AFCI testers (Ideal Shure Test)

[hurk27]

I'm including a message that I sent UL as I think there might be a problem with an AFCI on a long run to a bedroom:

To Steven A Brown

From what I have learned about AFCI testers is the signal is a very short duration high frequency event that applies about 75 amps to a given circuit under test. If this is true then if a run to a receptacle in a bedroom is long enough that there would be a voltage drop at this amount of current (remember resistance is current limiting) , then the AFCI will never see the full current that would normally cause it to trip.
This is why most after market AFCI testers will trip an AFCI breaker on a circuit close to the panel but when testing circuits that might be on the other side of the house they fail to produce the amount of current to cause the AFCI to trip. This could also render the AFCI inoperable due to a true arc also. So what's next install each AFCI protected circuit so it can pass a 75 amp signal?

I'm asking this to get an idea on how to respond to an inspector who has been redtaging a house because his Ideal Shure Test? AFCI tester will trip the AFCI's in the bedrooms close to the panel but when he goes to trip the AFCI's on the far side of the house it doesn't. We have replaced several of the breakers and it still will not trip them unless it is on a shorter run. I showed him what you wrote that the button on the AFCI is the only true way to test it but he insist that it is not because of a different brand as it does trip the ones close by the panel it is of a wiring problem or the breaker is bad. these are new issue Square D Home Line? with the green button. Is this possible that the voltage drop in an otherwise NEC compliant circuit could cause the tester to fail? And if it could would it cause the AFCI to not detect the correct arc signature? rendering the AFCI useless except for the GFP portion of it?

I would like to hear your commits.
Thank's Wayne

[ March 29, 2005, 08:13 PM: Message edited by: hurk27 ]

 

[George Stolz]

Re: AFCI testers (Ideal Shure Test)

 

[al hildenbrand]

Re: AFCI testers (Ideal Shure Test)

Wayne posted March 29, 2005 08:10 PM
I'm asking this to get an idea on how to respond to an inspector who has been redtaging a house because his Ideal Shure Test? AFCI tester will trip the AFCI's in the bedrooms close to the panel but when he goes to trip the AFCI's on the far side of the house it doesn't.

Wayne, print out this March 21, 2005, letter, AFCI Indicators, from UL and give it to your inspector.

 

[George Stolz]

Re: AFCI testers (Ideal Shure Test)

Al, that didn't work for me.

 

[hurk27]

Re: AFCI testers (Ideal Shure Test)

George The voltage drop @ 15 amps was only 3 volts, But if these testers pulse the circuit with 75 amps the voltage drop would be allot more. And if the AFCI's require seeing a 75 amp signature to detect an arc, it most likely will not ever see it as resistance is current limiting, Thus Rendering the AFCI useless on a long run to a bedroom.

Al yes that is the exact note I showed him as I mention in the above e-mail to UL when I said:

I showed him what you wrote that the button on the AFCI is the only true way to test it

And his response was the above:

but he insist that it is not because of a different brand as it does trip the ones close by the panel it is of a wiring problem or the breaker is bad.

The problem this inspector is having is that all three breakers was the same brand and since it tripped the one close to the panel he said it should trip all of them, At the time I didn't think about the resistance of the wire being a problem until I was reading about the UL test procedure's that they use the 75 amp arc signature to trip it? And that got me thinking about the voltage drop of #14 wire on a 15 amp bedroom circuit @ 75 amps.
75 amps would be a 1.6 ohm load which would be above the .638 ohms a 100'x2 of #14 would be, which would pass 188 amps on a bolted fault. But would the voltage drop of 47.1 volts be enough to cause the AFCI to not trip? 72.9 volts /1.6 ohms would only equal 45.6 amps? which is well below the 75 amps required?
Or I'm I just getting my math turned around again?

[ March 30, 2005, 12:49 AM: Message edited by: hurk27 ]

 

[al hildenbrand]

Re: AFCI testers (Ideal Shure Test)

George,

Here's the body of the UL letter:

UL Laboratories
Northbrook Division
March 21, 2005

AFCI indicators

Recently, there have been a number of questions from the field about the response of arc fault circuit interrupter (AFCI) circuit breakers to commercially available AFCI indicators. AFCI indicators operate by producing a waveform similar to an arc fault. However, because they cannot produce an actual arc fault, an AFCI indicator may not trip every available AFCI.

