Is my inline fan overkill??

MistaRasta

MistaRasta

Well-Known Member
Hey guys got a couple of questions.

I'm running a 4x8 grow tent which is 208 cu ft with a 6 inch 400 cfm fan.

By my calculation the air is getting refreshed in the room every 30 seconds.

I've heard this can be very stressful on the plants and that the air should be refreshed every 2-3 minutes. Which means I would need to run around 100 cfm for the air to be refreshed every two minutes.

I run 2 600s ducted from the fan and filter and I know that 100 Cfms aren't going to cool them. Should I put the lights on their own run and run a smaller outtake??

Or am I over thinking all of this?
 
jijiandfarmgang

jijiandfarmgang

Well-Known Member
Your over thinking it. You will actually lose quit a bit of flow with that filter.

Do you think with your vents open the exchange of air and slight breeze will hurt them? Think of all those weirdos that put oscillating fans on high directly on plants so its practically falling over.

- Jiji
 
MistaRasta

MistaRasta

Well-Known Member
jijiandfarmgang said:
Your over thinking it. You will actually lose quit a bit of flow with that filter.

Do you think with your vents open the exchange of air and slight breeze will hurt them? Think of all those weirdos that put oscillating fans on high directly on plants so its practically falling over.

- Jiji
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I've heard of about a 30% loss with the filter hooked up. Does this remain true even though my Cfms of my filter match that of my fan?

The fan is 400 Cfms and the filter is rated for 400 Cfms. So I'll be running what? About 300 Cfms?

When all the holes are closed my fan sucks in like crazy, still trying to figure out how to light proof my intake holes
 
skunkd0c

skunkd0c

Well-Known Member
i think your calculation maybe wrong
you need length x height x width to calculate the air volume in your space in cubic feet or cubic meters
you seem to have only given a 2 dimensional calculation
 
jijiandfarmgang

jijiandfarmgang

Well-Known Member
MistaRasta said:
I've heard of about a 30% loss with the filter hooked up. Does this remain true even though my Cfms of my filter match that of my fan?

The fan is 400 Cfms and the filter is rated for 400 Cfms. So I'll be running what? About 300 Cfms?

When all the holes are closed my fan sucks in like crazy, still trying to figure out how to light proof my intake holes
Click to expand...
Its hard to say, there are many variables on percent lost. Basically cfm is rated open fan, when you put flex duct on exhaust flex duct in intake, air turbulence through reflectors, variable of filter restriction and sizing, and restriction of intake.......you get the idea.

I just try to keep restrictions to a minimum. IMHO exhaust rate should be done to manage environment temp and or if necessary humidity (not for rules of thumb or for what some one says about CO2 exchange).

- Jiji
 
IgrowUgrow

IgrowUgrow

Well-Known Member
I also am curious about the amount of CFM lost due to a carbon filter, I want to know if a 4" inline fan will maintain temps for a small grow tent with a air cooled 400w hps with a carbon filter on it. The space is 3x3x5ft, also the fan is 190cfm.
 
Moderndayhippy

Moderndayhippy

Well-Known Member
IgrowUgrow said:
I also am curious about the amount of CFM lost due to a carbon filter, I want to know if a 4" inline fan will maintain temps for a small grow tent with a air cooled 400w hps with a carbon filter on it. The space is 3x3x5ft, also the fan is 190cfm.
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Yes that is plenty I have used a similar sized tent with a 4 inch inline fan and I put the fan on a speed controller didn't need it at full strength.
 
IgrowUgrow

IgrowUgrow

Well-Known Member
Moderndayhippy said:
Yes that is plenty I have used a similar sized tent with a 4 inch inline fan and I put the fan on a speed controller didn't need it at full strength.
Click to expand...

Thanks man been kinda worried about that so I wont need any additional fans to exaust air just to move air on the inside of the tent correct? Also what is a good way to light proof the tent, im new to this tent thing.

By light proof I mostly mean the intake, I want to have a passive intake but how would I do that and still be light proof without building a light trap or a long duct.
 
Moderndayhippy

Moderndayhippy

Well-Known Member
IgrowUgrow said:
Thanks man been kinda worried about that so I wont need any additional fans to exaust air just to move air on the inside of the tent correct? Also what is a good way to light proof the tent, im new to this tent thing.

By light proof I mostly mean the intake, I want to have a passive intake but how would I do that and still be light proof without building a light trap or a long duct.
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What kind of tent did you get? Assuming you bought a grow tent it should be light proof already and the intake should have double sided sleeves that will block almost all the light. I would still have some sort of fan in the tent but no you shouldn't need additional exhaust or intake fans that one fan will turn the air over in your tent.
 
IgrowUgrow

IgrowUgrow

Well-Known Member
Moderndayhippy said:
What kind of tent did you get? Assuming you bought a grow tent it should be light proof already and the intake should have double sided sleeves that will block almost all the light. I would still have some sort of fan in the tent but no you shouldn't need additional exhaust or intake fans that one fan will turn the air over in your tent.
Click to expand...

Double sided sleeves yes but they are not open unless I run a duct through them, that will hold them open but will also allow light to leave the tent. I don't want to run a long intake duct to keep the light in.
 
IgrowUgrow

IgrowUgrow

Well-Known Member
Its a stealth grow just because I don't like people knowing my business, my tent is light proof just not the intake.
 
MistaRasta

MistaRasta

Well-Known Member
skunkd0c said:
i think your calculation maybe wrong
you need length x height x width to calculate the air volume in your space in cubic feet or cubic meters
you seem to have only given a 2 dimensional calculation
Click to expand...
I forgot to mention that its 6.5 feet tall, this was included just thought it wasn't necessary when mentioning.
 
Moderndayhippy

Moderndayhippy

Well-Known Member
IgrowUgrow said:
Double sided sleeves yes but they are not open unless I run a duct through them, that will hold them open but will also allow light to leave the tent. I don't want to run a long intake duct to keep the light in.
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The sleeves on my tent have a drawstring you can open or close. Also a lot of tents have a mesh area near the bottom that is covered by a flap that will block the light but allow air in. Not sure where your tent it but none of the tents I have are 100% light proof if it's in a closet you should be fine. If you need 100% light proof I'm not sure how you would do it without using ducting or something like that where you could make a corner to block the light.
 
IgrowUgrow

IgrowUgrow

Well-Known Member
I just saw a video where a guy took a 2ft piece of 6" ducting and took a black t shirt and put one end of the t shirt through the duct and wrapped it around the outside of the duct on both ends so the duct is no longer reflective inside then put a slight bend in the duct and now it is completely light proof with very little air resistance.
 
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