Not Sold on AFCI's

[ELA]

kwired,
He is a more direct link to that information:
http://forums.mikeholt.com/showthread.php?t=111163&page=3&highlight=AFCI
second post down.

Rather than look up a data base of acceptable waveforms, this would take a long time and require a much more powerful processor, it "looks" for certain characteristics present in the signature of an arc.

 

[kwired]

kwired,
He is a more direct link to that information:
http://forums.mikeholt.com/showthread.php?t=111163&page=3&highlight=AFCI
second post down.

Rather than look up a data base of acceptable waveforms, this would take a long time and require a much more powerful processor, it "looks" for certain characteristics present in the signature of an arc.

Still not finding information I'm looking for in that thread, but I can buy what you just said. Maybe a database of unacceptable waveforms would be a better way to go about it, but at same time is still going to be a little slow so it maybe needs to look for certain signature patterns and then when one is close to unacceptable then maybe evaluate closer. Maybe if not what is actually going on, but maybe should be what happens to help with unwanted tripping from items that are not a problem. Just a thought. Don't ask me how to cram all that logic into such a small package - but yet it is probably not too far from reality to do so, How many people thought 30 years ago we would have some of the pocket sized technology with the processing abilities some of that stuff has? And it is still improving as far as being able to get more processing power out of a smaller unit.

 

[ELA]

Glad to hear that you can buy it given the expense was so minimal

I guess you were looking for something other than these points made in that second post:?

1) A minimum of 75 amps present in the 60 hz portion of the waveform.

2) You can see that the 60hz component of the current is ?chopped? near zero cross. This simulates the arc extinguishing and then re-establishing itself about zero cross. This satisfies the rapid di/dt requirement.

3 & 4 ) In the peaks you can see high frequency oscillations. These are a combination of ~35Khz and ~55Kz frequencies.

A further requirement that provides for enhanced immunity to false trips is that the high frequency content -must only appear- during the peaks and not during the zero cross.

Below is a trace of one of the high frequency detection op-amp circuits outputs during an arc event. From this you can see that 6 half cycles was all that was required when presented with this simulated arc for the device to trip.

 

[templdl]

There is nothing I can pinpoint as to the reason. Sometimes it's just turning on a light fixture and sometimes there is no event at all proceeding the trip.

Just for grins on the troublesome circuit turn of the breaker remove all of the loads of that circuit, then remove the breaker and disconnect the EGC and neutral.
Then use an ohm meter measuring the resistance between the neutral and EGC. It should show an open circuit.
If so add 1/2 of the loads back and measure the resistance which should show an open circuit. Remove those loads and add the other half again measuring the resistance which should show an open circuit. If either half fails got back an isolate the loads in that half until you have located the offending load. Any continuity between the EGC and the neutral will most likely cause the nuisance tripping.
Should noting be found then reinstall the breaker and connect the conductors.
Add the loads 1/2 of them at one time and disconnect them then the other half. If you get a nuisance trip then remove 1/2 of the half at a time in an attempt to identify the questionable load.

I was a beta test sight for the C-H AFCI just before if was release and months after they were installed I got a trip. When I rung out the offending circuit I found that a junction box for a 20a circuit crammed full #12 wire and duplex outlet where a grounding conductor had folded forward and come into contact with the neutral screw causing a trip. Since the green grounding screw on the outlet and the neutral are on the same side of the outlet should the EGC not be folded back if the box sufficiently it is possible for the EGC to fold forward as you are pushing the outlet into position. Thus, with that in mind it should be a common practice to assure that the EGC is folded such that it can not flip back and come into contact with that neutral screw on the outlet.

 

[kwired]

Glad to hear that you can buy it given the expense was so minimal

I guess you were looking for something other than these points made in that second post:?

1) A minimum of 75 amps present in the 60 hz portion of the waveform.

2) You can see that the 60hz component of the current is ?chopped? near zero cross. This simulates the arc extinguishing and then re-establishing itself about zero cross. This satisfies the rapid di/dt requirement.

3 & 4 ) In the peaks you can see high frequency oscillations. These are a combination of ~35Khz and ~55Kz frequencies.

A further requirement that provides for enhanced immunity to false trips is that the high frequency content -must only appear- during the peaks and not during the zero cross.

