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{{short description|Circuit breaker that protects against intermittent faults associated with arcing}}
{{Electrical Wiring Sidebar}}
[[File:Arc Fault Circuit Interrupter.jpg|thumbnail|upright=1.2|This AFCI (the circuit breaker with the yellow label) is an older generation AFCI circuit breaker. The current (as of 2013) devices are referred to as "combination type."]]
An '''arc-fault circuit interrupter''' ('''AFCI''') or '''arc-fault detection device''' ('''AFDD''')<ref>{{cite web |title=Do you know an Arc Fault Detection Device (AFDD) can prevent from an electrical fire? |url=https://blog.schneider-electric.com/power-management-metering-monitoring-power-quality/2013/07/03/do-you-know-an-arc-fault-detection-device-afdd-can-prevent-from-an-electrical-fire/ |publisher=Schneider Electric}}</ref> is a [[circuit breaker]] that breaks the circuit when it detects the [[electric arcs]] that are a signature of loose connections in home wiring. Loose connections, which can develop over time, can sometimes become hot enough to ignite house fires. An AFCI selectively distinguishes between a harmless arc (incidental to normal operation of switches, plugs, and brushed motors), and a potentially dangerous arc (that can occur, for example, in a lamp cord which has a broken conductor).
In [[Canada]] and the [[United States]], AFCI breakers have been required by the electrical codes for circuits feeding [[electrical outlet]]s in residential bedrooms since the beginning of the 21st century; the US ''[[National Electrical Code]]'' has required them to protect most residential outlets since 2014,<ref>2014 NEC(210.12)</ref> and the ''[[Canadian Electrical Code]]'' has since 2015.<ref>{{cite book
In regions using 230 V, the combination of higher voltage and lower load currents lead to different conditions being required to initiate an arc fault that does not either burn clear or weld to a short circuit after a short time, and there are different arc characteristics once struck. Because of this, in Western Europe (where in many countries a domestic supply may
In the US, arc faults are said to be one of the leading causes for residential electrical fires.<ref>{{cite journal|title=New Technology for Preventing Residential Electrical Fires: Arc-Fault Circuit Interrupters (AFCIs)|journal=Fire Technology|volume=36|issue=3|publisher=Kluwer Academic Publishers|date=Aug 2000|pages=145–162|url=http://www.cpsc.gov//PageFiles/108737/AFCIFireTechnology.pdf|doi=10.1023/A:1015410726786|first1=Douglas A.|last1=Lee|first2=Andrew M.|last2=Trotta|first3=William H.|last3=King|s2cid=108941129|issn=0015-2684|access-date=Feb 26, 2013}}</ref> Each year in the United States, over 40,000 fires are attributed to home electrical wiring. These fires result in over 350 deaths and over 1,400 injuries each year.<ref>Ault, Singh, and Smith, "1996 Residential Fire Loss Estimates", October 1998, U.S. Consumer Product Safety Commission, Directorate for Epidemiology and Health Sciences.</ref>
Conventional circuit breakers
==Operating principle==
The [[electronics]] inside an AFCI breaker detect electrical current alternating at characteristic frequencies, usually around 100 kHz, known to be associated with wire arcing, which are sustained for more than a few milliseconds.
When installed as the first outlet on a branch circuit, AFCI receptacles provide series arc protection for the entire branch circuit. They also provide parallel arc protection for the branch circuit starting at the AFCI receptacle.
==Electrical code requirements==
===US and Canada===
[[File:AFCI.jpg|thumb|upright=1|American-standard AFCI (arc-fault circuit interrupter) unit circa 2018. The white 'pigtail' is a low-power neutral connection, hard-wired into the unit.]]
Starting with the 1999 version of the ''National Electrical Code'' in the United States, and the 2002 version of the ''Canadian Electrical Code'' in Canada, the national codes require AFCIs in all circuits that feed outlets in bedrooms of dwelling units.
The AFCI is intended to prevent fire from arcs. AFCI circuit breakers are designed to meet one of two standards as specified by UL 1699: "branch" type or "combination" type (note: the Canadian Electrical Code uses different terminology but similar technical requirements). A branch type AFCI trips on 75 amperes of arcing current from the line wire to either the neutral or ground wire.
[[File:Leviton Dual Function AFCI GFCI Receptacle.jpg|thumb|upright=1|Dual-function AFCI GFCI (ground fault circuit interrupter) 110 volt receptacle circa 2016]]
AFCI receptacles are an alternative solution to AFCI breakers. These receptacles are designed to address the dangers associated with both types of potentially hazardous arcing:
In 2002, the NEC removed the word "receptacle", leaving "outlets", with the effect that lights and other wired-in devices such as ceiling fans within bedrooms were added to the requirement. The 2005 code made it clearer that all outlets must be protected despite discussion in the code-making panel about excluding bedroom smoke detectors from the requirement. "Outlets" as defined in the NEC includes receptacles, light fixtures and smoke alarms, among other things.
