'Proof' that AFCI devices really locate arcs.

[mbrooke]

Absolutely. Proof is all we're really asking for. That is what one of the "true believers" (a scion of afci marketing) on another afci thread (which seems to have been closed for some "mysterious" reason) on this forum couldn't seem to grasp and when pressed he only offered what amounted to speculatory conjecture that cannot be replicated at residential voltages. In this trade most of us try to do our best and you have literally tens of millions of safe residential installations without afci technology that have not, nor will ever, have an electrical fire due to negligence on behalf of a licensed qualified electrician. Considering how deadly even one loose joint can be (which an afci won't detect), that alone should speak volumes about necessity of afcis for fixed premises wiring. The claims about afcis preventing fires from damaged cords-very noble, possibly useful idea there, but prove it works. We don't need these sham devices "protecting" homes if there is no proof they protect anything.

A plug top fuse does the the same for damaged cords (parallel arc) as an AFCI.

IMO AFCIs are nothing more than clever marketing. Few are willing to question what sounds like a plausible claim from a trusted authority.

I asked for evidence in a dozen other threads, and still I fail to get an answer.

 

[don_resqcapt19]

...Few are willing to question what sounds like a plausible claim from a trusted authority. ....

Exactly, and when you get the non-technical fire and safety people on board first, it becomes a very hard trend to buck.

 

[Tony S]

A plug top fuse does the the same for damaged cords (parallel arc) as an AFCI.

IMO AFCIs are nothing more than clever marketing. Few are willing to question what sounds like a plausible claim from a trusted authority.

I asked for evidence in a dozen other threads, and still I fail to get an answer.

Only if the correct BS1362 fuse is fitted. Like any OCPD they are to protect the flex/cord only, not the appliance.

The most common ratings are 3A and 13A. They are available as 1, 2, 3, 5, 7, 10, 13 amp ratings

 

[mbrooke]

Only if the correct BS1362 fuse is fitted. Like any OCPD they are to protect the flex/cord only, not the appliance.

The most common ratings are 3A and 13A. They are available as 1, 2, 3, 5, 7, 10, 13 amp ratings

True, but am I correct to assume that a BS1362 plug top fuse blows in a few cycles on faults exceeding 40 amps?

One of the reasons behind AFCIs was parallel faults in cords not tripping the breaker fast enough. A proposal was made to lower the magnetic trip in 120 volt 15 and 20amp breakers down to 75amps but was rejected in that inrush could cause nuisance tripping. A plug top fuse in theory does the same but for some reason that idea was never mentioned that I know.

 

[mbrooke]

BTW I think you will really like this one Tony :


http://paceforensic.com/pdfs/Circuit_Breakers_The_Myth_of_Safety.pdf

 

[K8MHZ]

BTW I think you will really like this one Tony :


http://paceforensic.com/pdfs/Circuit_Breakers_The_Myth_of_Safety.pdf

I'm not Tony, but I liked it too!

 

[iwire]

BTW I think you will really like this one Tony :


http://paceforensic.com/pdfs/Circuit_Breakers_The_Myth_of_Safety.pdf

Its OK, but makes some leaps.

Like

If most North American do not prevent short circuit fires, what do they accomplish?

Sentences like that make me question the authors intentions. I find that sentence intentionally misleading. All of in the trade have seen countless instances of circuit breakers preventing short circuit fires.

It would be the same as showing the numbers of people wearing seat belts that have died in crashes and making the leap that seat belts don't save lives.

 

[user 100]

A plug top fuse does the the same for damaged cords (parallel arc) as an AFCI.

IMO AFCIs are nothing more than clever marketing. Few are willing to question what sounds like a plausible claim from a trusted authority.

I asked for evidence in a dozen other threads, and still I fail to get an answer.

I wonder exactly how many fires can be traced directly to fires can be traced to damaged cords. Ive been at this a long time and cannot remember when a damaged cord caused a fire.

 

[growler]

I wonder exactly how many fires can be traced to damaged cords. Ive been at this a long time and cannot remember when a damaged cord caused a fire.

It's my opinion that at one time extension cords were a real problem. I have worked a couple of small fires that were determined by the Fire Marshal to have been cause by faulty cords.

If you look at the number of receptacles in many older homes you won't find very many. This forced people to use extension cords. I think having inspections and requireing more receptacles for a house really did help prevent fires.

An extension cord is really not all that dangerous it's when people try to use it as permanent building wiring.

