Electrical Arc Fault Safety Advice for Homeowners & Home Inspectors
AFCIs ARC FAULT CIRCUIT INTERRUPTERS - CONTENTS: Electrical Arc Fault AFCI Advice for Homeowners & Home Inspectors. What is an AFCI or arc fault circuit interrupter? Fire Problem addressed by AFCIs. Types of AFCIs & How AFCIs Work. Where to Use AFCIs & Code requirements for AFCIs. Nuisance Tripping AFCIs. How to Install AFCIs & How to Test AFCIs. AFCIs vs. GFCIs, what's the difference between an arc fault circuit interrupt or and a ground fault circuit interrupt or? AFCI Recall in 2004 & Square-D & Federal Pioneer AFCI Notice. US CPSC Tips for installing & using AFCI's for arc fault protection to reduce fire risk in homes
POST a QUESTION or READ FAQs about buying, wiring, installing, & using AFCIs and the performance and about possible nuisance tripping of arc fault circuit interrupters
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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.
Electrical Arc Fault AFCI Advice for Homeowners & Home Inspectors
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
FACT SHEET provided by the US CPSC .
[Click to enlarge any image]
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).
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.
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:
The red arrow indicates the "hot" wire connection at the AFCI breaker.
The yellow arrow indicates the circuit neutral wire connection at the AFCI, and
the white arrow shows that the multi-strand coiled wire from the AFCI device is connected to the neutral bus in the electrical panel.
Our next AFCI breaker photo shows more closely the electrical circuit connection points at the AFCI breaker itself.
The red arrow indicates where the "hot" wire will be connected to the uppermost screw on the AFCI breaker.
The yellow arrow indicates the circuit neutral wire connection at the AFCI at the "lower" screw
The white arrow shows the end of the white insulated multi-strand coiled wire from the AFCI device that will be connected to the neutral bus in the electrical panel.
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.
The Fire Problem [intended to be addressed by AFCIs]
Annually, over 40,000 fires are attributed
to home electrical wiring. These fires
result in over 350 deaths and over 1,400
injuries each year Note 1. Arcing faults are one
of the major causes of these fires.
unwanted arcing occurs, it generates high
temperatures that can ignite nearby
combustibles such as wood, paper, and
Our photo shows a Rhinebeck NY home that was totally destroyed by a fire caused by an electrical cord that was passed under a carpeting - a possible cause of pinched, overheated cord, and a fire that might have been prevented by an AFCI.
Certainly the circuit involved was in an older home and was not protected by an AFCI (nor by a GFCI as we understood the case). In any event the heater cord did not blow a fuse nor trip a breaker in this home. Instead it just lit the home afire.
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:
puncturing of wire insulation from picture hanging or cable staples,
poorly installed outlets or switches,
cords caught in doors or under furniture,
furniture pushed against plugs in an outlet,
and cord exposure to heat vents and sunlight.
Coffee Maker Demonstrates Early warning about nuisance tripping of AFCI circuit breakers and consumer objections to these devices
AFCIs 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."
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:
Branch Feeder AFCIs - basically a special circuit breaker to be installed in the electrical panel and which will protect all of the devices on an individual electrical branch circuit. (15A or 20A 125V single phase wiring.)
Outlet circuit AFCIs - a device installed right in the branch circuit receptacle box. As with GFCIs this device may also protect wiring which is connected "downstream" electrically from the device itself.
Combination AFCIs - this device combines the function of Branch Feeder AFCIs and Outlet Circuit AFCIs and will protect power cords plugged into receptacles protected by the AFCI.
The following are additional types of AFCI's described by Underwriters Laboratories.
Outlet Branch Circuit AFCIs - this device, which sounds to us just like #2 above, is installed as the first outlet in a string of electrical receptacles on a single circuit; it protects the downstream receptacles.
Portable AFCIs - these devices can be plugged into a conventional electrical receptacle and provide one or more outlets into which additional devices can be connected. This device would be used by contractors working on a building to obtain additional electrical safety when using power tools.
