Question: Here's the deal: I want to capture the heat from the stove's flue and run it through a Heat-Exchange box ( a plenum?). If I hook it into line with the Central heating system (HVAC) then I can (or should) simply turn on the Fan and circulate the heat throughout the house. Answer: In many cases this does not make sense. There are wood burning furnaces available that can do the job much better than a home made rig.The main reason is the limited amount of heat exchange are on a regular woodstove. This will provide only a small amount of heated air, much less than the fan on your HVAC system is used to handling. The result will be air that is not warm. Another problem is that, if the stove smokes, this air will also be drawn into the system. Best to use each type of stove for the use i was designed for.