 

[user 100]

It's my opinion that at one time extension cords were a real problem. I have worked a couple of small fires that were determined by the Fire Marshal to have been cause by faulty cords.

If you look at the number of receptacles in many older homes you won't find very many. This forced people to use extension cords. I think having inspections and requireing more receptacles for a house really did help prevent fires.

An extension cord is really not all that dangerous it's when people try to use it as permanent building wiring.

Very true. My point was that (not trying to be facetious) is that are fires due to damaged cords an epidemic, let alone justify the use (assuming nema's intentions are benevolent) of the expensive yet to be proven afci? I have seen the burned brown six footers that were used to feed the space heater but nothing that led to a conflagration. In those instances, some standard ocpds or gfci did open-afci really doesn't seem to perform any better. Another concern is where exactly should the line be drawn with respect to concern about the end user? We install ocpds for short circuit protection (most of which do a pretty good job) and for protection of the conductors due to overloads. We bond and supply an egc to shunt voltage when that exposed metal is accidentally energized. We gfci to interrupt the deadly path that sometime arises when an egc isn't present or will be of no benefit. We even install t.p. devices in the homes of the childless. All in the name of prevention. How much further should we go?
The day the nec eliminates risks is the day that it will fold because in order to eliminate all risk one would have ban all electrical wiring and the nec's existence would thus be unnecessary. As for reducing risks due either to work of the unqualified or the end users ignorance and irresponsible behavior when using their own accessories, there are other much less expensive and more reliable ways for those risks to be mitigated.

 

[Curious nerd]

I wonder exactly how many fires can be traced directly to fires can be traced to damaged cords. Ive been at this a long time and cannot remember when a damaged cord caused a fire.

At least one. Three houses up the street from mine, an extension cord draped across a sofa totaled the house. They got the baby out a few seconds before the house flashed. My neighbors said they saw an arc working its way up the cord. Believe what you choose, after all they were not trained observers, had very little time to look, and were under an unusual amount of stress. A fuse in the plug, a better grade of extension cord, a new outlet where it was needed, a low magnetic trip, an RCD, an AFCI, all were valid prevention options.

 

[templdl]

BTW I think you will really like this one Tony :


http://paceforensic.com/pdfs/Circuit_Breakers_The_Myth_of_Safety.pdf

Excellent article!!! Thanks!
The residential breakers available at the present time are are in no way capable of responding to arcults. In addition the last time that I checked when comparing a standard residention breaker SqD's has a std breaker and a high mag version available as an option. When compared to Eaton (C-H), Eaton has a std breaker and a low mag breaker as an option. As such if you order a common SqD and Eaton panel you will actually a low mag in the SqD and a high mag in the Eaton panel.
The SqD std panel may be closer to the goal of responding to arc faults.
A look at an actual TC curve for the residential breaker will shead some light on them. They are crude.

Solenoid technoligy has been used for years with MCPs for 3-150a where 100% of the current goes through the coil of the solenoid and they are adjustasbel to correspond tho the FLA of the motor. As such the size on the conductor of the coil must be capable of handing the current. (With a 3/4 or 1" per pole breaker even be suitable for a 9 turn turn solenoid? Maybe.a breaker similar to the UL1077 devices?) The solenoid is adjustable to corispond to a motor's FLA to respond to a phase to ground winding fault. MCPs are designed based upon their quick response to such faults to limit motor damage and prevent fires.
In contrast the common mag element of a residential breaker I often call a clapper type which simply pulls a trip against the conductor when the current reaches a given magnitude. The simplistic design does not lend itself to being "fine tuned" that is to be calibrated to a level that would respond to arc faults. It is useless. As I recall the manufacturing tolerernces are +-20% of their published values in order to pass inspection. I have a sales sample an the original Westinghouse BR 1p 20at breaker but instead of a black molding it has a clear see through enclosure that you can actually see the thermal and mag elements as well as the trip mech. There is not much to be "fine tuned.".
Yes, without using electronic technology solenoids are the best answer as they have the capability of being more closely calibrated and the UL1077 supplimentasry protectors have been available with this technology for some time now. I discovered that EATON has the FAZ-NA available that may fit this requirement. Other manufactures may have a similar breaker.
This is a short excerpt of Eaton's description and its UL489 device is interesting:
-Current limiting design provides fast short-circuit interruption that reduces the let-through energy that can damage the circuit
-Thermal-magnetic overcurrent protection
-Three levels of short-circuit protection, Categorized by B, C and D curves
-Trip-free design. Breaker can not be defeated by holding the handle in the ON position.
These are available with 3different curves. The B curve seems to be the best.
FAZ-NA—B curve (3–5X In current rating) ............................................... FAZ-NA—C curve (5–10X In current rating)
FAZ-NA—D curve (10–20X In current ratng)

Why this technology isn't used for the common residential breakers is a good question. The

 

[romex jockey]

http://paceforensic.com/pdfs/Circuit_Breakers_The_Myth_of_Safety.pdf

Unfuzz me....


