dust collector closet exhaust ideas for 5HP high pressure DC ?

[Dave Burson]

OK Just got the new Oneida 5HP high pressure DC installed, and it's a beast! Love it already. Good news- it sucks 2150 cfm leaving ability to leave a few gates open if you choose to and still suck that proverbial tennis ball. Bad news, the 10" x 20" exhaust plenum I had in ceiling of sound proof closet is nowhere near big enough. The first clue was when I was unable to close the door once it started, I mean not able to even get it within a few inches of closed. Exhaust port of DC is 8" so I thought the 200 sq in exhaust was enough but obvious something was amiss. I called Oneida tech support- (those guys are great btw!). Adam said that 200 inches was more than enough for my 20 yr old 2 HP that was replaced. But this new technology produces so much more volume at much higher velocity and static pressure, the exhaust needs are way more significant. Need at least 1 sq ft/500CFM. So that means slightly more than 24"x24" sized duct (~620 sq inches). Since I already have 200 inch exhaust, looking to add one large port.
Shop is 55 x 24 x 9.5, so ~12.5 k cu ft.
So I am now looking for ideas to use for ducting. I live in Virginia, and the two mini splits would work all the time trying to replace air anytime it is on if I exhaust outside, so not interested in going that route. So the duct will probably just need to be 15-20' or so. Was wondering if there are any flexible ducting that yo know about that might work here for long term solution? I also like to keep noise at bay, which is why I built the current plenum using Jim Becker's (TY JIM!!) type design. It just is no where near big enough, so need to add another 400 sq inches of exhaust space. Would flexible ducting, say a 24" flex duct, if I made it an extra 10' long and made a few bends... offer the sound proofing I am hoping for? The space above is accessible, but it's simply the dead space under the trusses, so will take a lot of bending, which is good for noise proofing (I remember Jim told me, a bend is your friend in sound proofing).

Thanks so much for any feedback!! Look forward to hearing any input you got!
Dave




IMG_1956.jpgIMG_1955.jpg

[Jim Becker]

I think you can use any flexible duct product for this that is large enough and stiff enough to stay in shape/open. As you have picked up, you want that pathway to bo "non direct" so a nice big curve from the DC closet back to the workspace would be ideal. I'm actually going to make my return in my future new shop a little larger than the one you reference and without the "sharp" bends for even greater efficiency, even though I doubt that I'll upsize my cyclone...which coincidentally is that same ~20 year old 2 hp unit you reference. LOL

Congrats on the new system, BTW...that's a mighty fine solution!

[Dave Burson]

Thanks Jim. Wondering if by chance anyone is familiar with any of the large PVC (or similar) flex hose out there? I see this on amazon for a couple hundred, and hoping it'll last in attic over time. Some others have a product obviously stronger but also $xxxx so hoping to avoid that 4th digit.
MOUNTO 25FT PVC Flexible Duct Hosing for Exhaust Fan (24inch)

[Thomas Wilson]

Your problem made me think about return air from the dust collector in a different way. The return air is very clean HEPA filtered air. What about designing the return to provide that supply of clean air right where the operator is standing and pushing dust laden air away thereby creating a clean air bubble around the operator. I will do some 3D flow simulations to see how effective this could be.

[Jim Becker]

THomas, that's an interesting thought. The one challenge would be distance and other physical factors with putting such a large return-air duct.

[Thomas Wilson]

THomas, that's an interesting thought. The one challenge would be distance and other physical factors with putting such a large return-air duct.

It would be multiple ducts, always open. The diameters would be limited by practical design constraints. They would each need to be big enough to supply sufficient air to create a clean bubble. The total area would have to be sufficient to keep back pressure small. It is a math problem to determine whether it would be effective. As it happens, i have some free time. Sensitive lungs, pollen, a lingering cough and congestion following vaccination are keeping me out of the shop for a few days.