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Tuesday, August 23, 2016

Question:

Re: CQD answer published Thursday, July 21, 2016 - Replacement Receptacles -AFCI

I am somehow completely missing the possible technical issue between anybody's circuit breaker (or fuse) and a downstream AFCI receptacle/device. They are both "watching" the circuit.  If a trip-level problem occurs which is significant enough for the overload protection to operate, then the power is off and it matters not what the AFCI has done. If it is not that significant, then the circuit is still on and gives the AFCI the opportunity to trip. If it does, then the downstream power is off. If the problem is between the overload device and the AFCI device, and the AFCI device has tripped off, then what added risk is imposed ? What conceivable practical safeguarding does 210.12(A)(4)(d) provide ?

Scott Cline

A

Answer:

Hey Scott thanks for your question, it is confusing and a somewhat controversial topic. The issue is not about providing overcurrent protection, including those at overload levels, but about protection from arcing faults. An outlet type AFCI device will only denergize the downstream portion of the branch circuit. They can provide some protection from an upstream series arcing fault by interrupting current but do not provide protection from upstream parallel arcing faults. Section 210.12(A)(4)(d) states they must be identified and listed as a system combination. The rules in 210.12(A) require AFCI protection for the entire branch circuit but the rules in 210.(B) and 406.4(D)(4) allow the AFCI protection to be located other than at the point of origin of the branch circuit.

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