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ELECTRICAL INSPECTION, DIAGNOSIS, REPAIR
ACCURACY vs PRECISION of MEASUREMENTS
AFCIs ARC FAULT CIRCUIT INTERRUPTERS
ALUMINUM SECs & WIRING
ALUMINUM WIRING HAZARDS & REPAIRS
AMPS & VOLTS DETERMINATION
AMPACITY - the LIMITING FACTOR
APPLIANCE EFFICIENCY RATINGS
BACKUP ELECTRICAL GENERATORS
BOOKSTORE - ELECTRICAL
BUILDING SAFETY HAZARDS GUIDE
Cadet & Encore Heater Recall
CIRCUIT BREAKER FAILURE
CIRCUIT BREAKER SIZE for A/C or HEAT PUMP
Classified CIRCUIT BREAKER WARNING
CORROSION in ELECTRICAL PANELS
CORROSION & MOISTURE SOURCES in PANELS
CUTLER HAMMER PANEL FIRE
DEFINITIONS of ELECTRICAL TERMS
DIRECTORY OF ELECTRICIANS
DMM Digital Multimeter, How to Use
ELECTRIC METERS & METER BASES
ELECTRIC MOTOR DIAGNOSTIC GUIDE
ELECTRIC MOTOR OVERLOAD RESET SWITCH
ELECTRIC PANEL AMPACITY
ELECTRIC PANEL INSPECTION
ELECTRIC PANEL MOISTURE
Electric Power Frequency Table
ELECTRICAL DISTRIBUTION PANELS
ELECTRICAL GROUND SYSTEM INSPECTION
ELECTRICAL SERVICE DROP
ELECTRICAL SERVICE ENTRY WIRING
EMF RF FIELD & FREQUENCY DEFINITIONS
FEDERAL PACIFIC FPE HAZARDS
FIRE SAFETY Checklist, CPSC
GFCI PROTECTION,Testing GFCIs AFCIs
HEATING COST FUEL & BTU Cost Table
HEAT TAPE USAGE GUIDE
Hertz - Definitions of KHz MHz GHz THz
KNOB & TUBE WIRING
LIGHTING, EXTERIOR GUIDE
LIGHTING, INTERIOR GUIDE
LIGHTNING PROTECTION SYSTEMS
LOW VOLTAGE BUILDING WIRING
LOW VOLTAGE TRANSFORMER TEST
MAIN DISCONNECT AMPACITY
MOISTURE SOURCES in PANELS
MURRAY SIEMENS Recall
PHOTOVOLTAIC POWER SYSTEMS
PUSHMATIC - BULLDOG PANELS
REMOTE ELECTRIC POWER, PHOTOVOLTAIC
RUST in ELECTRICAL PANELS
SAFETY for ELECTRICAL INSPECTORS
SE CABLE SIZES vs AMPS
SIEMENS MURRAY Recall
UNDERGROUND SERVICE LATERALS
VOLTS / AMPS MEASUREMENT EQUIP
WIND ENERGY SYSTEMS
WIND TURBINES & LIGHTNING
ZINSCO SYLVANIA ELECTRICAL PANELS
Arc Fault Circuit Interrupt or Information: this article, adapted and expanded from a US CPSC article on AFCIs is supplemented with additional details and commentary answers most home owner and home inspector questions about installing, testing, and inspecting AFCIs - arc fault protectors in homes. Page top photo courtesy of the US CPSC.
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.
This material was originally prepared by DF for the American Society of Home Inspectors New England Chapter,( ASHI -NE) Educational Seminar, Sept 22-23, 2008. Portions of this text are quoted from the Arc Fault Circuit Interrupter (AFCI) FACT SHEET provided by the US CPSC . Additional notes and details have been added, drawing on a variety of sources listed at the end of this article.
Arcing faults: a series arc occurs in electrical wiring when there is a small gap or break in a conductor. a parallel arc occurs when a small gap or break which permits current to flow to ground (a ground fault) or between the hot and neutral wires (a short circuit). See Arcing Types in this article for more details.
