CG owner is full of $^&*. Three possible reasons why the breaker tripped - overload/short, defective breaker, low voltage or any combination of these.
Running an AC plus electric water heater plus whatever else might have been running is pushing the limit of the 30 amp breaker. Won't know unless you used an ammeter to check. Any idea what the voltage was? Pedestal breakers can become faulty. They are in a harsh environment compared to indoor use (temp. extremes, humidity) plus they get a lot of on/off cycles.
I can find nothing in the NEC regarding a different type of circuit breaker requirement for RV pedestals (covered by art. 551 and 240). RV pedestal manufacturers (Milbank, Midwest Electric, etc.) list a standard type inverse time-current, thermal magnetic type breaker like what is in your converter panel or at home. Local AHJs can amend the NEC and some jurisdiction have their own electrical code, but I cannot find anything pertaining to RV pedestals other than the NEC.
The 30 amp pedestal breaker would be the exact same type as the 50 amp. If there was an overload condition, when using the 50 amp adapter, the 30 amp breaker in the converter panel would have tripped. How old might the pedestal be? The 30 amp breaker would not be a CAFCI, AFCI or GFCI. They don't make a 30 amp CAFCI anyway.
For the 30 amp pedestal breaker to trip immediately upon resetting it would indicate either a short circuit or high overcurrent condition. If the 30 amp converter panel and 50 amp pedestal breakers aren't tripping, it would suggest a problem with the pedestal breaker. Maybe a damaged shore power cord but not by the sounds of it. Could try plugging into the pedestal 20 amp GFCI with loads inside turned off and see if that trips.
There is no problem using a 30 to 50 amp adapter. Yes the upstream overcurrent protection is greater than the ampacity rating of the shore power cord, but the 30 amp breaker in the converter panel will limit the current draw on the cord and protect it. Wouldn't do that in building construction, but it's okay in the RV world (and marine). If they were unsafe in any way, they wouldn't be CSA approved.
If the OP tried to reset the pedestal breaker while nothing was shut off inside, it's probably going to trip again. Could have tried turning off the AC to see what happens. If the current with the AC, HWH and anything else was running and it did not trip the 50 amp pedestal breaker or the 30 amp in the converter panel, than the pedestal breaker had to be faulty.
The condition of some CG/RV park wiring and electrical equipment is atrocious and the owners or workers will make up all sorts of excuses. BTDT. Sometimes electrical work gets done by unqualified staff too. Below is a photo of a pedestal in a large CG on the Wa. coast - in terrible shape and doesn't meet code (20amp recept. removed). Entire CG was like that.
It's good practice to always use 50 amps on a pedestal if available. If an area of a CG doesn't have 50 amps in pedestals, move to an area that does - much more likely to have better voltage.
