Arc-fault Circuit Interrupters

Got a few questions concerning this new technology...

How do they work?

How much will they cost?

Why does the NEC think that arcs only happen in bedroom receptacles? (Or realistically, why the requirement for bedrooms over any other part of the house?)

Why not protect every non-dedicated circuit with one? (probably cost prohibitive)

Should I start installing them in new dwellings now, or wait til 2002?

Hi 66' , i'd like to see a component schematic, like the gfi's. i have'nt found much on line as yet. My state (Vt) is stipulating installation this year 2001, on any new construction.

In the july/augest 2000 issue of IAEI magazine there where two articles on afci's"Arc-Fault circuit interrupters"&"Arc Detection with the AFCI".You may be able to access them from their website.

I saw those articles also, and thought they were good. But I don't think they are available online. I will write the webmaster at IAEI.

I wonder if they'd be good for those old knob& tube circuits that just won't go away?

I'm curious about how the local AHJ will be able to properly enforce this code.

If a couple with grown children decide to convert one of their three bedrooms into a den or office will the inspector approve of not having an arc fault in the office? Now let's say he does and a year later the couple put the house up for sale and still list it as a three family do they have to upgrade that "office"? If it got missed during the house inspection during the sale and three months later one of the new owners got electrocuted in the old "office" who would be liable?

Just a thought.

Vin,

That's a good point. I'm more curious to see what kind of problems develop with nuisance tripping of the AFCI. It is designed to open when arcing can cause a fire and is supposed to be able to tell the difference between a "good" arc (switch turning on) and a "bad" (dangerous) arc . We'll see ...

'66,
They probably only mention bedrooms as a minimum. I'm guessing that it's because they want to give you a little more protection in the place where you are sleeping. By the time a smoke alarm goes off it may be too late to get out of the room.

I finally got a decent explanation for the use in bedrooms, if you consider the widespread use of electric blankets...

I personally don't use E-blankets, so I didn't think of their hazards right away.

Any other ideas on why bedrooms circuits are more likely to arc?

Cost will be about $40 to $50 wholesale.

I personally know of two fires in my area that could have been prevented by AFCI's. Both fires were in bedrooms, luckily, only moderate property damage was involved.

Look here for information on the AFCI:
http://www.homesafetycentral.com/pdf/afci.pdf

Thanks Joe...the examples really look like they could be addressed by a GFI ???

Hey Guys,

I came across some additional information for your digestion on this subject. I seems to have some good information including some theory, diagrams and sample waveform data. You can follow page links for more info.
http://www.zlan.com/arc.htm
http://www.zlan.com/afci_c4.htm
http://www.zlan.com/waveforms.htm

Enjoy!

Bill

I would say not at all. A GFCI cannot detect any fault between hot and neutral.

Thanks for the info Bill, very informative.

Wayne

I recently read an article where AFI are being considered for use in aircraft (both commercial & Military) to detect cable faults.

Does anyone have the expected current draw of AFCIs? If they draw a few watts each multiplied by 20 breakers, that could be a pretty significant consumption.

It seem to me that having a pair (for redundancy) of tiny computers in the cabinet monitoring all circuits would be more efficient. If the computer in each CB is drawing only a few milliwatts, then it is no big deal.

On a related matter, I wonder how much juice the surge suppressors use and how much money the electric company makes selling spikes that are shunted to earth by the surge suppressors.

http://www.ourhouse.com/cgi-bin/prod_index.jsp?catOID=-97286&page_name=prod_index

(I can't guarantee that the link will work. Try www.ourhouse.com and use the Search feature to find "Cutler Hammer".)

If you figure in the 15% Mother's Day discount and free shipping on orders over $100, 15 & 20 Amp Type BR single poles AFCI breakers are about $32.50 each in quantity 3 to 13.

The GFCI price is $31.78 which puts the prices in line with Home Depot, I think.

