AFCI - Supplemental vs Combination vs Outlet Branch-Circuit

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mbrooke

Batteries Included
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That is a very good understanding. Now the only issue is whether AFCIs as currently delivered detect only dangerous arc faults. Or even only real arc faults whether dangerous or not.

One complication to the troubleshooting is that an arc fault may continuous and still not re-strike after the breaker has tripped and been enabled again. It may take some other external event to trigger the next "continuous" arc. Continuous by itself does not imply that it will be there immediately after a power cycle.


I agree, and you are correct, in building wiring unless the arc path is carbonized it will not re-strike let alone hold an arc. In fact in non carbonized cable, several thousand volts is needed to initiate a break down of air according to UL testing on damaged NM. However, in order to sustain an arc fault at 120 volts heavy carbonitzation is required, and thus where the cable is already carbonized, the fault will re-strike as soon as power is re-applied. This has been confirmed (in a way) through UL1699 as it mentions applying several thousands of volts to an intentionally damaged NM segment with satisfactory results for simulated arc testing occurring when the damaged section can light a 100 watt light bulb (dimly) in series. And according to Paschen's law, both the dielectric break down of air, and its ability to sustain arcing require a peak voltage well over 170 volts as seen on a 120 volt line.


With that sad, the video hints we may not be seeing a 120 volt arc ;)
 

peter d

Senior Member
Location
New England
But it does not change that being fact. The OP's supplemental arc protection breaker and an IEC breaker have much in common in the story of who AFCIs came to be.

The point being is that the European model uses RCD/GFPE sub mains. That would be unacceptable here.
 

romex jockey

Senior Member
Location
Vermont
Occupation
electrician
Wow.....Chickenman. Now we are really dating ourselves. I seem to recall this being around the mid sixties? Do you remember the year? I can still hear the Chickenman opening in my head. Are we the only ones that remember this show?

I can recall some radio show back when i was no more than a fresh hatch Tex

~RJ~
 

don_resqcapt19

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Staff member
Location
Illinois
Occupation
retired electrician
But it does not change that being fact. The OP's supplemental arc protection breaker and an IEC breaker have much in common in the story of who AFCIs came to be.
That breaker does not exist and there isn't even a standard to build one.
 

mbrooke

Batteries Included
Location
United States
Occupation
Technician
What else are we talking about? Oh, there is the idea that they are not effective.

Now we've got that covered get out there and get as much whole panel AFCI as possible in place. To do anything else in light of these facts would be shameful.

Even if they were 100% effective, it is still unknown how often dangerous arcing takes place, or if its even possible in North America... Overseas testing and documentation has proven some possibility when the actual supply voltage is on the high nominal side of 230 volts, hence one reason behind the mandatory requirements of RCDs and low magnetic trip breakers. The same concern was known to the NEC for decades, hence the GFP requirement on 277/480 volt 1000amp and over services. Utilities also have 100 years of documentation, where real world experience has demonstrated nearly all sustained arcing occurs on secondary networks running over 120/208Y. In fact, derived from UL's very research papers supported by Paschen's law, 330 volt peak is needed. This would then mean a minimum actual RMS voltage of 235 volts L-G is needed in order to have concern of sustained arcing. Key is sustained arcing, or at least what Paschens and the rest of the scientific community would call arcing. Of course UL's definition is less subjective: "a continuous luminous discharge of electricity
across an insulating medium, usually accompanied by the partial volatilization of the electrodes"

Thus, with less stringent definitions, even a short circuit can be called an arc fault, and that is just what happened:


A 1993 UL Fact-Finding Investigation sponsored by the Electronic Industries Association (EIA)7
recommended that the magnetic trip level of circuit breakers should be lowered to improve the ability of a
circuit breaker to react to arcing faults (particularly parallel arcing faults). This resulted in an EIA proposal
for the 1996 NEC Section 210-20,8 where breakers in living and sleeping areas would be required to
possess lower magnetic trip characteristics and be labeled as such. This proposal was rejected, in part
citing a potential for increased nuisance tripping due to large current transients common with
incandescent bulbs, compressor motors, etc.

Published literature from the early 1990s demonstrated the issue with high magnetic trip breakers failing
to mitigate arcing faults: for example, as cited by Franklin.9 Franklin’s work showed that 15A breakers
manufactured in North America at the time exhibited widely varying magnetic trip levels, as low as 120A
and potentially exceeding 800A. He contrasted this to European 15A breakers, which magnetically tripped
at 100A, allowing far less arc energy to dissipate. Franklin claims that experimental work with arcing faults
shows that arcing currents are “almost always” in the range of 150A to 400A. He further states that an
arcing current below 100A has “never” been observed. No substantiating information or references were
supplied, or any physical information on test conditions.

Found here on page 7:


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


Thus, because a luminous discharge takes place in most short circuits with pitting/volitization between the 2 points of contact, we can call this "arcing". Because the standard says "arcing" for more then 8 half cycles is a potential danger (never been proven to hold applicability to the real world), we can then call nearly all short circuits that do not open an OCPD within 8 half cycles dangerous arcing. In most cases the only thing that will open an OCPD that fast is its magnetic trip function, and because that does not happen every time for a variety of reasons (UL489 does not even require magnetic trip) standard circuit breakers are then said to be incapable of mitigating all short circuit arcing fires, or in today's terms parallel arc faults.


