AFCI Frequently Asked Questions

The information in this article is from the Siemens web site and was initially compiled by Tarry Baker of Broward County, Florida. Additional information was provided by Peter Spirito.

Click HERE for a direct link to Siemens complete information on AFCI’s

Click HERE for a direct link to UL Laboratories’ AFCI information


What is an arcing fault?

According to UL 1699, Standard for Arc Fault Circuit Interrupters, an arcing fault is an unintentional arcing condition in a circuit. Arcing is defined as a luminous discharge of electricity across an insulating medium, usually accompanied by the partial volatilization of electrodes.

There are 3 basic types of arcing faults: line-to-neutral, line-to-ground, and series arcing.

What causes an arc fault?

Arc faults may occur anywhere in the electrical system and may be a result of the following:

What is an AFCI?

As defined in UL 1699, Standard for Arc Fault Circuit Interrupters, an Arc-Fault Circuit Interrupter (AFCI) is a device intended to mitigate the effects of arcing faults by functioning to de-energize the circuit when an arc fault is detected.

Siemens a major manufacturer of electrical components offers two types of AFCI’s: a Combination Type AFCI and a Branch/Feeder AFCI. Both types of Siemens AFCI’s consist of a thermal magnetic circuit breaker with an electronic circuit board. The electronics detect the arc and activate a solenoid to trip the circuit breaker.

What is the difference between a Combination Type AFCI and a Branch/Feeder AFCI?

The Siemens Combination Type AFCI provides protection against all three types of arcs (series, line-to-neutral, and line-to-ground). The Combination Type meets all the 1999 and later NEC® requirements. It is specifically required by the 2005 NEC® beginning January 1, 2008.

The original Branch/Feeder AFCI’s provided protection against only two types of arcs (line-to-neutral and line-to-ground). It could used to meet the requirements of the 1999-2002 NEC® and the 2005 NEC® until January 1, 2008.

Does the term “Combination” mean that GFCI protection is included?

No, it only means that the device protects against all three types of arcing.  Any device that would include GFCI protection would be referred to as a dual function device.

Why is arc detection needed?

Arcing faults generally go undetected for an extended time and can reach high temperatures even at low current levels. These temperatures can easily exceed the combustion point of common building materials.

According to the Consumer Product Safety Commission, problems in home wiring, like arcing and sparking, are associated with more than 40,000 home fires each year. These fires claim over 350 lives and injure 1,400 victims annually. And while standard circuit breakers are intended to protect conductors from overload and short circuit conditions, they do not protect against arcing faults and ground faults.

How is an AFCI different from a GFCI?

Although the AFCI and GFCI may look very similar, their purpose is quite different. AFCI’s are designed to address the hazards that result from arcing, while GFCI's (Ground Fault Circuit Interrupters) are designed to address shock hazards and are intended for the protection of personnel.

Would you wire an AFCI circuit breaker differently than a GFCI circuit breaker?

No. Similar to a GFCI, you connect the neutral (pig-tail) wire on the AFCI to the load center neutral bar. The branch circuit power conductor connects to the terminal marked "LOAD POWER" and the load neutral wire connects to the terminal marked "LOAD NEUTRAL."

Can you use an AFCI on a two wire system with no equipment ground?

Yes, an AFCI does not require an equipment ground to perform its intended function. A retrofit into a home with a two wire system is an acceptable application for an AFCI. In fact, Siemens encourages the use of AFCI’s in these homes as aged wiring systems also present the potential for arcing.

What are the National Electrical Code® requirements for AFCI’s?

AFCI’s were added to the 1999 National Electrical Code® in Section 210-12 for bedroom receptacle outlets beginning on January 1, 2002.

The 2002 NEC® (Section 210.12) requires AFCI’s for all bedroom circuit outlets. An outlet is defined as any point on the wiring system at which current is taken to supply utilization equipment. This includes receptacles, lighting fixtures, ceiling fans, smoke alarms, etc.

The 2005 NEC® (Section 210.12) has the same requirements for bedroom circuit outlets with one exception – the wording changes to specifically require a Combination Type AFCI beginning January 1, 2008. In all cases the requirement is to protect the entire branch circuit.

NEC® Article 100 Definitions 

Please see the NEC® for the exact wording of the requirements. Some areas may adopt other effective dates and may expand the requirements beyond the bedroom circuits. Contact your local authority having jurisdiction (AHJ) to verify code requirements for your area.

Why do the 1999, 2002, and 2005 versions of the NEC® require AFCI protection for only bedroom circuits?

NFPA fire statistics show that a high percentage of electrical fires occur in bedrooms. There are many appliance cords in bedrooms, for example, radios, clocks, blankets, air conditioners, heaters, TVs, vacuums, as well as, lamp cords. All of these cords can be trapped/abused leading to arcing faults. Further, there are long runs of installed wiring (M-B, “Romex”) between the loadcenter and the bedroom outlets. The wiring can be abused during installation (e.g. stapling) and after installation (driving nails into the wall etc.) Therefore, the most logical room to start with would be the bedroom.

