How much venting do I need on DC closet?

[Doug Shepard]

I've just about got the closet done for my DC install. From what I've read, I think I need to add some vents on the closet? I do have one vent to the outside but think I also need to have venting to the GaShop airspace? If I pick up standard home vent(s) (I think they're 8x14?) will that be enough? I have the space to add 2 vents, but is 1 vent enough? One poster on the Knots forum advocated putting furnace filters behind the vent(s) to reduce noise. Any thoughts on that?

Thanks

[Jim Becker]

Your venting area should be at least the same area as your cyclone's output duct. And if you want to keep the noise level down, you need to do your return to the shop as a baffled structure to greatly reduce direct sound transfer. A furnace filter alone will help, but an indirect path is even better, with or without the filter. Mine does not have filtration, but is a reversed duct setup as shown here...

47737

[Cliff Rohrabacher]

Your venting area should be at least the same area as your cyclone's output duct. And if you want to keep the noise level down, you need to do your return to the shop as a baffled structure to greatly reduce direct sound transfer.

Absolutely. However I say more surface area, much more & especially if you are sound-proofing. The goal is to eliminate Delta P so as to not drain off power from the job of sucking and convert it to the job of pushing clean air through any baffles and vents.
All chambers plenums baffles etc create turbulence. Turbulence = resistance.

[Doug Shepard]

OK - by "same area as your cyclone's output duct" I'm assuming you're referring to the one going into the filters, and not the one going into the collection bin? If that's right, then ONE 8x14 would be enough, but TWO would be better if I read Cliff right? Right now the only place where I can put it (or them) is on the LH wall of my closet which is the same side of the closet that the filter stack will be. ONE vent would be about 12" from the filter stack, but TWO means the 2nd one will be right next to it. Does that affect the ONE vs. TWO situation? I was also checking online for some thicker furnace filters (2" for sure, and maybe 3" or 4"?). I'll try and take some pics tomorrow of my planned location.

Thanks guys.

[Doug Shepard]

OK - here's a couple of pics. For right now the LH wall is just lightly held in place by a few screws. Still need to cut a hole through it for the intake duct but that will come later. I'm planning on mounting 1-2 vents on that wall. The 2nd pic shows the inside and the bottom of the transition. The filter stack will sit directly under the transition and will actually protrude into the space between the studs a bit. I was originally thinking of placing the vent(s) down low, but higher on the wall might be better as normally the jointer is wheeled up next to that wall when it's not being used. It would be a few inches from the wall but might be too close to allow much air movement.
Let me know what you guys think - One vent or Two ?

[John Bush]

Hi Doug,
I built an attached shed to enclose my cyclone and added an opening window to match the shop design. I simply opened the window, with the DC on, until there was no longer any pressure on the door as I pulled it closed. There will still be some positive pressure in the room, but a 5 inch opening( by 30 inche window height) seemed to work. I haven't cut a vent to get the return air back into the shop yet, but I will likely incorporate a baffle system as Jim illustrated. JCB.
PS. Cyclone is a 2hp.

[Jim O'Dell]

I'd go for 2. You don't want that cyclone to start whistling as the air re-enters the GaShop! It doesn't look like you plan to put any insulation on the inside of your closet since you say the filter will reside slightly into the wall frame,, is that right? I'm going to line mine with insulation, open side to the interior of the closet, to help with the noise. I'm strongly thinking about ducting the exhaust outside to start with. If I end up heating the shop for the winter time, then I may add the filters and if so, I plan to build Jim B's baffel system. You could still incorporate the baffel system into your closet walls. I don't think that it has to be next to the filters. I will put mine in the ceiling above the filters, if I go that route, and have one of the 18"X18" air return grills on the shop side in the ceiling. Jim.

[Steve Rowe]

Doug,
If your closet becomes pressurized, it will reduce the flow through your dust collector. This is akin to restricting flow in the exhaust of your car. As a check for the adequacy of your venting I would suggest taking a section of clear tubing, drilling a small hole through the plywood into your closet and making a manometer to measure the pressure in your closet. Fill the tube with water (add a little food coloring to help visibility) and mark the level in the tube with the dust collector off. Then turn the collector on and measure how many inches of water pressure you get. If one vent provides less than 1/2" of pressure, I would probably call it good. If greater, I would probably add another vent.
Steve

[Doug Shepard]

Jim - I think you're right. As long as I can fit two, I might as well do it. I'll probably only be able to get 1" styro on the half of the wall where the filter stack will be, but the other half will have 2" styro like the majority of the closet. Styro might not be the most ideal choice, but it's getting glued to the wall and the whole wall will be attached with bolts into threaded inserts. In fact that middle stud will be permanently attached to the wall (it's only bolted to the other framing with heavy angle brackets) and removable along with the wall. So stapling standard fiberglass to the studs and having a removable closet dont really go together. I've got the whole affair in 4 main sections that all bolt into place. It's made construction of the closet go slow, but if I have to remove the cyclone for motor or other maintenance, the whole closet can be disassembled in about a half hour, then re-assembled in about the same time. I thought about going out the top with the vents, but that introduced a whole nother set of problems that I just didn't want to deal with.
Hurry up on your installation will ya! I still think I could win the slowest DC install race.:D

[Jim Becker]

Doug, I don't understand why you can't use fiber glass in your walls despite their, Um...positional flexibility...mine use un-faced (no staples, but you can use 3M spray glue to insure they stay in place) and the inside walls are pegboard with the rough side towards the noise. That creates a sandwich which doesn't add all that much weight and should still be easy to knock down and move as you intend. Just build the panels appropriately.

[Doug Shepard]

Jim
At this point it's a matter of economics more than anything else. I've still got partial sheets of both 1" and 2" styro that are enough to do the rest of the closet. For better or worse, when I did some initial online research into soudproofing it looked like styro, while not the best thing available, was as good or better for the price of what I thought would be available at the Borg. The rigidity also had some appeal to me as there are quite a few areas where I've got it installed without any adhesive or fasteners - just very snug wedge fits between studs. In hindsight it might not have been the best choice but since it doesn't cost me any more than what I've already spent, I'm at least going to stick with that choice for the time being and see where it gets me. Once it's all boxed in I'll take some measurements with the decibel meter and see how well it worked.