https://precisiontemp.com/wp-content/uploads/2018/03/Twin-Temp-2-and-Jr-Installation-Manual.pdfClick and look at the install. You will have numerous Hot water lines run thru out the RV for the Furnace zones. IF those hose parts are not used at the units and blocked off, he spent a LOT of money for a Water heater. Do you know if the original unit had a Water Heater or the Oasis system? He may have had the Oasis and replaced with the Twin Temp which would work with the Zone furnace radiators of the Oasis. IF you have a LP powered Furnace, then the unit did not come with a Hydronic system. Doug