General Stuff

[charlie]

Re: General Stuff

At some point a manufacturer has to freeze a design and ship it, and at some point a buyer needs to decide that some particular rev provides enough value that its worth deploying.

I agree Tonyi, however, why force everyone to use a product that has not proven itself and is not practical yet? It is not until the combination AFCI makes it to the market that any of this makes sense. Only the house wiring is protected with the existing technology and at a level that is just a little above a standard device.

I suspect that the organizations that are fighting the new requirement will prevail (at least I hope so) and we will have reasonable language for the 2008 Code cycle. Maybe at that time, the product will do what we had been told it would do during the previous cycles.

 

[pierre]

Re: General Stuff

Tonyi
What you may want to do is step away from this post for a moment and go to google and type in AFCI. Read some of the resultant websites about how the AFCI works, including the manufacturers sites. This will reinforce what Don has mentioned and you will see that both of you are correct, you are just talking about two different things.
Don is correct is his assessment of the way the current AFCIs work that are available on todays market. Sq D has a legimate combination AFCI that will be available sometime early spring of 2004. Their new combo unit will sense a 5 amp parallel fault as opposed to the 70 amp value the standards require now. That will greatly increase the cord protection the AFCI breaker can support.

Pierre

 

[iwire]

Re: General Stuff

Originally posted by pierre:
Tonyi
What you may want to do is step away from this post for a moment and go to google and type in AFCI. Read some of the resultant websites about how the AFCI works, including the manufacturers sites. Pierre

Tony I think Pierre has given some great advice.

From reading these posts it appears that you are basing your opinions on what you would like out of an AFCI.

While Don is basing his opinions on studying the issue.

Try asking Don about the fire statistics used in pushing for the AFCIs.

You have been around here long enough to know we all are interested in safety and I think it is safe to say that most of us would want a device like an AFCI.

A closed mind does not learn.

Bob

 

[tonyi]

Re: General Stuff

Bob, I'm basing my opinion on hard physical reality.

Go cut a lamp cord with cutters and prove it to yourself that there's enough amps available there to kick any ordinary breaker magnetically - that takes a lot of amps drawn quick. A plug and receptical are just tap connectors in this scenario. There's not enough resistance there to cut the available fault current below 70A. If there's 70+A there, the device will see it because it has no choice in the matter.

The only issue I'm seeing here is some people are willing to sacrifice some amount of property and lives because they don't think the 1st generation devices are "cost effective" because they're not sensitive enough. [wait till you see the physical footprint and prices on the 2nd generation, then this whole dance is going to start all over again!]

Well, you can still be electrocuted with ordinary GFCI protection and I don't see anyone complaining (any more) about how GFCI's are some how fatally flawed devices or not worth installing. GFCI is obviously imperfect technology, yet we install thousands every day without moaning about it because as imperfect as they are, they still do something that's worthwhile.

This is where I'm at - I understand very well how 1st generation AFCI operates and all the limitations of its detection capability. I simply believe there's enough added safety value present in the 1st generation to make it worth deploying TODAY(particularly as retrofit on older systems), while others plainly don't.

 

[iwire]

Re: General Stuff



[ December 20, 2003, 11:41 AM: Message edited by: iwire ]

 

[iwire]

Re: General Stuff

Originally posted by tonyi:
Go cut a lamp cord with cutters and prove it to yourself that there's enough amps available there to kick any ordinary breaker magnetically - that takes a lot of amps drawn quick.

No thanks I can do the math.

 

[bennie]

Re: General Stuff

A long circuit can have the ends wire nutted together and not trip the breaker. Don has the calculations for length required.

I do know that a 500 ft. roll of #14 can have each end stuck into a 120 receptacle and not blow the breaker.

 

[roger]

Re: General Stuff

Bob,

Originally posted by iwire:

Originally posted by tonyi:
Go cut a lamp cord with cutters and prove it to yourself that there's enough amps available there to kick any ordinary breaker magnetically - that takes a lot of amps drawn quick.

No thanks I can do the math.

