Manual Transfer Switch, MWBCs, and Bridging Adapter

[dmholmes]

I have a Reliance manual transfer switch (MTS) that I feed from 120v power sources through a 5-15 to 14-30 adapter. After finding out that my main panel has MWBCs that are wired into the MTS, I got the electrician to come back out and identify the MWBCs so I could make sure not to have both branches of a MWBC powered at the same time. Side note, my main panel is apparently not up to code because the MWBCs are not using double-pole breakers.

Until I get a 240v power source what is the best way to use the MTS if needed in an outage (or with main breaker off)? I thought it would be okay to only power one branch of an MWBC, avoiding any potential of overloading the neutral. Somebody suggested only powering one phase at a time which would limit to only running one half or the other of the circuits on the MTS. Thoughts?

 

[sumpower]

Just for clarification to those who might help you. Acronyms are terrible to use if you want help.
So does MWBC = Multi-Wire Branch Circuit?
If so, I never installed them. I always explained to customers why I don't like them with thier possibility that a Multi-Wire branch circuit can and will destroy appliances if the neutral conductor is lost.
Is this your concern?
The theory behind the Multi-wire branch circuit is that the current on the neutral conductor equals zero if both hot conductors have the same amount of current flowing through them. So in theory and practice you can not overheat the neutral conductor. Not a problem, but I never installed them.
But in your case, if they are on the same line then I would only use one circuit at a time.