Vent two different size tents with one fan?

[Calikron]

So I googled this question but didn't come up with an answer specific to my situation. I have two tents, a 4'x2'x5' I plan on using for veg and a 5'x5'x7' I'm going to use for flower. I have an 8" hurricane fan rated at 735 cfm that I plan on using to vent both tents through their respective light hoods.

As the plan stands now, both tents will be ducted to a plywood box holding an appropriate size carbon filter (Phresh 8"x24" @ 750 cfm), which will be attached the the fan and exhausted outside.

I have read that this design works, but the smaller tent has at best 6" ducting ports, while the bigger has 8", so my question is will the two different size ductings require me to change anything when it comes to restricting the airflow from the bigger tent, or will the power of the fan be enough to overcome the restriction of the smaller ducting? Both tents will be using passive intakes, and the air will be passing through both hoods.

 

[WeedFreak78]

Either restrict the 8"passive intakes down to 6" or put a damper on the 8" exhaust line so you can balance the airflow between the tents. I'm assuming airflow in each tent will be: passive intake>open tent(no ducting)>hood>out through duct work. Then I'm assuming both tents are tied to a Y, then to the filter/fan combo?

That's a huge fan for that space. Your area is 215cu ft, you only need a ~75cfm fan to get full air exchange every 3 minutes. I have a 440cfm fan for a ~600 cu ft room and it never runs over 75%. Even if you run it at 50%, I think you could be sucking the sides of the tents in, I've never used a tent, but I've heard too much fan can be an issue.

 

[Calikron]

Either restrict the 8"passive intakes down to 6" or put a damper on the 8" exhaust line so you can balance the airflow between the tents. I'm assuming airflow in each tent will be: passive intake>open tent(no ducting)>hood>out through duct work. Then I'm assuming both tents are tied to a Y, then to the filter/fan combo?

That's a huge fan for that space. Your area is 215cu ft, you only need a ~75cfm fan to get full air exchange every 3 minutes. I have a 440cfm fan for a ~600 cu ft room and it never runs over 75%. Even if you run it at 50%, I think you could be sucking the sides of the tents in, I've never used a tent, but I've heard too much fan can be an issue.

Yes, the routing of the ventilation you described is correct.
I went with 8" fan thinking I would rather have more than I need and dial it down. Plus I got it cheap. So I guess a fan controller is next on the shopping list. Or maybe an inlet to the open room with a damper for a quick, temporary fix?

 

[Roger A. Shrubber]

i vented two fairly even sized areas with on fan, using a y, and i found that the straight part of the y got at least 75% of the suction, while the angled arm got at best 25%. i'd try experimenting with how you have the y hooked up first and see what happens.

 

[VegasWinner]

The duct for the smaller tent needs to be 1/4 size the larger tent to get equal pressure in both tents negative. Example, 3" duct from the smaller tent to a combiner with a 8" duct from the larger tent. The smaller duct will restrict air flow from the smaller tent to 25%,and the larger duct will allow approximately 75% of the air to draw from the much larger tent, creating negative pressure relative to both tents and the pump running at 735 cfm, that would be about 180 cfm from the smaller tent and 550 cfm from the larger tent. peace