Arcing hazards in electrical systems have long been recognized as a problem and a potential hazard dating at least to the 1920's in the U.S. but devices to protect from arcing faults in the home are much more recent.
Arc fault circuit interrupters: an “AFCI” is an arc fault circuit interrupter first introduced in 1998. AFCIs are designed to protect against fires caused by arcing faults in the home electrical wiring.  What is the actual hazard?
Arcing faults, especially parallel arcing faults, lead to overheating and a fire hazard even if no shock hazard is present. Electrical arcing faults have been described in detail by Shea who explained how electrical arcing faults can be a serious fire hazard and one that is distinct from ground faults intended to be addressed separately by GFCIs. Also see GFCI PROTECTION,Testing GFCIs AFCIs
Typical wiring details for AFCI circuit breakers
Our AFCI photo at left illustrates a Square-D 20A AFCI breaker during installation in the electrical panel.
The light green arrow points to the AFCI device - you'll notice that it is much longer than conventional circuit breakers in the panel. Each AFCI breaker involves three electrical connections:
Our next AFCI breaker photo shows more closely the electrical circuit connection points at the AFCI breaker itself.
The molded case of the AFCI breaker also indicates which wires should be attached to which terminals, as will instructions included with the device.
Why are AFCI's [Possibly] Important?
AFCIs are an important safety addition to homes in part because they address an additional type of electrical fault that can cause a fire and one which may not be detected and interrupted by a conventional circuit breaker, nor by a ground-fault circuit interrupter (GFCI's).
We've seen that arcing of any type can result in burned debris on wire surfaces which causes an increase in electrical resistance and thus overheating at that point. Arcing was examined earlier in detailed studies of the aluminum electrical wiring fire hazard at connections in the wire. Arcing of any type, whether it is the micro-fretting type of arcing that occurs with aluminum wire or possibly larger arcing across a gap or short in a copper wire.
InspectAPedia Note: According to Mike Holt, "Studies have shown that over 60 percent of fires are from causes in the fixed wiring, switches, receptacle outlets and lighting fixtures that are part of the fixed electrical system of a residence." In other words, AFCI's are focused on detecting arcing and preventing fires in an area where the risk is significant.
Arcing faults often occur in damaged or deteriorated wires and cords. Some causes of damaged and deteriorated wiring include:
and cord exposure to heat vents and sunlight.
Early warning about nuisance tripping of AFCI circuit breakers and consumer objections to these devices
Watch out: we have heard several reports of excessive "nuisance" tripping of arc fault circuit interrupters, and our own limited testing has confirmed this problem in our laboratory where we installed the coffee maker shown at left.
On a newly-wired AFCI electrical circuit with tight, well-made connections and powering a string of electrical receptacles, we connected a single device: a Keurig™ coffee maker to the circuit (photo at left). The circuit also supports a wall mounted light that uses florescent bulbs. No other devices were connected to the circuit.
The coffee maker was set to turn itself off automatically after one hour of idle time. Yet consistently over 30 days of testing, every day we observed that the 15-A Square D AFCI for this circuit tripped off at least once.
We suspect that electrical properties of the coffee maker may have been the source of noise on the circuit that was causing the AFCI to switch off. Replacing the AFCI with a conventional 15-A Square D circuit breaker completely eliminated the nuisance tripping on this circuit.
Three other AFCIs were installed in the same electrical panel, but only one was connected to an electrical circuit in active use. On that circuit, also supporting a string of electrical receptacles powering lighting and computer equipment during the same 30-day test period, no nuisance trips of the circuit were observed.
Watch out: as with GFCI's discussed at MULTI-WIRE CIRCUITS, installing AFCIs on multi-wire branch circuits using a shared neutral requires installation of a common trip tie, and nevertheless the circuit and this circuit protection device may be subject to further nuisance trips or unexpected behaviors.
Watch out: An installing electrician informed us that many of his customers were complaining about nuisance tripping and that he was asked by those clients to remove the AFCI devices and to replace them with conventional circuit breakers. This raises an issue about national and local electrical code compliance and about building electrical and fire safety - removing a code-required safety device.
Further testing of the nuisance-tripping AFCIs as well as three others installed in the same electrical panel and samples of non AFCI breakers of the same age, rating, and brand is underway and will be reported here.
UL in January 2002 described various types of AFCIs which we summarize here. The first three types of AFCI's, Branch Feeder AFCIs, Outlet Circuit AFCIs, and Combination AFCIs are the three most basic types of arc fault detectors and are important definitions for the home owner or home inspector to understand:
Conventional circuit breakers only respond to overloads and short circuits; so they do not protect against arcing conditions that produce erratic current flow. An AFCI is selective so that normal arcs do not cause it to trip.
The AFCI circuitry continuously monitors current flow through the AFCI. AFCIs use unique current sensing circuitry to discriminate between normal and unwanted arcing conditions. Once an unwanted arcing condition is detected, the control circuitry in the AFCI trips the internal contacts, thus de-energizing the circuit and reducing the potential for a fire to occur.
An AFCI should not trip during normal arcing conditions, which can occur when a switch is opened or a plug is pulled from a receptacle.
Presently, AFCIs are designed into conventional circuit breakers combining traditional overload and short-circuit protection with arc fault protection. AFCI circuit breakers (AFCIs) have a test button and look similar to ground fault circuit interrupter (GFCI) circuit breakers.
Some designs combine GFCI and AFCI protection. Additional AFCI design configurations are anticipated in the near future.
It is important to note that AFCIs are designed to mitigate the effects of arcing faults but cannot eliminate them completely. In some cases, the initial arc may cause ignition prior to detection and circuit interruption by the AFCI.
The AFCI circuit breaker serves a dual purpose – not only will it shut off electricity in the
event of an “arcing fault”, but it will also trip when a short circuit or an overload occurs.
The AFCI circuit breaker provides protection for the branch circuit wiring and limited
protection for power cords and extension cords. Single-pole, 15- and 20- ampere AFCI
When did the NEC Begin Requiring AFCIs & Where should Arc Fault Circuit Interrupters (AFCIs) be used? Are Combination AFCI's effective?
The 1999 edition of the National Electrical Code, the model code for electrical wiring adopted by many local jurisdictions, requires AFCIs for receptacle outlets in bedrooms, effective January 1, 2002. Although the requirement is limited to only certain circuits in new residential construction, AFCIs should be considered for added protection in other circuits and for existing homes as well.
In 2008 the NEC added a requirement for AFCI protection in all living areas and also added that "only combination AFCI's are allowed". 
Older homes with aging and deteriorating wiring
systems can especially benefit from the added protection of AFCIs. AFCIs should also
be considered whenever adding or upgrading a panel box while using existing branch
Watch out: While AFCI-related patents date from as early as 1985, the current and most-widely installed AFCI designs were developed and patented by Joseph C. Engel, Robert T. Elms, & John C. Schlotterer with key patents assigned to Eaton Corporation. But Dr. Engel has argued that the current devices as marketed do not properly identify and address the types of electrical hazards that were addressed by his original invention. Quoting from Engel (2012) ,
InspectAPedia Notes: What are the code requirements for AFCIs?
In homes equipped with conventional circuit breakers rather than fuses, an AFCI circuit breaker may be installed in the panel box in place of the conventional circuit breaker to add arc protection to a branch circuit. Homes with fuses are limited to receptacle or portable-type AFCIs, which are expected to be available in the near future, or AFCI circuit breakers can be added in separate panel boxes next to the fuse panel box.
An AFCI hookup wiring diagrams and detailed instructions from GE is available here. Other manufacturer's Arc Fault Interrupter installation guidelines will be similar. Typically for an electrical circuit to be protected by AFCI, in the electrical panel the circuit hot and neutral wires are connected to marked terminals on the AFCI circuit breaker and a third wire connects the AFCI breaker to the neutral bus in the electrical panel. The AFCI installation wiring diagram shown here and others are available from GE, General Electric Corporation and GE circuit breaker distributors.
Do not attempt to work on your electrical wiring, switches, or outlets unless you are properly trained and equipped to do so. Electrical components in a building can easily cause an electrical shock, burn, or even death.