AFCIs are able to differentiate between the relatively clean sine wave which occurs under normal operating conditions, and the wildly asymmetrical waveform that occurs during an arcing fault. I assume that there is a time duration consideration factored in to allow switches to open without nuisance tripping. The bedroom is considered the most critical room to start this campaign,(as the technology progresses, and costs come down, they will be required elsewhere) due to the fact that when people are sleeping, they will not be aware of the smoke associated with a fire that likely follow an arc fault. Unfortunately, you still can not count on people maintaining smoke detectors.

[This message has been edited by Redsy (edited 05-03-2001).]

Dspark, the link worked, thanks.

Yeah, fires only spread while you're sleeping..



[This message has been edited by sparky66wv (edited 05-03-2001).]

ok, i'll stick my neck out here a tad...


does anyone think AFCI's are a cop out for other safety measures left unaddressed ?

How many here are tired of the manufacturing sector's overexposure in the marketplace concerning this?

Actually, I think they are a great idea in a way. There are some ceiling fans and such that work won't out of the box when installed on an AFCI circuit (I hope the AFCIs are that sensitive).

It may drive manufacturers to produce products that arc less -- which I hope means not at all.

What safety measures did you have in mind?
Minimum 12-2-G in extension cords for 3 to 12'?
Integral OPD on each device?
20 A plugs on blow dryers?
Different base for light bulbs above 60 W?
Metal conduit or armor everywhere above ground?
U prongs up?

Minimum 12-2-G in extension cords for 3 to 12'? If proper spacing is kept for Receptacles, extension cords are unnecessary.
But I like the idea.

Integral OPD on each device? As long as the circuit is protected as per Code, this would be unnecessary.

20 A plugs on blow dryers? Great Idea! for those above 1440W...

Different base for light bulbs above 60 W? Mogul base for 75W and up? Or similar? Not a bad idea either.

Metal conduit or armor everywhere above ground? Or sched. 80 PVC (assuming outdoors)

U prongs up? Don't get me started again...

Thanks for all the replies! I still can't get AFCIs through any of the suppliers in this area , though. Tom, have you had any luck?


[This message has been edited by sparky66wv (edited 05-04-2001).]

AFCI's are reqiured in bedrooms, this is due to statistical reseach showing that the majority of dwelling fires start in bedrooms. I question the variables included in this research to bring this to this conclusion. I also question the exclusion of other rooms. If some items as you suggest were addressed, being suspected to be the culprit of disaster, maybe this would have sugared off differently.

The problem with this requirement is that a many more fires start between the receptacle and the load, than between the receptacle and the panel. The code requirement is for "branch circuit" protection. Branch circuit AFCIs provide only limited protection for faults downstream of the receptacle. A receptacle AFCI would prevent MORE fires then branch circuit AFCIs, but the code requires branch circuit AFCI protection.
Don(resqcapt19)

I understand the CH literature to indicate their AFCI CB's, do monitor recp loads.

Glenn

If you read the fine print it says "limited" protection for receptacle loads.
Don(resqcapt19)

Is this due to V-drop? being a 75W threshold AT the device?

Branch circuit/feeder AFCIs (that is what the Cutler-Hammer AFCI breakers are listed as) are tested to detect series and parallel arcing on the fixed wiring and only parallel arcing on the portable wiring. A parallel arc is hot to neutral, a series arc would be an arc at a connection on one of the conductors.
Don(resqcapt19)

"A parallel arc is hot to neutral, a series arc would be an arc at a connection on one of the conductors." Don(resqcapt19)
How would any series arc be guaranteed to be picked up by an AFCI? The current would still have to go through the high impedance of the extension cord and load, no matter where the arc point is. Keep in mind arcing creates high frequency and impedance is seen differently at high freq and 60 Hz. Isn't the difference in frequency what the AFCI is really measuring when looking at the sine wave? The jagged spikes look like higher frequency to the monitoring circuits.

