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Grenade01
Registered: 09/25/01
Posts: 382
Loc: USA
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Flowhood math sanity check *DELETED* *DELETED*
#26983210 - 10/13/20 11:24 AM (3 years, 3 months ago) |
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Post deleted by Grenade01
Reason for deletion: Starting fresh
Edited by Grenade01 (10/13/20 11:36 AM)
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Becky G. Spot
Good Necky Becky

Registered: 10/12/20
Posts: 111
Loc: The Sunny Side
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Re: Flowhood math sanity check [Re: Grenade01]
#26983220 - 10/13/20 11:35 AM (3 years, 3 months ago) |
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Do you have a quick link to the item/sheet?
I just got done doing a flowhood project with my ex (I did the math/sizing of the blower), I can weigh in but want to double check some stuff.
XOXOX
-------------------- - Becky G. Ditch the double standards boys. Girls like to have fun as much as you do.
Sisters if you find yourself hating, read my bio.
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Grenade01
Registered: 09/25/01
Posts: 382
Loc: USA
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Re: Flowhood math sanity check *DELETED* [Re: Becky G. Spot]
#26983238 - 10/13/20 11:46 AM (3 years, 3 months ago) |
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Post deleted by Grenade01
Reason for deletion: Starting fresh
Edited by Grenade01 (10/13/20 11:52 AM)
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Becky G. Spot
Good Necky Becky

Registered: 10/12/20
Posts: 111
Loc: The Sunny Side
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Re: Flowhood math sanity check [Re: Grenade01]
#26983283 - 10/13/20 12:13 PM (3 years, 3 months ago) |
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I am assuming you will be using a prefilter, and that usually adds 0.1 - 0.2, usually 0.2 for the ones I used, making your static pressure 1.03 to 1.13 if your filter is truly 0.93.
I just tried to go to Grainger.com to size a blower for you as they post each blower's full spec sheets along with the graph we need to see it's various outputs at different static pressures, but the site appears to be down for me...
Is grainger.com down for you too?
-------------------- - Becky G. Ditch the double standards boys. Girls like to have fun as much as you do.
Sisters if you find yourself hating, read my bio.
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Grenade01
Registered: 09/25/01
Posts: 382
Loc: USA
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Re: Flowhood math sanity check *DELETED* [Re: Becky G. Spot]
#26983315 - 10/13/20 12:33 PM (3 years, 3 months ago) |
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Post deleted by Grenade01
Reason for deletion: Starting fresh
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bodhisatta 
Smurf real estate agent


Registered: 04/30/13
Posts: 61,889
Loc: Milky way
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Re: Flowhood math sanity check [Re: Grenade01]
#26983387 - 10/13/20 01:28 PM (3 years, 3 months ago) |
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There's absolutely no complex math just comparing numbers.
100 feet per minute is a flow speed you're aiming for
The size of your filter in square feet 24x24 is 4 square feet.
4*100 is all the math involved in making a hood. Multiplying a number by 100.
400 cubic feet per minute is then what you require from your blower. Your blower needs to push at least 400 cfm against the resistance of your filter
So if your resistance is 1.5"w.g. with filter and prefilter then you want s blower that does 400+ cfm at 1.5"w.g.
No math. Not hard. People pretend like they don't get it or need help because they don't try is my only guess.
They tested your filter at 600 something cfm it produced a hair under 1" w.g. resistance @ 0.93. They certify at test it won't be over 1". All the filters will have slightly different numbers that's why they're tested.
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Becky G. Spot
Good Necky Becky

Registered: 10/12/20
Posts: 111
Loc: The Sunny Side
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Re: Flowhood math sanity check [Re: Grenade01]
#26983603 - 10/13/20 03:57 PM (3 years, 3 months ago) |
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Quote:
bodhisatta said: There's absolutely no complex math just comparing numbers.
100 feet per minute is a flow speed you're aiming for
The size of your filter in square feet 24x24 is 4 square feet.
4*100 is all the math involved in making a hood. Multiplying a number by 100.
400 cubic feet per minute is then what you require from your blower. Your blower needs to push at least 400 cfm against the resistance of your filter
So if your resistance is 1.5"w.g. with filter and prefilter then you want s blower that does 400+ cfm at 1.5"w.g.
No math. Not hard. People pretend like they don't get it or need help because they don't try is my only guess.
They tested your filter at 600 something cfm it produced a hair under 1" w.g. resistance @ 0.93. They certify at test it won't be over 1". [b]All the filters will have slightly different numbers that's why they're tested.
I had a filter sent/ sold to me as an expected 1.0", but it arrived and the handwritten rating from the inspector on the sticker said 0.83"
So it can vary a good bit.
You're right. It's not hard. Nor is it math I think anyone would have a hard time doing themselves, you are totally right. It's simple multiplication and addition, and checking the blower spec sheet, but isn't it human nature to want a little help to make sure they don't waste time buying the wrong stuff?
I did.
XOXOX
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bodhisatta 
Smurf real estate agent


Registered: 04/30/13
Posts: 61,889
Loc: Milky way
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Absolutely. I'm always trying to get people to realize they're smarter than they think if they have the right perspective. If someone says man this book sucked it was an audacious task just to finish. You'll probably have a hard time getting started reading it yourself. If someone says wow it was amazing such a wonderful read. People become far more likely to jump onboard and read it too.
I try to treat math the same way. Think about it as easy not a burden or obstacle. Don't dismiss your abilities before trying to change perspective on the issue at hand
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Grenade01
Registered: 09/25/01
Posts: 382
Loc: USA
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Re: Flowhood math sanity check *DELETED* [Re: bodhisatta]
#26983789 - 10/13/20 05:52 PM (3 years, 3 months ago) |
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Post deleted by Grenade01
Reason for deletion: Starting fresh
Edited by Grenade01 (10/13/20 05:52 PM)
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bodhisatta 
Smurf real estate agent


Registered: 04/30/13
Posts: 61,889
Loc: Milky way
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Re: Flowhood math sanity check [Re: Grenade01] 1
#26983817 - 10/13/20 06:13 PM (3 years, 3 months ago) |
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The resistance of the filter increases over time. But they guarantee an initial resistance of less than some number. You can always use a more powerful blower and I suggest at least 120% of the calculation. You don't want a blower that does exactly 400cfm at 1" if you have a 2x2 1" resistance filter. You'll drop below optimal flow. You can restrict the inlet to your blower to choke the fans output to the correct flow without a speed controller which also saves your motor from unneeded wear and tear. Then as your filter ages you can open the intake up more.
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