Even when a hot line switch is off, one terminal on the switch is still connected to the power source. Before doing any work on the switch, the power source must be turned off by setting a circuit breaker to OFF or removing a fuse. See SAFETY for ELECTRICAL INSPECTORS and Electrical Wiring Books & Guides
AFCIs should be tested after installation to make sure they are working properly and protecting the circuit.
Subsequently, AFCIs should be tested once a month to make sure they are working properly and providing protection from fires initiated by arcing faults.
A test button is located on the front of the device. The user should follow the instructions accompanying the device. If the device does not trip when tested, the AFCI is defective and should be replaced.
Because it has been misunderstood and criticized it's worth noting that the test button on an AFCI does not simply force the mechanical internal switch of the AFCI to trip. Rather, the test button on an AFCI tests the arc fault detection circuitry to be sure that it is working properly, that it will respond to an arc fault, and that the circuitry will in turn cause the mechanical internal switch to open.
This is an important distinction to remember, since the Ground Fault Circuit Interrupter (GFCI) has faced similar criticism. We've certainly found lots of GFCI's which exhibited an error when the GFCI test button was pressed: the button caused the GFCI to trip but the device was defective or improperly wired so that it would not protect the circuit.
As of September 2008 we have found no test tool that reliably and completely tests the function of an AFCI. Only the integral test button tests the circuitry of the device as well as the trip mechanism. UL classes these "test" devices not as "testers", but as "indicators".
A problem is that some devices used to "inspect" an AFCI, in trying to produce a simulated arc fault condition, may fail to cause the AFCI device to trip even though it is perfectly fine.
Literature from the manufacturer of a popular "test tool" tells the user of the tool to go to the electric panel and use the test button on the AFCI device to make sure it trips. In other words the inspector cannot rely on the separate test tool. For this reason you will see such tools referred to as "indicators" rather than "testers": they are not a complete and reliable test instrument for AFCIs. -- Mike Holt
What is the difference between an AFCI Arc Fault Circuit Interrupter and a GFCI Ground Fault Circuit Interrupter? The AFCI should not be confused with the GFCI or ground fault circuit interrupter.
An AFCI is a device intended to prevent a fire. It detects a type of arcing in the electrical circuit that can lead to overheating and a fire. An AFCI can protect against some types of shock by detecting a short circuit if the short is also affecting an individual, but it is not designed as a shock protector and will not detect all of the same faults as a GFCI.
A GFCI is a device intended to prevent electrical shock. A GFCI will not necessarily detect the type of electrical arcing that can cause a fire. The GFCI is designed to protect people from severe or fatal electric shocks while the AFCI protects against fires caused by arcing faults. The GFCI also can protect against some electrical fires by detecting arcing and other faults to ground but cannot detect hazardous across-the-line arcing faults that can cause fires.
A ground fault is an unintentional electric path diverting current to ground. Ground faults occur when current leaks from a circuit.
How the current leaks is very important. If a person’s body provides a path to ground for this leakage, the person could be injured, burned, severely shocked, or electrocuted.
The National Electrical Code requires GFCI protection for receptacles located outdoors, in bathrooms, garages, kitchens, crawl spaces and unfinished basements; and at certain locations such as near swimming pools.
A combination AFCI and GFCI can be used to satisfy the NEC requirement for GFCI protection only if specifically marked as a combination device.
InspectAPedia Note: don't confuse this "combination" with the "Combination AFCI described earlier in this article.
While we're discussing the 2008 electrical code changes for AFCI's let's also update ourselves about GFCI's:
NEC 210.8 is the code section pertaining to GFCI's. (AFCI's are addressed in NEC 210.12.). These GFCI requirements are intended to address residential electrical wiring using 15A or 20A 120V electrical receptacles and circuits. Heavier-duty circuits such as a 30A welder circuit are excluded.
Basically GFCI protection requirements have been expanded to all basement, garage, and accessory building receptacles, and a wording change to drop "receptacles" and keep "outlets" expands GFCI coverage in other areas.
