I purchased a 9.6kwh tankless water heater (stiebel eltron) to find that it's minimum water flow requirement (3 liters or 0.79 gallons / min) makes me have to open several outlets in order to to trigger the device into heating. The problem is I live in a remote area of costa rica and have no means of returning the unit or the likes. I am looking for a solution to rig the unit so that it will work with a significantly lower water flow minimum. I will assume all risks as the unit as it stands is useless to me and the money wasted. To counter the 'excessive heating power applied to a lowered flow I was thinking of disconnecting the second live wire and feeding it only 110 volt instead of the 220.. . But again I have no idea if that would make sense. PLEASE HELP--thank you!

I agree... that minimum flow of 3 liters/minute is way too high.

Only thing I can think of is to install booster pump before the heater. It will push water faster through the heater making water to flow at higher rate.

Does the heater activate when you open tub faucet ( tub spout only ) ?

Also, try to remove flow restrictors and aerators from your faucets and shower heads.