My aqua hot has one exhaust pipe coming out, about 2" in diameter, not two as the OP has described. That said, if I leave the diesel switch on at night it will fire up for a few minutes. To prevent that, I leave the electric switch on and the diesel one off at night. If my batteries draw down, the generator will come on with the autostart but it will run for about 30 minutes to charge the batteries back up, not only for a few minutes...without more information, we're only guessing anyway.....wonder why the OP didn't just go over and ask...:h.....Dennis