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OfflineVisigoth
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Registered: 11/28/01
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Size of blower for flowhood??
    #828995 - 08/19/02 06:50 PM (21 years, 8 months ago)

In mycotopia's flowhood design, at least a 495 cfm blower is suggested for a box using a 24 x 12 filter. Well what size would u need for the same box only measuring 24 x 18?? Is it possible to have the air coming out too fast??

Vis


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"15 minutes in freezing conditions?!?! You'd become a popsicle before you made that!!!"

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OfflineVisigoth
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Re: Size of blower for flowhood?? [Re: Visigoth]
    #830763 - 08/20/02 03:17 PM (21 years, 8 months ago)

Bump Bump


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"15 minutes in freezing conditions?!?! You'd become a popsicle before you made that!!!"

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InvisibleAlkaloids
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Registered: 11/15/98
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Re: Size of blower for flowhood?? [Re: Visigoth]
    #830850 - 08/20/02 04:12 PM (21 years, 8 months ago)

Yes it is.
Depending upon the application you can have air coming out of the filter too fast. It could blow your spores all over the place for example. That and filter efficiency could (will) be affected by excessive air flow through.
If you can't find a rheostat to attentuate the incoming air flow you could simply stack additional pre-filters in front of the intake to do the same thing.
hope this is helpful


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InvisibleAlkaloids
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Re: Size of blower for flowhood?? [Re: Visigoth]
    #832971 - 08/21/02 10:31 AM (21 years, 8 months ago)

24X18 @ 1" static pressure = you will need a fan that can push at least 300 CFM at 1" S.P.
Sorry I can't remember right now (really tired)... there is a way to convert free air flow to air flow at a given S.P. If I remember it I will post it later. I think someone else should know the answer to this also.
?ggoooodd?


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InvisibleAlkaloids
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Re: Size of blower for flowhood?? [Re: Visigoth]
    #833016 - 08/21/02 10:39 AM (21 years, 8 months ago)

I think I remember... oooppss
to convert free air flow (CFM) to CFM @ 1" S.P. multiply your free air flow by 0.404
that should give you an accurate enough estimation.
ex.
your blower delivers 1200 CFM (free) sooo.. at 1" S.P. it would push ~485 CFM
maybe this will be more instructive
later


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OfflineVisigoth
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Re: Size of blower for flowhood?? [Re: Alkaloids]
    #833269 - 08/21/02 11:43 AM (21 years, 8 months ago)

Allright, I think I understand, I multiply the cfm of my blower x 0.404 and that's the number?? Shouldn't the dimensions of the filter be included in this formula? And what cfm do I want to be coming out of the filter onto my workspace? Is there a preferable number? Thanks Alkaloids!!


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"15 minutes in freezing conditions?!?! You'd become a popsicle before you made that!!!"

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InvisibleAlkaloids
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Re: Size of blower for flowhood?? [Re: Visigoth]
    #835484 - 08/22/02 07:56 AM (21 years, 8 months ago)

you want a _linear_ air flow rate of no less than 100 feet/min. I think you can do good work in environments up to about 120 ft/min maybe a bit more.
Oh I already figured out everything with the dimensions of your filter
300 CFM @ 1" S.P is what you need for yours minimum. You could go a bit higher if you wanted.
peace


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OfflineVisigoth
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Re: Size of blower for flowhood?? [Re: Visigoth]
    #836016 - 08/22/02 12:24 PM (21 years, 8 months ago)

Can it be a duct fan, or does it absolutely have to be a squirrel cage blower??

Vis


--------------------
"15 minutes in freezing conditions?!?! You'd become a popsicle before you made that!!!"

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InvisibleAlkaloids
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Registered: 11/15/98
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Re: Size of blower for flowhood?? [Re: Visigoth]
    #836345 - 08/22/02 02:45 PM (21 years, 8 months ago)

Duct fans are generally not suited for operating against back pressure (from what I understand.. if i am wrong someone please correct me).
I would go with a squirrel cage fan to be safe. If you need to I can direct you to a gentleman that sells refurbished ones at very reasonable prices.


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Invisibleshroomophile
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Re: Size of blower for flowhood?? [Re: Visigoth]
    #838468 - 08/23/02 02:09 PM (21 years, 7 months ago)

Go to your local HVAC dealer and strip it off of their trash.I've gotten 1/4 to 1-1/4 H.P.squirrels for free.


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Once the mighty oak,was a nut who held his ground.

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OfflineAnnoA
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Re: Size of blower for flowhood?? [Re: Visigoth]
    #839613 - 08/24/02 01:11 AM (21 years, 7 months ago)

>Well what size would u need for the same box only measuring 24 x 18??

Only?
24x18 inch is more than 24x12 inch...

Read http://www.shroomery.org/forums/showflat.php?Cat=&Board=Forum4&Number=798916&page=1&view=collapsed&sb=5&o=31&fpart=1 .

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OfflineVisigoth
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Re: Size of blower for flowhood?? [Re: Visigoth]
    #847018 - 08/27/02 01:08 PM (21 years, 7 months ago)

Well, I'm just thoroughly confused now. I don't understand this static pressure stuff at all, are different filters rated at diff. static pressures?? Because there's nothing on my filter or fungi's website that gives this info. I have one person here telling me to use a 700 cfm, another person telling me 300, fungi perfecti responded to my email and they're saying to figure it according to 8" static pressure while everyone else is talking about 1". Ughghghg!!!! I really don't want to shell out 200 bucks for a blower and have it not work. I already wasted 30 bucks on wood because Loe's failed to inform me before they started that they couldn't cut exact specifications. I really wanna build this flowhood but it is starting to become a friggin nightmare!!!

