Re: side stepping arc fault breakers
I'm not a promoter of that 80% breaker loading rule when you first size cable to carry the calculated load and then size the breaker to protect the wire the this 80% a moot point.
Now consider applying a 10a breaker with #14 wire, are you more apt to be in conflict with the 80% rule?
Also, I fail to understand the reasoning that a 10a breaker would provide even a fraction of the protection as an AFCI would. The AHJ probably doesn't have a clue with regard to the ways an AFCI provides protection which have been discussed at numerous time on this forum.
When one considers applying a 10a breaker, yes, the TC curve is based on 10a and not 15a. In addition, without wasting my time with getting out my trip curves I would almost certainly conclude that a 10a breaker has the same magnetic trip calibration as a 30a rated breaker. Off hand if magnetic calibration if ion the range of 7x 30,
that's 70a (+-25% tolerance of the manufacturer's published trip range per NEMA AB4). To avoid nuisance trips, which cause people to complain, manufacturers have a common practice of calibrating on the high side. On top of that it I would be most certain to conclude that the calibration accuracy my be +-20% at best.
I guess a 10a breaker may trip if the current which feed the arcing fault lasts long enough, Let's see, putting things into perspective, NEMA 4 testing standards state that breaker 250v or less with ratings to 30a must trip in less than 50 sec with 300% of their current rating (120v x 300a=3000w for a duration of 50 seconds). Remember that breakers respond to in I2t curve which means that, since current and time are not proportional, less over current much more time before tripping.
Then, consider that a 10a rated breaker will provide not better instantaneous protection than a 30a breaker.
