This is the tubing: AC Infinity Flexible 4-Inch Aluminum Ducting, Heavy-Duty Four-Layer Protection, 8-Feet Long for Heating Cooling Ventilation and Exhaust https://a.co/d/0gj3nlg
As far as bends, you can see it from inside to tent going out. From there from it’s an almost straight shot to the duct going outside.
This is my first time adding any intake or exhaust fans. This is my second grow and my first one started with no tent and zero intentions to be a indoor grow.
I added a few fans inside the tent and the temps were good but it was also a lot cooler out when I started.
I am reading what you wrote and the only thing I’m confused by is do you think I have the intake and exhaust fans connected?
If you’re going to a roof vent, you might be best-off hanging the exhaust fan outside directly above the top port of the tent, do a 4" to 6" step up flange on the intake-side of the fan & connect that directly to the tent port. You could stay with 4" ducting going to the roof vent, or do another step-up flange on the exhaust side of the fan & pick up a little more flow by going to 6" ducting to the roof vent.
6" intake port is probably too small for that exhaust fan, but you might be losing enough flow from the exhaust tubing that it is big enough for those losses. You would have to do some flow tests to see where to make improvements.
Aerodynamically, your fans are connected in series. You’d have around the same flow rate as you do now, if you took the 6" intake fan & connected it directly to the intake port of your exhaust fan & left the 6" intake port open.
I did upgrade to the AC Infinity 8 inch fan and bought their oscillating fan. Everything seems to be doing great. The weather is also going to be cooler the next few days so that should help, we’ll see if it ramps back up to the 90’s and 100’s.
Thanks, not a problem. Post if you need more help checking & optimizing your flow.
T8" might be a little overkill, but it will pull twice as much CFM at static pressure as a T6". Only thing to think about is at full power the 8" pulls around 2 1/3 amps, & the 6" is .95 amps.
Do you know how hot your lung room gets when it is hot out?
I lost both of my outdoor plants to something, they were not looking great, not sure if it was heat outside or something else. I fed and watered by weight regularly. Their terps seemed to just disappear one day and I ended up making the tough decision to toss em out.
Thanks to everyone who followed this thread and helped me learn.
My next grow will be all indoor with AutoPots, feel free to follow along.
Beyond that, for 2.3 amps, the 8" fan is not going to move much air through a 4" hole. (For reference, my couple of different exhaust fans that I bench-flowed for a couple different tents needed around 3x & 5x their intake port areas respectively in tent intake areas, in order to reach their max flows at 100% power.) Your 4" fan is also burning around an additional amp on top of the 2.3A from the 8" fan, & it is going to flow a little more cfm if it had been restricted by a smaller intake area which got bigger, but if so, then that’s all it needed. A bigger intake area. It might want more. The 8" fan definitely wants a lot more port area to flow through than 4" worth. 8" fan flowing into a 4" hole? With a 4" fan in there taking up even more area? Way too small. Plus 4" ducting adding even more negative pressure/ drag? Net gain of running fans in series will probably be a little more flow than before, but total flow will never be “max cfm of fan1 plus max cfm of fan2”, even with both at 100% power. You can only add their max flow together if you run them in parallel (side-by-side) & flowing in the same direction, & run them at 100% power, & with enough intake area to allow for that amount of airflow. If you’re running both of yours at max power in your setup, then you’ve got around 3.25 amps going into two fans & maybe getting just a little more flow than what the 4" can do in an optimal setup.
I think if your intake air is not too hot, & your target temp range in the tent is reasonable, then you can get to where you need to get to with one 6" proper exhaust fan such as a 6" version of what you have, plus a minimal run of straight 6" ductwork, & plus a tuned intake area.
But if you want to run the 8", give it 8" exhaust ducting with optimized install, & since I think it might be over-fanned for the tent, I’d probably see what it could do at 50% power & tune the intake area for that power level first, then go from there if it needs more power & more intake area.
8" fan clamped straight to the big tent port on top, keeps everything straight & deletes the ducting between the fan & the tent, but you’d probably want to re-route the cables currently going through that big port to another port. Put 8" ducting going straight from the fan exhaust port to the roof vent, & you might have to do something at the roof to handle the 8" ducting without hurting the flow. If it dumps into open space, that is ideal.
As for dialing in the intake port area, you want to have enough intake area to get into the sweet spot on the diagram, but not too much to go past it & into zero static pressure:
You can do some simple diy flow tests with a diy swing gauge for better accuracy, or just look for the tent to lose suction as you increase intake area. Once you lose suction, then reduce intake area slightly, & you should be close to the sweet spot for whatever power level you are running the fan at. Normally I would say to do these tests with the fan at 100% power, but the 8" might flow too much for your tent if you give it enough intake area, so I might start by dialing in the intake area to be in the sweet spot while running the fan at 50% power, see if it can do the job, if not, then go to 75% power & dial in the intake area again, & then if need be, go to 100% power & dial in the intake area a final time. Do it that way & you might avoid cutting holes in the tent if you don’t need to. I don’t know how much intake area is built into your tent. There might be enough already. But if sending 100% power to a fan like an S8 while giving it enough intake area to support max flow at 100% power, & it is not cooling your 3x3, something(s) else is wrong.
Here is a flow chart for Vortex S-Line which are hybrid centrifugal fans like your 8". It shows negative pressure vs. flow. As negative pressure builds, flow falls. Your fan probably traces similarly to the s-line since they are both hybrid axial/centrifugal designs. The 8" fan is the orange trace. These charts show the fans running at 100% power always, but I circled in yellow where the 8" probably would be flowing at 50% power (but at static pressure), probably around 400 cfm or around where the 6" (blue line, same chart) would be flowing at full power, static pressure. Would 75% power move you halfway up the orange line? Probably somewhere around there. The linearity looks like it might fall apart going the other way below 50% on the hybrids.
Here’s how their VTX full centrifugals run: Linear drop-off as negative pressure builds. These are better if you have a lot of negative pressure that you can’t avoid, such as a very long duct run. If you look at the 4" centrifugal here (blue line on the left), it outflows the 6" hybrid from the first chart at higher negative pressures. Once the negative pressure drops enough, then the 6" hybrid starts to flow more.
