AC Fan

[Technician1002]

Excellent diagram Dewey-1. It even shows swapping the ends of the start winding just as I described.

Forward


Reverse

[Zeus]

No one has mentioned creosote buildup, creosote and ash would bind up the motor in no time.

I'd run bevel gears into the chimney, and have the motor at 90 degrees to the chimney. A sealed set of bevel gears I should add.

[Technician1002]

Some high efficiency furnaces use a blower placed at the exit of the heat exchanger. To deal with products of combustion and heat buildup, the motor is placed outside the flue. The firebox and heat exchanger run at reduced pressure due to the fan. The hole where the fan shaft goes into the flue box is below atm pressure due to the fan. This prevents combustion products from reaching the motor. A pressure switch on the combustion chamber prevents operation if the fan fails.