Airflow is the other half of a comfortable system: the right CFM keeps the coil happy and every room supplied. Size it two ways here, straight from the equipment tonnage, or from a room's air changes per hour, and get the number in seconds. A field check, not a full duct design. Runs in your browser.
Airflow can be sized from the equipment or from the room, and both belong in a tech's head. From the equipment: about 400 CFM per ton of cooling, so a 3 ton system moves roughly 1,200 CFM across the coil. From the room: floor area times ceiling height gives volume, times the air changes per hour you want, divided by 60 gives the CFM that room needs delivered. The tonnage method sizes the blower and trunk; the air-change method sizes the branch and register feeding a particular space. This tool does both so you can check one against the other.
The 400 figure balances sensible cooling and dehumidification for a typical climate. In a humid region you deliberately slow to about 350 CFM per ton so the coil stays colder and wrings out more moisture; in a dry climate you speed up toward 450 to move more sensible heat. Drop the CFM-per-ton field to see how the airflow target shifts, that adjustment is exactly how the trade tunes comfort by region.
Get airflow wrong and the symptoms are obvious on the truck: a coil frosting over from too little air, a back bedroom that never cools because the branch is starved, or a whistling register from too much velocity. Matching CFM to both the equipment and the rooms is what separates a system that just runs from one that is quiet and even. Confirm the duct that carries it with the duct size calculator.
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About 1,200 CFM at 400 CFM per ton, 1,050 in humid climates, 1,350 in dry ones.
About 240 CFM at 8 foot ceilings and 6 air changes per hour. Adjust ACH for the room type.
No. Too much airflow hurts dehumidification and adds noise; too little freezes coils. Match the load.