Like Jumbojet stated,we had a 94 Winnebago DP that was set up to run the second stage compressor on the basement AC only when the generator was on,it had 30 shore power20 amp .I ripped that out and replaced the 30 amp transfer switch with a 50 amp,replaced the shore power cord with a Marinco 50 amp twist lock,ran both circuits through the new transfer switch ,ran a new circuit to the second stage compressor with a 20 amp breaker like Jumbojet did.Luckily Winnebago had run a # 6 set of wire to the main panel,I was able to change the main to a 50 amp breaker,I have seen the 94 Vectra with factory 50 amp set up,Ours just did not have it.There are several articles online that show how this is done. If you are not technical savvy I would not attempt it as it requires quite a lot of wiring changes.I have seen people with a roof AC put a pig tail on their second unit and just use an extension cord.Good Luck jg