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InvisibleWilly Wonka
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laminar flowhood blower question * 1
    #17528830 - 01/10/13 05:03 PM (11 years, 4 months ago)

Greatings evveryone,

I am getting pretty close to finishing my flow hood build. I need a little help understandding the blower requirements for my filter. I emailed the company who makes my filter and asked them what the working point where the amount of air flowing through my filter was sufficient to achive laminar flow.

This is what the wrote back, "In order to maintain laminar flow the air veloccity should not exceed 100fpm therefore, limit the maximum airflow to 350-400cfm. The drop at this point will be approx. 0.3-.35 in wg.

What does all of this mean? I am having such a hard time getting the information I need and figuring out what size blower I want and what the blower needs to deliver at what working point.
Does this information tell me what I need to know?

Please and thank you,

Willy


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OfflineTheCyndicate
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Re: laminar flowhood blower question [Re: Willy Wonka]
    #17529161 - 01/10/13 06:00 PM (11 years, 4 months ago)

Quote:

Willy Wonka said:
Greatings evveryone,

I am getting pretty close to finishing my flow hood build. I need a little help understandding the blower requirements for my filter. I emailed the company who makes my filter and asked them what the working point where the amount of air flowing through my filter was sufficient to achive laminar flow.

This is what the wrote back, "In order to maintain laminar flow the air veloccity should not exceed 100fpm therefore, limit the maximum airflow to 350-400cfm. The drop at this point will be approx. 0.3-.35 in wg.

What does all of this mean? I am having such a hard time getting the information I need and figuring out what size blower I want and what the blower needs to deliver at what working point.
Does this information tell me what I need to know?

Please and thank you,

Willy




The amount of air for your filter to achieve laminar flow is 350-400 cfm at this is at 100fpm "feet per min" and this is at 0.3-.35 static pressure.  I would go with a blower that ranges 400 -450 cfm

Cyn

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Offlinethiotimoline
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Re: laminar flowhood blower question [Re: TheCyndicate]
    #17529497 - 01/10/13 07:01 PM (11 years, 4 months ago)

Apparently "wg" stands for "water gauge" and means "inches of water" (analogous to the much more standard "millimeters of mercury" pressure unit). Sigh... why can't people all get along and use SI units?

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InvisibleWilly Wonka
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Re: laminar flowhood blower question [Re: thiotimoline]
    #17538141 - 01/12/13 03:04 PM (11 years, 4 months ago)

Ok so if I am understanding what you are telling me then the information I have at this point tells me that I am looking for a fan that pushes 350-400cfm at a resistance of .3-.35. I don't know if I am wording everything right but I think that I finally understand what I need to. Do I finally get it? I know I sure have posted alot of the same question over and over but I want to understand. Thanks to everyone for reading my posts and a big thank you to everyone who has taken the time to post replies to my questions. Without the help that I get from the people on Shroomery who are more expirenced than me I would have never learned as much as I have. I love this site.

Thank you,

Willy

Edited by Willy Wonka (01/12/13 03:14 PM)

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OfflineRogerRabbitM
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Re: laminar flowhood blower question [Re: Willy Wonka]
    #17540117 - 01/12/13 10:30 PM (11 years, 4 months ago)

What size filter?  Post the data plate or graph.

You asked the wrong question of the manufacturer.  You don't just want the speed to achieve laminar flow, but enough to push contaminants out of the way.  You got a good answer though, because 100 to 125 linear feet per minute is the speed you want the air leaving at.
RR


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OfflineKramer
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Re: laminar flowhood blower question [Re: RogerRabbit]
    #17541098 - 01/13/13 07:00 AM (11 years, 4 months ago)

I sent you that link to the blower that fits that filter perfectly a couple weeks back?

I also talked to Astrocel while buidling mine and they saw the specs of that 8 inch blower and said it was fine

The plenum on mine is kind of big but that shouldn't even really effect much because it will all pressurize the same, unless you have an extremely small plenum it could cause turbulence or dead areas.

Mine moves at the high end of that 120 ish linear FPM.

