over amps on multi branch

if you wire a sine inverter directly into a mains panel,disconnected from grid, and you have multi branch circuits you can have trouble with excess current on the multi branch neutral wire. But you would be ok if you never exceed the amp rating of the breaker even when using 2 different outlets..,yes?? I mean if you never exceed 15 amps then the single neutral wire,12-14 ga. will handle that ,yes??? THis is all providing that the inverter is ok for doing this,ie ground issues etc..
Comments
if you put both legs of the multiwire on the same breaker you would be the proper and code compliant way to go assuming you didnt actually need the full 30/40 amps. Due to the likely diversity of the loads and the fact that the"14 gauge 15 amps, 12 gauge 20 amps" rule is an additional "small conductor" de-rating which is much less than the actual table 310.16 ampacity used for most other conductors, I would almost certainly be fine on separate breakers anyway.
And then you feed it (via a transfer switch) from the output of 120V inverter without using a transformer, so that both buses are connected to the same hot output from the inverter.
If you are going to do that, you will need to rewire all of your MWBCs to have two separate neutrals. Doubling the size of the neutral will also resolve the safety issue, but will still not be code (NEC) compliant.
If you have only a 120 VAC inverter and connect Black from the Pure Sine Wave inverter to Line A+Line B (A and B shorted together), if you have any common neutrals in your house wiring (Red+Black+Neutral + Green/Bare copper ground), then Line A + Line B will add and the common current will over current the neutral wire.
Similar if you have two 120 VAC PSW inverters that are not "Stacked" (designed for 120/240 VAC operation). If you connect one inverter to Line A + Neutral, and the second to Line B + Neutral, the inverters do not coordinate the phases and you cannot guarantee the Line A and Line B are 180 degrees out of phase to each other--So it is unsafe to use a common neutral in this configuration too.
-Bill
wouldn't it just be easier to put a center tap transformer in?