Cord-AFCIs - this device is like the portable AFCI #5 above, but may be incorporated into the permanent power cord of a device or appliance so that when it is plugged into an electrical receptacle the appliance is protected from arc faults.
Leakage Current Detection and Interruption LDCIs - these devices are built into a device or appliance and detect current leakage from the device's electrical cord. If a hand held hair dryer contained this device and its damaged cord was dangled in a sink filled with water, the LDCI would detect the current leakage and would shut off the device.
How does an Arc Fault Circuit Interrupter (AFCI) Work?
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)
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
circuit breakers are presently available.
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) ,
Manufacturers and UL claim that arcing across a break in a cord’s conductor is hazardous, and that a Combination AFCI will respond to prevent a fire. The author believes the claim is unproven, and will explain why the disallowed Branch/feeder AFCI provides more protection at less cost.
AFCI Requirements under the US National Electrical Code NEC:
AFCI requirements have not been adopted uniformly in all jurisdictions, but the requirement is being increasingly accepted, and we certainly recommend the use of AFCIs as described by the US CPSC and the NEC.
The US National Electrical Code, the NEC, specifies the following requirements for AFCIs (quoted indirectly from the U.S. State of Vermont office of the state fire marshal, January 2007. Vermont has required AFCIs to the NEC 2008 standard since 2000.)
History of AFCI Requirements in Homes
The 1999 NEC rules, effective in 2002, in NEC Sec. 210.12. introduced AFCI's and called for their installation on bedroom receptacle circuits powered by single phase 125V(nominal) 15A and 20A circuits.
The 2002 NEC expanded the use of AFCI's to include all bedroom circuits (such as lighting and hard-wired smoke alarms), kitchens.
The 2005 NEC code expanded the section to include combination AFCIs combined with GFCIs, basically an update to reflect improvements in the technology. The technology of AFCIs was improved to add the detection of series arcing to the previously available parallel arcing.
By removing the word "receptacle" from the code in 2002, and by leaving the word "outlet" in the code, the 2005 code indicated that all outlets, including receptacles, light fixtures, smoke alarms, etc. must be protected.
Series arcing occurs in an electrical circuit when there is a small gap in a conductor in a home. Series arcs are less dangerous than parallel arcs because they do not usually get hot enough to start a fire.
Parallel arcs in an electrical circuit occur when there is a current leak from the "line" or hot wire (fault) to the neutral wire (ground or earth side of the circuit), or when there is a short circuit (a direct connection between the hot wire and the neutral wire, such as a wire being cut or damaged and its conductors brought into contact).
The 2008 NEC expanded the use of AFCI's to include all habitable rooms in new homes such as living rooms and dining rooms. The 2008 requirements mean that only only Combination AFCI's will meet all of the requirements of the code. GFCI's (Ground Fault Circuit Interrupters) continue to be required to protect areas of high shock risk: bathrooms, kitchens, garages, un-finished basements.
Combination devices required after 1 Jan 2008: Simplifying a bit, after January 1, 2008, AFCI protection must be provided by a "Combination AFCI's" . That's because these are an improved arc fault interrupter product that offer much more sensitive arc fault detection (5 A arc peaks as opposed to 75 A arc peak detection).
(A) Definition. An arc-fault circuit interrupter is a device intended to provide protection from the effects of arc faults by recognizing the characteristics unique to arcing and by functioning to de-energize the circuit when an arc fault is detected.
(B) Dwelling Unit Bedrooms. All branch circuits that supply 125-volt, single phase, 15- and 20-ampere receptacle circuits installed in dwelling unit bedrooms shall be protected by an arc-fault circuit interrupter(s). This requirement shall become effective January 1, 2002.
Beginning with the 2008 edition of the U.S. National Electrical Code, AFCI's are required not only in bedrooms but in other areas of the home such as dining rooms, living rooms, and other habitable areas, and apply to most electrical circuits including hard-wired smoke detectors, overhead fans, etc.