Vis


--------------------
"15 minutes in freezing conditions?!?! You'd become a popsicle before you made that!!!"

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InvisibleAlkaloids
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Registered: 11/15/98
Posts: 743
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Re: Size of blower for flowhood?? [Re: Visigoth]
    #847360 - 08/27/02 04:03 PM (21 years, 7 months ago)

Don't get too worked about it.
It can be a bit frustrating, but what I have told you so far is right. If you just get a squirrel cage blower rated for at least 700 -750 CFM (no static pressure) then you will be alright. It works out to about 300 CFM at 1"SP.
Fungi might be suggesting .8" SP but for these purposes using the 1" SP will do fine for calculations (if you have to make any, which you shouldn't now).
The filter my gorilla ordered has a 1" SP so that is what I use and many HEPA filters use that rating also.
Go back and read my posts again. I did explain the conversions, but if you have additional questions you can PM if you would like.
Don't worry mon 'tis a 'ting.
peace


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OfflineVisigoth
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Re: Size of blower for flowhood?? [Re: Alkaloids]
    #847467 - 08/27/02 04:50 PM (21 years, 7 months ago)

Damn, that fuckin 700 cfm is gonna freakin cost me bigtime!!!


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"15 minutes in freezing conditions?!?! You'd become a popsicle before you made that!!!"

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OfflineAnnoA
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Re: Size of blower for flowhood?? [Re: Visigoth]
    #848195 - 08/27/02 10:40 PM (21 years, 7 months ago)


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OfflineAnnoA
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Re: Size of blower for flowhood?? [Re: Alkaloids]
    #848197 - 08/27/02 10:43 PM (21 years, 7 months ago)

>to convert free air flow (CFM) to CFM @ 1" S.P. multiply your free air flow by
>0.404 that should give you an accurate enough estimation.

This works only for exactly one specific blower. Not even type, but a single model.

Every blower has a different flow-static pressure dependence, it?s imposible to calculate it by applying a factor....

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OfflineAnnoA
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Re: Size of blower for flowhood?? [Re: Alkaloids]
    #848304 - 08/28/02 01:59 AM (21 years, 7 months ago)

>Duct fans are generally not suited for operating against back pressure (from
>what I understand.. if i am wrong someone please correct me).

I use a duct fan. It works as good as any other blower, as long as you choose the right one(in terms of the correct flow at the correct static pressure).

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OfflineVisigoth
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Re: Size of blower for flowhood?? [Re: Anno]
    #849295 - 08/28/02 12:38 PM (21 years, 7 months ago)

So am I correct when I say that after figuring out the correct cfm, not only do I have to have a fan that delivers that cfm, but I have to have one that delivers it at exactly 1" static pressure?!?!?!

Vis


--------------------
"15 minutes in freezing conditions?!?! You'd become a popsicle before you made that!!!"

Extras: Filter Print Post Top
OfflineVisigoth
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Registered: 11/28/01
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Re: Size of blower for flowhood?? [Re: Visigoth]
    #849312 - 08/28/02 12:45 PM (21 years, 7 months ago)

Ok screw it, I just did some math and Alkaloids seems to be right. I do need a fan that delivers 300 cfm at 1" static pressure, and my filter says its rated at 429 cfm at 1" static pressure, so I guess that means the filter itself is rated for 1" static pressure. So I'm gonna go w. the 700 cfm fan. If anyone knows this is wrong (hint, hint) then speak now because I'm about to spend money that I don't really have to get this thing. Thank you all very much for your help, although I'm still a little confused I sincerely appreciate everyone's effort.

Vis


--------------------
"15 minutes in freezing conditions?!?! You'd become a popsicle before you made that!!!"

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OfflineAnnoA
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Re: Size of blower for flowhood?? [Re: Visigoth]
    #849985 - 08/28/02 07:04 PM (21 years, 7 months ago)

>So am I correct when I say that after figuring out the correct cfm, not only do I >have to have a fan that delivers that cfm, but I have to have one that delivers it at
>exactly 1" static pressure?!?!?!

Correct!
If of course the ststic pressure of your HEPA + prefilter is 1".....

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InvisibleAlkaloids
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Re: Size of blower for flowhood?? [Re: Anno]
    #851620 - 08/29/02 04:21 PM (21 years, 7 months ago)

thank You Anno, I stand corrected.
As I mentioned tech details on blowers are not my speciality. Although I will try and learn more about the subject in the future.
Visigoth if You want a cheap blower let me know. I know a guy who repairs and sells used ones at very decent prices. I got a 1200 CFM blower (free air) for $50 US. Don't go spending gobs and gobs of money.
peace


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OfflineAnnoA
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Re: Size of blower for flowhood?? [Re: Alkaloids]
    #851646 - 08/29/02 04:37 PM (21 years, 7 months ago)

>I got a 1200 CFM blower (free air) for $50 US

Wow, this is really cheap.

Edited by Anno (08/29/02 04:38 PM)

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