Is the requirement for AFCI’s expected to expand the use of AFCI protection beyond the bedroom circuits?

Yes, Section 210.12 of the 2008 NEC® has expanded the requirements for AFCI’s for almost all rooms and living areas in dwellings. The 2008 NEC is currently available for purchase; however, it has not yet been adopted for use by most municipalities. Contact your local authority having jurisdiction (AHJ) to verify which edition of the NEC or other electrical code is being enforced in your area.

What about nuisance tripping?

Siemens AFCI circuit breakers are designed to resist nuisance tripping when wired to a variety of loads found in the home, while keeping their full sensitivity to detect arcs. AFCI’s have been tested with a wide variety of products including fluorescent lights, hand drills, welders, hairdryers, dimmers, and other appliances containing electric motors to ensure that they will not nuisance trip and to ensure that these loads would not mask the presence of an arc.

How do I test to determine if my AFCI circuit breaker is functioning properly?

To test an AFCI, make sure there is power to the load center, or panelboard. Turn the AFCI handle to the "ON" position. Press the test button. Pressing the test button simulates an arc to the AFCI sensing electronics, causing the breaker to trip. The AFCI breaker is functioning properly when the circuit is interrupted and the handle moves to the tripped center position. To reset, turn the AFCI off and turn it on again. If the AFCI does not trip when the test button is pressed, it should be replaced. Refer to a qualified electrician for servicing. You should test your AFCI breaker monthly to insure protection against electrical arcing faults.

Is there a hand-held device that can test an AFCI circuit breaker?

At the present time, Siemens is not aware of a separate unit which can completely test the operation and functionality of an AFCI circuit breaker. If you do see an AFCI hand-held tester on the market, it is advisable to carefully read the manufacturer's packaging. UL has warned of potentially hazardous AFCI circuit testers out in the market.

The Push-to-Test button is always an acceptable test for the AFCI circuit breaker, whether Combination Type or Branch/Feeder.

Can you use a hand-held GFCI tester to test an AFCI circuit breaker?

No. While some GFCI testers may cause an AFCI to trip, these devices are not testing the arc detection capability of the breaker. AFCI’s utilize a differential sensor to detect leakage of current in a circuit. When the GFCI tester creates a leakage of current greater than the threshold level of the AFCI's differential sensor, the device will open. However, this fault detection is not intended to provide personnel protection, as the AFCI trip thresholds for differential current vary by manufacturer but are typically 30mA to 60mA – far above the 5mA level required for personnel protection. In addition, AFCI’s do not specifically include grounded neutral protection.

Will an AFCI trip when testing a GFCI receptacle installed on the same circuit?

If a GFCI receptacle is installed on the load side of an AFCI it is possible for both the AFCI and the GFCI to trip on a ground fault if the leakage current exceeds the threshold for both devices. It is also possible for the AFCI to trip and the GFCI to not trip since the two devices could race each other. The functionality of each device should be verified by operation of the Push-to-Test button.

Can I replace a 2-pole breaker feeding two branch circuits with two 1-pole AFCI’s?

No. The most common reason for a 2-pole circuit breaker feeding two branch circuits is the use of multi-wire branch circuits, also known as shared neutral wiring. This means that the two branch circuits use the same neutral conductor as a current return path to the loadcenter or panelboard. In these cases, a 2-pole AFCI, such as the Siemens Q215AF, should be used to replace the 2 pole conventional breaker. Two 1-pole AFCI’s cannot be used with this wiring method.

If separate neutral wires exist for both branch circuits, then two 1-pole AFCI’s can be used. Each branch circuit load conductor and its corresponding neutral conductor must be connected to the same AFCI for proper operation.

Multi-wire branch circuit inspections and repairs should be performed only by qualified electricians.

Could an AFCI feel warmer than other breakers in the same panel?

An AFCI breaker may feel warmer to the touch than a non-AFCI circuit breaker. This is due to the heat generated from the power supply for the electronics. Siemens AFCI breakers tested in an average ambient temperature of 23° C (73° F) operated at an average temperature of 38° C (100° F.) This is well within the UL Standard 489 Section which states - Temperature rises on handles, knobs, and other surfaces subject to user contact during normal operation shall not exceed 60°C (140°F) on nonmetallic surfaces.  It is warm enough to detect with the hand, but this heat does not impact the operation of the AFCI.

Can I add an AFCI to an old loadcenter?

Siemens AFCI circuit breakers are suitable for use in existing products manufactured by I-T-E, Gould, Siemens-Allis and Siemens Energy & Automation. Specifically the AFCI circuit breaker Types can be used in any of these products in accordance with the following table.

Breaker Type Marked
on Panelboard
AFCI Breaker Type
That Can Be Used

This usage of these AFCI circuit breakers also includes their use in any series ratings marked on the products at the same levels.


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