I have two adjacent 20A tandem breakers in my panel. I need to change one of the breakers on each tandem to 15A (in order to protect 14 gauge wires on the respective circuits).
The possibility exists that an MWBC is present amongst the four circuits in question, but it can’t be confirmed (or rejected) - the panel box is crowded and the relevant cable jacket(s) are recessed in the wall.
I want to swap the 20A tandems with BD1520 tandems, so that each of the four phase conductors originates from the original phase (preserving the voltage between any potential MWBC hot wires). Outside of the potential code violation (which I inherited) for not having a handle-tie (if indeed an MWBC exists), would this possible solution create any electrical hazards that I may be overlooking?
The label/diagram for the panel is missing.