AFCI - Arc Fault Circuit Interrupters (9/25/99)
Mike, I'm trying to stay current with the current codes and I ran across Section 210-12 in the 1999 code which covers the use of Arc-Fault Interrupters (AFCI's) in bedrooms. I am working on rewiring a house (once a one-room schoolhouse). I went to my supplier and requested some information on these devices and to my surprise they had never heard of this device. I recently received the information on GFCI's in your e-letter and was wondering if you could spread some light on AFCI's.
From: Bittinger, John R
Debbie is correct that the current NEC 210-12(b) requires AFCI's for Dwelling Unit Bedrooms. There are a couple of points that need to be clarified:
- This code requirement is not effective until January 1, 2002
- The requirement is to protect the branch circuits that supply 125vac, 1-phase, 15 and 20-amp outlets installed in dwelling unit bedrooms. A quick check of on-line resources reveals that both Square-D and General Electric manufacture 15A and 20A single-pole AFCI circuit breakers for their low-end loadcenters.
Square-D types QO115AFI and QO120AFI
General Electric types THQL1115AF and THQL1120AF
Follow-up calls to our local Graybar and GE Supply offices revealed that the above products are not currently stocked locally, but are stocked at the factory and readily available. List prices are in the $150 - $170 range! Cost to industrial accounts is $70 - $90. Lower prices may be available to some companies through special preferred supplier contract arrangements. I assume that prices will drop significantly when the supply/demand increases with Code implementation in 2002.
Similar to GFCI devices, I expect AFCI device requirements will migrate over to commercial and industrial applications in due course. E.g., Fire station sleeping areas, military housing, hospitals, outpatient clinics, rest homes, retirement homes, or other locations where extension cords or cord-connected equipment may be used, and where the general occupancy may be at risk.
AFCI's are readily available from Cutler Hammer, Sq D and GE and Siemens has a product in development. I have had a Sq D AFCI since Jan of 99. Cutler Hammer had the first UL listed AFCI and they are seeking UL Listing on a combination AFCI-GFCI circuit breaker, which should be available late this year.
Two government agencies now require AFCI's for retrofit/remodels State of Vermont and the City of Atlanta, Georgia.
I would suggest contacting a large wholesale house and have them check nationwide stock. You'll find ample stock of Sq D and CH. I don't know about other brands. I'm currently at an IAEI section meeting where we had a presentation by Sq D and Cutler Hammer on AFCI's. They are here to stay and look for more applications/requirements in future codes. The good news is that nuisance tripping does not seem to be a problem.
From: Myke Ridgeway
A ground fault circuit interrupter compares the current between the hot and ground looking for leakage current, or an imbalance. An arc fault circuit interrupter looks for an unintentional electrical discharge. The arc fault does not go to ground. Things that would create an arc fault might be a damaged extension cord or improperly installed wall receptacles.
An AFCI or Arc Fault Circuit Interrupter as covered in Code Article 210-12 does not take affect until the next Code cycle in year 2002. The AFCI receptacle is designed to distinguish a potentially damaging arc in the cord of the plugged in device. When such an arc is distinguished the power to the receptacle is terminated to help extinguish the arc before a catastrophe results. Possibly the supply house did not know about the AFCI because it is a relatively new device and is not required at this time.
From: Richard Currin
The Cutler Hammer Web site for one has information on these breakers. They will be required in bedrooms the next code cycle. I think they will greatly reduce fires over normal breakers.
From: Earl Dean
I recall I first heard about these devices last year at NFPA's 1999 NEC Seminar when it came to town. A person from the NFPA named Mark Ode indicated they would be similar in appearance to existing GFCIs either receptacle or CB.
From: Rosenthal, Mark A
See the NEC Handbook commentary on Section 210-12(b) for another perfect example of regulatory overkill. How many people will freeze to death as this thing shuts off the power to their electric blankets in the dead of winter. It took 10 years to get GFCI's to a point where they were not nuisance tripping all the time. How long for this turkey?
From: Scheidecker, Brad
Per Article 210-12(b), AFCI's are intended to mitigate the effects of arcing faults
that may pose risk of fire ignition under certain conditions if the arcing persists. The use of the
AFCI in bedrooms becomes mandatory 1/1/2002. This gives the industry time to manufacture the AFCI's,
now that UL has the standard to develop them to. UL announced the development of a standard for devices
that are intended to mitigate these faults. The standard is designated UL 1699.
From: Vigilante, Joseph
I checked the code handbook about section 210-12. It appears that the reason the supplier did not hear about these devices is that they are still in the testing stage. UL has designated them as UL 1699 and it is still a draft. That is most likely the reason the NEC states this requirement does not take effect until January 1, 2002. Reading the handbook this device is to be installed at the origin of the branch circuit. My suggestion would be to wire the bedrooms on circuits separate from other parts of the house, and when these devices become available to install them in your panel.
From: Haskin, Donald M (DynCorp)
AFCI's are arcing fault circuit interrupters. These devices can sense the variations in the sine wave caused by an arcing fault and trip in order to prevent fires. A normal, "inverse time" circuit breaker sees an arcing fault as a normal load unless the current flow exceeds it's trip rating. These devices will be required in "dwelling unit bedrooms", 15 and 20 amp receptacle circuits, beginning January 1, 2002. I checked with my local supplier and found that the devices are readily available but only as a circuit breaker unit (no AFCI receptacle as yet) at a price comparable to a GFCI breaker (about $40.00).
From: Rex Cauldwell
The history--allegedly one company came up with the design, talked the code people into it, and everyone
else had to come along. The fact--there is absolutely no data, in my opinion, that indicates we need
arc fault circuit interrupters because of past electrical problems in the bedrooms.
The data you want--Circuit breakers protect conductor insulation and the wire within from damage due
to overheating created by excessive current. We all know that you can arc weld with a hot wire and
the breaker will not kick. Most breakers trip off heat and if the surge is short enough even an excessive
amount of current can flow through the overcurrent device (breaker) without it tripping. This is why
lightning surges of 10,000 + amps can flow through a breaker. In addition, arcs can occur which are
less than the breaker overcurrent rating--if the arc current
doesn't exceed 20 amps for example we can't expect the device to kick and therefore a fire can start. The bottom line is circuit breakers are lousy at stopping fires. This is why we have electrical fires--the breakers don't kick--they aren't designed to. Knowing this, it is theoretically possible for an arc current to occur within the bedroom wiring and cause a fire. Thus the alleged need for a device that can recognize an arc fault.
What is an arc fault? It is ironic that the NEC requires the device in 2002 but yet they don't even define it. It is not in the definitions in the '99 code. Oh well, it is generally construed that an arc fault is an unintentional electrical discharge characterized by low and erratic current that may ignite combustible materials.
There are three types of arc faults common to your house:
- Parallel - This is the proverbial two wire direct short--hot to neutral zap.
- Ground - An arc between a wire and ground
- Series A wire that is cut coming back in contact with itself
The arc fault circuit interrupter is a device (circuit breaker with electronics) designed to recognize the unique current and voltage signature of the above arc faults. Hope this helps...the arc fault won't.