Has it ever been acceptable for a multi wire branch circuit to be on 2 separate breakers? My house, which was built in the mid 90s, has the dishwasher and the disposal on the same 12/3 cable, but not on a common trip breaker.
I'm going to replace the breaker, but I'm just curious if this was ever allowed.
Yes it is allowed, up through the 2020 NEC section 240.15(B)(1) single pole 120/240v breakers with handle ties are still allowed when the MWBC only feeds line to neutral loads.
I don't have my old books, but it wasn't until the 2000's that the common trip requirements entered the code, but even then your local authority may have not have immediately adopted the code or that section immediately upon publication. For instance 3 states are still using the 2008, four cycles behind.
Free access to the NEC at https://www.nfpa.org/codes-and-standards/all-codes-and-standards/list-of-codes-and-standards/detail?code=70
Yes, it was allowed to have MWBC on separate breakers. My house was built in 1981 and I had my refrig and two outlets on one MWBC and my dishwasher and disposal on another. They were not handle tied and not even next to each other in the panel but they were on different phases so the neutral wouldn't be overloaded. The whole subdivision was built like that and many panels that I've been in have had them wired the same way.
I suspect the handle-tie requirement came along either in the late 90s or the 00s. Back in 1994 they were still allowing 3-prong range and dryer connections to be built (though, not with NM nor UF cable).
