This particular model of bosch dishwasher uses an internal float to determine when to cut off the water, rather than just a timed amount of controlled flow.
The hot water heater has no tank, it only fires up the heating element when the flow rate is above a minimum amount, in this case .5gal/min. The dishwasher draws only about .45gal/min and so it would get cold water only.
Currently I do the following:
1. run the hot water in the sink until I get hot from the tap. This fills up the pipe to the kitchen with hot water.
2. start the dishwasher.
3. run to the basement and stand next to the water heater.
4. When I hear the water flowing due to the dishwasher taking hot water, I cut the hot water heater supply feed, and then turn it on, and the resulting surge is enough to kick the water heater into action. It then has enough flow to keep burning.
5. wait 12 mins for the next cycle.
6. repeat step 4.
7. wait 41 mins for the next cycle
8. repeat step 4.
9. breath a sigh of relief and wait until the next time I need the dishwasher.
The problem is that the dishwasher can't get the water heater started on its own all the time.
The dishwasher is not really happy trying to heat up the cold water that results from the tankless heater not running. It is just cold water.
Basically, if I could make the water surge when it starts, or flow >.5gal/min, it would be fine.