A solution to this problem is to add an additional 20 amp line coming into the motorhome.
The lower of the three plug in’s is a separate ground fault plug in which is wired to it’s own electrical source. I run an extension cord from the outside plug in a 20 amp breaker in the power service.
This works great, don’t have to worry about over heating the motorhome’s electrical system and we have heat in the bedroom.