You have a new boat. The marine air unit should operate with shore power and not trip the main ELCI breaker. The reason it doesn't trip with the generator is the ELCI is not used with the generator. The fact that the ELCI doesn't trip with any other user of power, hot water heater, stove top, or microwave would indicate that there may be an issue with the wiring going to the Air unit. The ELCI will trip because there is to much load over 30 amps, which should not be the case if the Air unit is correctly wired, connections are tight and clean. Or it will trip if there is an amp differential between the neutral and the Hot meaning there is some current going to ground. Not a good thing that is why the requirement now is to have a ELCI breaker. My advise is call your dealer. Ask your dealer or the factory why the ELCI is tripping? Did the Air unit work fine when the dealer delivered the boat to you ? Does the PDI indicate that the factory and dealer checked the proper function of this system? If it did and it was at a different marina maybe the issue is at the marina that the boat is moored at. There was post last week about electrical issues and wiring, another one a week before same issue ELCI tripping but with the stove top. It is probably a simple issue but it should be looked into.
I had this issue when my boat was new. The ELCI kept tripping when I had a higher load on it but not a high enough load that should trip a 30 amp breaker. After a couple of weeks of the dealer telling me I had to use power management I looked into it and found the electrical connections at the shore power receptacle mounted in the cockpit were loose and severely burned. They were not tightened properly. After repairing the connections and tightening them I had no issue. This year I found the same issue in my main electrical breaker panel, connections that were loose had finally burned and melted.
A 2020 Ranger just delivered should not have 120 Volt electrical issues. Make sure it is not the Marina then call your dealer. Be safe.
