While moving some wires around in my garage (to make space for attic storage), I discovered an electrical issue that might be concerning: In my garage there are two circuits delivered as a MWBC, but the two circuits are on the same bus (0V between the red and black, 120V between each of the hots and the neutral).
The two circuits are sitting completely separate in the panel (see attached image -- I highlighted the two wires in the MBWC). Interestingly, when I called a local electrician for advice he said it's nonsense and should work fine just as it is, but from everything I am reading it is not only a code violation but also a fire hazard... What would be the easiest way to fix this issue?
One quick fix I could think of was to swap one of those tandem breakers with one below or above it, so at least the two circuits will be on different phases. My concern with that one is that I'd first need to confirm that the other wire on that tandem breaker isn't also a part of another MBWC... And I'm not sure how to do that. Any better ideas?
I have to admit I am quite surprised: We purchased this house new from a builder and have never modified anything, so the home was built this way, which seems incredibly careless.
Update: Just occurred to me that SolarCity (now Tesla) installed the PV system years ago and likely moved circuits around on this panel, so I suppose it's possible they created this situation.