This is my design for an open source tankless water heater. It's going to be pretty simplistic so it's easy to replicate and any help/advice would be appreciated. Honestly I'm better with software than hardware engineering so I'd really appreciate help when the time for board design comes around. The initial design was done in paint in a few minutes I'll make a better one soon.
I have been going over designs in my head for the past week or so and have realized, I can't draw or model very well. I can explain everything but can't do a schematic so I will (for the moment) stick with what I can do to convey what this is.
Flexed copper tubing is inside the main housing, probably about 8 "wavelengths" across with ~2.5" spacing.
The three (as of now) coils should be positioned at the beginning, at the center peak, and the end.
The flow rate sensor will be hooked into the arduino that controls voltage to the coils and display on the LCD. Obviously the faster the water the higher the voltage to the initial coil while the center and ending coils will get the voltage amount based on the data from the temperature probe in the outlet of the unit.
The transformers that are going to be needed to run the induction coils can be mounted to the housing for proper grounding and could even be placed at the top with a few holes drilled for air cooling.
I'm going to have a max temp of 175F set up since that seems to be standard with most water heaters I've seen so once the water in the outlet hits the programmed max or the absolute max the voltage in the coils will remain steady to keep the water heated. When there is no flow the unit will be completely shut off (in terms of heating) and I'd like to try to put the arduino into sleep mode and use an interrupt, that goes off when the flow meter starts moving, to bring the unit back up so it uses less power. The whole assembly could probably fit into a breaker box housing with little to no modification which would also help keep the cost down and make it a bit more available.