(The first in what may end up being a series…)
It is only at the end of your shower that you figure out how to work the water heater.
In this case, at a hotel in rural Nepal, the stupid thing kept heating up and then turning off, so I had to continually turn the hot water tap off and back on again to restart it.
Turns out, I think it was overheating and shutting itself off as a safety measure. I changed the center dial from all the way on “Winter” to halfway to “Summer” and the water didn’t heat up to 45°C but it also didn’t turn off and stayed at a comfortable 37°ish.