Below is a trace of one of the high frequency detection op-amp circuits outputs during an arc event. From this you can see that 6 half cycles was all that was required when presented with this simulated arc for the device to trip.

Well a lot of it is kind of over my head to some extent, so it maybe did not really tell me a lot. If I read it right it is also a discussion of what happens when pressing the test button and not what is happening during a fault condition, which is what the so called "nuisance" trips are is something is happening the the device is recognizing as unacceptable.

Just for grins on the troublesome circuit turn of the breaker remove all of the loads of that circuit, then remove the breaker and disconnect the EGC and neutral.
Then use an ohm meter measuring the resistance between the neutral and EGC. It should show an open circuit.
If so add 1/2 of the loads back and measure the resistance which should show an open circuit. Remove those loads and add the other half again measuring the resistance which should show an open circuit. If either half fails got back an isolate the loads in that half until you have located the offending load. Any continuity between the EGC and the neutral will most likely cause the nuisance tripping.
Should noting be found then reinstall the breaker and connect the conductors.
Add the loads 1/2 of them at one time and disconnect them then the other half. If you get a nuisance trip then remove 1/2 of the half at a time in an attempt to identify the questionable load.

I was a beta test sight for the C-H AFCI just before if was release and months after they were installed I got a trip. When I rung out the offending circuit I found that a junction box for a 20a circuit crammed full #12 wire and duplex outlet where a grounding conductor had folded forward and come into contact with the neutral screw causing a trip. Since the green grounding screw on the outlet and the neutral are on the same side of the outlet should the EGC not be folded back if the box sufficiently it is possible for the EGC to fold forward as you are pushing the outlet into position. Thus, with that in mind it should be a common practice to assure that the EGC is folded such that it can not flip back and come into contact with that neutral screw on the outlet.

Forget the ohm meter get out the megger. Test in regular ohms mode first just to make sure there is no connected load that was overlooked that could be damaged by the meg test voltage. If meg test passes the problem is in a load or other item that was removed before meg test.

 

[templdl]

Well a lot of it is kind of over my head to some extent, so it maybe did not really tell me a lot. If I read it right it is also a discussion of what happens when pressing the test button and not what is happening during a fault condition, which is what the so called "nuisance" trips are is something is happening the the device is recognizing as unacceptable.

Forget the ohm meter get out the megger. Test in regular ohms mode first just to make sure there is no connected load that was overlooked that could be damaged by the meg test voltage. If meg test passes the problem is in a load or other item that was removed before meg test.

Sounds like a plan to me if he has a megger. Also, if there is a EGC to Neutral connection it would be helpful to be able to ring it out in locating the problem.

 

[A/A Fuel GTX]

Just an update......So far, 2 AFCI's removed and the remaining 7 are on nuisance watch.....c'mon, I dare you. My CH115's are on alert. I know, I'm a bad electrician

 

[A/A Fuel GTX]

Just for grins on the troublesome circuit turn of the breaker remove all of the loads of that circuit, then remove the breaker and disconnect the EGC and neutral.
Then use an ohm meter measuring the resistance between the neutral and EGC. It should show an open circuit.
If so add 1/2 of the loads back and measure the resistance which should show an open circuit. Remove those loads and add the other half again measuring the resistance which should show an open circuit. If either half fails got back an isolate the loads in that half until you have located the offending load. Any continuity between the EGC and the neutral will most likely cause the nuisance tripping.
Should noting be found then reinstall the breaker and connect the conductors.
Add the loads 1/2 of them at one time and disconnect them then the other half. If you get a nuisance trip then remove 1/2 of the half at a time in an attempt to identify the questionable load.

I was a beta test sight for the C-H AFCI just before if was release and months after they were installed I got a trip. When I rung out the offending circuit I found that a junction box for a 20a circuit crammed full #12 wire and duplex outlet where a grounding conductor had folded forward and come into contact with the neutral screw causing a trip. Since the green grounding screw on the outlet and the neutral are on the same side of the outlet should the EGC not be folded back if the box sufficiently it is possible for the EGC to fold forward as you are pushing the outlet into position. Thus, with that in mind it should be a common practice to assure that the EGC is folded such that it can not flip back and come into contact with that neutral screw on the outlet.

