Carbon Filter CFM compared to your fan CFM

[CA215]

Good evening 420mag goers,

So I have a carbon filter that's rated at 200 cfm and two inline fans, one at 400 & another at 240, the obvious thing is to go with the 240, but will the extra 40 cfm have a bad effect? Should I be concerned with this..?

Will experiment tomorrow..

-CA215

 

[bigblunts209]

You shouldnt have a problem running the 240. its only a little bit more air!

 

[KarlJay]

You really have to look at more than just the CFM rating of a fan. It's like MPG on a car ... Your Mileage May Vary ... The CFM rating on a fan is under ideal conditions, it doesn't take into account duct work.

I run a 6" booster fan hooked up to a 25' insulated tube, the tube makes several bends. I'm sure the fan is not pulling 220 CFM thru that tube. Just like your car gets better MPG downhill, it's easier.

Point: you need to account for the bends and distance the duct work is.

I'd check the mfg site to see if what type of fan the say you should use, but I'd also question why not go larger? The rating on the filter is for NET CFM, you may need a 300 fan to net 200 by the time you account for bends and the distance it has to move the air thru the ducts.

One option is to use several fans, one to push the air to the other. You could put a fan near each end of a duct.

 

[CA215]

bigbliunt Karl, thank you two!

This is kinda what I was thinking also, because I have about 2 6"x4" reducers and about 60 feet of duct with 5+ turns and bends that go right left up down. I got some research ahead of me. Thanks for the speedy response.

Got me on the right track now!! +REPS ALL AROUND YIPPIIEEKIYYAYY!!

-CA215

 

[bigblunts209]

Thank you! And good luck to your grow

 

[Cultivator]

just to keep it simple, its definately best to run a smaller fan than the filter u are using to be sure the filter is doing its job. basically the faster the air moves through the carbon the more chance of odours getting through.

 

[CA215]

just to keep it simple, its definately best to run a smaller fan than the filter u are using to be sure the filter is doing its job. basically the faster the air moves through the carbon the more chance of odours getting through.

I ended up riggin the 240cfm inline to the 200cfm carbon filter. Was blowing some clouds at it and it seemed to be doing the job, not what I expected as in sucking power but it was running I guess.. well see when I actually get to flowering, id rather keep it unplugged for now to save a little cash on electicity.

 

[KarlJay]

I use the home depot 6" inline fan to get fresh air from another room to the top of the grow. it's in the low/mid 200CFM range and it really doesn't move very much air. If it was covered with a filter, it'd be hard to know it was on, but it does help.

 

[Slye]

I realize this may be too late but my rule of thumb is to take your base CFM requirements and add 20% to compensate for an air filter, another 10-20% for your ducting.

For example, in a small grow space of just 125 cu/ft (4.5ft x 3.5ft x 8ft), you need just 25 CFM to exchange the air once every 5 minutes. With a filter and some ducting that would increase to ~33 CFM.

- Add 5% for each air-cooled hood
- Add 10-25% for each regular hood (i.e., open, or not air-cooled)
- Add 5% if co2 enrichment is being used
- Add 20-40% if external environment is extra hot or humid
- Add 20% for inline carbon filter
- Add 5-20% for ducting

So, get a fan large enough to meet your maximum CFM requirements and a knobby little controller to turn it down/up as needed.

 

[CA215]

I use the home depot 6" inline fan to get fresh air from another room to the top of the grow. it's in the low/mid 200CFM range and it really doesn't move very much air. If it was covered with a filter, it'd be hard to know it was on, but it does help.

Yup, Its barely doing anything but it is doing something!! So will see, Ill let it get nice and stinky then we will turn that mofo on and see how she handles through the ganj!!

I realize this may be too late but my rule of thumb is to take your base CFM requirements and add 20% to compensate for an air filter, another 10-20% for your ducting.

For example, in a small grow space of just 125 cu/ft (4.5ft x 3.5ft x 8ft), you need just 25 CFM to exchange the air once every 5 minutes. With a filter and some ducting that would increase to ~33 CFM.

- Add 5% for each air-cooled hood
- Add 10-25% for each regular hood (i.e., open, or not air-cooled)
- Add 5% if co2 enrichment is being used
- Add 20-40% if external environment is extra hot or humid
- Add 20% for inline carbon filter
- Add 5-20% for ducting

So, get a fan large enough to meet your maximum CFM requirements and a knobby little controller to turn it down/up as needed.

Good info Slye, ill take all that into consideration.. So I take it I should probably want a good 100+ CFM for my situation. Not bad at all, ill make something work!!

Thanks for the info all!!!

-CA215

 

[HeartWW]

I would put the 400 fan in and use a fan speed control. Run it as fast as you can to remove heat or until you smell the odor. Turn it down accordingly. I bought my fan control for $9.00 at Menards. Works for me. Good Luck..