question

You can't parallel two shore power cables. This would tie the two inputs together and there's no guarantee they are on the same phase. Even if they are, feeding power from one AC input back to the other AC input would be extremely dangerous.

What you probably have is two completely separate AC systems and there really is no way to combine them into a common Multiplus system. You can set up a pair of Multis for split-phase operation but the two inputs MUST have a common neutral and be 180 or 120 degrees out of phase. Two shore power inlets that are in phase will be rejected.

A sensible solution might be to just run a single Multi on the non-air conditioner side of the electrical system and leave the air conditioner side as is. You still need a transfer switch to switch from shore power to generator and since the Multi has only one input, this needs to be ahead of the Multi's AC input. It appears your existing setup uses interlocked breakers for a manual transfer switch. This would need to be replaced by separate breakers for shore and generator then an automatic transfer switch to feed the Multi AC input. The AC output would then need a main breaker before feeding the branch circuits.

Thanks for the reply.

I didn't think I could get them on the same Mulitplus unless there was a way to combine the AC inputs. I had already planned a transfer switch for the genset and one of the shore power (not the air cond).

The interlocked breakers are independent of each other. I can run the air conditioner on genset while the other breaker is on shore power. I just have to slide the cover and flip the breaker.

I was hoping I would never have to flip the breaker on the left. My thinking was it would always get its AC power from the Multiplus whether I was on shore power or the genset to the Multiplus.

As for the air conditioner, I was thinking that I could flip the breaker and slide to the generator side and flip the breaker and it would be running off the genset.

I'm not sure how the generator is wired to the panel. I'm guessing shore power is wired to one of the breakers on each side and the other side has the generator wired.

This seems like a good plan. An ATS between shore power and generator feeding the Multi would work. The existing manual transfer switch could serve as an emergency bypass: Multi / Shore or Multi / Generator.

Consider my ExternalTransferSwitch package that handles changing AC input parameters automatically:

https://github.com/kwindrem/ExtTransferSwitch