So instead of adoption EIA standards , which incorporated nine turns of wire around a toroidal coil for a whopping $.30 resulting in lower (75A) trips , NEMA's afci task force members ironically enough produced the afci with it's own 75A limits , by way of microprocessor technology @ $38.00 a pop ?

~RJ~

 

[mbrooke]

Its OK, but makes some leaps.

Like



Sentences like that make me question the authors intentions. I find that sentence intentionally misleading. All of in the trade have seen countless instances of circuit breakers preventing short circuit fires.

It would be the same as showing the numbers of people wearing seat belts that have died in crashes and making the leap that seat belts don't save lives.

I think the author is simply calling parallel arc faults short circuits. He explains his reasoning saying not all short circuits are zero ohms and may arc instead. Back then was no official term for various arcing conditions like there is today so I am sure he choose the best terminology he had available to him at that time.

 

[Tony S]

I'm not Tony, but I liked it two!

Make that three.

I’ve spotted a couple of anomalies but I need to look at the time curves for BS1362 and BS-EN60898

 

[mbrooke]

I wonder exactly how many fires can be traced directly to fires can be traced to damaged cords. Ive been at this a long time and cannot remember when a damaged cord caused a fire.

Truth is we dont have solid data. None.

Very true. My point was that (not trying to be facetious) is that are fires due to damaged cords an epidemic, let alone justify the use (assuming nema's intentions are benevolent) of the expensive yet to be proven afci? I have seen the burned brown six footers that were used to feed the space heater but nothing that led to a conflagration. In those instances, some standard ocpds or gfci did open-afci really doesn't seem to perform any better. Another concern is where exactly should the line be drawn with respect to concern about the end user? We install ocpds for short circuit protection (most of which do a pretty good job) and for protection of the conductors due to overloads. We bond and supply an egc to shunt voltage when that exposed metal is accidentally energized. We gfci to interrupt the deadly path that sometime arises when an egc isn't present or will be of no benefit. We even install t.p. devices in the homes of the childless. All in the name of prevention. How much further should we go?
The day the nec eliminates risks is the day that it will fold because in order to eliminate all risk one would have ban all electrical wiring and the nec's existence would thus be unnecessary. As for reducing risks due either to work of the unqualified or the end users ignorance and irresponsible behavior when using their own accessories, there are other much less expensive and more reliable ways for those risks to be mitigated.

A GFCI will do nothing in a 2 wire cord unless there is an EGC, and an AFCI is unproven only tripping if it can pick up and differentiate the correct arc signature produced by an actual danger. A plug top fuse on the other hand is simple, proven, selected for the cord itself and does the job better than an AFCI.


Look at it another way. The NEC gives to options for fault protection in AC window unit power cords: AFCI and LCID. That option was never given for none AC cords.

The day the nec eliminates risks is the day that it will fold because in order to eliminate all risk one would have ban all electrical wiring and the nec's existence would thus be unnecessary. As for reducing risks due either to work of the unqualified or the end users ignorance and irresponsible behavior when using their own accessories, there are other much less expensive and more reliable ways for those risks to be mitigated.

IMHO no matter how many laws are passed nothing will change. There are and always will be do-it-yourself homeowners and handymen who have no clue that they have no clue. The NEC already has tremendous safety factors built in to protect them. Punishing professionals while adding more safety does more harm then good at this point.

At least one. Three houses up the street from mine, an extension cord draped across a sofa totaled the house. They got the baby out a few seconds before the house flashed. My neighbors said they saw an arc working its way up the cord. Believe what you choose, after all they were not trained observers, had very little time to look, and were under an unusual amount of stress. A fuse in the plug, a better grade of extension cord, a new outlet where it was needed, a low magnetic trip, an RCD, an AFCI, all were valid prevention options.

An RCD would not have done much, but a plug fuse certainly would have.

