Please proof this article on AFCIs.

[Nick Gromicko]

http://www.nachi.org/arc-fault-circuit-interrupters.htm

[Jeffrey R. Pope]

AFCIs function by monitoring the electrical waveform and promptly closing the circuit they serve if they detect changes in the wave pattern that are characteristic of a dangerous arc.

They don't close a circuit, they open the circuit. . .

[Nick Gromicko]

Nice catch Jeff! Dummy me. I changed to "opening (interrupting)"

Thanks!

[Frank P. Newman]

Originally Posted by gromicko

When an electric current crosses an air gap from an energized component to a grounded component ...

I would think that this is only one form of arc fault. An arc fault can also occur when current crosses other high-resistance gaps between components (such as corroded connections). Likewise, an arc fault can occur between two ungrounded components, such as in a 240 volts circuit, but I don't know if any AFCIs are designed to detect those faults.

You may also want to note that the reason AFCIs were developed is because other types of circuit interrupters are unable to detect such conditions before catastrophic damage has occurred.

[Eric Krause]

Hi Nick,

You might want to add and/or clarify information about combination AFCIs. I keep encountering people who do not yet understand what is meant by a combination AFCI. The orginal AFCIs sensed parallel arcing (line to neutral or line to ground) but did not sense the problem of serial arcing (associated with a loose/cut/severed/corroded wire/connections). The combination AFCI protects the combination of parallel plus serial arc faults. The electrical manufacturer's websites (Square D, Murray, etc) have better descriptions than what I have just described but I hope this feed back helps.

Eric Krause

[Eric Krause]

As a follow up to my recent feed back, I believe all AFCIs are required to be combination type (parallel arc and series arc). I was also a little confused when proof reading the section with the bullet points about -Branch/feeder, -Outlet circuit, -Combination, and -cord. The NEC requires that the whole branch circuit be de-energized when an arc fault is detected. AFCI breakers do this. An outlet (at least up to now) would not de-energize the circuit upstream of the outlet (between the outlet and the box). I think that is where a six foot rule comes in (I believe an AFCI receptacle might be permitted within six feet of the panel). It looked as though to me a bullet point might have been referring to an AFCI outlet/receptacle which is not acceptable to the NEC on a branch serving the rooms that are now specified in the 2008 NEC.

Eric Krause

[Paul W. Abernathy]

Very Nice Nick.

Just keep in mind "Combination" type AFCI breakers are not a combination of Breaker and Device type units as the below statement eludes to. The Combination has to do with the detection of Parallel and Series types of arc fault situations.

"Combination—complies with the requirements of both the branch/feeder and the outlet circuit AFCI’s. "

You may want to add a small verbiage of the difference. The Branch-Feeder type are no longer allowed when being strictly called for Combination types.

FYI the exception for the 6' device AFCI was added in 2005 NEC, but as of yet it has not made it to the market that I am currently aware of. Below is the change to the 2008 NEC reflecting the removal of the 6' barrier.

Exception No. 1: Where RMC, IMC, EMT or steel armored
cable, Type AC, meeting the requirements of 250.118 using
metal outlet and junction boxes is installed for the portion
of the branch circuit between the branch-circuit overcurrent
device and the first outlet, it shall be permitted to
install a combination AFCI at the first outlet to provide
protection for the remaining portion of the branch circuit.

[Mark Thorman]

You might want to go into more detail regarding the nuisance tripping with attention to vacuum cleaners currently on the market. One of the most frequent question I recieve after an inspection is why does my high end vacuum cleaner trip the breaker. I now include a note about vacuums in all my reports now.


www.MauiHomeInspections.com

[Paul W. Abernathy]

Originally Posted by Mark Thorman

You might want to go into more detail regarding the nuisance tripping with attention to vacuum cleaners currently on the market. One of the most frequent question I recieve after an inspection is why does my high end vacuum cleaner trip the breaker. I now include a note about vacuums in all my reports now.


www.MauiHomeInspections.com

I am not aware of this being a real issue with the newer AFCI models. What needs to happen is if someone see's this happen ( which is more rare these days in my view and experience ) that they contact the manufacture with the model of Vacuume cleaner so that the manufactures can get the motors if needed, learn the waveform and get it into the next generation of devices.

I believe it is such a rare situation these days that it would not warrant being on a report simply because the AFCI is functioning properly and something within the motor is being recognized by the AFCI. While it may not be hazard and an inconvience it is not ( again my opinion ) not a wide spread issue....my parents have a high end electorlux and causes no problems on their AFCI circuits.

I believe that 95% of all nuisance tripping can be marked up as a real issue that was detected by the AFCI doing it's job. Many case to neutral connections downstream are diagnosed with these devices, many older pieces of equipment with motors going bad are diagnosed with these devices and with GFCI devices.....I will bring you to the example of a Nutone Bathroom Fan a few years ago that caused alot of issues for the AFCI manufactures.......once they received information on the model and could replicate the waveform the next generation of AFCI's solved the problem.....as with any technology ( which I happen to be VERY in favor of ) moves baby steps forward we will all benefit from the technology.

If only one life is saved......they are worth every penny of the investment.

[Mark Thorman]

I agree that the vacuum cleaner issue is not a significant one but when I do a walk thru with a new home and mention it to my buyers in front of the builder, the builder always agrees and tells us that they do get complaints and that they recommend getting a different brand vaccum. This web site is close to what my report says.


http://www.us.squared.com/us/squared...2homeowner.pdf

[Paul W. Abernathy]

No worries...but as of that printing it makes reference to Jan 2001 and we have come along way baby....lol