Our power was out for several hours today, and my brain got creative.  Curious to get the opinion of the electically minded people out there, like @arjedi , if this is a bad idea.

I've got a generator interlock that we use during outages.  I can run the big 220 gen if I need to, but typically don't need to, so I use a small 110v inverter generator.  Like many, I made a plug where the one hot from the 110 generator energizes both hots on the 220 plug, thus energizing both sides of the panel.  Yes, I know I can't run 220 stuff off that.

Question is, can I apply the same principle with TWO small generators, that each power one side of the panel.  They would share a ground and neutral on the 220 plug, but each would supply a separate hot.  Both 110 generators would still use way less fuel than the bigger 220 genset.

Internet seems to say two hots can share a neutral, so long as they are out of phase, so you'd never have both currents going across neutral and overloading the line.  But in this case both generators combined are WAY under the rating of the 10 gauge line.

So question is, would two neutrals from two different generators cause problems if they are on the same line?

Or am I gonna get blowed up?

Sounds like it would be hard to keep each generator loaded exactly the same

it will be fine

they don't have to be

They will to any 240 volt loads still connected to both phases.

I would expect the voltage measured between both phases to slowly vary between 0 and 240 volts, as each generator's output frequency and phase varies with respect to the other.

Wouldn't they have to be synced? If the neutrals are tied, the PTP voltages would be AFU. And if the frequencies weren't perfectly it would be even worse. I understand that amp loads could differ but phase has to sync.

PTP?

That's what I was thinking too.  There is no way to phase lock the two generators short of mechanically tying their shaft together.

It would be a better idea to use the splitter cord and apply the same 120v to both legs.  This leaves the 240v appliances at 0V.  An alternative that I'm use is a 120v to 240v split phase transformer.  I picked it out of a junk pile, but they are quite valuable.  You can input 120v (3000 watts in my case) and output 120v/240v split phase.

Assuming we forget about electrical codes and safety.................
Technically it will work as long as there are no 230V, dual pole devices connected to the panel. Neutrals can be shared. Neutral is always grounded at the service entrance (or main electrical panel).

Better way: If both generators are inverter type, they can be connected in parallel to double their power capacity while maintaining the same 120 VAC voltage. Disconnect both grid power hot wires from the panel and wire the double genset 120 VAC power output into the panel. Put a jumper between both sides in the breaker panel.

Do this at your own risk. Backfeeding the grid from a generator can cause major problems or a fatality. This is why a properly installed transfer switch must be used.

It would work.

It would be much, much better to use inverter generators that can be paralleled. With the split scheme, there would be no way to load balance between the two sides... you might end up with say your microwave on the same side as your furnace and end up overloading that generator, while the other side is doing nothing.

With the split scheme you would also have to take care to turn off all your 240 breakers or mayhem would probably ensue.

Maybe not exactly the same but if you overload one you'll have problems.  Won't be able to have full capacity I wouldn't think

Yes it would work OP but you would not be able to energize any 240volt loads unless the generators can be synced out of phase

Just to be clear, you're not trying to power 220 circuits correct? If you are, you can't simply add another generator, the 2 110 lines must be synced 180 degree out of phase to get 220.

As mentioned, if you just want 110 from the generators then paralleling both and powering the meter that way you've been doing it is the best option.

There was, at one time, discussion of scheme to "parallel" 2 inverter generators but trick them into running out of phase in order to get 220 out of them. IE, 2 Honda EU2000s with a special made parallel cord that tricks the 2nd generator into thinking it's running in-phase with the first when it's actually running out of phase.

The discussion was long, some said it couldn't be done, many thought it possible. One said he and an electronically talented individual were going to try it and sell them if it worked. He never came back to the thread and I don't see them for sale anywhere so I don't know if it was attempted and they failed or if they never tried.

My non-electrical-engineering oriented brain says it should be a simple afair to figure out, but then again, I do mechanical engineering with only some understanding of electronics and circuits...

In principle, you can do it.

Make sure to disconnect any 240 volt loads as they will cause interaction unpredictably between the two gennys.

Think of it as two independent systems.

If you understand what you are doing you will be fine.