How Much Does an AFCI Cost? Cost Benefit Calculation of AFCI's:
An AFCI circuit breaker typically costs about $30. to $35. U.S. A conventional 15A circuit breaker typically costs $2. to $4. There is an additional cost to install an AFCI circuit breaker, but as it's basically a "plug-in" device that is placed in the electrical panel, that number should be small, smaller still if the AFCI installation is combined with other electrical work needed at a home.
While these specialized AFCI circuit breakers cost more, our opinion is that this is not a significant cost compared with the value of a home, not to mention the more difficult to measure cost of possible injuries or fatalities should a fire occur.
If we use the current (2014) median price of a new home in the U.S. of about $260,000., the cost of adding AFCI to a home circuit is less than two ten-thousandths of the cost of the home. (An AFCI costs 0.00016 x median value of a home in the U.S.).
If a home needs a dozen AFCI's to meet the 2008 NEC, the cost should be less than $400., or less than two thousandths of the cost of the home. (0.0019 x the median value of a home in the U.S.).
What About Nuisance Tripping of AFCI's
Nuisance tripping refers to a circuit breaker or an AFCI that trips off, turning off electrical power when there was no apparent reason to do so. Some sources assert that what appears to be "nuisance tripping" of AFCI's actually occurs due to wiring practices of some electricians more than for any other reason. These include
Reversed hot and neutral wires - reversed polarity - which is an unsafe condition
Shared neutral wiring on single pole circuit breaker circuits: this is already an existing problem with GFCI's on multiwire branch circuits.
Incorrect or accidental connections between the ground and neutral wire: this is also an unsafe condition which can permit live current to flow on a ground wire that should normally never carry current. We've personally seen this condition lead to an electric shock.
A common source of accidental ground-neutral connections occurs when an electrician over-tightens the clamp connector on BX (armored cable) where it connects to a steel junction box. Our ex-brother-in-law made this mistake at every single BX connector when he did his own over-zealous wiring in a New York City apartment.
When he installed a GFCI circuit breaker to protect some circuits, he could not keep the breaker from tripping immediately whenever power was turned on.
We saw that his over-tightening the connector pinched inwards the edges of the BX cable. If the BX cable edge cuts into the hot wire the electrician (or Matthew) discovers this fault immediately when power is restored to the circuit. But if the cable edge cuts into the neutral wire, the electrician (or our brother in law) does not discover this fault until a GFCI or an AFCI is installed on the circuit, or until someone touches a supposedly safe armored cable wire exterior and gets a shock.
Normal arcing in appliances: Nuisance tripping that could occur from the normal arcing that occurs in some appliances (such as a vacuum cleaner motor) has been considered in the design of the AFCI circuit. The AFCI is designed to tell the difference between this ordinary arcing and the type of arcing in a circuit that may cause a fire.
How to Install an Arc Fault Circuit Interrupter (AFCI)
AFCI circuit breakers should be installed by a qualified electrician. The installer should
follow the instructions accompanying the device and the panel box.
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.
How to Test an Arc Fault Circuit Interrupter (AFCI)
Using the test button on an AFCI
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.
Using AFCI indicator tools vs AFCI "test tools" - AFCI Indicators is not recommended
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
AFCIs vs. GFCIs: What is the difference between an Arc Fault Circuit Interrupter and a Ground Fault Circuit Interrupter?
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.
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
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
A Summary of Current (2008) Residential Ground Fault Circuit Interrupter GFCI Requirements
GFCI's are required safety devices to be installed in the following locations:
are required to provide one 15A or 20A, 125V receptacle (or more). All bath receptacles have to have GFCI-protection, and at east one must be within 3 feet of the outside edge of each basin [210.52(D)].
The bathroom receptacle circuit cannot provide power to other outlets elsewhere in the house [210.11(C)(3)] - something that is commonly found in older homes.
There is an exception for a 20A circuit that supplies only a single bathroom: other equipment within the same bathroom, such as lights or a bath vent fan can be powered from the circuit. (A home inspector who detects this might point out the inconvenience of being left in the dark if the GFCI trips.)
