Exhaust Fan for a Hush Box... - AVS Forum
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post #1 of 10 Old 01-26-2013, 05:07 PM - Thread Starter
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I am considering buying a new projector that has the exhaust port in the back of the unit. I am looking for a good / quiet exhaust fan that I can put in the attic and attach via an air duct to a vent that would be located in the upper rear ceiling of the hush box to expel the hot air. A temperature sensor for the unit will also be something needed for this set up.

Any recommendations on a good unit and where to find it would be great!

Thanks,

Jim
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post #2 of 10 Old 01-26-2013, 07:20 PM
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a Fantech inline fan, I like the ones in a plastic body rather than metal. Use a $20 line voltage attic fan thermostat that you can mount inside the hush box. Be sure to get a back flow prevention damper. The fan and damper can be had at HVACquik.com. The thermostat at your local big box.

http://www.hvacquick.com/products/residential/Fans/Inline-Fans/Fantech-FR-Series-Inline-Centrifugal-Fans

and

http://www.hvacquick.com/products/residential/Kitchen-Exhaust/Silencers/Spring-Loaded-Backdraft-Dampers

one other word on this, venting to an attic space is generally frowned upon in building codes, Up north it can create ice under the roof. Not sure in your climate zone. It needs to go through the roof or exit under soffit. It would be even better to connect the duct to the return duct of your HVAC system. That way you aren't creating more negative pressure in the house which has to be made up for by outside air through any path possible. Drawing in hot humid air in the summer just makes your AC work harder. Putting the hot air back with other hot air going to the AC is overall more efficient.
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post #3 of 10 Old 01-27-2013, 04:17 AM - Thread Starter
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Big,

Thanks for the great information on the exhaust fan. So it looks like I would be using 4" air duct which would be the same size as the damper and exhaust fan. Just attach them both inside the air duct and plug it in. Does it matter how far or close I mount the damper and fan from the actual hush box?

Thanks again,

Jim
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post #4 of 10 Old 01-27-2013, 05:01 AM
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Thanks for those details, Big.

Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense. -Buddha

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post #5 of 10 Old 01-27-2013, 05:26 AM
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The further the fan from the hush box the quieter it will be. Attach the fan in the attic with rubber straps (bungee cords) or other non rigid material, or just rest it on something soft , you can wrap it in insulation to further dampen any sound.
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post #6 of 10 Old 01-27-2013, 07:17 AM - Thread Starter
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So I am guessing around 8 to 10 feet from the hush box. I would think that if you went to far away from the hush box the amount of air the fan would be able to draw out of the box would become less. Is that a correct assumption?

And I can never say thanks enough but your advice is invaluable. Thanks again!biggrin.gif

Cheers
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post #7 of 10 Old 01-27-2013, 07:36 PM
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Yes, the further away the less cfm it will actually push/ pull. Fyi every 90 degree turn is like adding 5 foot of pipe. also if you use ac flex it will tend to be a little noisier. i would use hard pipe from hush box to fan, then use insulated flex to your back flow damper/ termination point. The fan you are looking at is very similar to the ones we use on dryer vents that are over 25 feet. fantech fans are awesome!
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post #8 of 10 Old 01-27-2013, 08:42 PM
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hard pipe will transfer vibration and create noise, better to oversize the flex.
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post #9 of 10 Old 02-22-2013, 12:00 PM - Thread Starter
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We went with the Fantech FR 110 exhaust fan with 167cfm from the link above and it was way to loud. Our HAVC guy used 4" metal flex ducting the kind you would see coming out of your dryer. Is the ducting the issue for the noise and if so what should of been used. We had the fan 20' away from the projector box in the attic. You could see all of the dust being sucked into the projector box around the lens cut out in the front of the projector box. The HVAC guy is coming back on Monday to try a fan with less CFM of about 80 and see if that works... Maybe also change out the metal ducting as I told him that I did not think that was the correct material...

Thanks again for any ideas....smile.gif

P.S. We did use a variable controller to adjust the amount of air the fan was pulling and it still was to loud...
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post #10 of 10 Old 02-22-2013, 01:25 PM - Thread Starter
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Spoke with Jake at HVACQuick and he said use flex insulated duct that has poly liner wrapped with insulation and foil on the out side.... On to plan B then....biggrin.gif
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