I had an energy audit done on my home and the auditor mentioned that his personal hydronic set-up has a "dummy" indirect tank that is at the end of the return of the primary loop and the water coming in from the well goes through the heat exchange (or vise versa with the boiler water going through the heat exchange). Either way he is preheating the well water before it gets to the indirect with another indirect and was claiming that it helps to keep the boiler in condensation mode because of a lower return temp. I found the idea interesting and was hoping to get some comments on it.