ECN Forum Forums Code Related Discussion NEC & other Code issues AFCI Branch Circuit length

voltage drops your problem

I was talking to a freind of mine with NEMA about this the other day. He says that they are listed, but not available yet.

Speaking of combination types though...

In 2008, we will be required to use the combination type. It appears also that we will probably have to protect all 120 volt circuits in the house. Considering the fact that most manufacturer's can't get their combiantion type to pass the tests, and considering the fact they are supposed to trip on series arcs, does anyone else see a potential for disaster? I mean, what happens if the code requires them throughout the house, and they end up nuisance tripping because of series arcs? The branch/feeder type that we use today don't respond to series arcs because (alledgedly) you can't differentiate between a series arc and the closing of a light switch, or the unplugging of a device while under load. Can you imagine the black eye that the combiantion type would give the industry if they are required throughout, and they consistantly nuisance trip?

I had posed the question of circuit length to the technical staff at Cutler Hammer and I got this response:

So there you have it. I'm sure other manufacturers have that same limitation.

So does this mean in larger homes we have to install a sub panel just so we can be under 250' for the AFCI going to the far bedroom?

Sorry for the delay in answering questions, and the questions are good.

The latest Info on the AFCI and the listing test were presented to me by someone from UL. I believe his name is Warren ?, but I am remote from my office until Tuesday when I would be able to check.

Does the AFCI test button place an arc signature for the test? I don't know, this is a question I haven't asked. I was led to believe this was the case and thus I did not inquire directly. Yes, we are required to trust UL and the manufacturer that enough testing has gone into these to ensure the test button does work. UL is most adamant that this is the only true test of the circuitry (outside of a testing lab facility).

If I were the engineer assigned by a company to test a device as complex as these, would I do so by creating a fault? NO! I would not want the liability of burning down a structure when the thing failed. So, how would I test them? As I would have knowledge of the circuitry inside and out, I could design tests that would check out the complete circuitry and verify that it is working properly without subjecting it to a full blown hazardous test.

Anyway, I would not want to be holding a handheld tester with a 75 amp arc developing in it, especially if the device did not trip.

I can only guess as to why they are not available yet. As they are listed, you would think that someone would want to buy them for the additional safety. Could be Square D is being cautious and doing additional testing to avoid another recall. We can hope this is the case.

There are typical times in the life of an electrical system where things are more likely to burn down due to an arc in the distribution system.
1- When first built.
2- When ever new occupants move in based on the next item.
3- When remodeling or hanging things. And within about 2 years of any of the above.
You can all think of other items to add to this list. The AFCI are designed to help protect against these problems. They will not protect against all, or catch all. They add an additional level of safety that according to statistics (yes, I know there are some problems with these statistics) show is significant. If these statistics were from manufactures and not outside national fire agencies (I do not remember who), I would not trust them as much.

What about the 30 year old homes? Do they need protecting? You decide. Ul's project of examining old wiring has shown preliminarily that it is still functioning as designed and manufactured. I for one have given electricians more work by highly recommending service changeouts and in 2-wire homes I wish more manufacturers had a GFCI-AFCI device like Cutler-Hammer so I could avoid more attic and crawl spaces.

As for functioning after a giving service, I can not comment. I have read the report on GFCI's. I recommend that every service has surge protection installed and that we all test devices per manufacturers instructions. That is also why newly manufactured GFCI's have better circuitry to prevent operation after test failure.

Nuisance Tripping? I hear you Ryan. Using simile, I would rather work on a 200 MHz pentium that was 100 percent reliable, than a 10 GHz Pentuim X that had to reboot every 15 minutes. I hope that if Code requires this for 2008, that technology quickly catches up (like in Fall 2006). Look at the black eye they got with GFCI's, I hope that they have learned that lesson well.

Let's look also at other safety issues coming up as proposals, like tamper proof receptacles. Look at the cost it will add. Do I support it? Absolutely. It gets rid of all those silly plastic inserts that you need fingers of a three year old inorder to remove. Do I want to pay for them? No, I don't think I can afford it. Do I sound lame?

Now if you will excuse me, I need to go exerise my breakers and test all my GFCI's for the first time in 11 years. Oh, I take that back, my son regulary tests the GFCI receptacle on my kitchen island. Will someone help me remove this plastic thingy so I can plug in my vacuum?

Shane, P.E.

Ryan,
If you look back in some of the information on this issue, you will find that the manufactures maintain that there is no such thing as a series arc on 120 volt circuit. They do not exist, however high resistance and glowing connections do exist and do cause fires. The AFCI, even the new combination types do not directly detect this type of fault as far as I know. The AFCI only reacts to these faults after they progress to a parallel arcing fault or a ground fault.
Don

[This message has been edited by resqcapt19 (edited 05-19-2006).]

Shane,
That information is proprietary and will not be released to third party people who want to make AFCI testers.
I don't think that they have actually made them work with out excessive nuisance tripping.
However that does not match the fire data used to support the AFCI requirements. That data shows that 85% of the dwelling unit fires of electrical origin occur in dwelling units over 20 years old.
The testing of GFCIs brings up another issue. The new GFCI rules are another just scam in the name of safety. Until you look close at the information on how they work, you might think that they are actually fail safe. They aren't. With one type, when the electronics fail and you no longer have GFCI protection all the happens is a green LED changes to red. With the other type the device locks the power out, but only after a test or power failure. The electronics could have failed months or years ago, but the power is still available because most don't use the test button. We have the same issue with the AFCIs...very few will actually be tested monthly as required by the instructions.
Don

Don, take a look at the 2005 UL White book, and it will show that the combo types are supposed to open on a series arc, not just a high resistance series fault. I will try to post a quote from the book tonight if I can.

BTW: If you don't have the white book, e-mail me and I'll send.

You are probably refering to Warren Schill with UL. But that brings up another question...if you were in Wendover last week and attended Warren's class, why weren't you in my class next door?