Whether inspecting a new home, to which the 2008 NEC applies, or inspecting an older home that was wired before this code was written, the tracing of wiring to determine what devices are powered by each electrical circuit is not within the scope of practice of a normal home inspection meeting national or state standards. But some circumstances will require this level of scrutiny on existing structures.
Boathouses: do not require that electrical receptacles be installed at all, but if a receptacle is present it must be GFCI protected.
Crawl spaces (at or below grade): receptacles are not required to be installed in these areas unless HVAC equipment is installed in the crawl area, but if an optional electrical receptacle is installed in the crawl space, it must be GFCI protected. We pose that such receptacles may be in place for temporary work lighting or for powering sump pumps. (GFCI trips, no sump pump, flood).
Garages: must provide a GFCI protected electrical outlet, regardless of whether or not the garage is attached or detached.
There are exceptions in the garage for electrical outlets which are not readily accessible, such as a ceiling receptacle used to power a garage door opener, and an exception for dedicated circuits such as one to provide power to a refrigerator or freezer. (In freezing climates these appliances may not work properly in an un-heated space even if it's legal to hook them up there.) NEC 100 defines "readily accessible."
Kitchens: GFCI protected receptacles are required for all receptacles that serve counter surfaces. (We like this rule because in the past builders would skip the GFCI protection for a receptacle that was over a kitchen counter but was just one inch more than six feet from the sink.)
Exceptions to GFCI requirements for kitchens include circuits for built-in appliances like garbage grinders and dishwashers.
Laundry (and also wet-bars): require that GFCI protection be provided for any receptacles within six feet of the laundry sink (or wet bar sink). So a receptacle used to power a washing machine or a gas-fired clothes dryer needs to be GFCI protected if it's within six feet of a sink.
Outside electrical outlets that are GFCI protected are required, at least one for a single family dwelling. 210.52(E). All outside electrical receptacles must be GFCI protected, even those receptacles found under the roof eaves and typically used for holiday lighting or for an ice-dam stop-gap measure heat tape. (Better solutions for ice dam problems than a heating tape are discussed at Ice Dam Leaks.)
An exception outside is for a dedicated ice-dam snow-melting heating tape on a dedicated circuit that is not readily accessible and complies with 426.28 for ground-fault protection of equipment.
Unfinished basement areas: a single GFCI protected electrical receptacle is required in each room or area of an un-finished basement. 210.52(G), and all receptacles that are installed (thus including optional additional receptacles) must be GFCI protected.
Exceptions to the GFCI protected receptacle requirement for un-finished basements include the usual cases: receptacles that are not readily accessible and receptacles on dedicated circuits, such as a freezer appliance circuit.
AFCI Square D Arc Fault Circuit Breaker Recall
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 issue with the component has been corrected and we have significantly increased our manufacturing capacity of AFCI breakers, allowing us to replenish our distribution network as quickly as possible. We are shipping significant quantities of AFCI circuit breakers from our manufacturing facilities every day.
[intervening paragraphs addressing the ramp-up of production are here omitted as now obsolete-DF]
We are also initiating a program to recover product that has been installed during this timeframe and replacing affected breakers with newly manufactured AFCIs. we are working directly with electricians, homebuilders and homeowners to inspect and replace affected breakers. the nationwide effort is being managed by us directly with our customers. There is no specific action you need to take in this recovery program other than help us make sure everyone has accurate information.
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.
Current Limits of Protection of combination AFCI devices as sold & installed
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.
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.
Reader Question: Electrician complains of nuisance tripping and AFCI failure-to trip
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.
How to Report an AFCI or other Electrical or Product Failures or Incidents to the U.S. CPSC
Question: AFCI vs grandfathering homes older than 2008
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.)
Question: are AFCI's required on lighting-only circuits?
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 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.
Question: having trouble wiring 14-3 wired homes
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.
Question: Nuisance Tripping of AFCI devices on circuit used to power a TV
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
Reply: how to report AFCI problems to the US CPSC:
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.
Question: nuisance tripping of AFCI circuit with ham radio equipment.
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.
