Have a floating neutral 240/120 volt 30 amp plug. Wanting to back feed into a new house panel, main electric waiting on power company to set poles. Hooked the 240 volt. Wires to panel and the ground . At the generator with panel breaker off , 240 volt between the two hots and 125 volts to ground. With panel breaker on had 240 volts between the two hots and 240 volts between one side of the 120volt to ground the other side was 120 volts to ground. I think it has to do with the floating neutral but I don't know. The 4th wire 120 bot to ground at generator was not connected .