How are you connecting to the house system.
I am guessing you have a 20AMP 120VAC Receptacle maybe in the garage and then you are using an extension cord to get out close to the trailer. Then you plug into the extension cord using a RV30A-15A long DOGBONE type adapter (WALMART)...

The extension cord should be no smaller than a 12GAUGE (12-3) but would be very good if you was using a 10-GAUGE (10-3) Extension cord. I am using two 50-foot extension cords coming from my garage and connecting to my POPUP and 5th wheel trailers.

You must always use the LONG DOGBONE type adapter as the small round ones will get hot on you after just a few time of using them...
DO NOT use these type of RV 30A-15A adapters

This is what we do with our 15/20AMP Service receptacle out of our garage...
Works great here with my OFF-ROAD 30AMP POPUP and also my 5th wheel on a different 15/20AMP circuit in the garage... I can run my 13,500 A/C and all the other items just fine. I do have be cautious on what I have on when I try to use a couple of heavy current items at the same time like the A/C and the Microwave etc. Otherwise it will trip my garage breaker.
Roy Ken