On our Suburban Brand hot water heater we have an On/Off switch located outside the RV at the inside of the exterior access panel. Turn this switch on AND the inside panel 120V switch on and you will have H2O heated by electricty, only. Also, on the inside panel there is a 12V switch that controls the LPG side of the heater. Turn this 12V switch on alone and LPG heats the H2O. Turn both inside switches on (12V & 120V) and the H2O will be heated by both LPG & electric at the same time (provided the On/Off switch inside the exterior access panel is in the On position). Hope this helps.
Lakeside
