Battery back up for tankless...

[Frank DuVal]

It is a flow switch. If water flows the units turns on.

So this would work IF the flow switch is wired to control power to the water heating appliance. A flow switch internal to the unit would still rely on the unit being ON and waiting for the flow switch to close, turning on the burner solenoid. All other electronics is on all the time.

 

[hillbilly1]

So this would work IF the flow switch is wired to control power to the water heating appliance. A flow switch internal to the unit would still rely on the unit being ON and waiting for the flow switch to close, turning on the burner solenoid. All other electronics is on all the time.

It’s probably an external water flow switch that turns on the inverter, which in turn powers the water heater. There would probably be a delay in getting hot water, but would save the batteries, at least that’s the way I would design it.