Here are a few items of information that I hope will help balance the discussion with regard to the effectiveness of the AFCI. Some of you are already aware of this information, but there may be some who are not.

It has been stated that AFCIs do not protect against series arcing. This is not 100% true. There is protection against arcing faults that begin as series arcs and progress into line-to-ground or line-to-line (parallel) arcing faults.

Quote from General Electric Advertisement-

"GE AFCI breakers deliver 5 kinds of protection
1. Parallel Protection– direct contact of two wires with opposite polarity
(example: damaged extension cords)
2. Ground Protection – arc between a single conductor and ground
(example: improperly installed wall receptacles)
3. Series Protection – arc across the break in a single conductor, that
progresses to a ground or parallel arc (example: cable pierced by a nail
from a wall hanger)
4. Overload Protection
5. Short Circuit Protection"


It has also been stated that AFCIs do not protect against any arcing faults of less than 75 amps. This is not 100% true either. Some of the “carbonized path” arcing situations were tested with simulated load currents.(5 amps, 10 amps, and 150% of load)
The two Tables below are from a UL document titled “Arc Fault Testing and Arc Fault Scenarios - January 28, 2002”
http://www.ul.com/regulators/afci/AFCI_scenarios020502.pdf

Table 1 shows some details of the tests conducted. (X indicates which test was conducted)
(Combination AFCI – This is the (common breaker type) AFCI which complies with the requirements for both branch/feeder and outlet circuit AFCIs. It is intended to protect downstream branch circuit wiring, cord sets and power-supply cords.)



Table 2 shows which type of device provides protection under various conditions. Here again, “Series Arcing Protection” is assumed to mean - protection against arcing across a break in a single conductor, which progresses to a ground or parallel arcing scenario.



Ed

nice Ed.....

add 2 slices of stone ground wheat , and what kind of sandwich does this thread make??

The NEC does not require the use of "combination type" AFCIs. The code only requires "branch circuit" protection. Also the AFCI manufacturers tell us that a "glowing connection" or high resistance connection is not an arc of any type and the AFCI circuit itself won't respond to these types of faults. The GFP part of the AFCI breaker will respond to these types of faults after they become a ground fault. So will a GFCI. It is my opinion that this type of heating is the cause of most dwelling unit fires.
I still find it very strange that the AFCI requirement was put into code without any statements saying how many fires these devices would be expected to prevent. Where is the cost benefit study? We will never have the technology to make our electrical systems safe and even if it was physically possible to make them 100% safe, it would not be economically possible.
I have worked up some fire data numbers using information from "Fire in the United States, 12th Edition". http://www.usfa.fema.gov/downloads/pdf/publications/fius12th.pdf
This is 1998 data. The numbers in this report are based on NFIRS (national fire incident reporting system) data. The NFIRS data accounts for 39% of all fires that occur in the US. I have adjusted the numbers by this factor to account for all fires. This data shows that there were 401,695 residential unit fires in the US in 1998. The point of origin for 12.9% of these fires was the sleeping room. Of the fires that originated in the sleeping room, 19.9% were reported to have been caused by the electrical distribution system and 11.6% by appliances. Applying these percentages to the total number of residential unit fires shows that 51,819 fires originated in the sleeping room. Of these 51,819 fires, 31.5% were caused by the electrical distribution system or appliances. This would mean that 16,323 dwelling unit fires may have been electrical in origin.
Mr. Robert Clarey of Cutler-Hammer made the statement that AFCIs could be expected to prevent 40% of these fires. This statement was made in comment 2-68 in the '98 ROC. This means that if every dwelling unit bedroom branch circuit in both new and existing dwelling units had AFCI protection, we would prevent 6529 fires per year. We now have to look at the total number of dwelling units existing in the US and the number that are added each year. US Census data shows that there were 115,253,000 housing units in 1999. 1,640,900 new housing units were built in 2000. If you divide the 6529 dwelling unit fires that would be prevented if all dwelling units had AFCIs and then multiply that result by the number of new housing units being built, we can expect that 93 dwelling unit fires would be prevented the first year of full compliance with the AFCI rule. This number is likely somewhat high as fires do not occur nearly as often in new buildings. The fire data used to get the AFCIs into the code showed that 85% of the electrical fires originated in dwelling units over 10 years old. (This brings up the question of whether the AFCI breaker will still be functional, when it its needed, over 10 years after its installation. The GFCI data and new GFCI standard seems to indicate that they won't be function at that time)
If we assume an installed cost of only $50 per new dwelling unit, that means that we would be spending $82,045,000 to prevent 93 fires. That would allow for a loss of over $820,000 per fire. Yes, I know that in some cases these fires result in a loss of life and that we can't put a dollar value on that, but corporate America does just that every day. Does the AFCI requirement meet any reasonable cost benefit analysis?
Don

Don,
an excellent example of the old 'statistics ' addage, unfortunatly lost to CMP-2

I must admit I haven't been doing very well solving Steve's riddles up to this point, but I am curious about the sandwich one.
Tell us, what kind of sandwich?

