I received a call from a 13 unit Motel today and they told me that when all the units are rented out, they run out of hot water. When I arrived, they showed me how 3 years ago some other plumber removed the propane heater and installed a 120 gallon 240 volt electric. Besides that stupid action it is an A.O. residential model which means they would have NEVER been covered by ANY warranty in their commercial application. I checked and there is only 240 volt single phase electric available. There is no natural gas in the area and they do not want to have a propane tank. They don't have much available space for an extra heater so I was thinking of installing a 50 tall next to it. Have any of you done this and if so would it work better as a "pre-heater"? I figure there will be some trouble if I pipe the 50 in parallel with the 120 gallon heater.