Point well taken but if there was a neutral to EGC short, the breaker would trip instantly. That is not the case here. I'm pretty sure the culprit on one of the circuits is under cabinet lights that contain mini step down transformers to produce 12V at the sockets. Regardless, if AFCI's are not compatible with everday, common loads, I'm sure we'll see many removed after the final inspection is completed and the trouble calls come in.

 

[kwired]

Point well taken but if there was a neutral to EGC short, the breaker would trip instantly. That is not the case here. I'm pretty sure the culprit on one of the circuits is under cabinet lights that contain mini step down transformers to produce 12V at the sockets. Regardless, if AFCI's are not compatible with everday, common loads, I'm sure we'll see many removed after the final inspection is completed and the trouble calls come in.

It is possible there is something wrong with one of your suspected UC lights.

I don't think the GFCI section of AFCI's has the circuitry that instantly makes them trip if there is a N-G fault. They will trip once there is a load connected and not all the current is returning on the neutral.

 

[templdl]

Point well taken but if there was a neutral to EGC short, the breaker would trip instantly. That is not the case here. I'm pretty sure the culprit on one of the circuits is under cabinet lights that contain mini step down transformers to produce 12V at the sockets. Regardless, if AFCI's are not compatible with everday, common loads, I'm sure we'll see many removed after the final inspection is completed and the trouble calls come in.

I am assuming that you are referring to an AFCI tripping instantly as an EGC coming into contact with a neutral will not trip a standard TM breaker.
With an AFCI the level of the current returning to the source via the EGC will determine if the AFCI trips. In my case the AFCI didn't trip for some time after the original installation and the EGC was clearly in contact with the neutral screw on the duplex outlet.
It can?t be determined exactly how much neutral current will choose to return via the EGC, it only can be assumed.
Are there others that find that "AFCI's are not compatible with everday, common loads" as I have them installed in my home in as many circuits as a can and have just had one nuisance trip in over 13 years. The only circuits that I couldn't install then on were the homerun bedroom circuits.
I was nice having personal access to two of the engineers that had designed them. Most would never comprehend the amount of testing that was done with the AFCI. It was very intense.

 

[kwired]

I am assuming that you are referring to an AFCI tripping instantly as an EGC coming into contact with a neutral will not trip a standard TM breaker.
With an AFCI the level of the current returning to the source via the EGC will determine if the AFCI trips. In my case the AFCI didn't trip for some time after the original installation and the EGC was clearly in contact with the neutral screw on the duplex outlet.
It can?t be determined exactly how much neutral current will choose to return via the EGC, it only can be assumed.
Are there others that find that "AFCI's are not compatible with everday, common loads" as I have them installed in my home in as many circuits as a can and have just had one nuisance trip in over 13 years. The only circuits that I couldn't install then on were the homerun bedroom circuits.
I was nice having personal access to two of the engineers that had designed them. Most would never comprehend the amount of testing that was done with the AFCI. It was very intense.

I have not installed that many AFCI's - we did not have to install them until the 2008 NEC was adopted here, and that did not happen until sometime in 2009 or 2010 (think it was fall 2009). But I have not had a call back yet on any I have installed.

Now that I think about it was early to mid 2009, we were still on 2005 NEC, they lifted the AFCI exemptions and we did have to comply with 2005 AFCI requirements until 2008 was adopted, and it was adopted with no exemptions.

 

[ActionDave]

Are there others that find that "AFCI's are not compatible with everday, common loads".

Yes. Me.

as I have them installed in my home in as many circuits as a can and have just had one nuisance trip in over 13 years. The only circuits that I couldn't install then on were the homerun bedroom circuits.

What type? The old branch/feeder or the the new combo detectors.

I was nice having personal access to two of the engineers that had designed them. Most would never comprehend the amount of testing that was done with the AFCI. It was very intense

I'd like some personal access to the the people who proposed these things and to the CMP members that approved them.

 

[kbsparky]

....Forget the ohm meter get out the megger.....

Just TRY to megger a circuit with a surge power strip plugged in and see what happens .... :happysad:

(are you listening, ELA??)

...My point its that it was not the action of a "normally operating surge strip" suppressing a transient that caused the trip....

