Arc Fault protection how does it work?????


In another posting someone wrote .................. *Are you sure that was a GFCI on the end and not an AFCI?"
AFIK I haven't seen one yet ................ but after all this house and my neighbours are generally 30 to 40 years old.
A relative has spoken about them and their requirement for 'bedroom' circuits? A new house, infill, is being built nearby and will take an oppoortunity to talk with their electrician. I am presumng our local code will require them for 'new construction'.
For my info however please could somebody care to explain in basic terms how an AFCI works.
Many TIA
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I am not saying that AFCIs are a bad idea, but ... From <http://www.cpsc.gov/CPSCPUB/PUBS/afcifac8.pdf> "Annually, over 40,000 fires are attributed to home electrical wiring. These fires result in over 350 deaths and over 1,400 injuries each year"
If one compares the number of these deaths with other causes of deaths, AFCIs can only prevent a very small number, even if applied to all potential situations. Since I am guessing that most of these types of fires occur in old housing, not new, and are exacerbated by shady construction/renovation/illegal subdivision, it seems that only a very small percentage of potential lives saved would actually be saved by this new code requirement.
Question to the cognescenti: Are these devices really ready for incorporation in the code requirements? How will they hold up after 40 years of neglect?
--
Best regards
Han
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http://en.wikipedia.org/wiki/AFCI
In

They've designed to be neglected by bozos like you. What kind of PM would YOU do?
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The instructions that came with the Square D AFCIs I installed recently call for periodic testing.
Joe
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Thanks for the compliment (not). You now make perfectly clear that everyone except me will regularly check the AFCI, just like everyone except me checks their GFCIs on a monthly basis.
Oh, there are more people perhaps who do not check their A/GFCIs on a monthly basis?Those are the same people who to an exces use extension cords that are not rated for the load they use them for?
But, but that would make my point. Orderingthe use of safety devices that do not take into account the bozos who will be using them will at best give everyone around them a false sense of security.
--
Best regards
Han
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On May 30, Someon has written
"Those are the same people who to an excess use extension cords that are not rated for the load they use them for?"
Odd that it should be mentioned ..................................
Had just finished fixing relative's aquarium installation that had failed while the owner is away working. Bad extension cord sockets, coming out from behind a desk, staples through edges of extension cord! Defective starter in fluors. strip light designed for aquarium use. Another strip light; clearly marked 'Dry location only' had been added above tank ! And had smoked. And was so corroded it was hard to get the tube out even when dismounted. The smoking s/c possibly damaging the timer switch; fortunately light loads but the whole patched together with cheap dollar store adapters! With virtually nothing grounded! Not too impressed with this particular son in law's workmanship!
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*That was me. Short answer: If you have a loose connection which causes arcing and generates heat the AFCI will shut down the circuit.
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Some electric motors with brushes arc. If I plug in my drill will the AFCI shut down?
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AFCIs must therefore detect momentary breaks (intermittency?) in the circuit?????????????
And the AFCI feature is built into the circuit breaker; correct?
Cos many bedside lamps etc. have two (usually now polarized) wire plugs often plugged into duplex outlets behind beds and other furniture. Sometimes with a multiplicity of those darn el-cheapo adpters; again.
Reminds me also; have a defective (open circuit) duplex GFCI outlet in wall of outside shed I must replace.
Thanks for any AFCI info.
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In

http://www.arcadvisor.com/afci.html
From UL:
Quote: This category covers arc-fault circuit interrupters (AFCI) intended to mitigate the effects of arcing faults that may pose a risk of fire ignition under certain conditions if the arcing persists.
These devices have been investigated to determine their ability to recognize and react to arcing faults. They have also been investigated to determine resistance to unwanted tripping because of the presence of arcing that occurs in control and utilization equipment under normal operating conditions and to verify that operation is not unduly inhibited by the presence of loads and circuit characteristics that may mask or attenuate unwanted arcing.
It's alway amazing how lazy people can be to not bother to search out information themselves when it's so readily available. HTH, Twayne`
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Thanks for the link.
It reads in part; "When an arc fault occurs, AFCI opens the circuit and stops the flow of electricity in a fraction of a second. While connected loads, such as fluorescent lighting, motors, dimmers and switches, may have inherent arcing as a normal mode of operation, the AFCI is designed to distinguish these arcing faults from hazardous arcing faults by monitoring the intensity, duration and frequency of the arcing fault."
Yes that's what I thought it might do ......................... but how? What technology ....... method is used.
In a similar way that one explains that a 'GFCI' operates by detecting a small 'difference' in the AC current flowing in the live and neutral leads! At least this is how one explains it to some, who, because of the 'Ground Fault ....' designation assume it can ONLY be a GROUND fault that will operate the GFCI.
I must look further.
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Ah.
Just found this ............
"The AFCI is intended to prevent fire from arcs. AFCI circuit breakers are designed to meet one of two standards as specified by UL 1699: "branch" type or "combination" type (note: the Canadian Electrical Code uses different terminology but similar technical requirements). A branch type AFCI trips on 75 amperes of arcing current from the line wire to either the neutral or ground wire. A combination type adds series arcing detection to branch type performance. Combination type AFCIs trip on 5 amperes of series arcing. Advanced electronics inside an AFCI breaker detect sudden bursts of electrical current in milliseconds, long before a standard circuit breaker or fuse would trip. A "combination AFCI breaker" will provide protection against ........................... ".
Thanks anyway .............. had originally hoped someone knowledgeable would have written ................
"Oh yes; there is an electronic chip inside each AFCI that .......... ".
Interesting that the 'combination' type also detects series arcing as well as 'branch arcing'.
Cheers.
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terry wrote:

