The 30 AMP ELCI is tripping when we have the charger on and nothing else. Going so far as to turn off the DC main and everything else on the AC circuit at the breaker box. Since it trips at anything over 15 or so amps (12 volt) from the charger that means the ELCI is getting enough current
through it at 180 watts to trip it.
The rest of the AC system is behaving normally. We can run the 1500 watt water
heater, a coffee maker, and a window A/C unit all together and still the AC is fine... until we turn on the charger. So, if there is an A/C fault, then its isolated to the charger circuit.
Since A/C can be so dangerous and we happen to be in a marina, I asked the if the electrician could come by. He said to try a factory reset first, which I did and it had no effect. Next, we are going to swap out the charger with one he has on hand for such tests and we are going to see if the ELCI trips again. If it DOES trip then we know we have an fault somewhere on the boat, at which time we look for loose connections or simply swap out the AC (and maybe DC) wires in the charger circuit and try again.
He will also test the my unit in the yard hooked up to an isolated test system as he already suspects a bad diode.
If anything, this is a good learning
experience as I've not paid much attention to my AC system since we refitted 3 years ago. Interestingly, the culprit could also be the Blue Sea Systems ELCI - the electrician said that BSS produced ELCI with substandard components about three years ago; if we had one of those I would think we would have seen evidence of that previously.