I think that article is a bit biased, when you take into consideration Square D has yet to market a 2-pole combination AFCI breaker. They are trying to "downsale" a MWBC because those that want to use MWBC's will not buy their loadcenters.I'm new to this type of application, so please bare with me. (sounds like the gentlemen already decided which route to take).
I found this article that square d put together on AFCIs. i tend to agree with it, since if the use of a 2-pole AFCI is done, it will lead to a shared neutral, and then you have a situation where both circuits (one in either room) can be interrupted (sort of like lack of coordination you see in distribution), along with other issues related to over and under voltage.
http://ecatalog.squared.com/pubs/Ci...ircuit Interrupters (AFCI)/0760DB0203R902.pdf
Additionally, that article presents disadvantages fairly accurate, but does leave out an advantage of a MWBC... which is for balanced MWBC's, the I?R heat losses are reduced, saving the consumer money. Of course that is when operating nominally. Also on this matter, the article points out the disadvantage when an open neutral occurs. I believe it to be an exaggeration. Seriously, how often does that happen compared to operating nominally? Seems to me it happens most when an unqualified person disconnects a splice while the MWBC is energized than it does from a bona fide open-neutral fault.
Granted I don't know the loads for certain, but if you spare out one ungrounded conductor, you'd have to track down the loads it serves and switch them over to the not-spared conductor. Additionally, you could easily manage to overload the circuit in doing so, unless you track down and calculate all effected loads. And if the circuit could then easily become overloaded, the only other option is to pull a new circuit... which I believe is the last practical option from the homeowner's perspective.To me, it just seems like the simplest thing to do is spare out the conductor. yeah, its a waste of cooper, but you know you can still utilize the same panel and afci single pole breaker layout you already have, and avoid any issues, that are explained in the article, not to mention, not having to repull a 12-2w/ gnd.
Last edited: