A “COMBINATION” Arc-Fault Circuit Breaker is NOT equivalent to a “DUAL-FUNCTION” Circuit Breaker.
With ever changing electrical Code requirements, a circuit breaker with the ability to provide both Arc-Fault protection as well as Ground Fault (GFCI) protection was long overdue. But beware, the “combination” function that is identified on recently manufactured AFCI circuit breakers DOES NOT provide this AFCI/GFCI protection.
COMBINATION AFCI Circuit-Breaker: Provides protection against both parallel arcing conditions (which is a hot to ground arcing condition), and series arcing conditions (which is arcing that occurs along a single conductor where a portion of that conductor is broken, frayed, or otherwise partially disassembled, causing the current to leap an air-gap to continue on its path).
DUAL-FUNCTION AFCI/GFCI Circuit-Breaker: Combines both AFCI and GFCI branch-circuit protection into one OCPD.
The Combination Type Arc-Fault Circuit Interrupter
Branch circuit protection has steadily evolved over the decades concerning electrical safety for Family Dwelling Units. The Fuse being one of the first advances, then the circuit breaker, the GFCI, and most recently the AFCI. All of these devices are, by action, circuit interrupters; they de-energize the circuit being protected. The fuse interrupts the circuit when there is an overcurrent condition (short circuit or overload), but unlike the other devices, it is a one and done; when a fuse interrupts a circuit, when it blows, it must be replaced. The circuit breaker is also a circuit interrupter. It opens when there is an overcurrent condition in the branch circuit it protects, and it is resettable. Both the fuse and the circuit breaker are designed to protect the circuit against short circuit current and overloads.
The GFCI, the ground-fault circuit interrupter, and the AFCI, the arc-fault circuit interrupter, are devices designed to meet specific electrical safety issues. The GFCI is designed to protect personnel against electrocution while operating tools or equipment on a GFCI protected circuit. It is designed to interrupt and de-energize the circuit if there is an imbalance in current of 6 mA or greater between the line conductors (NEC 100IN). The GFCI is resettable. The AFCI is resettable and designed to interrupt and de-energize a circuit to protect life and property should anomalies that mimic arcing faults occur in an AFCI protected circuit.
Arc-fault circuit protection was first introduced as a requirement for bedrooms in the 1999 NEC that was to take effect in the 2002 NEC cycle. The Code requiring Arc-Fault Circuit-Interrupter Protection, 210.12, has evolved with the technology. The AFCI shall be installed in a readily accessible location, and protect all 120-volt, single phase, 15- and 20-ampere branch circuits supplying outlets or devices installed in dwelling unit kitchens, family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sunrooms, recreation rooms, closets, hallways, laundry areas, or similar rooms or areas shall be protected…, 210.12(A).
Several Code cycles through and including the 2017 NEC have amended the ACFI requirements such that the rooms or areas shall be protected by any of the means described in 210.12(A)(1) through (6). The means described in (A)(1) is a listed combination-type arc-fault circuit interrupter, installed to provide protection of the entire branch circuit.
According to Siemens, a supplier of combination-type arc-fault interrupter circuit breakers, “Combination Type Arc Fault Circuit Interrupters (AFCI) detects arcing faults (an unintentional arcing condition in a circuit) that standard circuit breakers are unable to detect. The device is intended to mitigate the effects of arcing faults by functioning to de-energize the circuit when an arc-fault is detected. A Combination Type AFCI detects all three types of arcing: line-to-neutral, line-to-ground, and series arcing.”
The most probable and convenient “means” to meet the AFCI Protection requirement for new construction dwelling units is through use of a Combination Type AFCI Breaker, 210.12(A)(1). This will allow the use of GFCI receptacles for those circuits where GFCI protection is required. Another possible and the next probable device to be used in new construction that would also meet the AFCI Protection requirements of 210.12(A) is the Combination Type ACFCI Breaker that also has GFCI Protection, a Dual-Function AFCI/GFCI Breaker. The remaining means described in 210.12(A)(2) through (6) requires a thorough understanding of the related Code and specific input at the local level from the Authority Having Jurisdiction.
What about when an existing circuit that is required to be AFCI Protected has to be repaired or modified?
The Code covers this in 210.12(D)(1) and (2), Branch-Circuit Extensions or Modifications – Dwelling Units and Dormitory Units. In any of the areas specified in 210.12(A) or (B), where branch-circuit wiring is modified, replaced, or extended, the branch-circuit shall be protected by one of the following:
(1) A listed combination type AFCI located at the origin of the branch-circuit
(2) A listed outlet branch-circuit-type AFCI located at the first receptacle outlet of the existing branch circuit.
The electrician could replace the standard circuit breaker with the Combination Type AFCI Breaker to provide the required AFCI Protection, but…. this may not be the best option on older homes. Circuit neutrals must remain separated for AFCI devices to operate correctly. Neutral maintenance is required on new construction, meaning that all neutrals are separated when leaving the panel and do not tie in with any other neutral outside the panel. The Combination Type AFCI Outlet Receptacle may be the better choice when existing branch circuit wiring is modified, replaced, or extended.