Prep Work... How much ventilation

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Apr 10, 2011
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I'm gonna use a 600W HPS in a 40"x40"X78" tent, and have the ballast outside the tent.

I'm going to pull fresh air from outside through the hood and back outside to cool the bulb. A closed loop for cooling the light. How many CFM will I need for this? I was thinking about a 340 CFM ecoplus inline or 465 CFM ecoplus blower for this. Will they be enough?

Then, I need to vent the tent itself. It is approx 72 cubic feet. I've read anywhere from once every 3/5 minutes to 3x per minute to vent the tent. I was thinking an ecoplus 180 CFM blower for this. Intake will be passive. Sound right? What about one of those cheapo duct booster fans? SInce this is not cooling the light, just clearing out the air, will one of those be enough? It will also vent outside.

The grow room is on the second floor, so I'm not too concerned about odor outside, but if it proves stinky, I'll clearly have to upgrade the exhaust and add a filter.

Anyway, I'm sure I'll have more questions, but for now thanks for input advice!!
No, the duct booster fan will not work. They are not meant to be stand alone fans--they are meant to assist larger fans on long ducting runs. Other than that, I think your plan sounds like it will work just fine. You may also find that you need a carbon filter and you will need a centrifuge type fan for that.

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