AFCI Update


I have pressed the manufacturers of AFCI devices to demonstrate the superiority of the AFCI circuit breaker (as compared to a standard circuit breaker) in preventing a fire from loose terminals and connections. My challenge was specifically directed to Cutler-Hammer because they disputed some of the comments I made in my newsletters. Cutler-Hammer had offered many times to "demonstrate their AFCI technology," but I refused this invitation. I requested, instead of their demonstration, a comparison test of AFCI circuit breakers against a standard circuit breaker, but Cutler-Hammer refused this request. As a result, I submitted a proposal October 30, 2002 to have the AFCI requirement removed from the NEC based on the following:

1. UL 1699, the AFCI standard, does not require the AFCI circuit breaker to protect against fires caused by arcing at loose connections, at loose wires in wire connectors, or at loose screws.

2. Many in the industry (including myself) felt that an AFCI protective device, as required by the NEC, will not significantly reduce the incidence of fires at loose terminations and connections and the AFCI protection device (as currently listed) will not prevent them.

3. The public and the electrical industry have placed their trust in UL and the National Fire Protection Association to protect them. The Code process must be a guardian of public safety and it must put the public interest first. We will fail to maintain public trust if we do not remove the requirements for AFCI's from the NEC until this technology is demonstrated to prevent a fire from loose terminals and connections.

4. If the AFCI protection device is not required to protect against loose terminals, then what good is it? The data available today does not support how many residential fires have been started from loose terminal connections as compared to an arcing fault. Nor can data support how many fires can be linked to faults in premise wiring as compared to faults associated with the plugged-in load.

5. The public and the industry should have the opportunity to see a demonstration where an AFCI will prevent a fire from loose terminals, under the same conditions that a standard molded circuit breaker and fuse could not, or did not. Since the manufacturers state that this device will prevent a fire from this condition (their promotion material), they should show us the proof.

6. What is needed is a comprehensive study on the true causes of electrical fires by a Task Force of people qualified for this purpose. This study should provide the details on the causes of fires, where they occur, and what actions the industry should take to help reduce them. This study needs to be available for public input and debate (just like the NEC process). I'm sure that with the proper study valuable information will be acquired. We may learn:


On October 31, 2002, Cutler-Hammer contacted me and offered to provide the comparison testing of protective devices as I requested. This meeting was held on Monday, November 4, 2002 in Pittsburgh, PA with Dr. Clive Kimblin [Manager of Standards], Mr. John Wafer [VP and Group Chief Technology Officer], Dr. Joe Engel [Electronics Engineering Manager], and Mr. Brendan Foley [Product Manager]. I personally paid all of the costs incurred for this trip, including transportation and lodging (very expensive when you make last minute reservations).

After having attended the comparison demonstration, and getting the chance to have my concerns and questions addressed directly by those that have the knowledge of this technology, I have changed my position on the effectiveness of AFCI protection devices. As a result, I will withdraw my proposal to remove AFCI's from the NEC.

It is true that AFCI circuit breakers are not required to protect against loose "glowing" connections, but AFCI circuit breakers that are dual-listed for AFCI/GFI or AFCI/GFCI should prevent most fires from high-resistance heating (glowing) at loose terminals and connections

The performance tests comparing AFCI/GFI with a standard circuit breaker demonstrated that AFCI/GFCI circuit breakers will save lives under the conditions identified by the manufacturers, including from loose terminals or connections. The comparison test was simple; there were two outlet boxes each containing a duplex receptacle with loose terminals. A 1,500W load was applied to each, and after an hour or so, the receptacles melted and the AFCI/GFI circuit breaker opened within three to eight half-cycles, whereas the standard circuit breaker did not trip.

I personally thought that it was the heat (650F at the hottest point) from the loose terminals that caused the fire. What I discovered was that the heat from the loose terminals melted the wiring device and the circuit conductors in the box, creating a line-to-neutral or line-to-ground fault. If the available short-circuit current of the fault was 100A, it could take between one and five seconds (120 to 600 half-cycles) or even longer to clear the fault with a standard inverse-time circuit breaker, whereas an AFCI/GFI circuit breaker would clear the fault in less than nine arcing half-cycles from a line-to-neutral fault or two half-cycles from a ground fault.

