Hi, I recently built a grow box. I modeled after Badgr's jumbo grow box (refer to his post for visuals) I have two 4 inch tubes one going from the utility compartment to the flower chamber and the other to the veg. chamber. Air is sucked from both chambers up the two tubes via a 8 in. s & P fan going straight out as exhaust. My question is how I hook up the two 4 inch tubes directly to the 8 inch fan to increase efficiency? I have not been able to find any connectors that do such a thing. I was thinking I might have to build my own little converter box, but I have limited space. Any ideas? If you referred to badgr's post he just has the fan sucking air into the utility chamber not straight to the fan.
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ventilation question
- Thread starter fifa
- Start date
Can you add more tubes? 2 4" tubes do not provide enough air flow for an 8" fan. Not even close.
Once you increase your intake sizes you'll notice the fan becoming a lot more efficient.
smokinshogun
Member
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I may bebut...
2" circle = 3.1 sq/in
4" = 12.6 sq/in
Your intake is half the size as the exhaust...
You need at least 6 (most would say 8) 2" holes..
common mistake
I have 2 eight inch by eight inch square intakes into the cab(one for each chamber). Then, this runs through the two four inch tubes (one from each chamber the veg. and flower). So, air is pulled in through two 8X8 squares, then runs up through the two four inch tubes into the 8 inch fan. I am simply looking for a way to convert two 4 inch tubes into one 8 inch tube into the fan. So you think I need two 4 inch tubes for each chamber instead of one?
The 8" intake provides 64 sq inches of opening area.
The 8" exhaust evacuates the air through 50.25 sq inches of area.
Assuming you didn't have the upper chamber, the two 4" pipes leading to the exhaust has choked your flow down to 25 sq inches of flow area.
And to add to the problem your fan is pulling on two separate areas of flow. If you have the same two pipes leading form the middle chamber up to the exhaust as well, then the exhaust fan will pull harder on the middle chamber than it will on the bottom, and this is due to natural physics which dictates that air will travel through the path of least resistance.
If it were me...
I would put BOTH square openings in the bottom chamber. Then I would put enough opening from the bottom to the middle chamber to equal at least 10% more than my exhaust opening. If I use 4" pipes, I will need to have 8 of them leading from bottom to middle chamber, and then another 8-9 of them leading from the middle to the top.
What you want is the air flowing from the intakes to the first chamber, then ALL of that air into the next chamber, then ALL of that air out the exhaust.
If you run separate areas, as in your photos, then one chamber will always be getting short changed, as the fan will pull from the chamber with the lease resistance and neglect the other to a point.
But no matter what, if you don't have the correct sizing of duct going on, you will have problems. (a chamber is a duct, as is any path that the air travels through)
You will never get the set-up you are showing us to work properly. It may well get to a point you will accept it, but it will never be efficient.
The 8" exhaust evacuates the air through 50.25 sq inches of area.
Assuming you didn't have the upper chamber, the two 4" pipes leading to the exhaust has choked your flow down to 25 sq inches of flow area.
And to add to the problem your fan is pulling on two separate areas of flow. If you have the same two pipes leading form the middle chamber up to the exhaust as well, then the exhaust fan will pull harder on the middle chamber than it will on the bottom, and this is due to natural physics which dictates that air will travel through the path of least resistance.
If it were me...
I would put BOTH square openings in the bottom chamber. Then I would put enough opening from the bottom to the middle chamber to equal at least 10% more than my exhaust opening. If I use 4" pipes, I will need to have 8 of them leading from bottom to middle chamber, and then another 8-9 of them leading from the middle to the top.
What you want is the air flowing from the intakes to the first chamber, then ALL of that air into the next chamber, then ALL of that air out the exhaust.
If you run separate areas, as in your photos, then one chamber will always be getting short changed, as the fan will pull from the chamber with the lease resistance and neglect the other to a point.
