[flybouy]

How is it plugged in? A dog bone adapter? A cheap extension cord?

Is there anything else in the trailer turned on? Is the refrigerator on 120vac? Is the water heater turned on with 120vac heating element on? Is the converter charging the battery? Do you have a lot of interior incandescent lights turned on? Is the television turned on? Is anything in the house plugged into that circuit like a freezer in the garage?

With a 20 Amp circuit and nothing else on that circuit running it should work but it may be close when the air conditioner compressor first starts. If anything else is pulling a load at that time then it will likely trip.