GFI Caused a Fire!

Page 2 of 6  
On 7/4/2013 8:13 PM, gregz wrote:

AFCIs include ground fault protection. I believe it is required at 50mA or less and is provided at 30mA. The cpsc.gov link I posted has information on ground fault protection and why it is included.
GFCIs will trip with a ground fault of 5mA, so AFCIs don't replace GFCIs. Another difference is that GFCIs have a couple additional components that will trip the GFCI whenever there is a downstream N-G connection, load or no-load. AFCIs will trip with a N-G downstream connection (as gfretwell wrote) but there has to be a load to produce a voltage drop on the neutral wire.
I don't think the NEC requires both GFCI and AFCI protection at the same location. GFCI wire-through receptacles can be used downstream from AFCIs.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 07/05/2013 07:37 PM, bud-- wrote:

OK, I see that the question was already answered... sorry...
I actually had a situation where I was required to use AFCIs and GFCIs together. In my last house while I was in the process of rewiring the upstairs, I had half of the floor properly grounded and half still using the original cloth covered ungrounded NM cable. Unfortunately the PO of the place had installed grounding type receptacles anyway throughout even though there was only originally one box with a proper ground. Strictly reading the code at that point I could not install ungrounded receps (I did order some but never installed them - my eventual goal was to rewire the rest of the floor including the original wiring that was still reasonably acceptable, but we sold the place first) alternately I could provide GFCI protection. So that is what I did, I installed a GFCI recep at the first box on the circuit and an AFCI breaker in the panel (since it was a floor with three bedrooms.)
It seemed like a Mickey Mouse setup, but I never had any trouble with it.
One concern I did have though was what if someone were living in a house that needed some kind of life support equipment? Could not a nuisance trim be potentially fatal? I'm guessing people more knowledgeable than I have already run the numbers on this and have determined that AFCIs are less of a net risk than not having them.
nate
--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 7/4/2013 8:13 PM, gregz wrote:

AFCIs include ground fault protection, but it is at about30mA. GFCIs will trip with a ground fault of 5mA, so AFCIs don't replace GFCIs.
I don't think the NEC requires both GFCI and AFCI protection at the same location. I haven't seen AFCI+GFCI devices. GFCI wire-through receptacles can be used downstream from AFCIs.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

It will in 2014 (kitchens for sure and maybe bath I don't have my ROP here). As usual in this AFCI boondoggle Cutler Hammer has the device and drove the change.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

I just looked at John's post on ECN The GFCI and AFCI will be kitchen and laundry,
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 07/04/2013 10:13 PM, gregz wrote:

yes they are but not at the same level as a GFCI. A GFCI intended for personnel protection will trip at 5 mA of fault current, the ones in an AFCI breaker are a higher threshold, I think 30 mA? so while they do pretty much the same thing you cannot rely on the AFCI to provide GFCI protection where required.
nate
--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 7/3/2013 4:07 AM, Robert Green wrote:

Looking at the current in the wire, a "spike" is made up of frequencies that are much higher than 60 Hz. My guess is AFCIs look at the low end of RF and what is in the audio frequencies. I would also guess AFCIs pick up the current signal with a current transformer on the hot wire. (GFCIs use a current transformer around both the hot and neutral.)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
news:51d42b22$0$1355$c3e8da3

<stuff snipped>

conditions?

It's interesting that in all my research I've yet to come across a circuit diagram or anything technically detailed about how AFCIs actually work. I'm going to bite the bullet and order an AFCI outlet to run some tests with. They ain't cheap!
(Amazon.com product link shortened)
runs $33 from Amazon. If anyone knows of a cheaper vendor, please advise. Also, how would one go about creating a deliberate arc for testing purposes? I've got some carbon rods lying around somewhere that I used to create a carbon-arc light with. I suppose that should work . . .
--
Bobby G.



Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I found this quote on a Inspectapedia, home inspection site:
"As of September 2008 we have found no test tool that reliably and complete ly tests the function of an AFCI. Only the integral test button tests the c ircuitry of the device as well as the trip mechanism. UL classes these "tes t" devices not as "testers", but as "indicators".
A problem is that some devices used to "inspect" an AFCI, in trying to prod uce a simulated arc fault condition, may fail to cause the AFCI device to t rip even though it is perfectly fine.
Literature from the manufacturer of a popular "test tool" tells the user of the tool to go to the electric panel and use the test button on the AFCI d evice to make sure it trips. In other words the inspector cannot rely on th e separate test tool. For this reason you will see such tools referred to a s "indicators" rather than "testers": they are not a complete and reliable test instrument for AFCIs"
So, trust the test button, because there is NO external way to verify the d evice works? Huh? Does that make sense?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

"As of September 2008 we have found no test tool that reliably and completely tests the function of an AFCI. Only the integral test button tests the circuitry of the device as well as the trip mechanism. UL classes these "test" devices not as "testers", but as "indicators".
Funny you should bring that up because the Eaton/CH site I was reading mentioned using a circuit analyzer *before* installing an AFCI to help scan for potential problems that would cause a nuisance trip. So I started looking at circuit analyzers that could tell me if there was a problem with the in-wall wiring. The cheapest I found was $90 for this:
NEEWER TRMS Voltage GFCI RCD Tester Circuit Analyzer MS5908A but it doesn't appear to test AFCIs although it does test for Residual Current Devices which turn out to be like a GFCI, but speak with a British accent <g>. From Mike Holt's forums:
< RCD is the term normally used in the UK, and the most common trip rating is 30ma though many other ratings exist. A UK type RCD normaly only protects against leakage to earth/ground, and does not protect against overload or short circuit, a fuse or MCB must also be employed to protect against short circuit or overload. A combined earth leakage and overload protective device is available, these are known as RCBOs. A UK RCD built into an outlet does NOT protect downstream outlets. The common 30ma trip current does in practice give good (but not total) protection against shock, especialy as they normally trip at about 20/25ma, and are faster acting than USA GFCIs.>
http://forums.mikeholt.com/showthread.php?t 2329
The other tester they just got pricier from there: Amprobe INSP-3 Wiring Inspector Circuit Tester Was almost $300 and folks on Amazon had some complaints about it.
The Ideal Industries 61-165 SureTest Circuit Analyzer weighed in at over $330 but deals with both AF and GF CI's but users complained that it was "short" some necessary adapters.
So it looks, at first glance, like a circuit analyzer that can "test" AFCI's will set me back the cost of at least 6 AFCI breakers. The question now is will testing all the circuits reveal the same sorts of problems that nuisance tripping of AFCIs would also "detect?" Is money better spent on the AFCI's themselves or on a tool that can reveal potential hazards?

produce a

even though it is

Gives you that "warm, fuzzy" feeling about their overall effectiveness, doesn't it? That's precisely why I've been thinking of buying a single OBC outlet AFCI unit and testing it under real world arcing conditions that I create - the kind of testing that drives SWMBO mad. (-:

of the tool to go

sure it trips.

this reason you will

not a complete and

Great. This AFCI investigation is rapidly spreading out into a murky wamp. )-;

device works?

Only in Bizzaro land. (-: What bothers me most about the lack of testers that can actually TEST and not just INDICATE is that I would always be suspicious that the AFCI's might not react to a real arc. There's something just not scientific about not being able to create a reliable, repeatable tester for a device intended to save your life. Sometimes, when manufacturers have problems like nuisance trips, their first corrective attempts overshoot the mark.
I guess I had just better order a single AFCI and start testing while I try to decide whether a $300 circuit tester would be a good investment.
--
Bobby G.



Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 7/5/2013 5:56 AM, Robert Green wrote:

I dug into my archive of downloads. Of particular interest is http://www.cpsc.gov/volstd/afci/AFCIFireTechnology.pdf why have AFCIs available fault current on a branch circuit AFCI detection - block diagram "bad" arcs and normal arcs 30mA ground fault detection It might answer some of your questions. Details of detection, as gfretwell wrote, are probably proprietary.
Likely of less interest is: http://web.archive.org/web/20080516051937/http://www.iaei.org/subscriber/magazine/03_a/magazine_03_gregmanche.htm includes info on 5A trip Note that "branch/feeder AFCIs" were the original ones that did not detect series arcs and are no longer available.
Prices likely will decline like GFCI prices did. But AFCIs are more complicated.

You can also use mechanical pencil leads wired in series with a load that runs at higher than 5A. Pencil leads give a pretty smooth arc. Is it a "bad" arc or a "normal" arc? Check the cpsc.gov link for some info on good and normal arcs.
I would just assume that if the test button works the AFCI is OK. There is a page at UL that says about what TimR got from inspectapedia. I do not find it surprising that testers are not available.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Wed, 3 Jul 2013 06:07:44 -0400, "Robert Green"

Most nuisance trips can be traced to a ground fault, not an arc, usually in the neutral.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
<stuff snipped>

I

added.

and

I wonder if it's really fair to call them nuisance trips if there's a real, underlying electrical fault causing the breaker to open? (-: The more case studies I read, the more I am convinced that installing AFCI's is a good thing if only because there almost always *is* a problem of some sort that they've revealed if they do seem to start tripping for no reason. While that may not have always been the case - I believe that the first AFCI's did trip too easily from what I am reading - it seems that now when people install them and they trip with regularity there's a good reason.
Now the question is - who makes the best AFCIs and do they make them in a format I can use (dual skinnies)? I can replace the bedroom breakers, which are mostly single, with full-sized AFCI breakers, but I'd like to protect other circuits that can carry northward of 10A regularly to be protected as well.
More Googling required. (It's hard to remember a time when if you wanted to look something up, you had to go to the library!)
--
Bobby G.



Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thu, 4 Jul 2013 11:02:49 -0400, "Robert Green"

A ground fault on the neutral will not open the overcurrent device but it will trip anything with ground fault protection. A common suspect is that big kludge of white wires under a wirenut in a ceiling box. That is a common cause of the "fan"problem. The fan vibrates the box and a bare ground bumps into an exposed part of a white wire. This is a case where taping up a wirenut may be a good idea.
The size of the AFCI precludes them being in a skinny format ... so far.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

<stuff snipped>

Yes, many sites I've scanned talk about vibration loosening connections in junction boxes. When a wire pops out of a wire nut it can really create havoc.

It looks like my options are not good for replacing all the current breakers with AFCI's. They're expensive, too, at least the list prices I've seen are. In most of the new lines I've run, I know where the first outlet in the circuit is located and I can replace it with a AFCI outlet instead of a breaker except that most of those outlet boxes are occupied by GFCI's. )-: I am not fond of using outlet protection devices because it means you have to go all over the house when a GFCI/AFCI outlet "pops" - been there, done that. That reminds me to annotate the breaker box legend with the location of all the GFCI outlets . . .
Besides, it's not the new circuits I am worried about. It's the old, cloth-covered wire circuits that I am most concerned about. I'll have to review the circuit panel and decide which ones regularly carry more than 5A and will consider replacing those regular breakers with AFCI units. From what Bud has said, an AFCI requires at least that much current to trip.
--
Bobby G.




Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 7/5/2013 5:22 AM, Robert Green wrote:

I have a post that covers receptacle-type AFCIs, including that you can install them adjacent to the panel and use them to protect the circuit downstream (about the same as an AFCI circuit breaker). For new circuits, the NEC is particular about the wiring method from panel to AFCI receptacle.

