Do you have 50 Amp AC plug or 30 Amp AC plug on side of trailer? Is the main breaker on your circuit breaker panel 30 A or 50 A ? Based on your post ti sounds like you have 30A and factory only wired the trailer for one AC unit. A 13,500 BTU roof air conditioner has a starting current of well over 15 Amps, and a running current well over 10 Amps, It might be possible to run two AC on 30 A if you never started them both at the same time and you never ran any large AC load like the microwave, anything with a heating element (hair dryer, coffee pot, electric toaster, electric skillett, etc., and you dont' have electric hot water heater. There are some smaller wall/window units you can browse at Sears, etc. that draw less amps that you might be able to use if could mount in a wall or window some how, that would cause you less problems if your trailer is wired for max 30 amps used at any given time.