NOTE: AFCI circuit breakers are not required by the NEC to be dual-listed (AFCI/GFI or AFCI/GFCI). Nevertheless, all four U.S. manufacturers include ground fault circuitry and Cutler-Hammer has chosen to dual-list their devices. The NEC should make dual-listing a requirement since there is no cost difference between dual-listing or not.

I still feel that a comprehensive study on the true causes of electrical fires by a Task Force is needed to provide accurate details on the origin of electrical fires, where they occur, and what actions the industry should take to help reduce them. This study should be available for public input and debate, just like the NEC process.

We all play a critical role in improving life safety by becoming involved in some manner, whether by submitting a proposal, commenting on a proposal, being a Code panel member, or an "outsider" like myself trying to keep people on their toes.

I know you must have lots of questions and I hope the following will answer most of them. I am organizing a meeting in Pittsburgh at the Cutler-Hammer Technology and Quality Center for December 17th from 9:00 a.m. to 3:00 p.m. to demonstrate how an AFCI circuit breaker protects against a fire from loose terminals and connectors, as well as the technology. If you are interested in attending, please contact me as soon as possible.

As always, please let me know your thoughts and feelings. Mike Holt


Would it be possible for you to give more information on how the tests were conducted?
A typical receptacle installed in a metal and nonmetallic box mounted on wood studs with drywall. The hot wire just touching the screw on the receptacle, it was move around so that it began a very small arc when the 1500W heater load was on. In less than one hour the receptacle and the wiring in the box would melt. The AFCI opened because of an arc fault (line-to-neutral) on one case (when the peak current of a half-cycle exceeded 50A, three times in a row) and it was the Ground Fault Interrupter (GFI - 30 mA) that opened in the other. In both of these examples, the arc energy was as low as could be detected.

What are the characteristics of an arc on the electrical circuit?
I teach an apprenticeship class and I would like to be able to explain the theory to the class.

What makes the AFCI protection any different from that in a standard circuit breaker?
AFCI's have the electronics to open the circuit for low-level line-to-neutral faults when three to eight half-cycles exceed 50A peak (within .5 second), whereas a standard circuit breaker might not open for many hundreds of half-cycles.

Why not trip the AFCI in one or two half-cycles, instead of three to eight half-cycles?
If the AFCI tripped in one half-cycle then, then many voltage surges could cause the protection device to trip and in many cases we might not be able to turn on the loads on. A light bulb sometimes takes two
Half-cycles to burn out, so two is out.

Does a GFCI circuit breaker offer equal or greater performance than an AFCI circuit breaker, given the same conditions for which an AFCI breaker was designed?
GFCI circuit breakers are designed to protect against ground faults of 4 to 6 mA or more, short-circuits, and overloads. Dual listed AFCI/GFCI circuit breakers are designed to protect against ground faults of 5 mA or more, short circuits, overloads, and arcing line-to-neutral faults. Dual listed AFCI/GFI circuit breakers are designed to protect against ground faults of 30 mA or more, short circuits, overloads and arcing line-to-neutral faults. A GFCI does not offer protection against arching line-to-neutral faults.

It seems to me that the demonstration you witnessed proved only that 30mA GFCI breakers improve safety, not that AFCI breakers improve safety. I don't understand why you feel a dual listed AFCI/GFI breaker is any better than a GFCI breaker.
Because a GFCI circuit breaker with ground fault protection of 5 mA does not have line-to-neutral arc fault protection.

What still doesn't make sense to me is that if a GFCI breaker trips at a lower level than an AFCI - why mandatory AFCI? Why not an option to use GFCI?
A GFCI protection device offers tremendous line-to-ground and neutral-to-ground protection (maximum 5 mA), but a GFCI will not clear a line-to-neutral arcing faults in three to eight half-cycles, only a AFCI can provide this level of protection.