Questions/comments: on AFCI's: Reference to Engel (2012)
DanJoeFriedman (mod) said:
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. In the article above we include a reference and link to
Joseph C. Engel, PhD., IEEE, "Combination AFCIs" What they Will and Will Not Do", IEEE, 2012
(Sept 2, 2011) Honest Electrician said:
How much money has been paid to the NFPA to make AFCI breakers code since there have been arc outs and fires on protected circuits and they were introduced as code before they were available
Questions: AFCI be used to protect Alum branch wire circuits
(Sept 19, 2014) Mike said:
Can a AFCI be used to protect Alum branch wire circuits
Yes, and no.
yes if the AFCI is connected using CPSC-recommended methods (AMP TYCO COPALUM or the King Innovations AlumiConn) to connect the device to the circuit
No if you are thinking of direct-wiring the device to the aluminum wire. I have personally seen an aluminum wired test circuit overheat and begin to burn (we turned off power at that point) while powered through an AFCI.
Your US CPC Incident report form link is obsolete. Here's the new link:
Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.
Steel, J. G., and D. T. Swift-Hook. "Statistics of circuit-breaker performance." Electrical Engineers, Proceedings of the Institution of 117, no. 7 (1970): 1337-1345.
Lai, M. L., S. Y. Park, C. C. Lin, H. Naidu, A. Soom, A. M. Reinhorn, Y. H. Lee et al. "Mechanical failure detection of circuit breakers." Power Delivery, IEEE Transactions on 3, no. 4 (1988): 1724-1731.
 AFCI Circuit Interrupters, US CPSC Publication www.cpsc.gov/CPSCPUB/PUBS/afcifac8.pdf, with extensive edits and additions by the website author. Original source cpsc.gov/CPSCPUB/PUBS/afcifac8.pdf
 Note 1 Ault, Singh, and Smith, “1996 Residential Fire Loss Estimates”, October 1998, U.S. Consumer
Product Safety Commission, Directorate for Epidemiology and Health Sciences.
 Schneider Electric, North American Operating Division, 1415 South Roselle Road, Palatine IL 60067
16 December 2004 , Letter addressed to Dan J Friedman, from Jim Pauley, Vice President, Industry and Government Relations.
 Underwriters Laboratories (UL) describes the the types of AFCIs and the types of tests performed on AFCIs at www.ul.com/regulators/afci/AFCI_scenarios020502.pdf. Also, UL 1699, “Standard for Arc-Fault Circuit Interrupters” at the UL website provides more detailed information on the differences between the older AFCI's and the new combination type devices.
 Nuisance tripping of AFCI's is described in detail, along with other details about AFCIs in an online article, "Arc Fault Detection: your questions answered", ecmweb.com, August 2008.
 Mike Holt, in our opinion the leading writer about electrical wiring and devices, has a nice article about AFCIs at https://www.mikeholt.com/mojonewsarchive/AFCI-HTML/HTML/Arc_Fault_Protection~20020124.htm Mr. Holt discusses current electrical code requirements for GFCIs (Ground Fault Circuit Interrupters) at http://ecmweb.com/mag/electric_branch_circuits_part_2/.
 Testing of AFCIs using external devices (not the test button): see article by Underwriter's Laboratories (UL) March 21, 2005 at http://www.ul.com/tca/winter05/news.html and this comment by Ryan Jackson at Mike Holt's website: (a reply from Jim Gregorec,
Group Manager - T&M Division, Ideal Industries posted at the website takes a different view which is also posted there)
 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.
 GE, General Electric Corporation, General Electric Company,
41 Woodford Ave., Plainville, CT 06062, one of the companies producing AFCIs, provides wiring diagrams and installation instructions for their product. See GE's DEH-40117R4.pdf for detailed installation instructions from GE for the wiring of a typical AFCI on a simple 120V home electrical circuit.
 The Minnesota Electrical Association has posted an article of the most important electrical code changes for 2008 at http://www.electricalassociation.com/catalog/2008NECTop10.aspx - by Michael J. Johnston, IAEI
 "HUD Regulation for Manufactured Homes; Requirement that Heat-Tape not include a GFCI [ copy on file as /plumbing/GFCI_Heat_Tapes_HUD_CPSC_Letter1994.pdf ] - ", Meeting Log, US CPSC, HUD, Dennis McCoskrie, ESEE, 2/14/1994
 Personal communication, [electrician P prefers to remain anonymous], to DJF, 1/29/2012.
