Fresh Air for grow Box

May only need fans pushing air though it vs AC, depending how much heat is being generated and the power of the ac unit BTU's, it might be overkill. I'd still have different fan going as you don't want to rely on the ac's fan to be an air exchanger, Its recycling air and cooling it, not introducing/pushing fresh air. Its also not designed for that purpose so just won't be that good. Almost better to run it outside the box and let the extractor pull in the cool air and then vent outdoors, more even and avoids cold spots in the tent. Good Luck!

a hygrometer and atmospheric co2 levels would be required to be certain. As long as not too humid, which an ac helps lower, and keep highest co2 levels possible. if adding co2, that could be a wrinkle causing adjustment to this suggestion... should be sealed up with climate control to maximize your co2 benefit / more easily maintain 1300-1400 ppm or whatever it may be. otherwise, i guess consider how often it runs -- which will vary based on daily temps -- and make sure the recirculation maintains some minimum that you want on a cooler day.