If it only has one ac unit and you close the vents that are directly on the ac unit all of the round ceiling vents should blow air. If you open the vents on the ac unit it's self you won't get much at all out of the round vents. There similar to your house where you have to adjust each vent to force more air where you want it to go. If you keep the ones over where you want the air wide open and partially or completely close the others it will force more air to the open ones. If you have two or more ac's they will be independent to each ac unit.
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