 Joseph Engel, "Ground Fault / Arc Fault Circuit Interrupter and Method of Testing the Same with a Test Button and a Resest Button", Patent No. 6,720,872 B1, Apr. 13, 2004. [copy on file as AFCI Patent US6720872.pdf and as AFCI_Patent_History.pdf]
 Engel, J.C., "Combination AFCIs: What they will and will not do", Electrical Safety Workshop (ESW), 2012 IEEE IAS, Jan. 31 2012-Feb. 3 2012, pp. 1 - 18,
Conference Publications, 9 March 2012, INSPEC Accession Number: 12578656. Mail: Joseph C Engel, PhD,
107 Overlook Circle,
Monroeville PA 15146
USA, Email: firstname.lastname@example.org
Abstract: All new home branch circuits are required by Code to be electronically protected, either by Ground Fault Circuit Interrupters (GFCIs) or Arc Fault Circuit Interrupters (AFCIs). Areas including kitchens, bathrooms, garages, etc. must be protected by GFCIs, while living areas must be protected by AFCIs. The AFCI is the fourth generation in residential branch circuit protection after fuses, circuit breakers, and GFCIs. National Electrical Code in 2002 first added AFCI protection, for bedrooms outlets. In 2008, coverage was expanded to all living areas, also adding that only “Combination AFCIs” are allowed. Manufacturers and UL claim that arcing across a break in a cord's conductor is hazardous, and that a Combination AFCI will respond to prevent a fire. The author believes the claim is unproven, and will explain why the disallowed Branch/feeder AFCI provides more protection at less cost.
Dr. Engel provides this link for a downloadable copy of this paper: http://www.combinationafci.com/
[18b] Engel, J.C., Aronstein, J., & Friedfman, Daniel J, personal correspondence 2/8/2013.
 Wafer, J.A., "The evolution of arc fault circuit interrupters", Electrical Contacts, 2005. Proceedings of the Fifty-First IEEE Holm Conference,
26-28 Sept. 2005, Eaton Corp., Pittsburgh,pp. 156 - 161
Traditionally, circuit breakers and fuses have provided overcurrent and short circuit protection in electrical distribution applications. Despite this protection, approximately 70,000 residential fires with more than 500 deaths and Å in property damage occur each year in the U.S. that are attributed to electrical initiation. When investigated it was found that in some cases the circuit breaker had not tripped. Arc fault circuit interrupters can recognize the unique signatures of arcing faults and initiate a trip condition to isolate and de-energize the arcing fault. This paper identifies the conditions that can lead to fire hazards. These include arcs to ground, wiring failure modes, earth leakage conditions and high resistance faults such as glowing contacts, and in-line low current arcs (sometimes referred to as series arcs).
 Douglas A. Lee,
Andrew M. Trotta,
William H. King Jr., "New Technology for Preventing Residential Electrical Fires: Arc-Fault Circuit Interrupters (AFCIs)",
August 2000, Volume 36, Issue 3, pp 145-162, Abstract:
A new generation of residential electrical branch circuit breakers that incorporates technology to detect and mitigate the effects of arcing faults is described. Fire loss estimates attributed to electrical wiring and the development of the arc-fault circuit interrupter for the prevention of residential electrical fires are discussed. The industry voluntary standard for arc-fault circuit interrupters as well as the 1999 National Electrical Code requirement are reviewed.
