OWB and indirect tank for combi LP system

[jjs488]

I have a Navien CH 180 combi LP heater with one zone in an ~3000 sq ft home in central Pa. I have purchased a used outdoor wood boiler (woodmaster 3300) with one supply and one return, I want to use a small dual coil solar heater tank(100L from duda diesel.com) as an indirect heat exchanger with tempering valve to heat both dhw and my radiant floor loop with the combi as backup if I go out of town for the weekend. can anyone draw a diagram to show me how to do this? The current setup is shown in this link.

http://media.blueridgecompany.com/documents/BlueRidge_recommended_install.pdf

I called navien and a tech told me it would be impossible to plumb it so the navien unit does not fire, he then told me to call back and ask for another opinion so i'm not quite convinced he understood what I wanted. I cannot afford to pay another winter's propane bill. I need help fast.

 

[heaterman]

I have no idea what your piping configuration is but the simplest way is to pipe a plate heat exchanger into the return line of the gas boiler. Run the gas boiler return through the HX and then into the boiler itself. If the heat exchanger is sized right it should keep the return water temp high enough to keep the gas burner from firing.

On the piping schematic you linked to the best place would be the last tee in the boiler loop and the boiler itself. All water returning to the boiler would be preheated that way.

That being said.....I have no idea how the Navien operates in regard to the domestic water side of the system.