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jellyfish


Registered: 10/02/05
Posts: 7,457
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Flow Hood Question
#18219204 - 05/05/13 06:57 PM (11 years, 16 days ago) |
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Well it's been a few years since I've experimented with this hobby (except for a couple pf cakes last summer) so I've decided to put some real effort in. I got myself a hepa filter and a fan that fits the specifics (I hope). I've been searching but can't find a straight answer, does the fan have to be mounted on the top? Every time I see a diy flowhood the fan blows are at a 90 degree angle to the filter but when I see pictures of professional flow hoods they look like the fan blows directly on the filter. What's the difference?
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Jeff
Addict



Registered: 10/06/12
Posts: 1,488
Last seen: 6 years, 5 months
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Re: Flow Hood Question [Re: jellyfish]
#18219627 - 05/05/13 08:32 PM (11 years, 16 days ago) |
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Every hood I have come across the fans blow at 90 degrees. I am pretty sure that I have never seen one that blow directly at the filter.
-------------------- Myco-tek
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fastfred
Old Hand



Registered: 05/17/04
Posts: 6,899
Loc: Dark side of the moon
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Re: Flow Hood Question [Re: Jeff]
#18219707 - 05/05/13 08:49 PM (11 years, 16 days ago) |
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The ones I build usually have the blower blowing right at the filter, but with a prefilter and polyfil loaded plenum in between.
I don't bother with laminar flow though. Blowing directly on the filter is never a good idea if you want laminar flow and your filter to last more than a few months.
-FF
-------------------- It drinks the alcohol and abstains from the weed or else it gets the hose again. -Chemy The difference between the substances doesn't matter. This is a war on consciousness, on our right to the very essence of what we are. With no control over that, we have no need to speak of freedom or a free society. -fireseed "If we are going to have a war on marijuana, the least we can do is pull the sick and the dying off the battlefield." -Neal Levine (MPP) 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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weetsie
unlicensed tub surgeon



Registered: 05/08/11
Posts: 572
Loc: United Kingdom
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Re: Flow Hood Question [Re: fastfred]
#18219781 - 05/05/13 09:03 PM (11 years, 16 days ago) |
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Mine has the blower (12" inline fan) inside the flowhood box mounted on the back blowing directly into the filter.
I wondered the exact same thing when I built mine and in the end saw no reason why it wouldn't work and would allow my hood to take up much less space as the fan is much wider than it is deep and I had space behind it to allow airflow in.
I have had no issues with it and even with the fan only 3" away from the filter there appears to be perfect laminar flow. I have done a test leaving an empty agar plate open in front of it for about 20 minutes and even after months it's as clean as the day it was poured.
-------------------- Active grow logs: Oysters on Straw Pellets Trade list
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Terry M
Stranger in a Strange Land



Registered: 06/18/10
Posts: 1,502
Loc: Rhode Island
Last seen: 9 years, 3 months
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Re: Flow Hood Question [Re: weetsie]
#18231557 - 05/08/13 08:09 AM (11 years, 13 days ago) |
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My flowhood also has the blower directly in back of the filter, too. Turns out a HEPA filter has enough flow resistance so that a big plenum isn't really necessary to even out the flow.
-------------------- Liberté, égalité, humidité.
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Amanita virosa
botanist by day


Registered: 12/04/11
Posts: 2,458
Loc: north kakalacky
Last seen: 10 months, 4 days
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Re: Flow Hood Question [Re: Terry M]
#18236795 - 05/09/13 07:47 AM (11 years, 12 days ago) |
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Like jeff, I have never seen a commercial one with the blower in back and i wonder if you were building one why you would not want the blower on top instead of in the back. That way the back of the hood can be against a wall and you are taking advantage of the vertical space of the room
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