Newbie question about return ducting

J

jstipins

New member
Hi everybody, my apologies in advance for my poor understanding of the system I'm about to ask about...

So I'm planning to install the CV1800 in a storage area adjacent to my garage shop. The storage area is separated from the garage by a wall with a door in it. Ultimately I'd like the air taken from the garage to be returned after it passes through the cyclone.

My system includes the filters, since I'm not blowing the dusty air outside of my house. I understand that for the purposes of noise reduction, I'd like to have a sizable muffler between the cyclone exhaust and these filters. So one possibility, I suppose, would be to have that muffler come back into the garage, so that the filters are in the same area that the air was originally taken from.

But I'd like not to do that. I'd prefer to have the cyclone, muffler, and filters all in the storage area. If I do it this way, how do I set up an air return into my garage?

Part of my confusion is that I don't understand how the filters work. Does the filtered air come out of a definite exhaust hole at the bottom? Or does it diffuse through the filter material?

Thanks in advance for any insights.

-JS3
 
One of the easiest ways to achieve good airflow return to your shop through a joining wall is to create a return air plenum using the space between studs with an opening at the base of the plenum inside the storage air and a grill-covered opening at the top on the shop side of the wall to allow the air to flow back into the shop. I've seem where some users have put the inlet side of the plenum at the top on the cyclone side and exit at the base in the shop so air passes by the cyclone motor to help with cooling the motor itself. Either of these configurations will attenuate lots of the sound generated by the cyclone; the addition of acoustic foam on the storage area wall adjacent to the shop will enhance the sound reduction as well. If you think you need a muffler, it should be placed in the airstream between the blower and the filters (if you search through the Photo Gallery, there are examples on user-built mufflers). I think most users find a muffler unnecessary (I personally user hearing protection when I run my tablesaw with my dust collection turned on because the saw generates sound I cannot otherwise muffle.

Air exiting the filters passes through the filter media throughout its length. Each of the Wynn 9L300NANO Filters used with the CV1800 has over 300 SF of surface area that minimizes the static pressure drop across the media while removing 99.999% of particulates over 0.5 microns. Any residual dust that collects on the filter surface is captured by the cleanout box one adds at the base of the filters.
 
Ah, that makes a lot of sense, thanks very much.

My main motivation for putting the cyclone in the storage area is that it makes my whole ducting run much shorter and simpler; but now that I'm thinking about noise abatement, it seems like it can help with that too.

Now that you've explained how the filters work, I'm actually thinking about the possibility of putting the filters back in the garage, and running insulated duct to connect it to the blower exhaust back in the storage area. This obviously fixes the return air issue, but it raises another question: If the cyclone is enclosed without the filters, is some other mechanism needed to keep the motor cool?

Thanks again for your help.

-JS3
 
The heat build up around the motor can be significant if you have it running for an extended period in a small enclosed area without any air circulation. I would suggest having a small fan (a window box fan would work well) that simply keeps a steady flow ir air moving past the motor -- if it is possible to add a vent or two to bring in fresh cooler air and exhaust it out, then that would alleviate any significant heat build up.

If you place the filters back in your shop, there will be some noise transmitted from the fan through to the filters. You may want to use some insulated HVAC flexible duct (available in several sizes at the BORG) to connect the filters to the fan outlet. I built a straight transition piece from the rectangular blower outlet to 10" flex duct that I can direct to an outdoor grille or to my filters, depending on the season.
 
McRabbet said:
If you place the filters back in your shop, there will be some noise transmitted from the fan through to the filters. You may want to use some insulated HVAC flexible duct (available in several sizes at the BORG) to connect the filters to the fan outlet. I built a straight transition piece from the rectangular blower outlet to 10" flex duct that I can direct to an outdoor grille or to my filters, depending on the season.
Click to expand...

Do you have a picture of your exhaust side? I'd like to see how you are venting outside as well as how you switch to your filters. Did you make a valve type box or are you simply disconnecting and connecting your flex duct to the outside grille or filters as needed?

I'm trying to figure this out in my shop before I mount and enclose the system.
 
Sorry for the delay in answering, but I've been out of town and just returned this evening. I don't have any pictures to share, but the way I did it was to make a Transition from the Blower outlet to 10" round, using a piece of sheet galvanized steel that I got at Lowe's. The transition (or "evolution" as some sheet metal guys call them) is pretty easy to make. There is a good explanation with an Excel spreadsheet here that I used. I made mine to fit inside the outlet of the blower and as I recall, it is 12" from the rectangular end to the round end. The spreadsheet give you cells to put in the correct dimensions and the web page shows how to do the layout. If you prefer, ClearVue make a PETG straight transition for either the 15" or 16" blower for $80. I move the 10" HVAC insulated duct (also available at Lowe's) that leads to my filters to a second transition piece I made to fit into an opening in the concrete block wall of my crawl space where my cyclone is located Hope this helps.
 
McRabbet said:
One of the easiest ways to achieve good airflow return to your shop through a joining wall is to create a return air plenum using the space between studs with an opening at the base of the plenum inside the storage air and a grill-covered opening at the top on the shop side of the wall to allow the air to flow back into the shop. I've seem where some users have put the inlet side of the plenum at the top on the cyclone side and exit at the base in the shop so air passes by the cyclone motor to help with cooling the motor itself. Either of these configurations will attenuate lots of the sound generated by the cyclone; the addition of acoustic foam on the storage area wall adjacent to the shop will enhance the sound reduction as well. If you think you need a muffler, it should be placed in the airstream between the blower and the filters (if you search through the Photo Gallery, there are examples on user-built mufflers). I think most users find a muffler unnecessary (I personally user hearing protection when I run my tablesaw with my dust collection turned on because the saw generates sound I cannot otherwise muffle.

Air exiting the filters passes through the filter media throughout its length. Each of the Wynn 9L300NANO Filters used with the CV1800 has over 300 SF of surface area that minimizes the static pressure drop across the media while removing 99.999% of particulates over 0.5 microns. Any residual dust that collects on the filter surface is captured by the cleanout box one adds at the base of the filters.
Click to expand...
I have read with interest your post on return air plenums as a way to get expelled air back into the shop. I have a similar issue, but with a different twist. My shop is heated and my cyclone with filters is in a adjacent unheated garage. In the summer, there is no problem; I just leave the door between the shop and garage ajar. In the winter, however, I would like to retain the heat in my shop, so I am looking for a device (perhaps a mechanical/electrical damper) which will close the return air vent when the cyclone is off, and will open automatically when the cyclone is on. Do you know of any such devices/installations, and are they effective in reducing heat loss?
 
The air diffuses through the filter medium so it comes out over the entire surface of the filters. I run mine in a closet and I do not use a muffler. In the shop the cyclone sounds like a distant whine and the noise is predominately from the airflow at the tools. Mufflers apparently have been found useful by many. If the closet wall is common with the shop or with livable area you will want to mount the cyclone so the vibrations are not carried through the wall. Also, you will want to line the walls with rock wool insulation to attenuate noise. The filtered air usually is returned to the shop with a vent placed near the floor. The vent should be fairly large (say stud spacing by a few inches height). Then build a "chimney " that draws air from up near the ceiling by the motor and returns it down to the vent. The chimney can be built in the corner of the closet to make it simple. The chimney cools the motor by removing the hot air. There are many posts on this subject and you can scan thru the gallery to see how others have attacked these problems. Welcome aboard and don't be timid about asking questions.
bababrown
 
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