As time went on the above theory began to develop holes. One question then was how does damaged insulation under a staple, with a mm or smaller gap suddenly turn into a conductor when 120 volt can and will never jump such a wide gap. Well, a theory was developed to make is sound plausible... The idea is that lightning strikes, and other induced surges coming in from the service cause a voltage potential of thousands of not tens of thousands of volts to develop across the damaged insulation. This brief surge causes a small arc to jump this gap which then extinguishes as soon as the surge goes away. Over the years the damage from multiple surges will add up where the gap becomes "carbonized". Once carbonized, the gap will conduct 120 volts across it without the help of high voltage spikes resulting in high current arcing. This high current arcing while 75 amps and over (current often limited by the source itself because we basically have a short circuit here lol), will not trip the thermal portion of the breaker fast enough (8 half cycles) to prevent fire, but can trip the magnetic portion of the breaker if pickup is low enough (not always practical to set the mag trip at 75 amps), or arc signature analysis looking for this high current waveform catches it. Thus, we have the modern branch feeder AFCI, looking for this short circuit oops I mean arcing signature.

Of course as time went on, the above still raised question, so the concern was then shifted to also include a new type of arcing called a series arc fault which supposedly manifests from loose or glowing connections. However, arcing is often the end stage of a glowing connection, not the beginning, and glowing connection, along with thee sparking from a cut across a cord, can take place under 5 amps...
 

iwire

Moderator
Staff member
Location
Massachusetts
Even if they were 100% effective, it is still unknown how often dangerous arcing takes place, or if its even possible in North America... Overseas testing and documentation has proven some possibility when the actual supply voltage is on the high nominal side of 230 volts, hence one reason behind the mandatory requirements of RCDs and low magnetic trip breakers. The same concern was known to the NEC for decades, hence the GFP requirement on 277/480 volt 1000amp and over services. Utilities also have 100 years of documentation, where real world experience has demonstrated nearly all sustained arcing occurs on secondary networks running over 120/208Y. In fact, derived from UL's very research papers supported by Paschen's law, 330 volt peak is needed. This would then mean a minimum actual RMS voltage of 235 volts L-G is needed in order to have concern of sustained arcing. Key is sustained arcing, or at least what Paschens and the rest of the scientific community would call arcing. Of course UL's definition is less subjective: "a continuous luminous discharge of electricity
across an insulating medium, usually accompanied by the partial volatilization of the electrodes"

Thus, with less stringent definitions, even a short circuit can be called an arc fault, and that is just what happened:




Found here on page 7:


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


Thus, because a luminous discharge takes place in most short circuits with pitting/volitization between the 2 points of contact, we can call this "arcing". Because the standard says "arcing" for more then 8 half cycles is a potential danger (never been proven to hold applicability to the real world), we can then call nearly all short circuits that do not open an OCPD within 8 half cycles dangerous arcing. In most cases the only thing that will open an OCPD that fast is its magnetic trip function, and because that does not happen every time for a variety of reasons (UL489 does not even require magnetic trip) standard circuit breakers are then said to be incapable of mitigating all short circuit arcing fires, or in today's terms parallel arc faults.


As time went on the above theory began to develop holes. One question then was how does damaged insulation under a staple, with a mm or smaller gap suddenly turn into a conductor when 120 volt can and will never jump such a wide gap. Well, a theory was developed to make is sound plausible... The idea is that lightning strikes, and other induced surges coming in from the service cause a voltage potential of thousands of not tens of thousands of volts to develop across the damaged insulation. This brief surge causes a small arc to jump this gap which then extinguishes as soon as the surge goes away. Over the years the damage from multiple surges will add up where the gap becomes "carbonized". Once carbonized, the gap will conduct 120 volts across it without the help of high voltage spikes resulting in high current arcing. This high current arcing while 75 amps and over (current often limited by the source itself because we basically have a short circuit here lol), will not trip the thermal portion of the breaker fast enough (8 half cycles) to prevent fire, but can trip the magnetic portion of the breaker if pickup is low enough (not always practical to set the mag trip at 75 amps), or arc signature analysis looking for this high current waveform catches it. Thus, we have the modern branch feeder AFCI, looking for this short circuit oops I mean arcing signature.

Of course as time went on, the above still raised question, so the concern was then shifted to also include a new type of arcing called a series arc fault which supposedly manifests from loose or glowing connections. However, arcing is often the end stage of a glowing connection, not the beginning, and glowing connection, along with thee sparking from a cut across a cord, can take place under 5 amps...

And yet you call me a fanatic. :lol:
 

romex jockey

Senior Member
Location
Vermont
Occupation
electrician
Tenacity utilizes grey matter fanaticism often misses Mr IWire

In response, Mr Mark Ode might help clarify>

Section 210.12(A)(4) covers similar installation requirements as (A)(3); however, the AFCI overcurrent device is not a supplemental AFCI. The new text reads: “A listed outlet branch-circuit type arc-fault circuit interrupter installed at the first outlet on the branch circuit in combination with a listed branch-circuit overcurrent protective device where all of the following conditions are met: 


Again, this requires a system installation but using a listed outlet branch-circuit type AFCI and a listed branch circuit overcurrent protective device—not an AFCI breaker as was required in (3).

The theoretical aspects of the 50' & 75' foot lengths being R factor constituting mag trip times for normally marketed OCPD's best addressing Franklin's findings 1/4 century ago.

Mag trips aren't something the ave NEC /CEC spark considers in the field , yet are in focus in other regs where they do. Here we are witness to what is the NEC response for what they apparently consider an incendiary event's possibility in terms of R value.


This then segways (yet again) the whole house main ,lamented as ridiculous utilizing enhanced and/or sensitive technology residentially , yet standard fare commercially via 230.95, with particular note of the voltages existing for their requirement (480 solid Y w/out impedance devicing)


Again, the NEC is addressing what is incendiary potentials ,in this case where a consuming arc CAN exist ,via GFP , R factor being the focus

~RJ~
 
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