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AFryia
Joined: 09 Mar 2006
Posts: 965
Location: S.E. Michigan VPH-G70Q
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| Posted: Sun Apr 20, 2008 1:34 pm Post subject: How Many CFM for a Hush Box? |
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How much CFM exhaust would a typical hush box require. My G70 has three 120mm DC fans. But there isn't a lot of air flow through the card cage due to all the boards and sinks.
The box ventilation would not have near the the resistance the PJ fans see.
So is the a general rule of thumb for CFM, maybe you match fans 2:1 
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mag
Joined: 09 Apr 2007
Posts: 17
Location: stockholm,sweden
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| Posted: Sun Apr 20, 2008 8:34 pm Post subject: |
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why dont build in a mufler and use 1-2 big fans (200mm (8")) ?
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kal
Forum Administrator
Joined: 06 Mar 2006
Posts: 18114
Location: Ottawa, Canada
TV/Projector: JVC DLA-NZ7
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| Posted: Mon Apr 21, 2008 3:52 am Post subject: |
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You have to be aware that if you have an external fan farther away somewhere exhausting your hushbox, you'll lose a lot of CFM due to the length of the duct/pipe and any bends. Most manfacturers have calculations to figure out what the drop is.
FWIW, my projector's similar to yours (8" EM LC) and I use a 130CFM Nutone silent bathroom ceiling fan about 20 feet away with a couple of 90 degree bends. All through 6" sheetmetal rounded pipe (standard HVAC stuff). It keeps my PJ cooler than no hushbox at all.
The fans in my PJ add up to a lot more than 130CFM (I think it's 3 80 CFM fans at the back but don't quote me on this). But they're speed/heat controlled so they never actually run faster than at the lowest speed. (Barco feeds the fans between 7-15V depending on the heat and they never get over 8V with this setup).
Kal
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My basement/HT/bar/brewery build 2.0
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kal
Forum Administrator
Joined: 06 Mar 2006
Posts: 18114
Location: Ottawa, Canada
TV/Projector: JVC DLA-NZ7
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AFryia
Joined: 09 Mar 2006
Posts: 965
Location: S.E. Michigan VPH-G70Q
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| Posted: Mon Apr 21, 2008 11:13 pm Post subject: |
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| kal wrote: | Y
FWIW, my projector's similar to yours (8" EM LC) and I use a 130CFM Nutone silent bathroom ceiling fan about 20 feet away with a couple of 90 degree bends. All through 6" sheetmetal rounded pipe (standard HVAC stuff). It keeps my PJ cooler than no hushbox at all.
Kal |
Kal,
I'll be exhausting directly from the box itself so I was thinking 2 120mm 12V fans or 4 80/92mm fans.
I'm trying to figure out some sort of 'S' bend arrangement foam lined to act like a muffler. I noticed the muffler on my central vac uses that technique, a simple 4" PVC pipe lined with foam.
Anthony
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