Enough cfm?

[greenfriend]

Hi all, I'm setting up a lil grow and in the interest of keeping my power bill lower I want to use just 1 fan for all ventilation. I need opinions on whether the one fan would provide adequate airflow. Have 3 1000W in 10' x 10' room, using 8" aircooled hoods. I want to split 12" ducting from the 1300 cfm can fan to 12" ducting connected to 6 ft. carbon scrubber, and 8" ducting connected to the hoods. So the one fan will be exhausting both the heat from the hoods and pulling odor free air out of the room, will it work?

 

[nouvellechef]

Be fine in winter months. Highly doubtful in summer though. Thats if the 3k watts are in a single line series of each other. As in hood>duct>hood>duct>hood. If not like that, between the bends and a carbon filter, be only a fraction of that 1200cfm being used. I use 440cfm for each set of 2k watts with carbon filter, no bends though. And real short duct length from start to finish and even now with 80 degree outside temps, it does fine.

 

[ShOrTbUs]

how much did your fan cost? b/c i was looking through some websites and have seen 12" fans with 1700 & 2000 cfm. if the one u got is around the same price, might be worth it buying a differen't one to give you that extra boost u need

 

[greenfriend]

Thanks chef, this run will be august-october and very warm most of the time and there will be a 90 degree bend in the ducting, so ill run another fan i suppose

shortbus: bought the fan 4 years ago, not really sure of the cost now. while running 1 big 2000 cfm fan is probably more efficient, I'll probably use an 8" inline ive already got for the 3 hoods.

 

[The Hemp Goddess]

I would think that if you are running these in series that the air going past the last light is going to be quite hot and have almost zero cooling capability. I am amazed how hot the exhaust air is that passes over a single 1000W light.

You are running 3000W of light, and you are concerned about the power an extra fan is going to use? That seems kind of like stepping over dollars to pick up dimes. The power used by the fans is a fraction of the lights, but good ventilation is almost as important as your lighting. With 3000W of light, do not scrimp on your ventilation. If you cannot afford the power, I would recommend taking one of the lights down and getting adequate ventilation.

 

[4u2sm0ke]

You are running 3000W of light, and you are concerned about the power an extra fan is going to use? That seems kind of like stepping over dollars to pick up dimes.

:aok:

 

[Old_SSSC_Guy]

nouvellechef really nailed that one good (smile). But I have more words... heh...

I got one of the 1200 CFM Vortex fans off Ebay for like $130, a really cheap deal. The 12" connectors and reducers ended up more expensive than the fan.

Like nouvellechef said, the straightness of the runs is critical. My first setup I tried running 6" ducted hoods in series; all that really did was bake the lights at the end. Then I moved to running each of three 1000w HPS feeding through 6" tube with one 90-degree elbow and two 6" T junctions. Kinda like a letter F on its side. Those junctions decrease the air flow in a major way, so I'm glad I got the 1200 CFM unit.

I use three carbon scrubbers, each maybe 3-foot long with 6" outlets, one for each light. Air is pulled individually from each scrubber, thru the light, into the F-like manifold of 6" insulated flexi duct to the fan. The fan is mounted inside a box about 3-foot square with two 6" intakes and two 6" outputs. One of the 6" input runs also has a 6"-to-4" reducer for a 4" duct over the ballasts.

I figure I am only moving maybe 700-800 cfm total through the fan when I'm lucky, the fan is running at maybe 60%-70% speed. That's just perfect for me, over twice what the 10x10 room needs and not running the fan at full duty cycle.

You need a speed controller for that monster fan, regardless. If you run them full bore they sound like a jet engine in a small grow. And you have to have fresh intake air matching the amount you exhaust. And the system will leave a large heat footprint at its exhaust point; which is why I split into two 6" outputs. Its also why (to me) you have to use insulated duct work. If you use open metal duct work the radiated heat is no small deal.

As the venerable Chef also said - its great for winter. Really works like a charm. But in hot weather it works against you. If your outside air is like 90-100 degrees you are screwed; you have to turn it into a recirculating system or be able to blast in as much cold air as you exhaust.