An unpleasant truth is that in North America most older homes have breakers with a 15, 20, 25, even 35x magnetic trip threshold. Push to reset fuses, FPE, (some) Zinsco breakers and ITE Bulldog don't even have magnetic trip. The end result being an arc or sputtering fault in a cord can continue for some length of time. This is because while the peak current is high, RMS current is low. Three reasons: 1. Arc current is rarely a perfect sign wave, often re-striking and extinguishing around peaks and troughs. 2. The fault current as a whole can be intermittent, skipping many cycles before restarting again. 3. Long runs and the cord itself being smaller than branch wiring limits current available to a fault. All three end up looking like a mild overload if not normal load to the thermal trip portion of a breaker. Magnetic trip on the other hand does no count on RMS heating, rather a quick burst of current. A fuse can do the same as it can be sized closely to the load with a time current curve selected around potential cord faults.

When one sits down and considers the ratio of new homes being built with AFCIs and the ratio of older homes without them there is a huge gap that will continue and with granfathering/DIY will probably never close. However, had the NEC mandated all new cords be equipped with a fuse, that gap would shorten each year as both new and old homes will fill with appliances having protected cords.

 

[mbrooke]

Excellent article!!! Thanks!

Welcome!

The residential breakers available at the present time are are in no way capable of responding to arcults.

I agree, but there is some hope. The magnetic trip threshold of single pole breakers for reasons unknown has gone down over the years to about 10x in most single pole breakers today. Double poles still have a high magnetic trip.

In addition the last time that I checked when comparing a standard residention breaker SqD's has a std breaker and a high mag version available as an option. When compared to Eaton (C-H), Eaton has a std breaker and a low mag breaker as an option. As such if you order a common SqD and Eaton panel you will actually a low mag in the SqD and a high mag in the Eaton panel.
The SqD std panel may be closer to the goal of responding to arc faults.
A look at an actual TC curve for the residential breaker will shead some light on them. They are crude.

If I am correct the high magnetic option came out in response to the magnetic trip going down over the years, but not sure to be honest.

Square D is not oblivious, thats for sure. QO breakers and Square D Homeline breakers have the lowest magnetic trip threshold of any residential breaker starting at around 100 to 120 amps:

http://static.schneider-electric.us...it Breakers/QO-QOB Circuit Breakers/730-2.pdf

http://static.schneider-electric.us...it Breakers/QO-QOB Circuit Breakers/730-3.pdf


In theory, if an arc fault does occur toward the beginning or middle of a typical circuit a QO breaker would actually trip:

http://library.ul.com/wp-content/uploads/sites/40/2015/02/BreakerMitigationofArcFaults.pdf

(Around page 30 this also goes a bit into UL1699):

http://newscience.ul.com/wp-content...lity_to_Mitigate_Parallel_Arcing_Faults_1.pdf

(Page 54 has nice tables on magnetic trip vs run length)

http://newscience.ul.com/wp-content...lity_to_Mitigate_Parallel_Arcing_Faults_2.pdf


Just to point out a lot of UL's equations assume a copper resistance based on 90*C running temperature which as we know in reality never happens, real world currents are a bit higher. So with that said I agree with you templd. Under many conditions Square D QO/Homeline breaker have been proven to be an AFCI. Keep in mind 100-150 amps isnt far off form the orignal proposed 75amp mangetic trip.


Since we are on the subject I find this just as fascinatiing. If you look at the trip curves of QO double and tri pole breakers you will notice Square D went through the trouble of keeping the magnetic trip thresholds the same for a range of breakers as the amper handle rating increases:

http://static.schneider-electric.us...it Breakers/QO-QOB Circuit Breakers/730-4.pdf

http://static.schneider-electric.us...it Breakers/QO-QOB Circuit Breakers/730-5.pdf


http://static.schneider-electric.us...it Breakers/QO-QOB Circuit Breakers/730-6.pdf

http://static.schneider-electric.us...it Breakers/QO-QOB Circuit Breakers/730-7.pdf


http://static.schneider-electric.us...t Breakers/QO-QOB Circuit Breakers/730-10.pdf


Clearly Square D knows something here.