AFCIs will be most useful when the new circuits they are installed on become old circuits.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload


radio

that

I'm not sure I understand the last sentence. Do you mean that the AFCI's don't use the powerline to transmit the "noise" created by an arc to the detector/signal processor in the AFCI? From what I've been reading at least some part of the detection process is based on detecting the RF noise from an arc. I also read that detecting an arc is difficult because it may not be drawing detectibly larger amounts of current than a normal device might.
One of my CCTV cameras is badly shielded an acts as an arc detector. Whenever I run a motor with brushes near it, the image starts to show random blips across the screen. It's really noticeable when an old power drill is operated anywhere near the camera. I've been assuming that noise is one part of what an AFCI "looks" for in trying to determine if arcing is present.
I'm asking because I've got three different items that appear to use the home powerline as "antennas" although perhaps that's not the right term. Each devices uses the powerlines in a slightly different way. X10 home automation controllers inject a 120kHz RF signal onto the powerlines to communicate commands. My Netgear Ethernet adapter sends networking signals over the home powerlines with plug-in adapters (sometimes - it's not very reliable):
http://www.netgear.com/home/products/powerline-and-coax/
I've seen numerous discussion refer to the HomePlug technology as "transmitting" ethernet signals over the powerline. Is the powerline acting as an antenna in those cases or is their a better terminology for what's happening?

I would also guess that the AFCI's are looking for several parameters to determine if there's an arc fault. I would suspect that sort of detection has improved greatly since the first units hit the market.
This site (from 1999!) claims:
http://ecmweb.com/content/using-arc-fault-circuit-interrupters-reduce-residential-fires
<<Enormous progress has been made recently by manufacturers of AFCIs and engineers/scientists developing the standard in understanding the variety of conditions an AFCI must respond to in order to be effective. A reflection of that understanding is in the variety of tests and conditions under the three categories of the draft standard. These address the majority of arcing conditions known to lead to fire.>>

Haven't been able to find information about how AFCIs and arc welders interact but it seems most run off 240VAC and would have their own circuit, probably without an AFCI.

a

fire

partially

This site talks about the original bedroom requirements and says it's because that's where many home electrical fires start:
http://www.peterspirito.com/afci_faq.htm#12
<<Why do the 1999, 2002, and 2005 versions of the NEC require AFCI protection for only bedroom circuits?
NFPA fire statistics show that a high percentage of electrical fires occur in bedrooms. There are many appliance cords in bedrooms, for example, radios, clocks, blankets, air conditioners, heaters, TVs, vacuums, as well as, lamp cords. All of these cords can be trapped/abused leading to arcing faults. Further, there are long runs of installed wiring (M-B, "Romex") between the loadcenter and the bedroom outlets. The wiring can be abused during installation (e.g. stapling) and after installation (driving nails into the wall etc.) Therefore, the most logical room to start with would be the bedroom. >>
The same site also implies that arc welders do not generate nuisance trips with the newer AFCIs.

The same site has a good roundup of arc fault types and possible causes:
What is an arcing fault?
According to UL 1699, Standard for Arc Fault Circuit Interrupters, an arcing fault is an unintentional arcing condition in a circuit. Arcing is defined as a luminous discharge of electricity across an insulating medium, usually accompanied by the partial volatilization of electrodes.
There are 3 basic types of arcing faults: line-to-neutral, line-to-ground, and series arcing.
What causes an arc fault?
Arc faults may occur anywhere in the electrical system and may be a result of the following:
a.. worn electrical insulation or damaged wire b.. misapplied or damaged plug in appliance cords and equipment c.. loose electrical connections d.. drill bits, nails, or screws driven into the wire e.. wire staples driven too deep f.. furniture pressing against electrical cords g.. broken wires h.. frayed wires More reading is in order before I bite the bullet and begin replacing the rather new <sigh> breakers I installed in the panel just recently. Does anyone reading this know if AFCI's come in "dual skinny" formats? One of the site above talks about how AFCI's run warmer than normal breakers because of the built-in power supply for the electronics. I wonder if they can squeeze all the required electronics into the dual space-saving breakers?
Thanks for your input, Bud!
--
Bobby G.




Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 7/3/2013 3:55 AM, Robert Green wrote:

RF from the arc is not picked up by circuit conductors acting as antennas.
AFCIs look at the current on the conductor. The arc "signal" is created by current variations through the arc.