Therefore, if an AFCI indicator plugged into a receptacle protected by an AFCI does not trip the AFCI, it does not mean that the AFCI protecting the circuit is defective and needs to be replaced. When this situation occurs, you should push the "Test" button provided as an integral part of the AFCI itself. If the integral test button does not trip the AFCI circuit breaker, it should be replaced.

To notify users of this product limitation, Underwriters Laboratories Inc. requires AFCI indicators to be marked or be provided with instruction manuals that state the following or equivalent:

CAUTION: AFCIs recognize characteristics unique to arcing, and AFCI indicators produce characteristics that mimic some forms of arcing. Because of this the indicator may give a false indication that the AFCI is not functioning properly. If this occurs, recheck the operation of the AFCI using the test and reset buttons. The AFCI button test function will demonstrate proper operation.

Your inspector is using his/er personal logic to claim the tester (AFCI indicator), when not tripping an AFCI, is reliable.

UL says the AFCI indicator is not reliable.

Your inspector needs to publish his research that is better than UL's.

 

[George Stolz]

Re: AFCI testers (Ideal Shure Test)

Thanks for reposting the letter, Al.

Your inspector needs to publish his research that is better than UL's.

Well put!

 

[eprice]

Re: AFCI testers (Ideal Shure Test)

Wayne,

As an inspector, I've been using the very same tester for a couple of years now. In one house that I was inspecting I found certain circuits on which the tester would not cause the AFCI breaker to trip. What I found substantiates your theory about the circuit impedance being the cause. Using the same tester, I found that the problem circuits had voltage drops in the range of 11% to 13%. I pondered this a bit, then reasoned that there was nothing that I could cite to fail the inspection. The NEC does not mandate a maximum voltage drop. The standard under which AFCI breakers are listed requires them to detect a 75 amp arc. The tester is most likely designed to similate a 75 amp arc on a circuit with a typical voltage drop. Because of the voltage drop on the circuits in question, it was probable that the AFCI was not seeing a 75 amp arc and was therefore not tripping. Since the breakers in question did trip when the test button was pushed, evidence indicated that they were working properly. As a side note, the circuits involved were not particularly long, but the electrician had used back stab receptacles.

Since that experience, I have viewed the tester as a means of showing that the breakers are functioning properly. But a negative result is not conclusive evidence that they are not.

Out of curiosity, ask the inspector, if bedroom lights were wired on a separate AFCI circuit without any receptacles, how would he test the AFCI breaker?

 

[hurk27]

Re: AFCI testers (Ideal Shure Test)

Ok Steve sent me a response to my concern over the voltage drop issue:

E-mail from Steve Brown At UL: Thanks for your interest in this area. Let me address your concerns.

You are correct in the operation of the AFCI indicators. They provide a series of pulses of around 75 amps to simulate an arc and try to cause the AFCI circuit breaker to trip from receptacles that the indicator is plugged into. We have found several reasons why the indicator may not trip the AFCI, (in our experience the indicators work as advertised most of the time). One reason, as you mention, is the impedance the line based on some receptacles being located remotely from the AFCI. Another is technology improvements in AFCI's. They are more able to differentiate between an actual arc and a simulated one. Due to these situations, we want to make sure the AFCI circuit breaker is functioning correctly. The best indication of this is the test button on the AFCI itself. When an indicator shows that an outlet that should be protected by an AFCI is not, pushing the AFCI test button is the proper determinant. If the test button trips the AFCI, it does not need replacement.

Your question about he ability of the AFCI to function is a good one. While the AFCI indicator sends a series of pulses to trip the AFCI, these can be subject to the impedance limitations you mention (based on location of the receptacles). AFCI's themselves detect actual arcs. Experiments and testing of these devices done when they were developed showed that their arc detecting ability will function in almost any conventional home branch circuit design. There should be little or no concern about an AFCI's ability to protect branch circuits in buildings they are used in. Again, the test button on the AFCI is the proper way to determine whether an AFCI is functioning correctly.

We are aware of the issues noted above and are working with indicator and AFCI manufacturers to resolve them.

