Don W wrote in news:QbfSf.39468
:

I think there has got to be a way to make it work like its
supposed to--even with raw water cooling.



Another point that needs investigating is the water pressure differentials
around this system the hot water hoses are hooked to.

If the supply hose can be connected to the high side of the thermostat, the
thermostat will provide pressure to drive water through the water tank.
However, if you look at the water inlets to the exhaust, you'll see it's
not just pouring every available gallon of water into the waterbox to flood
it. There are "jets" built into the manifold that keep the water from
swamping into the exhaust and flooding back into the open exhaust
valves/ports. They're like spray nozzles. If the outlet of the hot water
heater is hooked to the plumbing supplying these nozzles, there is
considerable back pressure fighting against driving the water through the
water heater's heat exchanger, which is counterproductive. I bet it's a
bypass through the water heater, not a full-flow system, like the heater in
your car.