purple_cow2k

How much do carbon filter's reduce the rated CFM's of a fan?
What is the optimum thickness of carbon?

purple_cow2k

does ozone work well for covering up grow's

afterburner

It will reduce your fan power by MORE than 50%. Depending on your duct fan strength. (Computer fans will not have enough juice to power a scrubber)

Optimal carbon depth for maximum cleaning power effectiveness and minimal backpressure is 26 mm or 2.6 cm.

Oh, and Cecil_b has pointed out that air is better "sucked than blown"... Something to think about while designing your scrubber.

Ozone works great IF you can vent directly outside. If you have to vent into any kind of living area, dont even concider ozone. The levels of ozone neccesary to kill odor far exceed human safety limits. Believe me, I had lung problems fast after getting my ozone gen. I have since stopped using it, only occationaly when I'm NOT at home will i turn it on.

Carbon scrubbers are the way to go!!!

Oh, depending on how big your grow is you'll want 4.5 pounds to 9 pounds of the "Activated Carbon" look for "Pelletesized" its the best kind. I use "Kent Marine" brand with exellent success. Many others will work too... Bioutimus (sp) coal based charcoal is superior to coco fiber based charcoal... Just a little more food for thought.


Goodluck
Afterburner

iwishicould

Pardon me,was just wondering how long the carbon lasted?

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naturall_mystic

Pack pressure problems can be reduced by having the exhaust fan at the very end of the air path. In other words put the carbon filter in between the grow box and the fan. In other words have your fan sucking or pulling the air, not blowing or pushing the air.

To answer your question, it is hard to say how much backpressure will be reduced because we don't know the type or rating of the fan you have in mind. Inline fans handle back pressure better than others.

THickness of the carbon layer is not an exact science either. In the application used here there really isn't a great deal of particles causing the odor, so a large amount of carbon isn't really needed. I made a 20" x 20" x 1" carbon filter and it seems to do the job. That should give you a starting point.

iwishicould, that depends on a lot of factors. The amount of air moving through the carbon filter, the amount of humidity, the type of carbon (all carbon is not the same), the amount of carbon, etc.

Also Afterburner gives good advice about the ozone generator. It is overkill and, as he knows from experience, not healthy.

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Mr.Bogart

Wha ... who came up with this rule? Maybe it's better for the carbon filter to not have the blown air concentrated on one spot, as you might get with a small fan pointed at a large filter, but whose idea was it that fans do better sucking than blowing?

In any event, such a rule, if true, is going to depend strongly on the type of fan - blade geometry and what not.

If you're going to be using ducts or a carbon filter, use a bathroom exhaust fan, or an inline fan, as long as it's a centrifugal fan. People have rightly observed that computer fans can't pull squat through a carbon filter; the same holds true for most propellor fans. Computer fans are fine as long as you're exhausting directly to the room and the intake is quite clear or has a similar fan on it as well.

naturall_mystic

We (you will find reference to this in several places on this site) don't consider it so much a rule as it is following the information provided by the fan manufacurer. Both Vortex and Fantech state in their documentation that placing centrifugal fans in the pulling position is most effective. They provide documentation on their websites. Feel free to check it out.

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Mr.Bogart

Interesting. I didn't find anything on the Fantech web site about preferred location, but it's not a big deal.

May be a characteristic of the inline fans? I've never heard of propellor or squirrel cage fans caring what side the impedance is on.

Or just to keep it as quiet as possible?

naturall_mystic

Mr. Bogart I hope this helps.

Take a look at the picture in this link of the installation and maintenance instructions it will help you visualize how to install the fan correctly. Note how the fans are conveniently located at the end of the duct line.

There is also the rather significant matter of the difference between negative and positive pressure systems. By placing the exhaust fan at the end of the duct line you create a negative pressure system. What that means is that the pressure inside the grow box and carbon filter is lower than the pressure outside the boxes. A negative pressure system avoids the potential problem of odor leaks as all air is sucked through the system, including any possible leaks. A negative pressure system also makes the seals on both the grow box door and filter work more efficiently as it sucks them closed rather than blowing them open. A postive pressure system (pushing the air through a grow box and or charcoal filter thereby raising the air pressure to higher than that outside the boxes) has the opposite effect.

Please do install your fans where ever you feel it works best for you.

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Mr.Bogart

Actually, in the case of the ceiling duct fan, they show it in the middle of the duct.

I don't mean to be a pain in the neck; I'm just curious whether there's a real effect or not. I've been doing HVAC work for a while and, like I said, this is the first I've heard of it.

Now those points I completely agree with! Especially with a grow box situated in an attic, where materials will dry out, get brittle, and so on. The same principle holds for air handlers; you want to make the suction side as short as possible in order to avoid sucking unconditioned, dirty, smelly attic or crawl space air into the system.

Like I said, just caught me by surprise ... not trying to be a pain or anything. In any event, kudos to you and the others for not trying to use a computer fan (duhhh ... why's my box so hot with a three hundred cfm fan? I've got fifty air changes a minute, don't I? )