This is concerning the Lexi 283ts. After reading previous posts about other Lexi models I was able to find the bypass for the 283ts. There was NO info in the generac owners manual, so I tried to find mine, if there was one.
For, at least the 2012 years (I'm sure other years are the same), you have to remove the drawer in the bathroom, the one next to the wall. Just flip the slide levers and give it a good pull and it will slide out. When it's removed, you will see the back of the WH, with the styrofoam covering. Look toward the back of the heater tank and you will see the hoses feeding into the unit. One of the hoses has a bypass lever/valve that turns 90%. And there you are.
Didn't know if it even existed, and you cannot possibly see it with the drawers in the bathroom or kitchen in place. After reading posts about the "hidden"valves, was determined to find mine.