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Safety -- Make sure you are safe! |
2012-04-09, 4:00pm
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Senior Member
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Join Date: Jun 15, 2007
Location: Richmond, BC
Posts: 131
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Upgrading my ventilation
I've just had new workbenches built in my little shedio and am upgrading the ventilation as well. I have an HVAC guy building my hood out of galvanized steel.
My new Scorpion will face into a corner and the hood will be 3 sided. The measurement from wall to wall is 5'. The measurement from the front edge of the hood above the torch to the corner at the back of the bench is 3'.
My little shedio is 8' x 12'. The fan will be mounted on the roof directly above where the torch is so no extra ducting with bends. I have a door and window directly behind me for makeup air.
What CFM fan do you think I should get? I was thinking 650CFM. I don't want anything that sounds like a jet fighter taking off....don't want the neighbours to complain. and with that in mind any ideas about how to soundproof a rooftop fan?
Thanks for any help you can provide.
Suzanne
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2012-04-09, 7:00pm
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Curmudgeon Engineering
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Join Date: Feb 15, 2006
Location: Near Seattle, WA
Posts: 1,723
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So the bench front is 5' wide? How high is the hood edge above the bench? 5 feet X height above bench to lower edge of hood x 100 = cfm needed. Working backwards; 650 cfm fan divided by 100 = 6.5 then divide by 5 width means your hood has to be about 16 inches above the bench. But you didn't say what shape your hood is or how/where it would be mounted so the afore calculations take a lot of factors for granted and are probably wrong.
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2012-04-09, 8:17pm
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Senior Member
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Join Date: Jun 15, 2007
Location: Richmond, BC
Posts: 131
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Upgrading ventilation
Hi, thanks for answering.
Yes, the bench is 5' long. I just measured and the edge of the hood will be 18" above the workbench. So if I'm doing this correct 5 x 1.5 x 100 = 750CFM?
The hood will be a triangular shape across the front of the bench and into the corner the torch is facing. The ceiling is 6.5' high. The hood will cover the entire bench.
If this calculation is correct I'll have to let my HVAC know I need a different fan.
Suzanne
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2012-04-10, 7:47am
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Gentleman of Leisure
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Join Date: Jun 10, 2005
Location: A Little Bit West of Yosemite Valley
Posts: 5,200
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Yep 750CFM minimum...
Dale
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San Francisco - A Few Toys Short of a Happy Meal
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2012-04-10, 10:42am
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Curmudgeon Engineering
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Join Date: Feb 15, 2006
Location: Near Seattle, WA
Posts: 1,723
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How about baffeling off about 6" at each side so the opening is only 4' long then 650 cfm is in range. My thought is a 6" wide stripe of material parallel to the bench front edge running from the bench top to the hood bottom; one on each side at the corners/ends of the bench. If these baffels were wood the they would also be a good place for hooks to hang tools . Just a thought to save getting a larger fan...or not.
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2012-04-13, 9:56am
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Senior Member
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Join Date: Jun 15, 2007
Location: Richmond, BC
Posts: 131
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Upgrading ventilation
I had the same thought. I think I could even bring it down to 3' for maximum benefit....then I could have a 650 CFM fan with a speed control.
I'm just waiting to hear what the sones are to be sure I'm within the noise bylaw of my city. I've got a cranky neighbour that will question everything I do on my property.
Thanks for your help.
Suzanne
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2012-04-25, 2:10pm
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Salt Box Beads
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Join Date: Oct 23, 2005
Location: Heading to Paradise
Posts: 4,161
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Those pesky neighbors! We have some here too.
Some people have used sound board that muffles the sound and said it helps a lot.
I love having three speeds on my fan. It is a real plus.
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