"Branch/Feeder" AFCI were required starting with the 2002 NEC and were required only for bedrooms.
"Combination" type AFCIs are required since Jan 1, 2008. The 2008 NEC also greatly expanded where the AFCI protection is required. In general for a residence they are required where a GFCI is not required.
AFCIs are more useful in older houses, but most new houses will become old houses.
"Branch" AFCIs are required to detect arcs at a 75A level, and commonly actually detect at a 60A level. This will only detect a "parallel arc" - line to neutral or ground. But they can trip much faster than a breaker, particularly for an intermittent arc. They can't detect a "series arc", like a loose connection, because the current will be less than 15 (or 20) amps. Note that the AFCIs installed before about 2008 will be this type.
"Combination" AFCIs (now required) detect arcs at a 5A level, and can also detect a series arc.
AFCIs "look" at the current waveform to separate "bad" arcs from "normal" arcs (switch opening, incandescent light bulb failing). Would think that would not be easy at a 5A level. I kinda wonder if they use a version of a digital signal processor.
All the AFCIs also include ground fault detection - required at a level of 50mA (but commonly is 30mA). (This is higher than the 5mA level for GFCIs.) The idea is that an arc in a cable (romex, extension cord) with a ground wire present will soon produce a ground fault. Also testing has shown there is a fairly good chance that a loose ("glowing") connection at a grounded receptacle will eventually produce a ground fault and trip an AFCI. Loose connections (including failing aluminum connections) may produce plenty of heat ("glow") but not produce any arc, at least until later in the failure.
A couple of good sources of info (if they are still there): http://www.cpsc.gov/volstd/afci/AFCIFireTechnology.pdf http://www.iaei.org/subscriber/magazine/03_a/magazine_03_gregmanche.htm
--
bud--

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(bud--) writes:
| "Combination" type AFCIs are required since Jan 1, 2008. The 2008 NEC | also greatly expanded where the AFCI protection is required. In general | for a residence they are required where a GFCI is not required.
Does this mean you can still use GFCI breakers for bathrooms, outdoor outlets, basements, etc? I ask because I really prefer GFCI breakers to outlets, especially with old small boxes. Or will there maybe be a flavor of AFCI with 5mA GFCI protection?
In looking at AFCI availability for a common panel (Cutler-Hammer BR series) it appears that combination AFCIs come only in 15A and 20A single-pole versions. Does this mean that multi-wire branch circuits (Edison circuits)--in particular ones where a duplex outlet is split and fed from both legs--are no longer an option?
What about other types of 220V circuits and circuits > 20A?
                Dan Lanciani                 ddl@danlan.*com
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Dan Lanciani wrote:

"210.12-B Dwelling units. All 120 volt, single phase, 15- and 20-ampere branch circuits supplying outlets installed in dwelling unit family rooms, dining rooms. living rooms, parlors, libraries, dens, bedrooms, sun rooms, recreation rooms, closets, hallways, or similar rooms or areas shall be protected by a listed arc-fault circuit interrupter, combination type, installed to provide protection of the branch circuit."
(There are a couple very limited exceptions.) (A note references another standard - I believe all line-powered smoke alarms (stand alone or tied together) that are installed on AFCI circuits are required to have battery backup. One of the exceptions covers alarm panels.)
AFCIs aren't generally required where GFCI protection is required, in particular bathrooms, outdoor, unfinished basements. And NEC requirements are for new wiring.
I don't know of combined AFCIs with GFCIs, but they are probably coming. They probably need 2 test buttons.
If you actually needed both, you can put GFCI receptacles on AFCI circuits, and could put a GFCI outlet at the panel feeding the downstream circuit. Similarly you could put an AFCI outlet on a GFCI circuit with the AFCI outlet feeding the downstream circuit. I don't know if AFCI outlets actually exist, and the exception for using them is very strict.

I think some 2 pole AFCIs are available - don't know about CH. Two pole are probably much higher cost. I expect multiwire branch circuits are not generally practical anymore.
Another change in 2008 that probably doomed multiwires is the requirement for a common disconnect for all wires of a multiwire circuit - a multipole circuit breaker or hand tie for the breakers (210.4-B). I don't think, fofr example, many commercial buildings with 3 phase want to take out 3 circuits to work on one of them.
The arc detection of an AFCI probably doesn't care if there is a common neutral, but the ground fault detection does.

Not required.
--
bud--

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