Here is the link again.

http://www.ebay.com/itm/New-8-Inch-Inline-Exhaust-Cooling-Duct-Fan-Vent-Blower-/160954470061?pt=LH_DefaultDomain_0&hash=item2579a24ead

Specs are on there in the description too.

I know it is not a squirrel cage blower however, it works perfectly with that filter, and it has a 5 year warranty.


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Edited by Kramer (01/13/13 07:01 AM)

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InvisibleWilly Wonka
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Re: laminar flowhood blower question [Re: RogerRabbit]
    #17543916 - 01/13/13 07:15 PM (11 years, 4 months ago)

Quote:

RogerRabbit said:
What size filter?  Post the data plate or graph.

You asked the wrong question of the manufacturer.  You don't just want the speed to achieve laminar flow, but enough to push contaminants out of the way.  You got a good answer though, because 100 to 125 linear feet per minute is the speed you want the air leaving at.
RR



The filter is 24"x24"x12."


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InvisibleWilly Wonka
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Re: laminar flowhood blower question [Re: Kramer]
    #17544000 - 01/13/13 07:37 PM (11 years, 4 months ago)

Quote:

Citadel_7 said:
I sent you that link to the blower that fits that filter perfectly a couple weeks back?

I also talked to Astrocel while buidling mine and they saw the specs of that 8 inch blower and said it was fine

The plenum on mine is kind of big but that shouldn't even really effect much because it will all pressurize the same, unless you have an extremely small plenum it could cause turbulence or dead areas.

Mine moves at the high end of that 120 ish linear FPM.

Here is the link again.

http://www.ebay.com/itm/New-8-Inch-Inline-Exhaust-Cooling-Duct-Fan-Vent-Blower-/160954470061?pt=LH_DefaultDomain_0&hash=item2579a24ead

Specs are on there in the description too.

I know it is not a squirrel cage blower however, it works perfectly with that filter, and it has a 5 year warranty.



I did get the link thank you very much. I really want to understand the application of the formula behind selecting a blower. I want to be sure I am matching the right blower to the right filter and if I understand what I am looking for then I can shop around to find the best blower at the best price.

There are a few hydroponic stores in my local area and if I know and understand the blower requirements for my filter then I might be able to find a blower at one of the hydro shops that will work with my filter and I will at least save on shipping charges if nothing else. I am glad that I have that link because if I can't find a blower that I can pick up in person then I can alwayss fall back on the link you posted as a sort of default. Thank you again.


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OfflineRogerRabbitM
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Re: laminar flowhood blower question [Re: Willy Wonka]
    #17544313 - 01/13/13 08:57 PM (11 years, 4 months ago)

Quote:

Willy Wonka said:

The filter is 24"x24"x12."





That's really not the best choice in filters to use.  At 1000 cfm, it only developed .4" W.G. of static pressure behind it. You'd probably be better served with a filter which flowed 1000 feet per minute at 1" or so.

That said, you're going to want a 500 cfm blower @ at least .5" W. G. or so.  Resistance isn't linear so go with that spec and you'll be fine.  You can always block part of the intake off to reduce flow.

The problem is with such a small resistance, it's going to be hard to build enough pressure on the back side to get laminar flow without blowing too hard.
RR


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InvisibleWilly Wonka
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Re: laminar flowhood blower question [Re: RogerRabbit]
    #17548182 - 01/14/13 05:32 PM (11 years, 4 months ago)

Thank you


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Invisiblehostyle
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Re: laminar flowhood blower question [Re: Willy Wonka]
    #17930818 - 03/09/13 07:39 PM (11 years, 2 months ago)

Willy,

Did you end up getting a cheap inline fan that does xxx cfm @ 0.0 S.P.?

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InvisibleWilly Wonka
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Re: laminar flowhood blower question [Re: hostyle]
    #17931232 - 03/09/13 09:16 PM (11 years, 2 months ago)

No I haven't purchased a fan yet.  I am just about to .  I am looking at these two fans.  The first one is this one: http://www.grainger.com/Grainger/DAYTON-PSC-Blower-12G805 it pushes 605 cfm @.5 and will run me $247.50 brand new, or this one http://www.grainger.com/Grainger/DAYTON-PSC-Blower-12G804 which will push 450 cfm @ .5 It is a little under what RR was saying to shoot for but it only costs $188.75  I really like the idea of saving almost $60 but I don't want to get something that ends up being too weak.


