Originally Posted by EricInColorado
The geek in my thinks designing the hybrid unit is a fun Thermodynamics problem. (Sad thing is, I'm fascinated by thermodynamics, but never took the class while getting my BS in Civil E. That was dumb.)
Interesting. Thermodynamics was a required first year Eng course for us, before we supposed to pick a particular branch of Eng to study. (Myself? I picked Comp Sci. Turns out I wasn't a very good Eng, but I did have a knack for software.
I don't know what comes in the RV, but in my studies to replace the home HW tank I've found they come in two flavours:
1) Constant burn - Flame turns on when water flows, turns off when not. Rate of flow controls amount of heat transfer. In this system, the less the HW is turned on, the hotter it gets.
2) Variable burn - A thermocouple measures the temp of the incoming water supply and adjusts the flame height accordingly. More expensive option but produces a more constant temp on the output side.
For the hybrid to work, you'd want to follow the design of #2.