For 2008 the NEC deleted Nos. 1 and 2 to 210.8(A)(2) and Nos. 1 and 2 to 210.8(A)(5) from the prior NEC version.
210.8(A)(2) & (A)(5): Expanded GFCI protection requirements by deleting exceptions for receptacles that are not readily accessible and receptacles located in dedicated spaces to supply an appliance.
Deleting "receptacle" and leaving "outlet" in the NEC expands the required coverage of any device being discussed. That's because a "receptacle" is taken to mean an electrical outlet (a wall socket) while "outlet" is any place in the electrical wiring system from which electrical power is taken (a ceiling fan, a hard-wired smoke detector, etc.).
• 210.8(B)(4): Expanded GFCI protection requirements to include all outdoor 15- and 20-ampere, 125-volt receptacles, and added a conditional exception to permit use of assured equipment grounding conductor program in industrial establishments.
• 210.8(B)(5): Added GFCI protection requirements for all 15- and 20-ampere 125-volt receptacles installed within 6 ft of the outside edge of sinks, and added exceptions for receptacles in industrial laboratories where the loss of power would introduce a greater hazard and for receptacles in patient care areas where critical care equipment may be utilized.
Basement GFCI changes: The GFCI protection requirements for receptacles in basements, garages, and accessory buildings have been expanded to all 125-volt, single-phase, 15- and 20-ampere receptacles regardless of accessibility or movability of an appliance from one location to another. - Minnesota Electrical Association
GFCI's are required safety devices to be installed in the following locations:
In 2004 Schneider Electric issued a recall of early model Square D® AFCIs manufactured between March 1 2004 and September 23, 2004 because tests indicated that "... arc detection in these breakers may become inoperable due to an issue with a third party-supplied internal component in the electronic detection unit."
Schneider's letter emphasized in an opening statement that "... Square D Company, the leading manufacturer of electrical equipment, is committed to the safety of our people, our customers, and our products." The company's letter provided additional detail:
While these circuit breakers will continue to function normally, providing short-circuit and overload protection, a small percentage of the breakers may not function as an arc fault circuit breaker (AFCI) and detect a high-resistance low-current arc fault. The unique role of an AFCI is its ability to detect an electrical arc and shut down a circuit before a fire can start or spread. It is important to note that the affected circuit breaker itself does not pose a hazard.
[The company was concerned about inaccurate and misleading information in the electrical products market and asked that concerned parties turn to them for information regarding their products, including AFCIs.]
The positive responses we have received from electrical inspectors regarding our honest and direct approach to resolving this issue have been appreciated. Many inspectors have been working actively with us as well as their local electrical contractors and builders to minimize the disruption in the construction process. Those combined efforts have been successful at a vast number of localities.
We believe that we can accept nothing less than excellence when it comes to safety. For more than 100 years, our customers have associated the Square D brand with industry leadership, safety, quality, and reliability. We intend that our efforts through this AFCI program will continue those qualities.
See FREEZE-PROOF A BUILDING where we describe GFCI protection on heat tape circuits powering heat tapes for manufactured and mobile homes. Similar issues regarding building water entry control are discussed at Sump Pump Inspection. Also see Testing Receptacles GFCIs AFCIs. AFCI's are discussed at AFCIs ARC FAULT CIRCUIT INTERRUPTERS.
This does not address grandfathering for homes older than 2008! - John, 7/24/2011
Granfathering and the AFCI requirement: good point, John. We find a variety of opinions among building code officials. At a recent building addition project the BCO wanted AFCIs in the new sub panel in keeping with the new electrical code AFCI recommendations, but he also decided that other areas in the home needed certain updates too.
Other electrical inspectors and building code inspectors look only at the new work - I'd say that's the most common case. Only when an older home is being renovated to include electrical work will most inspectors call for current codes to be complied-with.
