How can I use a 120v generator to power both legs of my electrical panel?

Question

I was recently gifted a Champion brand, 3550 watt, 120 v generator.  I had intended on hooking it up to my electrical panel via generator plug inlet box and interlock kit, but after doing some research I've come to realize I've got a complex problem.
In theory, I could rig something up to jumper the single hot into two separate hots and power both legs of my panel.  But, I have several MWBCs in my house, and my understanding is that would create a situation where I am overloading the shared neutral because the generator is only producing a single phase of 120v power.  Is this correct?
What are my options, other than trying to exchange or sell for a 240 v generator?
Thanks!

Harper - Reinstate Monica · Accepted Answer

Yes! That is correct.  Well done with  the MWBC investigation.
The cheap/fast answer is simple: Since you are familiar with MWBC, it is safe for you to rearrange your loads to place all your critical loads on one phase. For instance, that would mean powering only 1/2 of any MWBC.  Attach the 2-pole generator breaker in  the usual way, but only connect your "hot" to one leg.
For the sole purpose of researching which leg a load is on, it is OK to temporarily pull 1 wire off a 2-pole MWBC breaker, or defeat the handle-ties.  Just put it back when you're done :)
In fact make sure they are handle-tied while you are in there.

gbronner · Answer

You could transfer some of the 120V circuits to a box that can be powered from the generator via a transfer switch.
Otherwise, you are correct — trying to run both legs of your power will create problems for all of your 240V circuits, and you can consider a MWBC a 240V circuit with a neutral for this purpose.  Much cheaper to buy a 240V generator than to deal with these issues.

How can I use a 120v generator to power both legs of my electrical panel?

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