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Old 04-20-2013, 09:25 AM   #1
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Adding an intake fan


I have an airtight vocal booth with an inline exhaust fan turned down to approx 200 CFM. I've been popping my ears frequently and I'm wondering if that is because of pressure difference or some such. And if adding an intake bathroom fan at 150 CFM would help my ears. Right now, the intake is passive. The intake/exhaust holes in the wall are 4" diameter. And the exhaust fan is 6".

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Old 04-20-2013, 10:12 AM   #2
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Adding an intake fan


Use a speed controller on the exhaust fan and slow it more. Or the intake larger.

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Old 04-20-2013, 04:41 PM   #3
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Adding an intake fan


The variac is already set to run the fan at 50%. Any lower and damage will occur to the fan, I'm told. Also, any lower and ventilation would be compromised. Making the intake larger is not an option.
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Old 04-20-2013, 06:26 PM   #4
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Adding an intake fan


Then use a bath fan in the intake.

Must be a large booth that you need 200 CFM. Does it also have equipment in it.
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Old 04-20-2013, 10:35 PM   #5
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Adding an intake fan


Air in should equal air out to prevent the pressure difference you have been experiencing. Try to match your fans' output.
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Old 08-27-2013, 07:04 AM   #6
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Adding an intake fan


Added the bathroom fan, a 6" Panasonic FV-15VQ5 at 150cfm, but have to run it at approx 50% speed hooked up to the variac, with the Sunleaves Windtunnel 6" 409cfm as exhaust. My ears are still popping, probably because the fan cfm's are not approximately equal, as chitownken suggested.

The reason I hooked up the bath fan to the variac as well is because it's too loud at full power. So I'm thinking I should redo the ventilation setup for the booth, making the holes in the wall 6" instead of 4". I think that would allow me to increase the speed of the fans without raising the noise level because of the increased duct size. Is my assumption correct?

To answer beenthere's question, the booth is almost 5x7 inside and 6x8 outside, but it has two layers of 2" Roxul stone wool insulation and staggered stud construction all around, except the floor. The effective cfm of the exhaust is probably only about 150cfm after accounting for static pressure loss.
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Old 08-27-2013, 08:19 AM   #7
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Adding an intake fan


Or look at using in-line fans like those from Fantech. That and insulated ducts. I've got Fantech units on all my bathrooms, with at least 6' between the grille and the fan motor. It's dead silent in the rooms.
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Old 08-28-2013, 06:04 PM   #8
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Adding an intake fan


A 5X7X10 room would be 350 cubic foot of air, without any contents or occupants.

Even a only 100CFM. that would be 17 air changes an hour. At 150 CFM, that would be 26 air changes an hour. Do you really need that many.

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