A more subtle exception occurs in the case of egregious electrical hazards: when an older home is being purchased, some lenders and some insurance companies may require certain updates such as in panel ampacity or in replacement of some of the more troublesome brands (FPE Stab-Lok is an example.)
do you have to use arc fault on lighting only circuits? - Hugh Owen 8/22/2011
Yes. On the illustrations I've seen the overhead lighting circuits were included. see 210.12(B) Dwelling Units - quoting the Minnesota Electrical Association reference found at the bottom of this article:
Combination-type AFCI-protective devices are now required in all dwelling unit rooms, except for kitchens, bathroom, garages, basements, and rooms or areas not specified in this section. This continues the incremental migration to provide whole-house AFCI protection for dwelling units that was the objective of the original proposals in the 1999 NEC development cycle.
This section was revised to include a list of rooms and areas where the serving branch circuits are to be protected by arc-fault circuit-interrupter protection. Essentially, the requirements for this protection are expanded to most areas and rooms in the dwelling unit with the exception of those named above and other areas or rooms not specifically identified in this section. The AFCI-protective devices must be listed combination types.
I don't have space in the panel to make proper ground bus connections. - Roger 9/11/11
Roger, as long as your panel won't be overcrowded, you can always add an additional ground bar (or neutral bar) in the existing panel, connecting it to the originals and locating it where your AFCI white wire will reach.
I'm still asking how these AFCI devices became code prior to it being available on the market and proven effective. To date I have encountered false tripping from these devices where a HO was nearly overcome from fumes from bedroom gas fireplace, other nuisance tripping from TVs, Vacuums, Hair dryers. I have a picture of one of these breakers with a molten branch circuit conductor emminating from a loose connection on the AFCI breaker itself, another report of a fire that started in a ceiling fan box where the AFCI also failed to trip. These devices are absolute garbage made code by the manufacturers on the NFPA to boost revenue. Somebody here show me some proof of them actually preventing a fire other that remaining on and tripping for sudden loads from appliances. - Honest Electrician 9/3/2011
Honest, you should contact the US CPSC directly to make your concerns known. We publish studies and field reports on various electrical hazards but have no financial interest in the sale of any products or services.
InspectAPedia is an independent publisher of building, environmental, and forensic inspection, diagnosis, and repair information provided free to the public - we have no business nor financial connection with any manufacturer or service provider discussed at our website.
I have a Sylvania main breaker panel in an existing dwelling. I am adding 3 circuits to basement finish.
Inspector wants a Listed product for the panel . Any idea what AFCI breaker I can use? - Nice Article 12/10/11
Any AFCI breaker sold at any electrical supplier will be code compliant. Just how well the product works is a different issue as discussed in this article. Be sure to see the comments and links to Dr. Engel's paper given in FAQs. below.
How to deal with 14-3 wired rooms. I need AFCI for the outlets and the lighting, I have wired 14-3 and would need a special AFCI that doesn't seem to be offered by Square D. - Eric J 5/22/2012
You raise an important question: how to use AFCIs or GFCI's on 3-wire circuits. I don't know a solution and so far the solution certainly is not offered in the device itself. We have ongoing reports as well as direct experience with nuisance tripping and so unreliable behavior when AFCIs or GFCI's are installed on shared-neutral circuits. The electrician I worked with most recently says he's changed is policy and won't install 3-wire shared neutral circuits where an AFCI or GFCI is going to be required.
In sum, AFCI's are NOT going to work properly on shared-neutral electrical circuits; niether do GFCIs.
I have two Seimen's AFCIs for 3 bedrooms. They were placed approx spring 2004 in a new build. No problems until several months ago with LED TV in master bedroom. Breaker would trip upon trying to turn on tv on rare occasion. At first seemed overload but now it trips every time TV is turned on. TV is tripping the other AFCI in the other bedrooms as well. It IS NOT tripping the standard breakers elsewhere in the house. Are these older model AFCIs needing replaced to handle the load of the new appliances? Have new breakers become more reliable as stated above at avoiding nuisance tripping (which I assume this is)? - Kathy 8/20/2012
You are reporting nuisance tripping.
