Insufficient tankless electric hot water flow

[5030tinkerer]

You've actually hit upon another drawback of the tankless unit - the manufacturer claims that the unit cannot take preheated water warmer than 86 degrees. The Tempra 36 unit says it can take incoming water up to 107 degrees. Apparently, neither unit will come on at all if the water is warmer than their spec.

The coldest temperature setting I've been able to find on an electric storage tank unit was 90 degrees. Does anyone know of a 50 gallon or so electric that has a setting colder than that?

 

[Highbeam]

Maybe consider a tempering valve like they use in Forced hot water heating systems which introduces cold water to the flow to maintain a set temp. I like the idea of using a tank heater as a preheat.