If you have any additional questions on this please let me know.
Regards,

Steve. Brown

But it seems that he skirted the question about if the AFCI would function if it did not see the 75 amp pulse it is design to look for? As I stated before I wanted to know if it would still trip with only 45.6 amps (100' run) instead of the 75 amps if it won't then there useless on a long runs. Even a 50' run would only allow the AFCI to see 60.3 amps? would it still trip at this level?
I'm going to send another e-mail to ask about these figures and see what he says.

Edited to add: If AFCI's themselves detect actual arcs then why is the 75 amp arc setting needed?

[ March 30, 2005, 07:12 PM: Message edited by: hurk27 ]

 

[George Stolz]

Re: AFCI testers (Ideal Shure Test)

Originally posted by hurk27:
One reason, as you mention, is the impedance the line based on some receptacles being located remotely from the AFCI.

That seems like he's agreeing with you--he probably just didn't pull out a calcuator to check your numbers, maybe?

 

[George Stolz]

Re: AFCI testers (Ideal Shure Test)

Originally posted by eprice:
As an inspector, I've been using the very same tester for a couple of years now.

I have a question for you, then. That tester simulates a 15 amp load to figure out it's voltage drop information, right? What happens if there are other loads on the circuit when you conduct that test? Wouldn't it give you a bad reading, as in a greater % voltage drop?

 

[hurk27]

Re: AFCI testers (Ideal Shure Test)

Well It seem's like I stirred something up as he e-mailed me again:

Your e-mail earlier today has raised some questions for our concerns about the indicators. Looking back at some estimates for branch circuits that use AFCI's, we had determined that a typical branch circuit can deliver 500 amps thru 20 AWG wire at a receptacle at about 130 ft. length from the panel with no significant impedance. Most AFCI's are designed to trip at 75 amps fault current (and most mfrs. put a safety margin in so actual trip levels are at 35 to 60 amps). It seems that with an indicator producing 75 amps, it would take significant impedance for an AFCI to not trip considering the 35-60A trip points they are designed for.

Based on this, we are very interested in the actual conditions that caused the AFCI's to not trip. We were wondering you could provide us with specific information.
1) What are the wire run length's at which the AFCI wouldn't trip? Are these very large homes or buildings where the runs are significantly more than 130 feet.
2) Could it be a coincidence that the actual reason for the AFCI not tripping at long distances were actually based on the AFCI technology being able to discriminate between an arc and a series of pulses?
3) Do the branch circuits where the AFCI's don't trip have any special features or devices which would increase the impedance?

We are very concerned about resolving this issue correctly and any info that would help us do this would be appreciated.
Regards,

Steve. Brown

This is getting me to wonder why are they basing there current levels on a bolted fault level?

we had determined that a typical branch circuit can deliver 500 amps thru 20 AWG wire at a receptacle at about 130 ft. length from the panel with no significant impedance.

Edit to add I think this was a typo as I think he meant that it can deliver 500 amps thru 12 AWG wire on a 20 amp circuit? But who knows? Table 8 in chapter 9 of the 2002 NEC shows 18awg @ 130'x2 with 2.1 ohms resistance will only give you 57.12 amps with a bolted fault? so how will 20awg give you 500? so it must be a typo. End edit.

Do they think that a typical arc signature will produce the full bolted fault level of current? :roll:

[ March 31, 2005, 12:20 AM: Message edited by: hurk27 ]

 

[pierre]

Re: AFCI testers (Ideal Shure Test)

Hurk
Maybe with your inspector creating a problem for you, he will be inadvertantly helping all of us with finding the answer to your problem.

This is just what this industry needs, people like you who will not stand for misinformation and inspections based on BS. Good for you!!! I am looking forward to see how this all gets resolved.

P.S.
I have not purchased one of the mentioned testers yet, and may not based on this and other posts, than again maybe some improvements will be made... then I will purchase it

[ March 30, 2005, 10:06 PM: Message edited by: pierre ]

 

[hurk27]

Re: AFCI testers (Ideal Shure Test)

Thank's Pierre.
I don't think the AFCI technology is a bad idea, it's the misrepresentation that troubles me. Yes it was the red tag by this inspector that set me on a quest to find out what is going wrong and as a trouble shooter I will. The fact that the tester did not trip the same brand AFCI was a trigger that made me go back to the basic circuit and how it is tested. Which led me to the problem that if these circuits are on a long run, will an AFCI even be effective? If not would it open a doorway to law suits? The problem is when the public puts there trust in a new idea they expect it to work. And when it involves a potential to take life or property then it must work as advertised or there will be law suits.
The two e-mail's I posted above is from UL which I think the first one was a general response to the question I asked before any real thinking was done. But the second one looked as if they woke up and now think there is a concern. I'm going to present the e-mails to our chapters IAEI meeting this Tuesday Which should clear up the inspector problem but I am deeply concerned that there is other problems with AFCI's yet to be found.