Solenoid technoligy has been used for years with MCPs for 3-150a where 100% of the current goes through the coil of the solenoid and they are adjustasbel to correspond tho the FLA of the motor. As such the size on the conductor of the coil must be capable of handing the current. (With a 3/4 or 1" per pole breaker even be suitable for a 9 turn turn solenoid? Maybe.a breaker similar to the UL1077 devices?) The solenoid is adjustable to corispond to a motor's FLA to respond to a phase to ground winding fault. MCPs are designed based upon their quick response to such faults to limit motor damage and prevent fires.
In contrast the common mag element of a residential breaker I often call a clapper type which simply pulls a trip against the conductor when the current reaches a given magnitude. The simplistic design does not lend itself to being "fine tuned" that is to be calibrated to a level that would respond to arc faults. It is useless. As I recall the manufacturing tolerernces are +-20% of their published values in order to pass inspection. I have a sales sample an the original Westinghouse BR 1p 20at breaker but instead of a black molding it has a clear see through enclosure that you can actually see the thermal and mag elements as well as the trip mech. There is not much to be "fine tuned.".
Yes, without using electronic technology solenoids are the best answer as they have the capability of being more closely calibrated and the UL1077 supplimentasry protectors have been available with this technology for some time now. I discovered that EATON has the FAZ-NA available that may fit this requirement. Other manufactures may have a similar breaker.
This is a short excerpt of Eaton's description and its UL489 device is interesting:
-Current limiting design provides fast short-circuit interruption that reduces the let-through energy that can damage the circuit
-Thermal-magnetic overcurrent protection
-Three levels of short-circuit protection, Categorized by B, C and D curves
-Trip-free design. Breaker can not be defeated by holding the handle in the ON position.
These are available with 3different curves. The B curve seems to be the best.
FAZ-NA—B curve (3–5X In current rating) ............................................... FAZ-NA—C curve (5–10X In current rating)
FAZ-NA—D curve (10–20X In current ratng)

Why this technology isn't used for the common residential breakers is a good question. The

My understanding is that a 75amp magnetic trip was rejected due to nusince tripping concerns (I know, how irnoic :lol. But that assumes parellel arc faults are common in home wiring. In truth, this report actually proves an over driven staple is not likelly to create a parellel arc:

http://www.nfpa.org/assets/files/aboutthecodes/70/investigation_damage_degradation_nmcables.pdf

The only real risk of parellel arcs exists in flexible cords which usally dont have an EGC. Low magnetic trip will work here of course, but a plug top fuse will provid the same level of protection.

As for branch wiring the majority of dangers involve the EGC, so therefore an RCD/GFP/GFCI at the branch circuit origin would take care of the rest.

This is the plan that should have been implemneted, with lab tests even giving proof RCDs and low magnetic trip do the same.

In fact, all but two UL tests can be passed withtout any arc logic. And if you consider the 1699 series arc test is in reality a parallel fault only one test would not pass (the series arc generator).

 

[templdl]

http://paceforensic.com/pdfs/Circuit_Breakers_The_Myth_of_Safety.pdf

Unfuzz me....


So instead of adoption EIA standards , which incorporated nine turns of wire around a toroidal coil for a whopping $.30 resulting in lower (75A) trips , NEMA's afci task force members ironically enough produced the afci with it's own 75A limits , by way of microprocessor technology @ $38.00 a pop ?

~RJ~

Personally if a solenoid can physically fit into a 3/4 or 1" per pole breaker it would be much more visit effective than a micro preprocessor that must still incorporate some sort of current sensor.
Yes, much less cost for as solenoid.
Stds are not the issue as the device can still be manufactured such that it complies with UL489 requirements. The capabilities and technology exist to do so. Use solenoid technology.

 

[templdl]

Mbrooke,
Thanks for your kind compliment. I must have spent 2 hour putting it together an trying to edit the grammatical and spelling errors and still missed many.
Yes, I have been very disappointed in the actual field applications of the AFCIs. I would have trusted that the engineers would have evaluated solenoid technology which appears to be more relavent which has been used in supplimentasry UL1077 devices. That FAZ-NA Eaton product may be more suitable if made in a plug on residential breaker package.

 

[mbrooke]

Mbrooke,
Thanks for your kind compliment. I must have spent 2 hour putting it together an trying to edit the grammatical and spelling errors and still missed many.
Yes, I have been very disappointed in the actual field applications of the AFCIs. I would have trusted that the engineers would have evaluated solenoid technology which appears to be more relavent which has been used in supplimentasry UL1077 devices. That FAZ-NA Eaton product may be more suitable if made in a plug on residential breaker package.

Dont sweat it, I highly respect what you are doing


I think AFCIs are a giant fraud, the same issues could be addressed others ways, assuming they are responsible for so many dwelling fires to start with.