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Invisiblefastfred
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Re: laminar flowhood blower question [Re: Willy Wonka]
    #18065688 - 04/06/13 02:47 AM (11 years, 1 month ago)

That's a lot of cash to dump on a blower motor.

I'd call around to some HVAC or appliance places and see if you can't get one for free or scrap rate prices.

I used small blowers on my first and 2nd flow hoods.  For the third I just opened up the yellow pages and started calling.  The very first place actually offered me a nice big blower for free.  They all have boneyards of furnaces, ductwork, and blowers.

Lately I've built a few things with microwave blowers, which are surprisingly powerful.  In the end you just can't beat free, and you're saving them from being melted down in China.


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I find the whole "my drug should be legal but yours should be illegal" mindset disgusting and hypocritical. It's what George Bush and company do when they drink a cocktail and debate the best way to imprison marijuana users. -Diploid

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OfflineDmix005
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Re: laminar flowhood blower question [Re: RogerRabbit]
    #18159409 - 04/24/13 03:25 AM (11 years, 27 days ago)

Hello,

I'm about to build a flow hood...I think I have the right parts picked and I just wanted to make sure of that before i ordered it.

The filter I want to use is 24X24X5 

my calculations are:

= 4ft^2 * 100 FPM = 400ft^3/min

= 400ft^3/min + 10%-20% for inefficiencies

= 440 to 480 cfm (call it 500)

so now, as I understand it, I need a blower that can push 500cfm at the filter's static pressure.  I've put the link for the filter below as well as a pic with the info:


FILTER LINK



I'm pretty sure that "Pressure Drop in Inches Water Guage" is the static pressure for the corresponding airflow (is that right?)

so, looking at the green line, I need a blower that can move 500cfm at about 0.35 Inches. I went to Grainger and found this one:

http://www.grainger.com/Grainger/DAYTON-PSC-Blower-1TDT2?Pid=search

Have I done this right?

I also have one other concern.  In my research, I keep reading that the blower is a small cost of building a flow hood, but this one is $185, more than the hepa filter.  Is this normal? or have I picked the wrong blower?

Looking forward to you Feedback

Thanks!

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OfflineKramer
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Re: laminar flowhood blower question [Re: Dmix005]
    #18170840 - 04/26/13 08:39 AM (11 years, 25 days ago)

You need to be mindful that, the CFM is relevant but it isn't I made the mistake of buying a blower based off of its CFM cpabilities and it did not work for the project I had.

What I really needed was a blower that could move that much air but had some power to it, so you have the right idea by focusing on the static pressure as well.


That setup should work, I think that fan is over priced and you should check eBay that have good fans for cheaper than that. I ended up using a inline blower which worked just fine and has a 3 year warranty.

Post pics of the finished product man.

    C7


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Offline10KOysters
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Re: laminar flowhood blower question [Re: Kramer]
    #18171651 - 04/26/13 12:31 PM (11 years, 25 days ago)

Scroll further down that page.

The stats for that blower say 360cfm at .8 inches.

So, no.  That blower is too small for your filter.

Peace


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OfflineDmix005
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Re: laminar flowhood blower question [Re: 10KOysters]
    #18175456 - 04/27/13 01:53 AM (11 years, 24 days ago)

Thank you very much for the reply!! just saved me a lot of frustration

so I haven't correctly identified the filter's resistance then eh?

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Offline10KOysters
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Re: laminar flowhood blower question [Re: Dmix005]
    #18175874 - 04/27/13 06:40 AM (11 years, 24 days ago)

Well, that fan does 500cfm at .3 and 480cfm at .4

It's borderline for your original .35 figure.  If your .35 figure is wrong, I wouldn't know.  :smile:

Peace


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