When I had a 30 amp system I used the 50 amp surger....mainly because the 30 amp receptacles of many rv parks are aged and burned,,,,,that creates burnt prongs on your plug. Use the 50 in line on your 30,,,,,the 50's are less abused at parks than the 30's.....you'll take better care of the prongs and receptacles on your own equipment that way by not stressing and maxing out the 30. There's absolutely no problem with doing that. I have 40 years of AC/Heating/ and Electrical servicing behind me to make this claim. Keep it and your prongs will last a lot longer. Besides,,,someday,,,,you might get a 50 amp system.