You should also contact the US CPSC directly to make your concerns known. Use this US CPSC Incident Report Form to report Zinsco or Sylvania-Zinsco equipment failures and problems. Please also report incidents to this web author.
i have ham radio equipment
the afci is reading the flucuating current demands as arching. breaker constantly trips. this is a pain! can i safely replace the afci with a standard breaker? - Paul 8/23/2013
Paul this sounds like another instance of nuisance tripping. You can replace the AFCI with a standard breaker and stop the tripping problem; you will be giving up what limited added safety protection the AFCI offered, and you could face a technical issue with your local electrical inspector.
You should also contact the US CPSC directly to make your concerns known. Use this US CPSC Incident Report Form to report Zinsco or Sylvania-Zinsco equipment failures and problems. Please also report incidents to this web author.
You and your readers should take a look at Combination AFCIs" What they Will and Will Not Do - an IEEE publication available for public non-commercial use - Steve 1/31/2013
Repeating Steve's suggestion 1/31/13 that we read Joe Engel's paper on Combination AFCIs, we contacted Mr. Engel as well, and appreciate your contribution of a publicly-available copy of this important paper. Indeed thanks to a pointer from Dr. Jess Aronstein, we contacted Dr. Engel and have discussed AFCI issues by private email. I was concernred that his article was not available for free to the public, as it appeared in an IEEE publication. However both reader Steve and Dr. Engel have provided links to this document.
In the references section to this article as well as immediately below we include a reference and link to Dr. Engel's critical article about combination AFCIs and their capability.
Joseph C. Engel, PhD., IEEE, "Combination AFCIs" What they Will and Will Not Do", 19th Annual IEEE IAS Electrical Safety Workshop, Daytona Beach, Jan/Feb 2012.
My understanding of a fundamental concern is that as presently mandated, defined, manufactured and marketed, AFCIs do not provide the protection that was the original intent of Dr. Engel  as he has made amply cleaer .
Below are excerpts from the conclusion of this important article:
The primary goal of this paper was to describe what a Combination AFCI circuit breaker can do, while also clarifying what it can’t do. The features of the Combination AFCI, and the earlier Branch/feeder AFCI [... ] Neither provides series arc protection, the Branch/feeder provides the extra important feature of 30mA ground fault protection.
The paper goes on to explain, but not justify, how the Combination AFCI came to be mandated, while the Branch/feeder that provides more protection at less cost is disallowed. The key drivers behind this were the AFCI manufacturers, their NEMA organization, and UL. The author hopes this paper will stir discussions amongst the principals and correct any errors that were made concerning their products’ performance. This would also include supporting removing the Combination AFCI mandate from the NATIONAL ELECTRICAL CODE (NFPA 70).
Finally, the author, having participating actively during the AFCI development, would encourage the IEEE engineering communities of these great institutions to become more engaged to insure their codes and standards representatives fully understand the technical issues. These are their products; they have a responsibility to insure their products are not inadvertently misrepresented.
Questions & answers or comments about buying, wiring, installing, & using AFCIs and the performance and about possible nuisance tripping of arc fault circuit interrupters.
Ask a Question or Enter Search Terms in the InspectApedia search box just below.
Related Topics, found near the top of this page suggest articles closely related to this one.
 To paraphrase the article, there is no such thing as an AFCI tester, other than the test button that is an integral part of the AFCI device itself. The reason for this is that an AFCI device is very complex, and recognizes the actual waveform of an arcing fault. While the advertised "AFCI Testers" do produce a waveform similar to that of an arc fault, they cannot produce an actual arc fault. Because of this, the "tester" may not trip the AFCI circuit breaker, despite the breaker having nothing wrong with it. For this reason, UL classifies these devices not as "testers", but as "indicators", which is much more accurate.
 These devices are tested under the UL 1436 standard, and are required to have included in the instructions the following clause (or equivalent):
"CAUTION: AFCIs recognize characteristics unique to arcing, and AFCI indicators produce characteristics that mimic some forms of arcing. Because of this the indicator may give a false indication that the AFCI is not functioning properly. If this occurs, recheck the operation of the AFCI using the test and reset buttons. The AFCI button test function will demonstrate proper operation."
 While these indicators may have some value for convenience to determine if the outlet in question is on an AFCI protected circuit, they are not to be substituted for the test button of the AFCI circuit breaker, and they are not an AFCI tester.