exhaust fan question

I want to use computer fans for my exhaust on my stealth dresser grow but I need to know which is more important. The size of the fan or the pull? and If i had 2 fans next to each other do you add the cfm to get the overall pull?

Not sure about the size or pull, but general rule of thumb is to exchange the grow rooms air mass once every 3 minutes. Hope that helps.

I messed around with the computer fan thing. They did not work for me. One of those 4 inch vortex fans with a fan speed controller and the fan packed in a box with foam moves like 100's of times more air and is just as quiet. I wish I had never messed with the computer fans, they don't produce any air pressure. I had substandard buds until I got good ventilation. What kind of light are you cooling?

If you know the CFM rating for each, then together they should move the sum of their CFMs. But then you add airflow resistance. Also a major factor: is your cab fairly airtight when closed up? Try one low for cool air intake and one high for hot exhaust. If you want positive pressure, put the higher-CFM one on the intake. Vice versa if you want negative pressure in the cab (sealing cracks is more imortant here, otherwise you'll suck in unfiltered air, which can be asking for trouble, depending on...things. Spores anyone??)

curious.george said:

I messed around with the computer fan thing. They did not work for me. One of those 4 inch vortex fans with a fan speed controller and the fan packed in a box with foam moves like 100's of times more air and is just as quiet. I wish I had never messed with the computer fans, they don't produce any air pressure. I had substandard buds until I got good ventilation. What kind of light are you cooling?

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I am using CFL's and I dont have Vortex fan money. lol So computer fans, regardless of the cfm didnt work?

PoeEttic said:

I want to use computer fans for my exhaust on my stealth dresser grow but I need to know which is more important. The size of the fan or the pull? and If i had 2 fans next to each other do you add the cfm to get the overall pull?

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Computer fans come in different streaths depending on their job... Like a case computer fan will have CFM ratings between 30-40max. Computer Power Supply fans (the ones inside the pw supply) will have CFM rating from 50-100 and we are only talking about the 80mm standard ones... As for the pull the bigger the fan the more pull it will have of course... Like the next computer fan size is 120mm and they are for the full size server computers with 3+ hard drives.. SLI graphics card setups.. and the 120mm fans have CFM rating above 100. Also im not liking ur idea to have two computer fans next to one another to try to generate more CFM's... it would not work because the fan in the back would be forcing air into the next which would over time cuz it to wareout/burn out.. They are to simple of a electronic to force to do anything really then wat they are made to do... So what I am saying here is select the right computer fan for wat u need it for... or buy a vent fan

One of these might work:



Are you trying to vent heat, or just have good airflow for your plants?

Cr8z13 said:

One of these might work:

Are you trying to vent heat, or just have good airflow for your plants?

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im just going for airflow. I dont think cfls will produce enough heat to need to much heat ventilation. Will they?

PoeEttic said:

im just going for airflow. I dont think cfls will produce enough heat to need to much heat ventilation. Will they?

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You should be fine with computer fans if you set them up right... Ventilation is not just for heat.. but also very important for the plants themselfs...

PoeEttic said:

im just going for airflow. I dont think cfls will produce enough heat to need to much heat ventilation. Will they?

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Depends on how many bulbs and what wattage. I have some 42w bulbs that get kinda hot. You're best off setting up all of your lights and doing a dry run for a little while to find out how hot it gets without ventilation. If it stays below 80 you need only be concerned with airflow, in which case 1 or 2 modest output PC fans will do. If temps are well over 80-90, you need better fans.

PoeEttic said:

I am using CFL's and I dont have Vortex fan money. lol So computer fans, regardless of the cfm didnt work?

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ok, for CFL's the computer fan should work. CFL's have the ballast included with the bulb, using tube floro's and mounting the ballast outside the box would produce less heat inside the box.