AFCI question

[Tom Raymond]

I was speaking with an electrical inspector today about AFCI breakers vs receptacles. He had never seen an AFCI receptacle, but thinks that the branch wiring between the device and the panel needs to be in conduit. Any truth to this? I don't have a copy of NEC or I'd look it up.

[Jim Katen]

He's correct.

I've seen and touched an actual AFCI receptacle, so I know they exist, but I've never seen one installed in a building.

[Jack Davenport]

There's an allowance to run NM cable straight from a circuit breaker ( panel) to the first outlet of the circuit uninterrupted. ( no j-boxes/splices) This allowance has restrictions on the length of this run. It also requires labeling on the the first outlet as well

I underlined this allowance in the cut & paste below

From 2014 NEC

210.12(A)(4)

(4) A listed outlet branch-circuit type arc-fault circuit interrupter installed at the first outlet on the branch circuit in combination with a listed branch-circuit overcurrent protective device where all of the following conditions are met:

a. The branch-circuit wiring shall be continuous from the branch-circuit overcurrent device to the outlet branch-circuit arc-fault circuit interrupter.

b. The maximum length of the branch-circuit wiring from the branch-circuit overcurrent device to the first outlet shall not exceed 15.2 m (50 ft) for a

14 AWG conductor or 21.3 m (70 ft) for a 12 AWG conductor.

c. The first outlet box in the branch circuit shall be marked to indicate that it is the first outlet of the circuit.

d. The combination of the branch-circuit overcurrent device and outlet branch-circuit AFCI shall be identified as meeting the requirements for a system

combination-type AFCI and shall be listed as such.

[Garry Sorrells]

Here is something to read over. Worth a few minutes of your time. [:-magnify

What's New about AFCIs in the 2014 NEC? From IAEI March-April 2015

http://iaeimagazine.org/magazine/2015/0 ... -2014-nec/

[Douglas Hansen]

There's an allowance to run NM cable straight from a circuit breaker ( panel) to the first outlet of the circuit uninterrupted. ( no j-boxes/splices) This allowance has restrictions on the length of this run. It also requires labeling on the the first outlet as well

I underlined this allowance in the cut & paste below

From 2014 NEC

210.12(A)(4)

(4) A listed outlet branch-circuit type arc-fault circuit interrupter installed at the first outlet on the branch circuit in combination with a listed branch-circuit overcurrent protective device where all of the following conditions are met:

a. The branch-circuit wiring shall be continuous from the branch-circuit overcurrent device to the outlet branch-circuit arc-fault circuit interrupter.

b. The maximum length of the branch-circuit wiring from the branch-circuit overcurrent device to the first outlet shall not exceed 15.2 m (50 ft) for a

14 AWG conductor or 21.3 m (70 ft) for a 12 AWG conductor.

c. The first outlet box in the branch circuit shall be marked to indicate that it is the first outlet of the circuit.

d. The combination of the branch-circuit overcurrent device and outlet branch-circuit AFCI shall be identified as meeting the requirements for a system

combination-type AFCI and shall be listed as such.

Jack- the draft of the 2017 NEC eliminates item d from the list (probably a good thing since no such listed combination of breaker and OBC AFCI seems to exist). Here is their statement justifying the deletion of d:

The Panel has deleted 210.12(4)(d) which required listing of both the OBC ACI and the Branch Circuit Overcurrent Device as a "System Combination."

The previously cited UL research report titled "Effectiveness of Circuit Breakers in Mitigating Parallel Arcing Faults in the Home Run" provided significant statistical assurance that the "home run" portion of the branch circuit is protected from parallel arcing faults. UL issued another research report titled "Influence of Damage and Degradation on Breakdown Voltage of NM Cables" that had the following conclusion from pages 58 - 59:

"In summary, the work described here shows that damage and degradation of a residential NM cable can lead to an arcing event, through voltage surges that break down the cable insulation and ignite arcing. However, the test results also indicate that the breakdown event is unlikely to initiate arcing that is sustained long enough to ignite the cable insulation or surrounding materials. In this study, arcing for hammer-damaged cable exhibited arcing during less than 10% of the surge events, and exhibited arcing that lasted over a single half-cycle. The arcing observed in this study is much shorter than what is required for an AFCI reacting to the event (eight half-cycles within 0.5 seconds, per UL 1699); however, the energy released in that short event is not expected to ignite the cable insulation."

So whatever that means, it sounds like one part of this gets easier in the 2017 code.