Let me clearly break this thread into two sections, "Reporting" and "My Opinion."
Reporting: The current (Jan/Feb 2010) issue of theIAEI magazine has an article "Safety in Our States," by Thomas Domitrovich.
The article begins describing a "fire investigation" conducted by a homeowner and 'their electrician." A quote from the article: "... the wire had been punctured by a staple ans had started to warm the stud.Deteriorating and warming of studs .... are familiar words you will hear with respect to electrical fires."
The article contains several pictures of charred wood in the vicinity of badly heat-damaged wires. There are numerous descriptions of such bamage taking place along the path of the wire, as the wires crossed into different parts of the homes.
While the pictures are all of NM ("Romex"), the text also describes this happening with "BX."
The article equates 'parallel and series' arc faults with 'high and low energy' arc faults. The text alludes to AFCI's detecting arc faults.
The author closes by expressing his opinion that the value of AFCI's is "obvious," infers that opponents do not understand the value of AFCI's, and urges adoption of the latest AFCI requirements.
Let's begin with one fact: where the author alludes to the ignition of the paper backing on fiberglass insulation, he fails to mention that all UL-listed insulation has a paper that is very, very resistant in terms of spreading a fire or flame. How resistant? In flame-spread tests, the paper typically has exactly the same behavior as aluminum foil.
IMO, a fire, or heat source, caused by a staple damaging the wire would be a point source, and any fire / charring / damage would spread from that point is all directions - not solely along the path of the wire. Like a weldor at work, the heat is at the arc, and not in the cable.
I have seen a few examples charring like that in his pictures, and in every case the cause was massively overloaded wires, over an extended period of time. That is, the 30-amp fuses on the 15-amp wire. Such overlaoding is not relevent to arc-fault technology.
Even if a sustained arc took place in a BX assembly (no matter if it is really AC, MC, FMC, or LTFMC), I would think the arc would ground out through the metal jacket, and that the metal would serve to contain the heat within the cable, making complete circuit failure more likely.
Following up his emotional appeal by casting aspertions on critics is dispicable. Considering the resume listed at the end of the article, we can only assume that he speaks for his employer, Eaton, which manufacturers AFCI breakers.
I am more concerned by his description of a 'save' by AFCI's. "These events (presumably the event that I assume led to the AFCI tripping) saw the studs being warmed and there wasn't enough time for charring to begin to take shape." Wait a minute ... I thought the article started with 'the electrician' following the path of charring? I'm confused. Yes, we're talking the same person, the same event as at the start of the article.
As with the 'global warming' crowd, it appears that AFCI advocates are singing the same song: "Trust us, we know what's best for you. There's research, but we won't let you see the data. Anyone who opposes us is a bad guy."
I say: If the technology is that important, and he cares so much about our safety .... I expect him, and his employer, to enthusiastically endorse the use of AFCI devices, rather than opposing them. Let's make it both easy, and affordable, to extend this protection to the very homes most likely to have that penny in the fuse box.
Let me clearly break this thread into two sections, "Reporting" and "My Opinion."
Reno, if you really wish to post inverstigative reporting, you should start with the source(s) Dave Dini and Ray Marchand did a two part piece called 'The truth about AFCI's in NEC digest , about a decade ago.
These were two of CMP-2's 210-12 proponents, one an ex-UL man, the other an ex-square d rep
you could also reference the George Washington chapter of the IAEI about the same time, lot's of colorful banter to be had there
As to opinion, you'll not find any that yanks the lions tail (per se') in any trade mag. In fact a number of trade writers who used to post in electrical chat rooms disappeared after being confronted on this very topic, some pointing out forum disclaimers being their problem
One rarely finds an Op-Ed in any trade mag that directly confronts a manufacturer. And as this chat room is connected to one as well, it's rather obvious that any opinion going down the same road will be met with disdain and rejection. (and don't i know it)
That said, truth is like little bubbles, eventually rising to the surface. This , i predict, will happen when enough of us (the folks that actually DO the work, not the shill cheerleaders) are over their heads in afci-mania
Whenever I have confronted someone about cooking the books on the fires this thing might prevent I get the old saw back "well if it just saves one life...". Unfortunately that is not how cost benefit analysis works. We could make houses safer if we wired everything with MI cable but nobody could afford to buy one. All that safety would be thwarted when they plug in the space heater and put it too close to the bed spread.
