have never seen them specify "peak" . If no qaulifier is made I usually understand it to mean average or RMS.

Here is one link that specifically says 75A RMS.

www.eaton.com/ecm/idcplg?IdcService=GET_FILE&dID=69015

I do not have access to UL1699 but that should be the definitive.

Besides that does not matter in terms of what I posted about the SureTest upgrade. Either way the device would not trip if the line impedance was too high. So surely they encountered issues in the real world where the line impedance was too high.

 

[Fulthrotl]

Fulthrotl, thanks for a great run-down, you should be in sales! I'll look for the current feature you mentioned.

i am in sales. ask my customers.....

"of course, i'd be happy to do that for you as well.."
"if you need something done, and i can't do it, i'll hook you up
with someone good who can, and it'll be someone good..."

and the 4 most expensive words ever spoken to a customer:
"while you're at it...."

or, even better:
"while you are at it, it would be a shame not to......"

nobody wants to live in shame. and for only $xxxx,
i can remove the source of the shame.
i specialize in shame reduction.

this one isn't as good, however... don't use it:
"we can get this little job done, if it takes every penny the poor thing has."

 

[Fulthrotl]

Thanks Fulthrotl,
Sounds like a nice tool to have if you need to deal with AFCI installation and troubleshooting.

I read a while back about a firmware upgrade needed to help it detect if the line impedance was too high when using the AFCI test portion of the unit.
Does your have that upgrade?

not yet... i printed out the letter, and have to get a rma, and send it in.
for my model number, and serial number, there is no charge for the upgrade.

wonder if the firmware upgrade would allow it to measure the current in
the branch circuit.... hmm.... we can only hope.....


randy