I don't see the value of an AFCI protection device that is not GFI or GFCI listed because it only senses a line-to-neutral fault, and really how often does that happen in branch-circuit wiring?
I agree with you, the likely hood of a line-to-neutral fault in branch-circuit wiring causing a fire is very rare. But a line-to-neutral arc could occur in two wire NM cable or knob-and-tub wiring (particularly in the outlet boxes). Line-to-neutral faults are very common inside an outlet box when the conductor insulation melts because of excessive heat from loose terminals or connections. Only an AFCI is capable of clearing the fault within three to eight half-cycles.

I can't imagine any type of fault on a Code compliant building wiring system that will not develop into a ground fault which would be protected by a GFCI.
The likely hood of a line-to-neutral fault not evolving into a ground-fault is not likely in today's NEC compliant wiring systems consisting of metal boxes, raceways and cables. Installations consisting of metal enclosures, raceways and cables should be safe from a fire if GFCI. But a GFCI protection device cannot be installed on all circuits because of leakage current from induction loads such as motors and fluorescent fixtures. The ground-fault setting on an AFCI is no lower than 30 mA, much higher than the mA setting of a GFCI.

Does an AFCI/GFI provide the same level of ground fault protection as a GFCI device?
No, AFCI/GFI circuit breakers will de-energize the circuit when the ground fault exceeds 30 mA, whereas an AFCI/GFCI circuit breaker opens at 5 mA. However, a AFCI/GFCI circuit breakers should only be installed on circuits where nuisance tripping would not be a problem.

There are many homes dating back to the 1920's that still have knob-and-tube that has outlasted subsequent wiring technology, such as BX with rubber insulated conductors and early forms of romex. Do AFCI breakers protect existing knob-and-tube wiring systems?
An AFCI circuit breaker will trip and clear the circuit when a line-to-neutral arc occurs (often caused by the melting of the conductor insulation at loose terminals) within three to eight half-cycles, whereas a standard circuit breaker might not open for many hundreds of half-cycles. Note: If the AFCI is dual listed as a GFCI, the two wire receptacle can be replaced with three-wire receptacles and no equipment grounding conductor is required to be run to the receptacles [406.3(D)(3)].

Is it okay to replace a regular circuit breaker with an AFCI circuit breaker if there are GFCI receptacles on the circuit in question?
Yes. The GFCI receptacle should not interfere with the AFCI protection circuitry.

What type of arcs are the most common factors in electrical fires, and will today's AFCI circuit breakers detect these faults?
An AFCI is designed to detect and clear a line-to-neutral fault under conditions where a standard circuit breaker might not (3 to 8 cycles as compared to 600 half-cycles, depending on the available fault at the failure). Loose electrical terminations and connections should generate enough heat to create a line-to-neutral fault or a line-to-ground fault, which will be detected by the AFCI or GFI circuitry.

I have heard that the AFCI technology would be improving in the future. What do you think?
I don't know if the AFCI technology in a circuit breaker can be made to do more than it does right now. You have to understand that this technology is not new. The manufacturers have been working on this for almost 10 years.

I've heard that AFCI devices won't protect against fires from 2-wire NM cable. Is this true?
False. AFCI's have superior performance protection over a standard circuit breaker when it comes to low-level line-to-neutral faults. In an old house I would surely install them, even though they are not required by the NEC.

Would an AFCI circuit breaker work as a service or feeder protection device?
No, because they are limited by UL to 15A and 20A, 120V.

Are the electronics in AFCI devices subject to the damaging effects of high-voltage surges? And if so, do they continue to energize the circuit giving the false impression that they are working properly?
Yes and yes. The electronics in AFCI devices are subject to the damaging effects of high-voltage surges, just like a GFCI circuit breaker. The instructions supplied with both GFCI's and AFCI's stress that they should be tested monthly to ensure that they are operational.