How can you be certain that it didn't?

 

[Open Neutral]

A friend had a fire & remodeled. Under code {almost} all the outlets were AFCI.

The drywall & carpenters would trip them with power tools, and just move to the next circuit. He would come home and reset them all. Next day...

 

[ELA]

Kbsparky,
I explained why, but you appear to have not been listening as you did not answer my question.

 

[kbsparky]

Kbsparky,
I explained why, but you appear to have not been listening as you did not answer my question.

Why should I have? You answered your own question as part of your lecture....

That was but one possible scenario.

Here is another possiblity:

You have a surge-protected power strip plugged into an AFCI or GFCI protected outlet. A hefty surge comes along (from the OUTSIDE), which the strip shunts to ground. Doing so minimizes the surge, and also trips out the breaker. Nuisance tripping. Nothing is wrong with the wiring of the circuit, or the breaker. As I stated elsewhere, just TRY to megger test a circuit with such a strip plugged in. Ain't gonna happen!

Unplug the surge strip and the nuisance tripping stops. Customer is now happy camper. I've seen this on several occasions and will continue to rule this out before spending lots of time and $$$ investigating other possibilities.

 

[templdl]

Yes. Me.

That's one.

What type? The old branch/feeder or the the new combo detectors.

You may have missed the point that I was a beta test sight for the original AFCI and that rules out the combo detectors.

I'd like some personal access to the the people who proposed these things and to the CMP members that approved them.

Personal access to a design engineer isn't going to happen.
Even in the company that I worked for there must be a level of trust as a development of a relationship. I have sat down and had lunch with them at the engineering design center and as a breaker applications engineer I relied on them as a brain trust in addressing application issues. Having knowledge of confidential design and manufacturing was expected as well as having knowledge of what we manufactured and name branded for the competition which even today I would not share with anyone. As OEM sales we sold components to our competitors where we got beat up by our own divisions in their attempt to find out competitive information.

But I had to do my homework first in applying all of my technical and application knowledge before I even attempt to get them involved. I tried to address my application issues on my own before I involved a design engineer. In doing so they recognized that I had did my homework and reached the end of my rope by exhausting all of me recourses earning their respect. They did know me and my phone calls were note ignored.

I was privileged to be associated with a well respected OEM sales group that by itself did $1B in sales back about 1990.

What I?m saying is that relations ships that are built on trust takes years to accomplish which mine was 18 years.

 

[ELA]

Why should I have? You answered your own question as part of your lecture....

That was but one possible scenario.

to learn

Here is another possiblity:

You have a surge-protected power strip plugged into an AFCI or GFCI protected outlet. A hefty surge comes along (from the OUTSIDE), which the strip shunts to ground. Doing so minimizes the surge, and also trips out the breaker. Nuisance tripping. Nothing is wrong with the wiring of the circuit, or the breaker.

Surge from outside is shunted by AFCIs internal MOV (to neutral which is bonded at that point to ground) (no differential current)

As I stated elsewhere, just TRY to megger test a circuit with such a strip plugged in. Ain't gonna happen!

I believe you were addressing someone else there. I said nothing about meggering. I perform hi-Pot testing on equipment regularly and we remove MOVs prior to testing.

 

[kwired]

Just TRY to megger a circuit with a surge power strip plugged in and see what happens .... :happysad:

(are you listening, ELA??)



How can you be certain that it didn't?

Along with owning/using a megger comes knowing how to use it, what to disconnect from the circuit being tested, how and why to make resistance tests at low test voltage before performing on a high test voltage reading. The power strip, and pretty much anything plugged into receptacles should be unplugged when testing the premises wiring. Then go to individual equipment for more tests - megger may not be acceptable for all equipment - if premises wiring has passed tests.

If your megger is capable of adjusting test voltage level, you should be able to test the surge strip with 100 volt test voltage to see if there is leakage to ground, if there is then the surge strip is no good.

 

[Vicktor]

AFCI

AFCI

I have had to trouble shoot one house that started tripping after homeowner lived there for one year. It turned out to be a broken neutral in the ceiling fan j-box. Fan had very heavy usage in the summer prior to fault; it appeared fan vibration cause a breakage in faulty wire install.