[C320-list] Power supply for AC install

[Alan Goodman]

Hello all:  I am self-installing my air conditioner over the next month.  I bought a 12K BTU from Flagship Marine.  I need to install a 20A 120V circuit to supply the unit.  I have found a source for the exact same breaker as the factory installed AC breakers.  I rather not have to install a second shore power circuit to supply the power, but on the other hand I'll be installing a 20A breaker in a 30A circuit.  Obviously I should not run the water heater (about 12 A @ 120V) while the AC is on.  This is a downside I can live with.  Are there other considerations I should consider?  My question is what have others done? 

Alan Goodman   Hull #67  Holland, Michigan