I've got a high efficiency natural gas furnace, and a wood stove in the same room. I get wood for free, so I'd like to use it to supplement heating with natural gas. The problem is a severe lack of air circulation, that particular room gets very hot, but the air doesn't circulate to the rest of the house, because the furnace's air circuit is closed.
What I'd like to do is disconnect the cold air return from the air intake of the furnace, and have the furnace intake hot air from the wood stove. The returns can still send air back to the furnace room, but not directly to the furnace. I can close the door to that room, to effectively seal it and use it as a buffer/pre-heater for the furnace air.
I don't see any issues with this, as I'm not breaking the furnace circuit in any way, just adding a large buffer area. Any excess combustion air that the wood stove requires will be pulled in through the air returns (I may eventually add a fresh air supply for the wood stove if I have draft issues), and the furnace can be run in fan-only mode to pull just air from the wood stove, or run in heat mode, but will operate more efficiently as the air it is heating is already very warm. I don't foresee that I will generate negative pressure, as there are air returns, so I can't see how this could be a concern of pulling exhaust gases out of the wood stove.
Are there any issues with this that I don't see?