NOTE: The AFCI UL standard was recently revised to raise the surge voltage test from 4kV/2kA to 6kV/10kA and all permanently connected AFCI's must meet this requirement by July 15, 2004.

I read there's a nuisance-tripping problem with AFCI devices. Has this problem been resolved yet?
The major problem is that some installers do not yet understand how the AFCI circuit protection device operates. If there is a neutral-to-ground connection on the load side of the circuit breaker, the breaker will not trip until a load has been applied, whereas a GFCI, even without load, will not operate until the neutral-to-ground connection has been removed.

What occurs is that the electrician leaves the property after installing and turning the devices on, then the homeowner calls two hours later complaining that there is no power. Trouble-shooting determines that as soon as a load is applied, the AFCI trips because of a faulty neutral-to-ground connection on the load side of the device.

Why does the NEC only require AFCI protection for bedroom circuits?
This is an area in the home where the disabled, elderly, and young children spend a great deal of their time. The ratio of the bedroom space to the total area is relatively large as compared to the ratio of the number of bedroom circuits to the total number of circuits. So, basically, you get the most protection for the cost.

Mike, do you think the data supports the requirement that AFCI protection devices should be required by the NEC in new homes?
No, but if the NEC does not require it when the home is built, then there is no way to require it later when it's really needed. However, newer homes have fires via electrical origin as well, just statistically at a lower rate than older homes.

Will you be replacing the breakers in your home with AFCI breakers?
Well, that's a tough one. They are very expensive (about $30 each) and if I replaced all of them, it would cost me about $1,500. I will have an electrical contractor visit my home and check all terminals for tightness. Since it's a new home, I don't feel the risk is that great.

Yes, but Mike what's a life worth?
Okay, okay… I will install AFCI breakers for all 15 and 20A general-purpose circuits (before the electrician checks all terminals, he'll probably find some neutral-to-ground connections), but not the individual circuits. This should give me the greatest level of fire protection for the cost.

Should the NEC expand the requirements for AFCI's?
It's easy for me to give opinions because I don't have all of the facts and it won't cost me anything. Since I have confidence in the NFPA Code process, I'll leave this tough decision to the experts that sit on Code Panel No. 2.

What do you do about an older house with fuses? Are you required to upgrade your panel if you do any modifications within a bedroom?
AFCIs are not required for existing homes.

Do AFCI breakers work with multiwire circuits?
Yes if it's of the two-pole AFCI type.

I was under the opinion that when any renovation/modification is done to a bedroom, even adding an outlet, the wiring was required to be upgraded to the AFCI protection requirement. Is this the correct assumption?
This is up to the local electrical inspector/building official.

To the best of my limited knowledge, there is still no way to test any of these breakers. How can an AHJ approve a device that may or may not be working properly?
Sure there is I have one!


Mike, I am proud of you and Cutler Hammer for going the extra mile in your efforts. The electrical industry is better today than it was due to the apparent success of this meeting. Don't stop asking for better data on how fires start so that improvements in safety will continue to improve.
Dan Prather, Inspector

Mike, I wish that I could have witnessed the testing. Your interest in the AFCI has had an extremely positive effect on our industry. I respect your ability to put in writing that you have changed your position on a serious issue.
Jim Dollard, IBEW

I'd really like to know exactly what changed your mind. Don't tell me these devices will work to detect loose connections…and don't tell me that with better technology we can't detect loose connection-type arcing either.
Bob Huddleston, Engineer

I read the "AFCI New Thoughts" file. I thought it was very good and showed integrity and graciousness in changing your point of view. I do agree with a couple of comments you added at the end. I too, would have liked to see the test that changed your mind, and what do you base your statement on that "AFCI technology is probably about as good as it is going to get?

I would not have expected anything less than you changing your viewpoint immediately and without hesitation once you have proper facts. You have always been the first to admit it if you're wrong or incorrect on anything. That is part of what I mean by integrity.
Mike Culbreath, Graphic Designer, Mike Holt Enterprises, Inc.

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