Math is a much better way.


Roger

 

[iwire]

Re: General Stuff

Tony, no one has said that a bolted fault across a lamp cord will not produce over 70 amps.

As has been pointed out by yourself a bolted fault will open a standard breaker.

The need for the AFCI is for an arcing fault.

An arcing fault could continue for quite some time without exceeding the 70 amp threshold of the currently available AFCIs.

This is where I'm at - I understand very well how 1st generation AFCI operates and all the limitations of its detection capability

It is sad when a person thinks their knowledge has reached it's highest level.

Bob

 

[roger]

Re: General Stuff

Hello Bennie, that had to be an FPE or Challenger breaker.

#14 = 3.19 ohms per kft

3.19 x .500 = 1.95 ohms

120 / 1.95 = 61.5 amps

Roger

 

[bennie]

Re: General Stuff

You are correct Roger, for a straight wire. The total impedance of a coiled wire only has to be 8 Ohms to permit 15 amps to flow.

 

[iwire]

Re: General Stuff

Originally posted by bennie:
You are correct Roger, for a straight wire. The total impedance of a coiled wire only has to be 8 Ohms to permit 15 amps to flow.

Cool Bennie, is there a way to figure that out.

We have a Hot Box for bending 4" PVC it takes 20 to 30 amps at 240 volts.

Some one grabbed a 1000' spool of 10/2 and only unrolled enough to make the connection to the breaker.

The other end was sticking out of the spool enough to tie in the SO cord to to the hot box.

It worked...... for a while then the insulation failed somewhere in the spool.

The whole spool turned into one "block" of insulation.

 

[don_resqcapt19]

Re: General Stuff

Tony,

It would seem to me that direct contact produces an ordinary dead short (with one brief arc as the wires approach and contact is made). An air gap and ionization is what makes an arc an arc.

It that is true, then there is no reason to even have AFCIs as the standard OCPDs will do the job. In the case of household voltages, the air does not ionize enough to support a continuing arc. The arc self extinguishes itself at the zero crossing and the voltage level is not high enough to reestablish the arc on the next cycle. This fact is the very reason that ground fault protection of 1000 amp services is not required for 208/120volt systems, but is required for 480/277 volt systems. In a household parallel arcing fault the carbonized insulation is the conductor and limits the fault current to a level that that a standard OCPD will not detect. If the arcing fault has a current of 75 amps or greater the AFCI will open the circuit in 0.5 seconds or less. A standard 20 amp OCPD would open the circuit between 1.75 and 6 seconds. There may be some fires prevented by the lower trip time of the AFCI for this level of current.
I would have had a lot more support for the AFCI rule if the manufacturers had not provided so much misinformation about how they work and how most fires are started. At the beginning they insisted that the only possible cause of an electrical fire was a parallel arcing fault. They would not even acknowledge the existence of high resistance connections producing enough heat to cause a fire. They strongly implied that AFCIs would prevent all electrical fires. If you dig deep in their technical files you will find statements that in reality the AFCI device is expected to prevent only about 40% of the electrical fires on the building distribution system. They have implied that the AFCI will work well in preventing fires in old two wire systems when they know that for the most common cause of electrical fires that the AFCI currently on the market will perform no better than a standard OCPD. This extreme amount of misinformation to promote the sale of their product is what has triggered my opposition to the current AFCI rule. These devices were placed into the code about 10 years before they should have been.
Don

 

[tonyi]

Re: General Stuff

Originally posted by don_resqcapt19:
There may be some fires prevented by the lower trip time of the AFCI for this level of current.

So the current devices have some value and will prevent some losses. I don't have the same desire to place people/property at greater risk as a means of somehow punishing manufacturers financially for some real or imagined past transgressions. You've betrayed your real agenda here and it sounds like it has nothing to do with deploying safer systems.

I view the fact that it is a somewhat safer breaker than a standard one as goodness TODAY - and I wouldn't care if the devil himself were hawking them if they're in fact better than a standard breaker even if only in limited situations.

