dust collector closet in new built detached garage ext- ?s about outlet & inlet air

[Dave Burson]

Building a 20x24' extension to detached garage, so all in all will have 33' x 24' portion used for shop. shop pic.pdf picture attached hopefully?
My question today, is I am planning a 3' x 9' closet for 2 hp oneida DC (as well as air compressor) to quiet it down. I'm a little confused about best way to do the venting? I could surely vent it out side via dryer hose or?, but then where would inlet air come from, since that would be big problem if doors/windows arent open in shop while DC on, yes?
Was also told to just put an air return in closet back to shop with a filter, and maybe something to deaden sound. That scares me as counterproductive to deadening noise. Ideas? What do y'all do with inlet/outlet air? Also, what kind of doors should go ?? TIA!!!

[Frank Pratt]

Venting outside is okay if you're not concerned with heat loss. If you are, then build a return air plenum with at least a couple of bends in it & line it with acoustic insulation. Make it plenty over sized to compensate for those sharp bends in it.

I have done that same in my shop & the noise coming through the return air is minor.

[Dave Burson]

Venting outside is okay if you're not concerned with heat loss. If you are, then build a return air plenum with at least a couple of bends in it & line it with acoustic insulation. Make it plenty over sized to compensate for those sharp bends in it.

I have done that same in my shop & the noise coming through the return air is minor.

Frank,
Not sure I get what you mean exactly. Any chance you could post a pic of the return plenum?

[Jim Becker]

Not sure I get what you mean exactly. Any chance you could post a pic of the return plenum?

I'm sure that Frank will contribute what his setup is, but here's a graphic of how my air return is setup from my sound-reduced cyclone and compressor closet. I used the space between the ceiling joists to create a "bent duct" and it's worked great for me.



John Jordan used a length of very large flexible HVAC duct via a bendy route over his ceiling for his return. The same principle applies no matter how you do it...you want an air return pathway that is not "direct" since a direct path will, well...directly transmit sound. Turns and bends are your friend for this particular purpose as the remove the direct pathway for sound transmission. You want the effective area of the return to be larger than the outlet from your DC system by a reasonable margin so there is no "back pressure" and to compensate for the bendy pathway and the associated resistance it incurs.

[Jim Andrew]

I used 8" snaplock pipe with a T on top of the cyclone to run outside, went straight out through the wall from the cyclone, and made a flange of 3/4" plywood, and built a flapper from 1/4" plywood and a door hinge, bent some sheet metal into a U shape and use that to protect from rain, put the thing under the overhang to also protect from rain. It shoots the air downward, and you hardly notice it until the barrel over fills. From the other half of the T, I went to the filter. Forgot to add, also made a blast gate from plywood, so when it is open, the unit vents outside, close the gate and all the air vents through the filter.

[Frank Pratt]

Frank,
Not sure I get what you mean exactly. Any chance you could post a pic of the return plenum?

Jim explained it very well. Mine is not exactly like his, but is the same principle.

[Paul F Franklin]

Regarding exhausting outside, there was another thread recently that covered that in detail. To summarize: Performance will likely be better if you can exhaust outside because you won't have the pressure loss of the filter. But you have to have a low resistance source of makeup air (from the outside to the inside) or performance will suffer because of the effort required to suck that much air though cracks and leaky windows and doors.

If you are heating or cooling your indoor air you will waste some money by blowing conditioned air out the exhaust. How much depends a lot on particular circumstances, climate, indoor/outdoor temperature differential, how long you run the dust collector, etc. And it's not just heating or cooling, but humidity you need to think about. If you are in an area where outdoor humidity is high, then you are sucking a lot of moisture into your building as well.

Finally, if you have any combustion appliances in the area that do not have direct outside combustion air supplies, you absolutely must supply low resistance make up air from the outside to avoid backdrafting the appliances and releasing potentially dangerous fumes into the building.

Also, a single 4" dryer type hose is not sufficient to exhaust to the outside, nor to bring in fresh air. As others have pointed out, you want the cross sectional area of the exhaust, and the makeup air vent, to be at least as large as the cross sectional area of the intake of the dust collector. Twice the area would be better. You are trying to minimize the resistance to air flow in either direction so the collector can do its job as efficiently as possible.

[Dave Burson]

Regarding exhausting outside, there was another thread recently that covered that in detail. To summarize: Performance will likely be better if you can exhaust outside because you won't have the pressure loss of the filter. But you have to have a low resistance source of makeup air (from the outside to the inside) or performance will suffer because of the effort required to suck that much air though cracks and leaky windows and doors.

If you are heating or cooling your indoor air you will waste some money by blowing conditioned air out the exhaust. How much depends a lot on particular circumstances, climate, indoor/outdoor temperature differential, how long you run the dust collector, etc. And it's not just heating or cooling, but humidity you need to think about. If you are in an area where outdoor humidity is high, then you are sucking a lot of moisture into your building as well.

Finally, if you have any combustion appliances in the area that do not have direct outside combustion air supplies, you absolutely must supply low resistance make up air from the outside to avoid backdrafting the appliances and releasing potentially dangerous fumes into the building.

Also, a single 4" dryer type hose is not sufficient to exhaust to the outside, nor to bring in fresh air. As others have pointed out, you want the cross sectional area of the exhaust, and the makeup air vent, to be at least as large as the cross sectional area of the intake of the dust collector. Twice the area would be better. You are trying to minimize the resistance to air flow in either direction so the collector can do its job as efficiently as possible.

OK, if I were to decide to vent outside then, which I kinda like the idea, would venting it into attic be okay (with soffit venting, and ridge venting)? So basically I'd setup a good sized exhaust vent from DC closet into attic, and then a separate good sized air return from attic back into shop. Any reason that wouldn't work? I would like the influx of fresh air (will have a good sized mini split and not overly concerned about wasting some cold or hot air in the rare times it's extreme temps here in VA). Having hardy plank siding and brick, I really don't want to make a huge cutout of either to add two vents, so thinking the attic option might suffice. Thoughts?? TIA!!!

[Jim Andrew]

Venting into your attic would result in the finest of dust coating your attic. And, if your barrel runs over, could result in sawdust and chips being sprayed up there. I miss dumping the barrel occasionally, and as a result have chips on the ground outside the air dump when that happens.

[Tony Latham]

Venting into your attic would result in the finest of dust coating your attic. And, if your barrel runs over, could result in sawdust and chips being sprayed up there. I miss dumping the barrel occasionally, and as a result have chips on the ground outside the air dump when that happens.

Jim is spot on.

I have a 2HP Grizzly over a Super Dust Deputy XL with 6" inlet/outlet that vents outside. To see what I get out the vent, I can sweep a pile of sawdust to my floor sweep, step outside and hit the remote switch.

I get an acceptable amount of fine dust that blows out and disappears.

This probably wouldn't work in a tight subdivision.

For ventilation, I keep a window cracked in the summer. If I don't, and the door isn't fully closed it'll pop it open.

T

[Jim Andrew]

About venting outside and makeup air, if you have an overhead garage door in your shop, the way those doors are designed, they will allow enough air to slip in around the door itself to allow for makeup air. I have 3 overhead doors, and don't even notice venting outside. And I have weatherstrip on those doors, it is just that the vacuum pulls the doors into the shop and sucks air from around them.