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MillionsOfPeaches
Just Some Newbie
Registered: 08/18/16
Posts: 3
Last seen: 7 years, 3 months
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Are My Numbers Right for this Flow Box Build?
#23559932 - 08/20/16 01:06 PM (7 years, 5 months ago) |
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I've been doing a lot of research on building a flow hood, and even though I've spent at least 10 hours yesterday and today alone researching this and trying to figure the math out, I'm finding some pieces difficult to figure out. So basically what I'm thinking is getting either this or this HEPA filter and matching it up with a blower that's at 715m^3/h to 760m^3h blower at 300Pa. Since I'll also have the furnace filter before it too. But I duuno, maybe my math is way off. Hopefully this is the right section, still learning my way around this site. +First post.
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Thadeous
On the path

Registered: 08/02/11
Posts: 1,101
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As I understand it (and am literally seeking advice for building my own laminar flow hood) you need to take the surface area x 100ft/m, add 10-20% and find a blower that matches that rating with a given static pressure. So: 2ft x 2ft = 4sqft 4 sqft x 100ft/min = 400 cfm 115% of 400 cfm = 460 cfm @ whatever static pressure.
Static pressure is usually on some data sheet for the filter (I couldn't find one on the pages you provided) and can be added with the static pressure of the pre-filter (this is small, but not negligible) which can be ~0.2inches
Hope that helps somewhat. Finding a filter is difficult :/
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MillionsOfPeaches
Just Some Newbie
Registered: 08/18/16
Posts: 3
Last seen: 7 years, 3 months
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Re: Are My Numbers Right for this Flow Box Build? [Re: Thadeous]
#23560095 - 08/20/16 02:25 PM (7 years, 5 months ago) |
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Quote:
Thadeous said: As I understand it (and am literally seeking advice for building my own laminar flow hood) you need to take the surface area x 100ft/m, add 10-20% and find a blower that matches that rating with a given static pressure. So: 2ft x 2ft = 4sqft 4 sqft x 100ft/min = 400 cfm 115% of 400 cfm = 460 cfm @ whatever static pressure.
Static pressure is usually on some data sheet for the filter (I couldn't find one on the pages you provided) and can be added with the static pressure of the pre-filter (this is small, but not negligible) which can be ~0.2inches
Hope that helps somewhat. Finding a filter is difficult :/
Hmmm. I guess it would be best to keep looking until I found one with datasets. I contacted the company but they won't answer until at least Monday. I just don't want to fuck up my calculations. 460cfm×1.7=782 so I'd need 782ishm^3/h @ whatever static pressure I'd end up with? I'm pretty sure I did that right. The HEPA filter seems to be the most difficult part of shopping, and I can't imagine building will be too difficult for me so maybe the most difficult part of the whole shebang. Good luck on your build
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morty422
Wuba-luba-dub-dub!



Registered: 07/06/16
Posts: 988
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spore-ty



Registered: 01/21/16
Posts: 1,028
Loc: In the bush
Last seen: 2 years, 10 months
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Re: Are My Numbers Right for this Flow Box Build? [Re: morty422]
#23561480 - 08/20/16 09:44 PM (7 years, 5 months ago) |
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Remember 90 degree flame 
But ya from my math in my head you'd need based on the first filter (what's your pre filter? ) about 410 cfm blower
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mushpunx
Fungus Punk


Registered: 04/20/14
Posts: 13,394
Last seen: 11 days, 17 hours
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Re: Are My Numbers Right for this Flow Box Build? [Re: spore-ty]
#23561740 - 08/20/16 11:38 PM (7 years, 5 months ago) |
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The sp that is listed on them, is what they are tested at with a particle counter, and the corresponding cfm coming out of the filter. So you dont need the Static Pressure listing off. he filter.
For a 24 x 24 x 6" filter you will need a blower that pushes at or above (as close as you can, but you can block the intake to power down the blower) 400CFM at a Static Pressure of 1.0 or 1.2 I add .2 to compensate for the pre filter.
You will want to build the hood with a plenum of at least 6" (Id go deeper) behind the filter.
Blowers are listed by CFM they blow at free air. You will have to call/email the seller and ask for the blower specs chart BEFORE you buy it.
I have an 18 x 24" filter. It needs a blower that pushes 300CFM @ 1.0SP. My blower pushes 560CFM @ free air and that's what it was listed at. On the blower specs I just looked up the chart to 1.0 SP and saw that it pushed a little over 300CFM so I knew it was a match. M
Hope this helps!
--------------------
 Amateur Mycologists United AMU Q&A
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MillionsOfPeaches
Just Some Newbie
Registered: 08/18/16
Posts: 3
Last seen: 7 years, 3 months
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Re: Are My Numbers Right for this Flow Box Build? [Re: mushpunx]
#23566855 - 08/22/16 06:16 PM (7 years, 5 months ago) |
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Quote:
mushpunx said: The sp that is listed on them, is what they are tested at with a particle counter, and the corresponding cfm coming out of the filter. So you dont need the Static Pressure listing off. he filter.
For a 24 x 24 x 6" filter you will need a blower that pushes at or above (as close as you can, but you can block the intake to power down the blower) 400CFM at a Static Pressure of 1.0 or 1.2 I add .2 to compensate for the pre filter.
You will want to build the hood with a plenum of at least 6" (Id go deeper) behind the filter.
Blowers are listed by CFM they blow at free air. You will have to call/email the seller and ask for the blower specs chart BEFORE you buy it.
I have an 18 x 24" filter. It needs a blower that pushes 300CFM @ 1.0SP. My blower pushes 560CFM @ free air and that's what it was listed at. On the blower specs I just looked up the chart to 1.0 SP and saw that it pushed a little over 300CFM so I knew it was a match. M
Hope this helps!
Thanks, this is definitely helpful. I saw a blower for sale that pushed over 850cfm at free air for $60. It seemed nice at the time, now I realise it probably would've been way more power then I would have needed.
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mushpunx
Fungus Punk


Registered: 04/20/14
Posts: 13,394
Last seen: 11 days, 17 hours
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Well maybe not... see the thing is without seeing the blower specs you won't know. That's why you have to contact the seller and find out what it pushes at 1.0 SP (the blower specs chart)
And not all blowers are equal... you might have two blowers listed at 850CFM @ free air might push different numbers at 1.0SP
--------------------
 Amateur Mycologists United AMU Q&A
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PirateSwazey


Registered: 12/12/12
Posts: 2,993
Loc: Here, Now
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Re: Are My Numbers Right for this Flow Box Build? [Re: mushpunx]
#23567927 - 08/23/16 12:41 AM (7 years, 5 months ago) |
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Peaches,
You should order your filter first. Then you can get the specs for the resistance. I have the filter you are looking at from filtera and mine is 1" W.G. I'm not sure if that measurement changes with each one though, as they are made to order. When you receive it, they will put a sticker on the side that shows what static pressure the filter was tested at.
For your blower, check Grainger's website. Most of their furnace blowers have a chart underneath the pictures that show its output at different levels of static pressure.
You will need a blower that puts out at least 450 CFM @ the SP of your filter.
Remember you can always overshoot the power of the blower and regulate the flow down by either stacking pre filters or adding a speed controller.
Best luck!
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