▲AFCI receptacles are an alternative solution to AFCI breakers. These receptacles are designed to address the dangers associated with both types of potentially hazardous arcing: parallel and series. AFCI receptacles offer the benefit of localized ''test'' and ''reset'' with such buttons located on the face of the device. This can save a journey to the breaker panel but can also encourage simply resetting by a user without investigating the underlying fault, as would presumably happen if someone with access to the electrical panel was notified.
▲In 2002, the NEC removed the word "receptacle", leaving "outlets", with the effect that lights and other wired-in devices such as ceiling fans within bedrooms were added to the requirement. The 2005 code made it clearer that all outlets must be protected despite discussion in the code-making panel about excluding bedroom smoke detectors from the requirement. "Outlets" as defined in the NEC includes receptacles, light fixtures and smoke alarms, among other things. Basically, any point where AC electricity is used to power something is an outlet.
As of January 2008, only "combination type" AFCIs meet the NEC requirement. The 2008 NEC requires the installation of combination-type AFCIs in all 15 and 20 ampere residential circuits with the exception of laundries, kitchens, bathrooms, garages, and unfinished basements, though many of these require [[GFCI]] protection. The 2014 NEC adds kitchens and laundry rooms to the list of rooms requiring AFCI circuitry, as well as any devices (such as lighting) requiring protection.<ref>{{cite web|url=http://iaeimagazine.org/magazine/2015/05/22/whats-new-about-afcis-in-the-2014-nec/ |title=What's NEW about AFCIs in the 2014 NEC? ‹ IAEI Magazine |website=Iaeimagazine.org |date=22 May 2015 |access-date=2017-03-28}}</ref>
As of January 2023, there are a total of 6 means of protection covered as part of 210.12(A). These include the following:
1. A listed combination-type AFCI which is the primary method used to meet these requirements.
2. A listed branch/feeder-type AFCI that is installed at the origin of the branch circuit working in combination with the listed outlet branch-circuit-type AFCI (OBC AFCI) installed at the first outlet box which must also be marked that it is the first outlet box of the branch circuit.
3. This option includes a listed "Supplemental Arc Protection Circuit Breaker" which does not exist. there is no standard for this device and so this is not an option that can be used.
4. This option does have a single manufacturer who has a solution on the market. This option includes a listed outlet branch-circuit-type AFCI that is installed on the branch circuit at the first outlet in combination with a listed branch-circuit overcurrent protective device when the following 4 conditions are met:
a. The "Home Run" circuit must be continuous from the branch circuit overcurrent device to the OBC AFCI.
b. Maximum length for a 14 AWG conductor is 50 ft and the maximum length for a 12 AWG conductor is 70ft.
c. the first outlet box has to be marked as such
d. the circuit breaker and the OBC AFCI must be listed to meet the requirements of a system combination-type AFCI.
Options 5 and 6 are the same options as we've seen in this section in the past but just included as positive text instead of being an exception.
These options are required for the following areas in dwelling units:
(1) Kitchens
(2) Family rooms
(3) Dining rooms
(4) Living rooms
(5) Parlors
(6) Libraries
(7) Dens
(8) Bedrooms
(9) Sunrooms
(10) Recreation rooms
(11) Closets
(12) Hallways
(13) Laundry areas
(14) Similar areas
===United Kingdom===
In the UK, the [[BS 7671|Wiring Regulations]] 18th edition (BS 7671:2018) is the first edition to make any mention of arc fault devices, and indicate they may be installed if the design has an unusually high risk of fire from arc faults. The annexes relating to testing indicate that when AFDDs are installed, their correct operation must be verified before completion, but the method of testing is not described. This is in contrast to
[[File:Siemens AFDD combination LS or FI.png|thumb|upright=0.8|AFDD combination circuit breaker circa 2012]]
===Germany===
The German Wiring rules VDE
===Australia and New Zealand ===
The Australian and New Zealand regulations
==Limitations==
AFCIs are designed to protect against fires caused by electrical arc faults.
AFCIs are also known to be sensitive (false tripping) to the presence of radio frequency energy, especially within the so-called ''[[high frequency]]'' (HF) spectrum (
AFCI circuit breakers include a standard inverse-time circuit breaker but provide no specific protection against "glowing" connections (also known as a [[high resistance connection]]), high line voltages, or low line voltages.
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* [http://www.AFCIsafety.org AFCI Educational Web site]
* [https://www.cpsc.gov//PageFiles/137798/5133.pdf CPSC AFCI Fact Sheet]
* [https://web.archive.org/web/20140413143838/http://www.iaei.org/blogpost/890108/159112/AFCIS-Emerging-Technology-Solutions-for-Fires-Resulting-from-Electrical-Arcing AFCIs: Emerging Technology Solutions for Fires Resulting from Electrical Arcing], from ''IAEI News: The Magazine''
* [http://www.popsci.com/scitech/article/2009-06/plugged-smartplugs-are-simple-way-save-energy EFCI / OFCI on Popular Science]
* [https://code-authorities.ul.com/wp-content/uploads/2014/05/AFCI_scenarios020502.pdf Arc Fault Testing and Arc Fault Scenarios], [[Underwriters Laboratory]]
{{Electricity delivery}}
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