fan cfm less than filter min cfm question

if a fan that is to big (to much cfm) for the filter pulls it air to fast for the filter to scrub the odor from the air, what about a fan that has less cfm than the filters recommended min cfm...example can 33 filter recomeds a fan with a cfm of min 100 and a max 0f 200 cfm if the fan is rated at 150 cfm but it is ran at half speed ( 75 cfm due to noise issues ) how does that effect the performance of the filter ?

Hmm, I would only think that it would allow smell to escape since it might not create negative pressure, assuming you use a tent. Have you thought about putting the fan in something to help cut back on noise? I have been thinking about doing that myself....just been too lazy. I've heard its as easy as buying a pre-made single cabinet....or using a big storage bin and memory foam. I've seen DIY here on RIU.

840/2 said:

Hmm, I would only think that it would allow smell to escape since it might not create negative pressure, assuming you use a tent. Have you thought about putting the fan in something to help cut back on noise? I have been thinking about doing that myself....just been too lazy. I've heard its as easy as buying a pre-made single cabinet....or using a big storage bin and memory foam. I've seen DIY here on RIU.

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i dont know about the op's question but i agree with this poster above. you can get a small rubbermaid container and place it over the fan with pillows or a cover in it to muffle sound. im gonna do the same thing whenever i get my 6 inch

I am going to change the ducting to isnulated ducting to see if that helps with the noise, and I do have negative pressure inside the tent., Ill let you know how the new duct helps with the sound.

IMO, most carbon filters are more effiecient running at a lower CFM then what they are rated for. Buy a $20 fan controller and reduce the speed. Sound will go down too. Win win.

skunkfish1 said:

if a fan that is to big (to much cfm) for the filter pulls it air to fast for the filter to scrub the odor from the air, what about a fan that has less cfm than the filters recommended min cfm...example can 33 filter recomeds a fan with a cfm of min 100 and a max 0f 200 cfm if the fan is rated at 150 cfm but it is ran at half speed ( 75 cfm due to noise issues ) how does that effect the performance of the filter ?

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I think i can answer this question for you, as i personally do exactly what you're saying. I run a Can33 filter, and 2 inline fans that i know aren't hitting the minimum 100cfm. You know why they have a max, air won't be scrubbed enough,.. well if air is coming out of your duct, then a negative vacuum, or "pressure" as 840/2 called it, IS being created, and furthermore, that's all you need to keep smell in only the grow room. The longer the air particles have to pass across the activated carbon in the filter, the cleaner that air will be when it comes out, and the longer your filter will last. Win win indeed

Cool, Thanks for the Info.

I run a 8" 650cfm filter with my 6" 440cfm fan and have no odor issues and can run it at 2/3 speed to quite it down nicely. Supposedly best to use a higher cfm filter with a fan of less cfm's and the filter is said to last a little longer running it at lower cfm's.

Quick update, the Insulated ducting made a big difference to the fan noise, I would say cut it in 1/2.

It is more a pressure issue. The lower CFM the better it will clean your air but if you drop below a certain amount the fan will not be generating enough pressure to push through the filter material.

I dont push through the filter I pull through the filter and push through a cool tube then exhaust into another room with the exhaust hooked to a muffler then into an old used filter just to catch anthing that may have been missed from thr primary filter...works good so far. I can feel air being pushed out the 2nd fiolter so I think im good on air movement and my temps stay between 79 and 82.