Proheat + flat plate heat exchanger to make on demand hot water

[Darkspeed]

I have a 80Kbtu Proheat that I am going to use for bus heat , engine preheat, and hot water. Has anyone used a flat plate heat exchanger to make on demand hot water like this? >

http://turtleexpedition.com/into-hot-water-again/

http://turtleexpedition.com/nice-caravanes-france-1213-2/

http://turtleexpedition.com/watts-thermostatic-water-temperature-mixing-valve-a-perfect-solution/

[scanzel]

With 80 thousand btu's I would think that the unit would suffer from cycling on and off to much. On an X45 Proheat it continues to run for a short time after shut down of start power. How would you get it to start up when calling for hot water. Usually on a demand hot water maker it has some sort of flow sensor that starts the unit and then when flow stops it shuts down. Why not put in a small 5 or 10 gallon tank and do a preheat of that water with the Proheat.

[Darkspeed]

The Proheat has a minimum volume requirement so there would be a small tank inline with the Proheat but it would be an antifreeze / antiboil liquid circuit. This hot circuit would have its own circulation pump. My goal was to use this hot circuit on one side of the plate heat exchanger and run fresh water through the other side. It would use a flow switch to call for heat cycle start.

On another topic I wonder if the proheat could be part of the bus cooling circuit or does it need isolation?

[Oonrahnjay]

      I don't have much info on the Proheat but every one that I have seen used a manifold to provide for circulation selection.  They are basically a series of valves that will allow the different circuits to communicate with each other (i.e. use hot water from the Proheat to connect to the engine cooling system for engine preheat, or use Proheat to connect to the exchanger coils in the water heater for domestic hot water, or use Proheat to connect to the heaters for your house heating system.  I see the use for this, but it may be over-engineering, I dunno.
      My Atwood water heater will heat domestic water with an electric coil (approx 1500 watts, 120V), propane, or exchanger coils.  The exchanger coils are made to connect to output from the engine but hot water is hot water.
      Will you heat the interior of your bus with hot water heaters ("heat exchangers")?