I'm still missing any plausable explanation on how cord differs from fixed wiring and how this somehow matters to the device. If the amps are there, how can the device care? Educate me.

[ December 20, 2003, 07:06 PM: Message edited by: tonyi ]

 

[don_resqcapt19]

Re: General Stuff

Tony,

So the current devices have some value and will prevent some losses.

I've never said that they would provide some benefit, I just said that they are not cost effective and don't do what the public has been lead to believe.

I'm still missing any plausable explanation on how cord differs from fixed wiring and how this somehow matters to the device. If the amps are there, how can the device care? Educate me.

If the current device can provide protection for faults beyond the outlet, why are they not listed for that purpose? Why are the manufacturers scrambling to bring out the "combination" device that is listed for that purpose? Why did the representee of one AFCI manufacturer submit a proposal that would have required the use of both AFCI breakers and AFCI outlet devices? All of these facts are what tells me that the currently available devices do not provide protection beyond the outlet.

You've betrayed your real agenda here and it sounds like it has nothing to do with deploying safer systems.

Once someone distorts the facts to sell a product, I lose a lot of respect for that company and will have a very hard time believing anything that they say about this issue. I think that once the "combination" device is on the market and proved, that then the AFCI requirement should be placed into the code. I don't think that the manufacturers should have a product required by the code before it is proved. I think that there will be a number of product liability suits that will be lost by the AFCI manufacturers due to their exaggeration of the effectiveness of the product. I believe in safer wiring systems, but I don't believe that the public should be forced to use a product that is not really ready for use. This amounts to the public funding the research and development of the product. The research and development costs should be funded by the stockholders, not the public.
Don

 

[alex winkler]

Re: General Stuff

Last January I did some limited bench testing on AFCIs here in my shop. I found what Don has said to be accurate. The magnetic trip on standard and AFCI breakers are set about the same (130 amps RMS + or -). The average AFCI does not see an arc fault below 75 amps. That leaves an arc fault detection range of 55 amp.

I was not able to create arcs in this 75 to 130 amp range using 120 volts and the 630 available fault current at my test equipment. Any parallel arc using a guillotine or other casual contact would rapidly generate amperages above the 130 amp range causing the breaker to trip on the magnetic sensor. In fact the breaker I used ahead of my subject AFCI breaker would trip at the same time or faster.

Using a 250 foot roll of 14-2 NMB in the test circuit lowered the available fault current to 80 amps where I could then test the AFCI function of the test breakers. They did function as advertised at this level of fault current.

The GFP portion of the AFCI is by far the most valuable and is in my opinion worth the price. The GFP detects any line to ground at 30 ma. In the flat NMB carbonized arc test I could not generate arcs greater than 5 amps, well below the 75 amp AFCI detection range. But with flat cable this arc would pass over the grounding conductor causing a GFP trip at 30 ma.

After my testing I convinced myself of the value of AFCIs if mainly in the GFP portion. The arc fault detection is of limited value but every little bit helps. Just my two cents.

 

[bennie]

Re: General Stuff

Gentleman and Ladies, this is a high quality thread. All of the 13 thousand plus members, should print this entire article.

 

[tom baker]

Re: General Stuff

Comning from Bennie, thats quite a compliment.

 

[pierre]

Re: General Stuff

Sq D will have a combo unit on the market early in 2004. I met with a rep from Sq D and was able to take a look at a 'clear' housing model of the new combo unit. I asked if I could have a copy of the clear housing model, and was told they would give me one of the standard models, but not the 'new' combo type - that they were going to 'protect' their technology as long as possible. That is true competition, I bet it will be a hot item.
I believe there may be wording accepted for the 2005 cycle that is going to make the combo units mandatory for a date that is future to the 2005 cycle, like the wording in the '99 version that made AFCIs mandatory later than 99. This is to get everyone 'ready' for the change.

Pierre

 

[bennie]

Re: General Stuff

There is a problem when laws are passed to require purchasing a sole manufactured item.

The device can be marketed on it's own merit but not by legislation.