MWBC CAFCI Common Trip
MWBC CAFCI Common Trip
The basic GE single pole combination-type arc fault circuit breaker has been providing arc fault protection without any ground fault sensing for over three years now. It works just fine on a multiwire branch circuit with, OR WITHOUT, the load neutral of the multiwire branch circuit conntected to the GE AFCI breaker.
You can read GE's shared neutral application documentation
by clicking here.
Hi Al,
Thanks for the link about GE's AFCI technology. Even though the NEC is based on safety as a rule, the use of MWBC protection being compliant with a common trip handle or tie-bar [210.7] does have it's safety setback in two ways. The main safety concern of shared neutrals is more of a sensitive function in arc fault protection shutting down two circuits at the same time. This is applicable to safety in commercial contracts depending on the local facility requirements. (I.e. NFPA Life Safety 101).
Repair efficiency and safety of getting lighting and critical equipment back on the line together become a problematical hazard when simultaneous circuit shutdown becomes a home emergency situation. The second aspect of circuit transient coupling is a factor when the branch cabling is split into bundled pairs, then low level AFCI detection becomes a factor in distance runs. Just saying, that is one of the safety reasons for the 50ft and 70ft restrictions in the NEC 2014 [210.12(A)(1-6)] length constraints.
Noted in the reply comments, as mentioned, that more than one AFCI circuit is affected in some cases. Saving copper is nice, but labor costs in fixing the problem is doubled when two BC's take time in troubleshooting a re-occuring failure when various loads interact from combined EMI coupling. Eliminating MWBC's in NM cabling is almost a fact of economics now...IMO, rbj