Ed

Eventually they will come up with little micro-robots that run up and down the cables to check what sort of electrical connection is occuring, it will then run back to the breaker and tell it to trip, or stay contacted.

-ed,


A wish sandwich?

the riddle is UL1699 Ed, however we as consumers & contractors bear the brunt of the joke.....


more fat for the fire here......


from feb/mar 00' necdigest:



Q for extra credit...

Are we implying a combo device here only?

AFCI Information, Links, Opinions, and Comments:

http://www.cpsc.gov/cpscpub/pubs/afcifac8.pdf
http://www.cpsc.gov/cpscpub/pubs/afci.html


https://www.electrical-contractor.net/ubb/Forum1/HTML/000125.html

https://www.electrical-contractor.net/ubb/Forum1/HTML/000487.html

https://www.electrical-contractor.net/ubb/Forum1/HTML/000922.html

https://www.electrical-contractor.net/ubb/Forum2/HTML/000352.html

https://www.electrical-contractor.net/ubb/Forum1/HTML/001120.html

https://www.electrical-contractor.net/ubb/Forum1/HTML/001167.html

https://www.electrical-contractor.net/ubb/Forum1/HTML/001181.html




[This message has been edited by Joe Tedesco (edited 09-09-2002).]

Resqcapt19,

Good thought provoking post.

Don

Sparky,
The standard AFCI has a GFP circuit in it, but it is not a combo device as the ground fault trip is 30 to 50mA. It appears that in many cases, the GFP part of the AFCI breaker will clear the fault, not the AFCI part. I believe that CH does have a combo device that is dual listed as both AFCI and GFCI.

I don't see how the manufacturers can use this premise to claim that the AFCI "detects" a series arc.

It'd be like a doctor saying "Yes, I can diagnose a common cold, but you'll have to wait for it to turn into pneumonia first."

If I invented a new wonder drug that would instantly cure pneumonia, wouldn't it be OK to say that it will also cure pneumonia that begins as a common cold?

Seriously, most "hot spots" that I have encountered in appliance cords have developed either near the plug, or at the appliance end, where most of the flexing occurs during use.
Individual strands break until there are only a few conducting, and finally they let go and one of the conductors opens. It would be a quite a coincidence if both conductors were to break at the same time.
I believe that most appliance cord failures begin as series arcs. Fortunately, it is difficult to maintain a series contact arc. Usually the device stops working and this results in the required repairs being done.

My wife is complaining that she has to hang the iron cord a certain way to get the iron to heat up, so I guess I had better go fix it before it develops into a parallel arc.

Ed

Maybe someone should come up with a receptacle that senses heat at the terminal and sends a digital signal to an X-10 circuit breaker telling it to shut off. That would not be a horrible idea for bedroom circuits. Loose terminals under load melt receptacles. I saw this first hand at an apartment building complex. The construction crew was doing the apartment upgrade including the electric. 1 circuit had two A/C's plus the load of the other 3 bedrooms. They hooked the conductor to the receptacles but never tightened the connections. The receptacle next to the young boys bed melted. The plastic was actually running down the outlet. Luckily the wire burned open and stopped the fire. If receptacles sensed heat by the terminals this would have been prevented. Of course the contractor would have never used them in the first place...

Don,
i posted as example of the double talk the manufacturer's tend towards, which i'm really getting tired of.

note UL1699 uses a guillotine type device across NM , 3 wire....the idea of a series arc of any progressing into a parralell fault becomes realistic due to the proximity x magnitude.

this does not exist for K&T.....which i'm installing AFCI's on....

so the perfect 'lab' scenario then has wide variables in the real world, Ed's original post is greatly compromised.

the efficy falls off the bell curve.....

there will be no change in the previous 'hot spots' the K&T has had....

I have just installed GE type AFCI breakers.
When I turned it on it tripped right away.I checked for neutral to groung contact and for shorts. I turned off the light switches reset the breaker it stayed on. As soon as i turned on one of the light switches the AFCI tripped. I started taking apart light fixtures nothing obvious. I called a friend of mine and he said test install a regular breaker and see if it trips voila all lites were on and no tripping. I did notice a loose connection under one of the wire nuts for the hots. I tightened and reinstalled the GFCI breaker and everything worked fine since. I guess my question is was this supposed to happen
?

correction reinstalled the AFCI breaker

One thing to consider with the new "device model" is whether it will survive a bolted fault. I know <from experience> that is usually the kiss of death for a device GFCI. They also fail "closed". I assume the relay contacts weld. I even had one go when the fault was just a light bulb with a standoff failure.