That is the current variations created by the arc.

A "series" arc (loose connection) is limited by the normal load that is on the circuit. The AFCIs that are used now may detect a 5A or larger arc.
Parallel arcs (H-N and H-G) can be a lot larger. The current can be up to the available short circuit current at the point of the arc. If I remember right, an investigation found that is very likely over 60A out to 6 ft of line cord in a house.

The signal from the camera isn't very large so a small noise can be quite visible.
AFCIs need a 5A or larger "noise" on power wiring that runs at much higher voltage and current than the camera.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload


AFCI's

from

might.

60A through a 14GA cord is going to do some damage. I remember when I was a kid an electrician working on the circuit panel with a screw driver shorted it out inside the box with a huge spark that spattered molten metal inside the circuit panel. I still have that screw driver around somewhere. He just tossed it in the trash because the tip was cratered but I retrieved it because I thought it made a great souvenir and reminder to be careful.

random

is

It's clear now from what you've said and what I've read that it's not a "radio" process but a monitoring of the instantaneous current draw that detects the arc. I wonder if the radio telegraphs used in the Marconi era would work today with all the background RFI that exists today?

The camera is only of use in detecting things like motors with brushes that need replacing. It even detects when a gasoline-powered leaf blower is nearby.
--
Bobby G.



Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
news:51d4287d$0$7154$c3e8da3 <stuff snipped>

I've noticed that almost all the AFCI breakers I've been looking at have pigtails attached. Those are going to make for a very messy looking installation in my cramped box, IMHO. I see that one of the newer circuit panels has accommodations for the AFCI pigtails but now we're talking serious expense and time to replace my old panel with an AFCI compatible one.
One of the sites I browsed made an interesting comment:
<<The new arc fault breakers cost about $25 - $50 each depending upon manufacturer, but it is a very small price to pay for peace of mind. An experienced electrician can install a new arc fault breaker in a matter of minutes. It actually takes longer to remove and replace the cover to the circuit breaker panel than it does to switch out the breaker>>
The breakers, to my surprise, all seem to be more expensive on the whole than a OBC (Outlet Branch Circuit) outlet-format protector. So $50 x 20 breakers is $1,000. The real problem is that now I know that the AFCI's require pigtails and full breaker slots, it means I would feel compelled to pull the old box, replace any cloth-wired circuits coming into back to their source (that's the long pole in the tent) and put in a new box designed for AFCI's and then probably have to heavy-up the service to the pole. So the math isn't quite as clean as $50 by 20. I'd think that's a multi $K job for a licensed electrician and at least $2K for a homeowner DIY'er if everything listed is done.
What do electricians charge to run a new branch circuit in old plaster/lathe construction? I've always done it myself so I confess, I have no idea.
The question now is how much is piece of mind worth? Is the money better spent on a panel full of GFCIs or on smoke, heat, CO detectors or other safety technology? AFCI's, once perfected, could just as easily ride the main breaker, couldn't they? The arcing "information/signature" should be detectable at the service entrance, shouldn't it? Admittedly nuisance trips that bring the whole home "grid" down aren't going to be pleasant, but I know that the new home industry would rather not have to add over $1000 in AFCI costs to new homes if there's a cheaper way to do it.
One site said that there are at least 111 arc-fault based fires in the US each year. Statistically, that's really not a light. Can't vouch for the accuracy of the number. Seems like it should be higher. Could be CRS or the webmaster took a WAG. (-:
Is it time to switch out the old breakers or will there be combo AFCI/GFCI breakers sometime down the line? I see that some of the AFCI's incorporate a form of GFCI, but the trigger appears to be 30mA and GFCI's appear to operate at a more life-saving 5mA level.
I did notice that more than one site (Leviton and Eaton/CH, I think) took pains to point out that they are continuously improving their arc detection capabilities. Cynical people might take that as an acknowledgment that they feel they are "not quite there yet" in terms of 100% reliability.
--
Bobby G.




Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.