 Shea, J.J., "Conditions for series arcing phenomena in PVC wiring", Electrical Contacts, 2005. Proceedings of the Fifty-First IEEE Holm Conference on
Date of Conference: 26-28 Sept. 2005, Eaton Corp., pp: 167 - 175
Under certain circumstances, unintentional series arcing, caused from damaged line cords and loose connections, can pose a serious fire and safety hazard. This work, focusing on residential 115 Vac applications, shows how continuous bursts of ignited gases can be created from overheated PVC insulation created from glowing contacts with subsequent series arcing, or surface breakdown with subsequent series arcing. Also, surprisingly, these potentially hazardous fire conditions were created with currents as low as 0.9 Arms, at 115 Vac (100 W lamp load). Little research is available about the interaction of glowing contacts, formed from loose or broken copper conductors in wiring (outlets, switches, line conductors, etc.), with electrical insulation. This work shows how glowing contacts and surface arcing can decompose PVC insulation, form ignitable gases, and that it is possible for the subsequent series arc to ignite, and burn insulation. Two conditions are identified that can create an overheated connection - a glowing contact and/or breakdown over a charred insulation surface. Mechanisms are discussed along with data for glowing contact voltage drop, photographs of glowing connections, and a gas chromatograph analysis of the evolved gases emitted from overheated PVC wiring. Selected high-speed video frames (1000 fps) taken from videos of the series arc and bursts of ignitable gasses along with synchronized current and voltage waveforms over a current range of 0.9 Arms to 5 Arms are presented. These findings are useful for advancing the state-of-the-art in fire protection by providing a better understanding of how electrical fires can initiate.
 Restrepo, C.E., "Arc Fault Detection and Discrimination Methods", Electrical contacts - 2007, the 53rd ieee holm conference, 16-19 Sept. 2007, pp. 115 - 122 , Siemens Energy & Autom., Norcross,
Abstract: Arc waveform characteristics can be evaluated with various methods to recognize the presence of hazardous arc fault conditions. Discussion covers the arc phenomena and how it is generated in a low voltage electrical distribution circuit, as well as the isolation of the presence of hazardous conditions versus conditions that could falsely mimic the presence of an arc fault. Many waveform characteristics and conditions support the detection of hazardous arc faults and foster a more robust design, capable of withstanding unwanted tripping conditions.
 Parise, G., "Arc-fault protection of branch circuits, cords and connected equipment" Industrial and Commercial Power Systems, 2003. 2003 IEEE Technical Conference, 4-8 May 2003,
Dipt. di Energia Elettrica, Rome Univ., Italy
Martirano, L. ; Nabours, R.E., pp: 85 - 88,
Abstract: In electrical power systems, the fault frequently involves arcing and burning for all the wiring exposed to mechanical damage and other insulation stresses including wiring not fixed and connected by flexible cords and cables. The IEC Standard 60364 stops the design of electric power systems at the outlets of branch circuits or at the fixed equipment. A complete design instead should take care of the connections of the portable equipment and of extension cords (as requested by NFPA 70) that are exposed to arc-faults and may cause fire and/or electric shock hazard. The cords supplying the Class II equipment are without a grounding protection conductor, so the failure of the double insulation, caused by external damage, can't be expected to be easily detected as a ground fault. A protection must be provided to prevent the fault from extinguishing itself without being detected and remaining energized, thus presenting an electric shock hazard by direct contact with a live part, rendered accessible after local insulation failure. The authors highlight this worst case and suggest the protection achieved by wiring the circuits, particularly extension cords, with special power cables. Ground-fault-forced cables, GFFCs convert a line-to-line fault into a line to ground fault, that will be detected and protected by ordinary ground fault protective devices (GFPDs). By adopting the GFFC type of cables internally to Class II equipment, the disconnecting supplying measure could be extended to equipment also.
 Gregory, G.D., "More about arc-fault circuit interrupters" Industry Applications Conference, 2003. 38th IAS Annual Meeting. Conference Record, 12-16 Oct. 2003
Author(s): Gregory, G.D. Schneider Electr., Square D Co., Cedar Rapids, IA, USA, Kon Wong ; Dvorak, R.
Volume: 2, pp: 1306 - 1313 vol.2
Abstract: Since the arc-fault circuit interrupter (AFCI) was commercially introduced in 1998, questions have arisen about how it detect arcs, whether it detects series and parallel arcs, and what types of AFCIs are available. Types other than the original branch/feeder AFCI are emerging. This paper is intended to provide an update regarding answers to those questions, following an earlier paper that introduced the basic functioning of the AFCI (see G.D. Gregory et al., IEEE Trans. Ind. Apps., p. 928-33, 1998).