But no matter what, if you don't have the correct sizing of duct going on, you will have problems. (a chamber is a duct, as is any path that the air travels through)
You will never get the set-up you are showing us to work properly. It may well get to a point you will accept it, but it will never be efficient.
The slimmest answer is to use darkroom vents. IF you have a few inches to spare on each side of the wall, you can use 2 pieces of 90 degree PVC, but that really sucks a LOT of space for the airflow.
I would suck it up and spend for the darkroom vents. That option will last you the longest and be the most effective without doing major re-mods.
Your exhaust size is the key. It is ~50 sq inches. Four 4" PVC Elbows painted black inside, are all that you would need to have enough vent opening, and it be light proofed.
(each 4" opening is 12.56 sq inches)
Wait...you need at least 10% MORE intake than exhaust so add one more 4" hole.
Your bottom chamber is best for flower. If you have the elbows in the divider between lower and middle chamber, that will allow the air into the next level and be light proofed.
Then all you need are holes in the divider between middle and top levels. This will complete the duct run to the scrubber and exhaust. No elbows are needed there as the lights aren't a factor any more.
I would still move the louver in the middle to the bottom and seal up the middle. They are mucho restrictive, to a point one needs to think about double with them.
And you want ALL of your intake air to go into the bottom first and then flow through the proper elbows into the middle, then through the holes and out through the scrubber.
With an 8" and a controller, you can have the very best cab of that size.
Add a dedicated light cooling run with a 4-6" and run just about any light you want.
Then all you need are holes in the divider between middle and top levels. This will complete the duct run to the scrubber and exhaust. No elbows are needed there as the lights aren't a factor any more.
I would still move the louver in the middle to the bottom and seal up the middle. They are mucho restrictive, to a point one needs to think about double with them.
And you want ALL of your intake air to go into the bottom first and then flow through the proper elbows into the middle, then through the holes and out through the scrubber.
With an 8" and a controller, you can have the very best cab of that size.
Add a dedicated light cooling run with a 4-6" and run just about any light you want.
Yea, I have planned all along to make the bottom chamber the flowering. I will be running a 400 W cool tube with a digital lumatek ballast running ventilated seperately by a four inch S&P fan just for the light. In the veg. I am running T-5 Fluros(6 of the tubes) Thanks for all of your input it is a huge help. I was thinking I might get a 12 X12 dark room louver in the flowering chamber where the 8X8 was, then mount the two 8X8 that I already have(from the veg, and the flower) into the middle shelf, (sealing the middle) to avoid running so many tubes, then just cut 8 four inch holes going out of the veg up into the utility compartment. I don't have a digital camera or I would take photos to help show what I mean. If anything is unclear just tell me so. Thanks again hoosierdaddy. Also, what do you mean by controller, I have not built this complex of grow box before. You talking about a humidity controller or CO2 or what? Also I would put the 2 8X8 on the middle shelf on the left side of the grow box, then the 8 four inch holes on the top right part of the cab to make sure air flows across the cab, instead of straight up. So you might have already answered this, but you think I can just have the eight inch exhaust fan just blowing from the utility compartment out, instead of fastening it to each individual 8 four inch holes then out, as this would take much engineering?
That will work...expensive, but will work fine.
Just food for thought...
You can always just cut a couple 8" holes in the flower/veg divider. If you have a shelf that is exactly one inch smaller both length and width wise, and mount it on 1" pegs at the bottom of your veg chamber (over top of the holes), it will block the light and provide air flow.
Just food for thought...
You can always just cut a couple 8" holes in the flower/veg divider. If you have a shelf that is exactly one inch smaller both length and width wise, and mount it on 1" pegs at the bottom of your veg chamber (over top of the holes), it will block the light and provide air flow.
That is a very good idea. My only question left is how to light proof the intake for the fan so no light is visible from the outside of the cab, the exhaust is covered. n Oh and would you mind explaining the controller? Hoosierdaddy you are the shit. Your response time and knowledge are absolutely incredible.
