There Are Simple Way's to Get it Done Right...
What shophound & others stated is true.
Those that live in very cold climates can have a different equation, whereby the usually oversized N-gas & fuel oil heating equipment may require considerable more airflow than the cooling system.
My brother's oil furnace has around a 112,000-BTUH output, he has a 1.5-Ton A/C with a 2-Ton TXV metered evaporator coil.
The furnace requires around 1130-CFM airflow to keep heat-rise from going above 90-F max.
His cooling system requires 675-CFM, & for the heating mode the coil has a limit of 900-CFM before the static pressure skyrockets.
Even with the coil raised at least 6" above the furnace & a third HP motor, with his duct system I doubt it could deliver much more than 875-cfm in heating mode
On top of that the furnace has a mere quarter HP belt drive motor, later they went to a third HP motor - on same model but even smaller BTUH oil furnace.
The evaporator was installed directly on top of the furnace causing a bad airflow restriction between the coil & the huge Ht-EX.
On top of that the A/C is low on refrigerant... non of these problems have been resolved, though the solutions are obvious! - Darrell
