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Offlinekrypto2000
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Time for a flow hood, have a few questions before choosing my equipment
    #20592957 - 09/20/14 02:13 PM (10 years, 3 months ago)

Finally time for me to upgrade to a flow hood. I've been doing some reading for a few days, but still have a few questions.

What is the deal with the filter depth? Obviously there's a space difference and from what I can gather it will affect the static pressure and thus your fan, but otherwise does it matter? I remember reading RR recommending a, iirc, a 2" deep filter stating something about how it affected the plenum and it's better for a flow hood where as a deeper filter, 11.5-12", is better for full room filtration. I didn't quite understand that though. 2" would be better for me as that would mean the filter is more shallow and easier to fit on my work bench, but I also imagine they'll cost more. I was looking at those ASTROCEL I 24x24x12 filters as they seem popular due to the price, but the only thing that concerns me is the 12" depth.

My next question is how does one seal the filter to the cabinet? Do you just build the cabinet snug and then silicon the gaps, is that it? Is there a better way? I've seen some that seem to do this however that seems like it'd be a pita if you ever had to replace or clean the filter as it's permanently fixed, is this not a problem in practice?

Ok, and I think my last question is in regards to the prefilter. So far I'm thinking of something akin to this. If I were using an inline fan which would largely rest inside of the cabinet then mounting the prefilter is easy, you just place it over the inlet of the fan essentially covering the top of your cabinet. With a blower though I'm unsure how you would go about mounting the pre filter as it's a rather awkward shape and you can't just wrap the filter around the fan as it'll likely be sucked in and screw things up. The example above the guy doesn't even use a pre filter which makes me wonder, however I hear it can dramatically extend the life of your hepa so I see no reason not to.

Edited by krypto2000 (09/20/14 02:14 PM)

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Offlinekrypto2000
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Registered: 12/05/06
Posts: 11,579
Last seen: 5 years, 2 months
Re: Time for a flow hood, have a few questions before choosing my equipment [Re: krypto2000]
    #20597258 - 09/21/14 01:48 PM (10 years, 3 months ago)

Hope it's ok if I give this a bump slightly sooner than the rules dicate (it's 30m shy of 24hr). I'm about to go to work and may not be able to bump until after midnight otherwise.

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OfflineMonkeyJesusFresco
am i suspended in agar?
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Re: Time for a flow hood, have a few questions before choosing my equipment [Re: krypto2000]
    #20598064 - 09/21/14 05:57 PM (10 years, 3 months ago)

:threadmonitor:

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OfflineMonkeyJesusFresco
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Re: Time for a flow hood, have a few questions before choosing my equipment [Re: MonkeyJesusFresco]
    #20598075 - 09/21/14 05:59 PM (10 years, 3 months ago)

shit, sorry for the needless bump;

I don't know nuth'n 'bout no flo hoods, but here are the links I'm going to be basing my build off of

http://www.shroomery.org/forums/showflat.php/Number/19798444

http://www.shroomery.org/forums/showflat.php/Number/13850394

http://www.shroomery.org/forums/showflat.php/Number/13445133#13445133


you could read through 'em :shrug:

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Offlinekrypto2000
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Re: Time for a flow hood, have a few questions before choosing my equipment [Re: MonkeyJesusFresco]
    #20598663 - 09/21/14 08:05 PM (10 years, 3 months ago)

Thanks, I'll check those out. I've seen the second one, but not the other two. Also in regards to my first question I just came across this quote by RR:

Quote:

RogerRabbit said:

12" filters generally have less resistance than thinner ones.  This makes it easier to achieve laminar flow with thinner filters because it's important to have a steady static pressure in the plenum.
RR




That's not the original one I'm referring to, but it supports the same thing. To me it makes it seem like a thinner filter is better, they're also cheaper and more convenient since they take up less space. Still just doesn't make sense why they'd have less resistence to me though as it seems as though there's more material for it to pass through, maybe deeper filters are just constructed differently, I thought the depth mostly had to do with their filtration capacity. This is where that RR quote is from btw, the context doesn't seem to matter to me, but for the curious.

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Offlinekrypto2000
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Posts: 11,579
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Re: Time for a flow hood, have a few questions before choosing my equipment [Re: krypto2000]
    #20598702 - 09/21/14 08:13 PM (10 years, 3 months ago)

I actually posted that too soon, a few posts down in the thread someone asks my very question and he says this:

Quote:

RogerRabbit said:
Simply look at the specs.  Most 12" thick filters have a lower resistance than the 5" thick filters. It's counter-intuitive, but simply the way they're made tighter, and not because of drag or wetted area.

You don't calculate for the blower based on depth of filter, but on the cubic feet per minute which must pass at a given resistance.
RR




I'm still confused though, is that true of all or filters or just a general rule of thumb? I guess I just have to find out the specs on every filter. :frown:

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Offlinekrypto2000
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Re: Time for a flow hood, have a few questions before choosing my equipment [Re: krypto2000]
    #20600286 - 09/22/14 09:06 AM (10 years, 3 months ago)

Ok, well right now I'm thinking of getting this hepa filter along with this blower. I'm not quite sure what the blower pushes at 1" SP, but it's 560 at .8" and I've seen many others get it. I should need about 4-500cfm, will this work?