The AFCI looks at waveform distortion that is cause by the arc.
Don(resqcapt19)

For a series arc the waveform will be what the equipment completing the circuit from the receptacle allows. Current in a series circuit is the same at all points. If an arcing connection is in the branch circuit portion the current will still need to pass through the extended part of the circuit from the receptacle. Would the waveform be distorted the same whether the arc is in the equipment or the branch circuit wiring? It is the same current.

The AFCI is not looking at a waveform like we would see it on an O-scope. It needs some criteria to determine that an arc is present. If it is counting the jagged edges of the wave it is counting more peaks than would be present in 60 cycle. That is why I think it would be looking for a higher frequency than 60 HZ. I know it is looking at the waveform for an abnormality. I am guessing at how it determines the wave is not clean and is not going to trigger erroneously on harmonic loads. Do you have more information on exactly how this is done?

Bill's first link explains series/parrallell arcing....has some waveforms...

Bill's second link shows a pictoral , ends in a microprocessor...

not that i understand it all, but pix's help !



[This message has been edited by sparky (edited 05-07-2001).]

Thanks, Sparky, for referring to the links. I had thought they were some links I had already read. The one at http://www.zlan.com/arc.htm mentions "ability to detect the distinctive difference between normal current and intermittent arc current" so it must be the sputtering nature of the current instead of the jagged wave signature. It looks like the current is at zero longer in an arc than in normal current so a fast switch could be the detection device for the input to the processor.

This is more complex than the GFI pix, i can view them and grasp how the mechanism works, these AFCI's have more 'guts' to them..

Yes, AFCIs have a microprocessor (computer) in their guts.

Okay. Somehow until now I had missed your response to me.


>>Integral OPD on each device?
>As long as the circuit is protected as per Code, this would be unnecessary.

>Great Idea! for those above 1440W...
Cool.


>Mogul base for 75W and up? Or similar? Not a bad idea either.
I see we agree on a lot of things...


>>Metal conduit or armor everywhere above ground?
>Or sched. 80 PVC (assuming outdoors)
That would be a lot of cutting and bending or gluing... Call a plumber!

How much will they cost?

Previously I posted: http://www.ourhouse.com/cgi-bin/prod_index.jsp?catOID=-97286&page_name=prod_index

I note that the price appears to have been increased a couple of bucks since I posted that. Perhaps they are planning on offering a larger discount soon. Today's price is $40.58.

Is there a tester, like a GFI tester that anyone has seen for an AFCI???

Two wires and a steady hand?

Just Kidding...

Sparky,

Have you installed any of these?
I understand that VT went a year ahead in requiring them. Just wondering.

I heard that the AFCI protection may be extending to everything in the bedroom including lighting. Has anyone else heard that?

Bill

Bill;
yes, we are required to install for bedroom AND livng ( a VT addition) areas. This is something that is required for a service change here.

I'm trying to get a jump on the manner of diagnoising circuits involved via AFCI. I know of no 'tester', or other way to verify AFCI performance as yet.

'cept those 2 wires!

p.s.--my cost is $28, siemens...




[This message has been edited by sparky (edited 05-28-2001).]

Sparky,

So what is included in 'Living Areas' or should I say what is not?

Do you think that VTs' early and overzealous jump on this has anything to do with lack of credentials required for residential wiring there?

Bill

Like WV, it'd just be another rule they can't enforce, if that's the case...

Guys;
don't throw me in the blast furnace, but i think you've hit the nail on the head. Jethro Bodine yankin' wire with the rest of the Clampets up here have made AFCI's look pretty good.
So it's living rooms, dining rooms, bedrooms, play, hobby etc rooms. We are required this also at a service upgrades, so i guess we're the AFCI state in the trade!
( and i can't find a 2-pole!)
VT always seems to be either the first or the last state to do things, home of the crusty yank, stubbornest creature short of the mule!
ayuh!