Long time listener first time caller. I've searched through your forums somewhat and haven't really found the answer i'm looking for. Forgive me if this was already asked. A little background first.
I burn quite a bit of wood in the winter, generally about 4 cords a year. Pretty much use it for a primary heatsource, sweep the chimney a couple of times a year since I choke off the box at night. Usually the heater will kick on about 5am and run for a bit until I restart the fire, this has saved me a bunch of money on propane. I also frequently check my smoke and carbon monoxide detectors too. So... that should cover basic safety questions.
On to my setup and question.
I have a woodstove insert with a heat exchanger and a pair of 3-speed 200cfm fans. The insert is roughly 20 years old made by Long Manufacturing (since out of business) and came with house. I've happily used this system for the last 8 years but one of the motors went out. These things are $150 a pop and I'm afraid the other one is one it's way out too. Instead of dropping 300 clams, why not add some ducting under the hearth down through my crawlspace and tap into the hvac return? I would love to be able to reduce the fan noise in the room also. I imagine I would need a gate at the tap so when the heater is on, the return is not getting air from the fireplace duct.
Anyway, just wanting a few experts to chime in and test the validity of this idea.