 Gammon, T., Matthews, J., "Instantaneous arcing-fault models developed for building system analysis", Industry Applications, IEEE Transactions on, Jan/Feb 2001, Volume: 37 , Issue: 1
Page(s): 197 - 203.
An arcing fault is a dangerous form of short circuit that may have a low current magnitude. In the case of such faults, the magnitude of the current is limited by the resistance of the arc and may also be limited by the impedance of a ground path. This lower level fault current is often insufficient to immediately trip phase overcurrent devices, resulting in the escalation of the arcing fault, increased system damage, tremendous release of energy, and threat to human life. Despite modern advances in system protection and the adoption of National Electrical Code Section 230-95, people continue to be injured or killed from arcing faults, initiated by accidental physical contact or through a glow-to-arc transition. The initial phase of an arcing-fault research project was to review the historical evolution of arc modeling for low-voltage systems. A summary of the electrical aspects and the physics involved in arcing faults appeared in previous work. Today's better analytical tools facilitated the development of new instantaneous arc models with current-dependent arc voltages, which better represent the arcing phenomenon than the assumed arc voltage associated with previous instantaneous arc models. The arc currents in a typical medium-size building system are determined and harmonic analysis is performed
Excerpt: "ARCING FAULTS have been recognized as a potential hazard in low-voltage systems as far
back as the 1920s "
 Gammon, T. & Matthews, J., "The historical evolution of arcing-fault models for low-voltage systems", Industrial & Commercial Power Systems Technical Conference, 1999 IEEE.
An arcing fault is a dangerous form of short-circuit that may have a low current magnitude. In the case of such faults, the magnitude of the current is limited by the resistance of the arc and may also be limited by the impedance of a ground path. This lower level of fault current is often insufficient to immediately trip overcurrent devices, resulting in the escalation of the arcing fault, increased system damage, tremendous release of energy and threat to human life. Despite modern advances in system protection, many people are critically injured or killed each year as a result of such faults. The initial phase of an ongoing arcing-fault research project was to review the pioneering work, dating back to the 1920s. After a comprehensive literature search was completed, today's sophisticated analytical tools are aiding development of a new arc model. An improved arc model will more accurately calculate the arc currents in an actual arcing event. This paper summarizes the physics involved and describes the historical evolution of arc modeling. The condensed review presented in this paper facilitates a better understanding of arcing faults in low-voltage power systems; in addition, it serves as a foundation for current and future research
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
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Recommended books on electrical inspection, electrical wiring, electrical problem diagnosis, and electrical repair can be found in the Electrical Books section of the InspectAPedia Bookstore. (courtesy of Amazon.com)
"Electrical System Inspection Basics," Richard C. Wolcott, ASHI 8th Annual Education Conference, Boston 1985.
"Simplified Electrical Wiring," Sears, Roebuck and Co., 15705 (F5428) Rev. 4-77 1977 [Lots of sketches of older-type service panels.]
"How to plan and install electric wiring for homes, farms, garages, shops," Montgomery Ward Co., 83-850.
"Simplified Electrical Wiring," Sears, Roebuck and Co., 15705 (F5428) Rev. 4-77 1977 [Lots of sketches of older-type service panels.]
"Home Wiring Inspection," Roswell W. Ard, Rodale's New Shelter, July/August, 1985 p. 35-40.
"Evaluating Wiring in Older Minnesota Homes," Agricultural Extension Service, University of Minnesota, St. Paul, Minnesota 55108.
"Electrical Systems," A Training Manual for Home Inspectors, Alfred L. Alk, American Society of Home Inspectors (ASHI), 1987, available from ASHI. [DF NOTE: I do NOT recommend this obsolete publication, though it was cited in the original Journal article as it contains unsafe inaccuracies]
"Basic Housing Inspection," US DHEW, S352.75 U48, p.144, out of print, but is available in most state libraries.