AFCI - Square D Responds
I have received several e-mail's from you and others on a wide range of AFCI questions. Hopefully this will address most of those questions. Having been involved with this whole issue from the beginning, I can speak with some degree of expertise.
The Square D brochure you referenced (see http://www.mikeholt.com/htmlnews/nec/pdf/squaredafci.pdf) only provides a frame of reference for a general AFCI discussion. Can a branch feeder AFCI detect conditions described in those general scenarios? The answer is yes. What folks are missing is the history of how we got to this point. I have attached a bulletin called "The Truth about AFCI's" (http://www.mikeholt.com/htmlnews/nec/pdf/truthaboutafci.pdf) that provides the history as well as descriptions of the protection modes. Hopefully, it will clear up a lot of the misinformation that is flying around.
On the scenarios in the brochure... Most of them are obvious. The ones that seem to cause some folks heartburn are the "loose electrical connections" and "overheated or stressed electrical cords". For the loose connections... AFCI's have never claimed to detect a loose electrical connection. What it does do is detect the arcing conditions that typically result from loose electrical connections and that is what the brochure says. In the vast majority of these scenarios the loose connection ends up in an arcing condition to ground or to the grounded conductor. If the arcing it is to ground, the AFCI will detect it. If the arcing is to neutral, then the AFCI will detect that condition based on the arc signature (see the bulletin I included and its description of why the protection is set at 75A in the standard). Everyone seems to focus on the occurrence of a series arc at the loose connection... tell me how this occurs. Generally a loose connection that doesn't result in arcing to another surface is an overheated connection... not an arcing connection.
On the issue of electrical cords, everyone is focusing on why the 5A level series arc is not detected in a cord. Again, you have to look at the history. Cords that are damaged, pinched, cut, etc. result in faults that typically involve both conductors. In fact, the testing is done with SPT-2 cord as part of the AFCI standard. This is the most likely scenario and also the most difficult to detect. This is why the historical information on the 75A is important. EIA's study showed that you will have 75A available at a receptacle outlet. Can a single broken conductor occur... sure it can, but it is not the more likely scenario. I saw one of your e-mails that provided a wiring diagram of a "tester" somebody had built. When you consider the history of the entire issue (and all of the research that has been done over the last 12 years), it's clear why AFCI's didn't work on this "tester". It doesn't even represent a likely scenario because you don't have zip cord stretched out in single conductor configurations.... it's either two or three conductor.
A number of folks are trying to claim that the code panel was misled. All of this information has been presented to the panel... including the issue about 5A series testing versus 75A arc testing. The panel indicated that the issue needed to be dealt with in the product standards.
As a way of trying to reconcile the confusion over the entire issue, we (Square D) made a proposal to UL to revise the branch feeder AFCI requirements into a "Combination AFCI" requirement... one that basically met all of the tests including the 5A series test. Our proposal was rejected by the UL 1699 STP by a vote of 9 affirmative, 10 negative. I have attached the copies of the negative comments on vote (http://www.mikeholt.com/htmlnews/nec/pdf/UL1699_Comment.pdf ). One question I have.... where were all of you when this proposal publicized by UL and out for public comment? They received one comment from the public on the proposal... that's it.
Does that mean branch/feeder devices don't do what they set out to do? Absolutely not. The device provides excellent arc-fault protection for the branch circuit... which is exactly what the NEC requirement entails. What about the cords? You still get a high degree of cord protection with the B/F device because of the parallel arc detection. The device would not detect a series arc in the cord that was at the "load" level. Would protection be even better with the B/F device if it provided the 5A series arc detection? Sure (at least we think so), but that is above and beyond the increased protection already afforded by the B/F device.
A little about experience. There are a large number of devices installed and being used. Guess what? Contractors are telling us that the AFCI is finding wiring problems. Are the devices doing their job? Absolutely!
The bottom line about the misinformation is that most people haven't followed the history all the way back to before the 1993 NEC. When you consider how we got here, the device makes perfect sense. It provides and order of magnitude increase in circuit protection.
Mike, we have tried to be very careful in making sure everyone has understood the facts. Our brochure you reference (see http://www.mikeholt.com/htmlnews/nec/pdf/squaredafci.pdf) is only confusing if you have a frame of reference focused on the 5A series arc test. The only reason why folks have that frame of reference is because they haven't looked at the history and the facts that got us here today. In fact, the 5A test only came up because of a device that is not even on the market... not because it is the highest probability scenario of arcing occurrences.
I ask of you only this.... make sure that solid technical information is used to educate folks. Not rhetoric.
Jim, Pauley, Square D firstname.lastname@example.org
Copyright © 2002 Mike Holt Enterprises,Inc.