there is a 3 position sliding switch...1,2,3....
indicating the heat setting....you then regulate temperature of the water with water volume ...easy to figure out ... i rigged my own solar water heater...works great...used pex and a solar circulating pump...resulting in instant hot water at each spigot...nobody washes clothes nor dishes in hot water ....except me ...lol
i do have 2 instant hot water heates that i use in extreme cases...such as a house full of company that would exhaust the 65 gallons of solar heated water....i had 3...but one spring a leak....lots of americans take a lot for granted...including me!!!
i think mr rye understands...lol