AFCI - Supplemental vs Combination vs Outlet Branch-Circuit

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romex jockey said:
Tenacity utilizes grey matter fanaticism often misses Mr IWire

In response, Mr Mark Ode might help clarify>



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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Mag trips were studied greatly in the matter of AFCIs. 75 amps however is not an arbitrary number:


Line-to-neutral faults will generally be at higher current
levels, close to the system available short-circuit
current at the point of the fault. In a study done by
Underwriters Laboratories for the Electronic Industries
Association (EIA), data shows that available short-circuit
current at receptacles in residences ranges from
approximately 75 A to 1650 A with an average of 300 A
for 15 A branches and 467 A for 20 A branches.1 This
data gives a good idea of the current levels available in
branch circuits and it is for this reason that the point
contact tests for AFCIs in UL 1699, Underwriters
Laboratories Inc. Standard for Safety for
Arc-Fault Circuit Interrupters, are done at 75
amperes and greater.
Click to expand...



https://www.schneider-electric.us/d...s/arc-fault-detection-with-afci-iaei-news.pdf


As theorized, 75 amps is actually the lowest short circuit current one may find in a resi during a short circuit. This would be a combination of the longest run length plus the lowest available fault current at the service. For this reason, a circuit breaker with a magnetic pickup of 75 amps was originally proposed as serving the function of a branch feeder AFCI. Irony came into play that 75amps would cause nuisance tripping, so an electronic device was then developed, the first generation branch feeder AFCI that would look for current ripple in those 75 amps rather then magnitude alone.
 
Thank you Mr MBrooke

The article , written 16 yrs ago by two of acfi manufacturers employees , who also represent them on CMP's openly admits the chief goal is a low mag trip, regardless of how it is assessed.

How European, eh? :)

So if one can elevate one's understanding of mag trips to include all impedance possibilities , one sees this as relevant

~RJ~
 
mbrooke said:
Almost, UL had a standard and that standard was available for purchase.
Click to expand...
I don't think that is correct. As of the end of 2014 there was no such standard per an e-mail I received from a UL Senior Regulatory Engineer when I asked that question to UL. [FONT=&quot][/FONT]
 
romex jockey said:
Thank you Mr MBrooke

The article , written 16 yrs ago by two of acfi manufacturers employees , who also represent them on CMP's openly admits the chief goal is a low mag trip, regardless of how it is assessed.

How European, eh? :)

So if one can elevate one's understanding of mag trips to include all impedance possibilities , one sees this as relevant

~RJ~
Click to expand...

Franklin, the fellow who fathered the idea of parallel arc faults was all over low mag trip (Euro) breakers:


http://paceforensic.com/pdfs/newsletter/KeepingPace-15.pdf

http://paceforensic.com/pdfs/newsletter/KeepingPace-7.pdf

http://paceforensic.com/pdfs/newsletter/KeepingPace-37.pdf


While the idea seems grand, to this day it has never been verified or proven. He sites no sources or testing evidence to back up these claims. In fact to this day I know of no studies, even those done by NRTLs that demonstrate the incident energy at a short circuit clearing a conventional breaker via thermal means result in ignition or wooden studs or other building material around NM cable/device boxes.

As is, a rather important fact (though irrelevant as it has never been proven) he claims that most short circuit arcing fires take place in lamp/appliance cords rather then in wall wiring. If that be the case, a simple fuse in the plug would be far more effective.
 
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