I have a 15 year old "Nikota" 3000/3500W generator. It has performed pretty well as a home backup during power outages. I've always used 120V only via extension cords through the window and all around the house. This generator has a selector switch for 120 vs 240 operation, a 120 outlet and a L14-30 connection. (There are no GFIs). I understand the L14-30 is what is used to feed the house though an inlet box connected to the house main panel through a 240V breaker controlled by an interlock. I decided to install this set up. Before connecting the gen to the house, I tested it at its 240 receptacle. The generator produces 240 across the "X" and "Y" terminals but does not produce 120 from the X or Y terminal to the neutral. The wiring diagram is on a label on the case (hard to read). It appears that the neutral terminal of the L14-30 connection isn't connected to anything inside the generator! I opened the case and confirmed that is true. I got one opinion that this is a "floating neutral" generator and it needs to be connected to the house in order to obtain a neutral bonded to ground. I connected it up to the house with only two 120 circuit breakers turned on (one X and one Y) with no loads and measured the voltage. It was not 120 or zero; It was 28V. When I tuned off one circuit breaker, the voltage on the other dropped to about 14V. Any ideas? I was going to try a few more tests but thought I better quit while the gen still functions on extension cords and the house wiring is undamaged! Attached are pics of the wiring diagram.