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Machine (Machine)
Senior Member
Username: Machine

Post Number: 219
Registered: 07-2003
Posted on Tuesday, October 21, 2003 - 07:42 pm:Edit Post Quote Text Delete Post Print Post Move Post (Moderator/Admin Only)

After much consideration I've decided to build a flow hood. I would like to go with a 36"x24" HEPA and I'm wanting to make sure I buy the right blower. According to Stamets, I should use a blower capable of 500cfm for that size filter in order to achieve "100 feet per minute air velocity". So then would 1/5hp be sufficient for this project? Or should I go with 1/2hp in order to give myself some leeway? Ebay has some refurbished 1/5 and 1/2hp blowers listed at very reasonable prices so 1/2hp wouldn't cost me much more anyway.
"Count not him among your friends who will retail your privacies to the world."
-Publilius Syrus
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rodger rabbit (Skyypilot)
Senior Member
Username: Skyypilot

Post Number: 950
Registered: 02-2003
Posted on Wednesday, October 22, 2003 - 02:22 am:Edit Post Quote Text Delete Post Print Post Move Post (Moderator/Admin Only)

That's an awfully big flow hood size for a small grower. I use a 12 X 24, and it's plenty big enough. You're going to need at least 1/3 hp. However, you need greater than 100 fpm for biological work. 500 fpm would be more appropriate. Stamets sells a hepa filter here: http://www.fungi.com/tools/airfilters.html
look at the model MFDI4824, at 106 feet per minute, paul says it isn't powerful enough for tissue culture work.
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Jater Noslo (Dastats)
Member
Username: Dastats

Post Number: 36
Registered: 09-2003
Posted on Wednesday, October 22, 2003 - 08:41 am:Edit Post Quote Text Delete Post Print Post Move Post (Moderator/Admin Only)

Hey Roger, How about 4, 4" 105 cfm fans, they are like computer fans, only steel. Just a question. I can get a squirrel or an inline, but I'm just curioous if they are all together, if they would output enuff cfm.
Thanks dawg

Jater
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rodger rabbit (Skyypilot)
Senior Member
Username: Skyypilot

Post Number: 953
Registered: 02-2003
Posted on Wednesday, October 22, 2003 - 09:00 am:Edit Post Quote Text Delete Post Print Post Move Post (Moderator/Admin Only)

You want a squirrel cage fan. You need both flow and pressure for a laminar flow hood to work.
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Machine (Machine)
Senior Member
Username: Machine

Post Number: 228
Registered: 07-2003
Posted on Wednesday, October 22, 2003 - 12:30 pm:Edit Post Quote Text Delete Post Print Post Move Post (Moderator/Admin Only)

So for a 24x18 HEPA to get at least 400fpm I need 1200cfm worth of blower. I wonder why all the commercial flow hoods say they arer 90-114 fpm and Stamets says in Mushroom Cultivator that 100fpm is optimum?
"Count not him among your friends who will retail your privacies to the world."
-Publilius Syrus
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Machine (Machine)
Senior Member
Username: Machine

Post Number: 230
Registered: 07-2003
Posted on Wednesday, October 22, 2003 - 02:39 pm:Edit Post Quote Text Delete Post Print Post Move Post (Moderator/Admin Only)

Oh, I see that we also said that 100fpm is based on the filters resistance rating. Too bad fungi.com doesn't specify that. I'm sure 1/3 hp will be adequate for my purposes.
"Count not him among your friends who will retail your privacies to the world."
-Publilius Syrus
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relic (Relic)
New member
Username: Relic

Post Number: 3
Registered: 07-2003
Posted on Wednesday, October 22, 2003 - 03:14 pm:Edit Post Quote Text Delete Post Print Post Move Post (Moderator/Admin Only)

1200cfm is going to blow you away. that is the standard rating of the av. heating/cooling blower = to 3 tons of air conditioning, i.e. 400 cfms per ton or pper 12,000 btu's. the hp rating means little. you can get motors that are 1/5 1/2 1/3 1/4 and all of them rated at 1075rpms. also, the enclosure controls the actual cfm output. you can change the speed of any squirrel cage blower by simply strangling the air supply and contrary to popular belief, this isn't hard of the motor(within a reasonable range) and the motor will draw less amps as it slows down. the only way to know for sure what you end up with is to measure the velocity of the air. i would get an 800 cfm blower(standard heating only funace blower) and a variable speed motor control, make sure the motor is compatible with the control.
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relic (Relic)
New member
Username: Relic

Post Number: 4
Registered: 07-2003
Posted on Wednesday, October 22, 2003 - 03:16 pm:Edit Post Quote Text Delete Post Print Post Move Post (Moderator/Admin Only)

i meant to add that the hp moreso signifies the strength of the blower or how "heavy duty" it is.
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Machine (Machine)
Senior Member
Username: Machine

Post Number: 231
Registered: 07-2003
Posted on Wednesday, October 22, 2003 - 04:31 pm:Edit Post Quote Text Delete Post Print Post Move Post (Moderator/Admin Only)

Ok so what if I already bought a 1200cfm blower? I had intended on hooking it up to a solid state control to limit the flow anyway. The blower also has a 6" adapter on the output which I was planning on taking off. That should limit the cfm right? Sounds like I will be ok as long as I don't take the adapter off and don't turn the thing up full blast.

(Message edited by machine on October 22, 2003)
"Count not him among your friends who will retail your privacies to the world."
-Publilius Syrus
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relic (Relic)
New member
Username: Relic

Post Number: 5
Registered: 07-2003
Posted on Wednesday, October 22, 2003 - 04:59 pm:Edit Post Quote Text Delete Post Print Post Move Post (Moderator/Admin Only)

as long as you have a variable contol you're golden. 2'x3' is quite a large filter area too. that coupled with the depth of the hepa will factor into what it will take. i'm curious if the recommended cfm's is actually the velocity past the filter or the velocity w/o the filter installed?
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rodger rabbit (Skyypilot)
Senior Member
Username: Skyypilot

Post Number: 955
Registered: 02-2003
Posted on Wednesday, October 22, 2003 - 09:14 pm:Edit Post Quote Text Delete Post Print Post Move Post (Moderator/Admin Only)

You can always block part of the intake if you want reduced airflow.

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