My hope is that this will benefit all. Home owners, Contractors, UL, and Inspectors.

 

[sandsnow]

Re: AFCI testers (Ideal Shure Test)

If the AFCI tester simulates an arc to cause a trip, then what does the test button on the c/b do? I would assume it simulates an arc also.

I think Wayne has got to a much more important issue than the tester working.

I would like to present this to the UL rep at our local meeting. The more input UL gets from the field, the more they will address problem.

Could you please PM me Steve's his E-mail address?

 

[eprice]

Re: AFCI testers (Ideal Shure Test)

Originally posted by georgestolz:

Originally posted by eprice:
As an inspector, I've been using the very same tester for a couple of years now.

I have a question for you, then. That tester simulates a 15 amp load to figure out it's voltage drop information, right? What happens if there are other loads on the circuit when you conduct that test? Wouldn't it give you a bad reading, as in a greater % voltage drop?

Interesting question. I haven't thought about that befor, since the voltage drop function is a feature of the tester that I rarely use. Having other loads on the circuit would have to introduce some inaccuracy into the calculations, but without knowing how the tester makes its calculations, I'm not sure how much. I don't know whether it simply imposes its load, takes readings, and calculates, or if it takes readings, imposes it's load, takes more readings, and then calculates. In the latter case I think other loads on the circuit would have far less effect on the final calculation since it would be calculating the additional voltage drop due to it's load. The tester uses a 12 amp load, then extrapolates results for 15 and 20 amps.

[ March 31, 2005, 02:17 PM: Message edited by: eprice ]

 

[George Stolz]

Re: AFCI testers (Ideal Shure Test)

Just curious about that. Thanks for the reply!

 

[hurk27]

Re: AFCI testers (Ideal Shure Test)

I'm still trying to figure how to answer Steve's question's? I haven't had any more e-mails from him yet?

Based on this, we are very interested in the actual conditions that caused the AFCI's to not trip. We were wondering you could provide us with specific information.

1) What are the wire run length's at which the AFCI wouldn't trip? Are these very large homes or buildings where the runs are significantly more than 130 feet.

A. Most of our run's are between 50-100' And the circuit in which the AFCI wouldn't trip was only around 65'

2) Could it be a coincidence that the actual reason for the AFCI not tripping at long distances were actually based on the AFCI technology being able to discriminate between an arc and a series of pulses?

A. This would take having some lab equipment (oscilloscope) on the job site to see if the resistance of the circuit is causing the current peeks to flat top. Thus the AFCI not being able to see the arc signature?

3) Do the branch circuits where the AFCI's don't trip have any special features or devices which would increase the impedance?

A. No

We are very concerned about resolving this issue correctly and any info that would help us do this would be appreciated

Has anyone else had this problem?

Edit to add that my answers are after each (A.)

[ April 05, 2005, 02:20 AM: Message edited by: hurk27 ]

 

[George Stolz]

Re: AFCI testers (Ideal Shure Test)

Originally posted by hurk27:
2) Could it be a coincidence that the actual reason for the AFCI not tripping at long distances were actually based on the AFCI technology being able to discriminate between an arc and a series of pulses?

A. This would take having some lab equipment (oscilloscope) on the job site to see if the resistance of the circuit is causing the current peeks to flat top. Thus the AFCI not being able to see the arc signature?

I think this could be asking, "Was there a control in your situation? Did you try another type of AFCI tester? Were the AFCI's from the same box?"
Maybe.

 

[luke warmwater]

Re: AFCI testers (Ideal Shure Test)

Wayne,
out of curiosity, did you swap one of the breakers that did trip(on a short run from the panel) with the one that didn't trip(on the longer run from the panel), and test them again??