[Richard]

The stove is 220 and so is the aquahot electric heater. When you are on 30 amp both legs are in phase and actually the same leg. When on 50 amp the legs are separate. If you put your voltmeter on a 30 amp pedestal, it should read nothing between the two hot legs and 120 to ground. If you measure a 50 amp plug you should get 220 between the hot legs, and each leg will measure 110 to ground or neutral