After looking around it seems the rubber gasket on the filters + some furring strips inside is sufficient to keep an air tight seal around the filter so that's what I was going to do. In order to do that I do want the gasket on the downstream right? The options are upstream, downstream, or both. This is the 99.999% effective model which is about 20$ more than the 99.99%, is it worth it? I figure it's a small cost towards the whole project.

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Offlinekrypto2000
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Re: Time for a flow hood, have a few questions before choosing my equipment [Re: krypto2000]
    #20605628 - 09/23/14 11:16 AM (10 years, 3 months ago)

I don't think I'm going to get any help at this point :confused: so I went ahead and ordered the filter. I think the 2" would have been ok, but I went with the 6" just in case, if nothing else at least it will last me longer. I also think I had it wrong before, I got one with the gasket on the upstream as I want it on the side in which it is blowing from, inside the box. Hopefully that's right.

I'm going to hold off another ~24 hours in hopes that someone can validate this blower will work, but otherwise I'm just going to get it and hope it does. That's a lot of money to possibly spend on the wrong thing, but it doesn't seem like anyone else is going to chime in. If only I could remember how to make graphs/plots I could figure out what cfm this thing should put out at 1"SP, but I dunno, high school was too long ago now.

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Offlineblojo02184
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Re: Time for a flow hood, have a few questions before choosing my equipment [Re: krypto2000]
    #20605967 - 09/23/14 12:44 PM (10 years, 3 months ago)

I couldn't find the static pressure for your filter anywhere...

if you find.d that out I can let ya know.

been in the market for a flow hood for awhile now... just saving my money.

if it's. .6 then you'll be pushing too much, which isn't bad. just add a bunch of prefilters

it's looking good so far.
really try to find a static pressure on the filter,  it will be labeled on the filter itself.

your filter is also disposable, in a plastic frame and a 6 month life.

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Offlinekrypto2000
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Re: Time for a flow hood, have a few questions before choosing my equipment [Re: blojo02184]
    #20606531 - 09/23/14 02:54 PM (10 years, 3 months ago)

You have to email them. They just got back to me yesterday, but it was in regards to the 2" depth filter, not the one I ended up purchasing. The 2" is  223 CFM at 1” w.g. Just sent them an email to ask about mine, but I'd guess it would be around ~150 or so based on what I can recall from other similar filters.

Can you tell me why you needed to know that? I thought you did at first, but then as I did more reading (and I may have misunderstood) it seemed as though people were just ignoring it and aiming for 100cfm @ 1" regardless. I can dig it up if I need to, but I remember a post where RR specifically said to ignore that and go for 100cfm because the rated flow for the filter is too high for our purposes. Eh.. something like that anyway, am I confusing two different things maybe?

Edited by krypto2000 (09/23/14 02:56 PM)

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InvisibleMr. Alien
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Re: Time for a flow hood, have a few questions before choosing my equipment [Re: krypto2000]
    #20606580 - 09/23/14 03:09 PM (10 years, 3 months ago)

Hmmm i don't understand anything about CFM and blowers Stattic pressure and all that kind of stuff, i'm like :confused:

I just bought a HEPA and a blower for the HEPA in fungi.com, they gave me the exact measurements for the Hepa wood box and the blower box, etc.

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InvisibleGhatti
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Re: Time for a flow hood, have a few questions before choosing my equipment [Re: Mr. Alien]
    #20606935 - 09/23/14 04:03 PM (10 years, 3 months ago)

So krypto I assume you gave up on your ceiling fan sterile work area idea? Lol

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Offlineblojo02184
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Re: Time for a flow hood, have a few questions before choosing my equipment [Re: Ghatti]
    #20607330 - 09/23/14 05:05 PM (10 years, 3 months ago)

you are correct in one part but not the other :lol:

your aiming for 100com at the static pressure of your filter.

your blower has a graph accompanied with it showing the downcurve that is made when adding more and more pressure.

now your filter is an upward curve, gaining more and more air flow when more pressure is exerted.

where these two lines cross is the point you want.
people usually add .2"sp for the prefilter.
your filter, lets say roughly is .8"so, you want a blower for 100cfm@ 1"sp.

it's physics :smile:

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Offlinekrypto2000
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Re: Time for a flow hood, have a few questions before choosing my equipment [Re: Ghatti]
    #20609074 - 09/23/14 10:47 PM (10 years, 3 months ago)

Quote:

Ghatti said:
So krypto I assume you gave up on your ceiling fan sterile work area idea? Lol




Ha, not sure how serious you are, but yes, I never tried it. It was just a novel idea that I'm guessing wouldn't work (the one guy testing it never got back with his results :frown:). I probably wouldn't have used it either way though as I had/have a pretty nice SAB, but now I have the money for a flow hood :bananadance:.

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