Mosaic
Well-Known Member
Ok, as is typical in 3rd world countries; our local Stiebel Eltron tankless water heater dealer sells new units for $350USD and replacement flow sensors for $50 USD.
Also, they have none in stock and cannot say, if ever, they will restock.
Thus is born the need for a substitute.
My poking around has revealed a 3 pin plug flow sensor similar to a muffin FAN RPM capable power plug with a middle wire providing around 100 to 500Hz 5V square wave as the speed. Note the pic in the link below.
http://www.stiebel-eltron-usa.com/dhc-e.html
Now all we need is a 100Hz+ signal to enable the water heater as it's water temp is controlled by a temp sensor on the output. A fixed 100hz won't do since the temperature is measured on the copper pipe well away from the actual heater coil and could burn the heater coil with no actual water flow.
So I am considering something like this:
http://www.discovercircuits.com/DJ-Circuits/h2oflowindicator.htm
based on piezo sensing vibration.
As a note, the actual flow sensor has a little spoked water wheel spinning a cylindrical magnet with a hall sensor pulse switch in the housing detecting magnetic poles.
Advice is needed.
Also, they have none in stock and cannot say, if ever, they will restock.
Thus is born the need for a substitute.
My poking around has revealed a 3 pin plug flow sensor similar to a muffin FAN RPM capable power plug with a middle wire providing around 100 to 500Hz 5V square wave as the speed. Note the pic in the link below.
http://www.stiebel-eltron-usa.com/dhc-e.html
Now all we need is a 100Hz+ signal to enable the water heater as it's water temp is controlled by a temp sensor on the output. A fixed 100hz won't do since the temperature is measured on the copper pipe well away from the actual heater coil and could burn the heater coil with no actual water flow.
So I am considering something like this:
http://www.discovercircuits.com/DJ-Circuits/h2oflowindicator.htm
based on piezo sensing vibration.
As a note, the actual flow sensor has a little spoked water wheel spinning a cylindrical magnet with a hall sensor pulse switch in the housing detecting magnetic poles.
Advice is needed.