I do this at my home here with my RV Trailer parked in the back yard.. Everything works just fine just have to watch what I have on at the same time.
The high wattage items like the air conditioner, microwave, Vacuum, etc can only be operated by them self other wise it will trip the breaker.
If you add up all of the wattage rating of what is installed in the 30AMP RV you will find it over the 30AMP RATING. I have tripped the 30AMP breaker at the camp ground pedestals a few time by having too many high wattage appliances on at the same time. Will only be worse when using a 20AMP service.
If the campground pedestal had 20AMP BREAKERS on two separate 20AMP service receptacles I would definitely bring along a 25-foot extension cord and try to run some items in the trailer plugged into the separate extension cord.
Since the RV's at these sites are probably all 30AMP units I would really bet the campground 20AMP circuit breakers are worn completely out. You know everyone that is hooked up is going to trip the 20AMP several times during their stay... The circuit breakers can only be tripped a known number of times.
"Everything was fine until I turned on the ceiling light in the bathroom" hehe...
I don't think I have ever been to a campground with only 20AMP Service. Have been to a few over-night pull-off areas that had 20AMP service available.
You can pick up a RV30A-15A Adapter at WALMART. I also saw a RV50A-30A adapter there last time I was looking. Chaining all of these together will allow you to plug your 50AMP Shore Power cable into the 20AMP Service receptacle.
Roy Ken
My Posts are IMHO based on my experiences - Words in CAPS does not mean I am shouting
Roy - Carolyn
RETIRED DOAF/DON/DOD/CONTR RADIO TECH (42yrs)
K9PHT (Since 1957) 146.52M
2010 F150, 5.4,3:73 Gears,SCab
2008 Starcraft 14RT EU2000i GEN
2005 Flagstaff 8528RESS