Furnace started acting up so it was neccesary to install an alternative means of heating water. Winter is over and furnace will be replaced later this year. Anyway I got the biggest tankless WH they sell. It has 3 copper heaters and requires 3 double pole 40Amp breakers. It supposed to turn on with only a quarter GPM flow. I had 1 GPM at the kitchen faucet and it was not turning on. Called their service dept and they said remove all the airators in all the faucets. Did so and it turned on at every faucet except the 2nd floor one. I imagined this might have increased the flow another quarter gallon a minute. I got the WH temp set to 140 def F and the water still isn't hot enough at any of the faucets. But on a hot day once it was hot enough to take a shower. I suppose this was because the cellar was warmer. The heater is about 20 feet from the water pump inlet through the foundation. So as it stands, the heater's flow switch is no where sensitive enough to turn the thing on at under 1 GPM. And when it does turn on. The faucet has to be wide open. The heater does not heat the water sufficiently even when set to 140 degrees F. I could increase the flow by changing the 1/2" 20' pipe supplying the heater to 3/4" pipe. Also I can insulate all the pipes going in and out. But darn- the fact that the flow switch won't activate the thing until 4 + the advertised flow rate is flowing through it? The heater is wired correctly and passes all the electrical tests the manual says to check with a voltmeter. The unit is a EcoSmart 27. Any help is greatly appreciated.