Since I do fire investigations in support for the local FD. IE If they say it is electrical they have to get me to agree or find another cause. I have gone to fires where the investigating officer insisted the fire was caused by a heater plugged into an electrical cord only to prove the cord was not energized so I know how electricity is often blamed when ever the skill or knowledge of the investigator is challenged, I don't know how many fire will not happen because of AFCI breakers but I am sure that at least 4 would have not occurred if an afci protected those circuits. The too tight staple is not likely going to be revealed nor would the overloaded, over protected circuit. Bad splices are in my opinion the number 1 cause of electrical fires and in that category I would include poor screw terminations and the whole aluminum wire thing too.
The mechanism of Pyrolysis is fascinating in that you can actually lower the ignition point of paper or wood to a temperature lower than the boiling point of water. We have seen a fire caused by pyroforic action and a hot water pipe causing paper business records to ignite. Most of the fires caused by wood burning stoves were caused by pyroforic action where by the constant heating of studs inside a wall changed the wood chemically until a fire starts inside the wall. These were originally attributed to errant sparks, electrical wires, and way too hot fires.
So AFCI breakers have become the next holy grail of fire prevention and I do believe there will be some benefit and less fires too. Of course other code things have changed too and we install dedicated circuits for more loads that used to get plugged into a general purpose outlet. We have more receptacles installed and less devices on a circuit too. All of these are in houses less than 40 years old so it will take a rather long time to garner any data either way. AFCI do add a measure of protection from series arcs and some parallel arcs both of which tend to be less than 5 amps of current which no regular breaker would trip. these low voltage arcs just don't draw enough power to cause any breaker to trip on overload never mind over current. AFCI are supposed to recognize this condition and trip. The failure to detect the real cause is often related to the experience of the electrician to detect and reveal the problem. From my experience a lot of the problems I have seen with AFCI breakers has been traceable to an installation error and at least 1 nail. The most common error being the bond and neutral touching. As a minor benefit AFCI do add a small amount of ground fault protection but don't think that is the same protection offered by GFCI as the trip levels are 5 times higher in an AFCI or around 30ma.
Mike, I really would hope you have access to the article - let me know if you don't - as I would like your take on the 'fire analyses' in it.
IMO, the author has forsworn dazzling us with his brilliance, and has chosen to instead try to baffle us. IMO, he's showing us a picture of a turkey and trying to tell us it's a chicken, tossing in a lot of fancy names for feathers in the process.
If your investigations are not likeely to reveal an over-fused circuit .... there's something wron there. Perhaps you mis-spoke?
I'll let this thread simmer for a bit before I return to the magazine. Trust me, there are plenty of whoppers in the other articles as well!
The AFCI situation is upon us here in NJ with adoption of the '08 NEC as of 10/26/2009. Up to today, the only AFCI installs I have seen are within one 55+ resi, 3 bldg project that started in late '05. Not 'code' required, but Architect mandated in the BR's. There have been no issues that I am aware of.
That said, I also teach at a County Vo-tech, and have obtained AFCI info from mfgs (Sq, Siemens, etc) in Powerpoint, video, PDF & print. I have a few items from NEMA also. I also peruse ECN, and note some of the discussions & problems.
Reno, I'm not an IAEI guy, I belong to NJEIA, and there has been a LOT of heated debates on AFCI since the days of the '05 NEC changes, even though NJ did NOT adopt AFCI's until now. Is the IAEI article you reference available to non-members? On line??
As to being a 'god send' (my words) to fire prevention; IMHO, it may help but there are other causes, ie: the space heater & overfusing & cooking wiring over long periods.
My opinion on 'electrical cause' from fire investigators should have a 'breakout' something like, extension cords, appliance failure, house wiring, etc.
BTW, whatever happened to that elusive "AFCI device"???
AFCI do add a measure of protection from series arcs and some parallel arcs both of which tend to be less than 5 amps of current which no regular breaker would trip
i had thought it predicated on the arc signature more than an actual threshold
Sparky You are correct. My point about current magnitude is related to tripping of a normal breaker. Series arcs in low voltage circuits don't draw enough current to make a regular breaker trip and allows that series arc to perpetuate and possibly ignite adjacent combustibles. An arc fault breaker recognizes the wave form or electrical characteristics of an arc and opens the circuit. The common misconception was that a regular circuit breaker should protect us from all the hazards. parallel arcs are usually revealed as a ground fault, phase to neutral or phase to phase fault. AFCI Breakers also are designed to detect ground faults and trip around the 30 ma level. These are not life safety GFCI which trip at 6 ma and should resist small leakage currents like we might see in a heating element.
Has anyone done an objective analysis an how well these AFCIs actually perform on series arcs? Series arc detection really didn't even show up until version 3.0 As a side note, how do you figure out which version you have?