New member---just joined---DC question

[jim bradley]

Hi,
I am setting up new hobby shop. I have 2hp PSI dual bag dust collector. How do I compute duct system size and air flow. Any books I should read?
Thanks,
Jim

[glenn bradley]

Welcome aboard Dad! You'll get plenty of responses from the gang here.

[Jeffrey Makiel]

Hi Jim,
Performing calculations are not necessary for small systems that most of us have in our home shops. Besides, calculations won't be that accurate given the many unknowns about our hoods, machine ports and dust collector performance data.

Here are some suggestions...

1. Hopefully your Penn State dust collector sports a 12" wheel ('impeller'). That size wheel with a 2hp motor (10A or greater at 220V) is a nice match for a one-man hobby shop. Also, the collector should sport some decent felt bags. If they are woven fabric, an upgrade is recommended.

2. Make all of your ductwork 6" diameter. This includes the main and branches serving your machines. Thinwall PVC pipe ('sewer & drain') or metal duct are fine. The material preference is yours. Just don't use hvac duct from the hardware store; the crimped ends are meant for supply air, not return air. Try to use long radius elbows if available. If not, try using two 45 degree elbows instead of a short radius 90 degree elbow. Use wyes at branches; do not use tees. Do not use a floor sweep hood; this can be hazardous with a single stage dust collector.

3. If your woodworking machine has a 4" port, think about enlarging the port, or adding a second port. Tablesaws (with overarm dust hoods) and bandsaws benefit the most from two ports. If you don't want to modify your machine, use 4" flex duct and a 4x6 transition to the 6" duct branch. With a 6" duct branch, you can always upgrade the machine's ports later. Adding hoods may be required for older jointers that only have a chute, or radial arm saws and sanders that were not equipped with hoods by the manufacturer. The hoods should be large enough to capture the dust is thrown towards it.

4. Add blast gates on each branch conveniently located near the machine. The position (vertical or horizontal) does not matter, and the location along the branch does not matter. So keep them conveniently located.

5. Keep all the duct runs as straight as possible. Avoid putting an elbow within 30" of the inlet to the dust collector if possible. Also, avoid long runs of flex duct serving the machine; flex duct really reduces suction performance. Further, do not use the very limp and flexible duct that is offered by some vendors if the machine is not constantly moved around.

6. Fasten all the metal ductwork using screws; pop rivets can be difficult to remove later. If using PVC, also use screws; do not use glue. Chances are, you will modify the duct as your shop grows. Adding duct tape (the adhesive backed foil type) on metal duct joints is a good idea. If using PVC pipe, these fittings fit well without any further treatment.

cheers, Jeff :)

[Brian Gumpper]

These folks have a lot of good info on DC systems.

http://www.airhand.com/

[Ken Fitzgerald]

Jim Welcome to the Creek!........If you haven't....you might want to go to Bill Pentz' website concerning DC.

[jim bradley]

Hi Jeff,
Sorry for the delay in replying. I thought my message had gone to limbo. This is the first time I have used anything like this. Anyway Glenn Bradley, my son, showed me how to search and find my thread.
You gave a very good, simple explanation that shot my previous plans in the head. I was thinking a 6" main with 4" branches. Guess I will have to go 6" all of the way. I was afraid that the large duct might reduce the air velocity.
I have a Penn State DC 2000-B. That is 2 hp, 1 micron bags, 220 v. with steel impeller and one 6" input (it came with a wye so the 6" can become two 4").
The shop is definitely a work in progress---strike that---it is a work in beginning. At this point I have complete freedom of tool location within the parameters of 16' x 16'. In addition there is an additional 1 1/2 car width if I drive the car onto the driveway. and an additional 6' ninty degrees from that (unless my wife is doing laundry). In addition there is an el that is approx. 6x10' where the DC and the air compressor will be walled away to reduce sound. Yes the DC room will have a vent to the outside.
Actually the garage is 24 x 29' inside. However, I have to share with one car, laundry, freezer, Hot Water and furnace.
Sorry, I am wandering. I will pursue the 6" situation. The big boxes don't have 6" pvc (which is what I planned to use). I am going to investigate an irrigation supply as recommended by someone on a DC thread.
Yes I have read the Bill Penz site on DC. The information this man has about protecting lungs is fantastic. I hate to think of the hours it took him to learn it.
I use Visio to move my ducts, tools, etc. This is a great way to visualize where things should go. Yeah! I know reality will set in once I actually place the tools.
Old but good tools I have: Delta 6" jointer, 10" contractor's table saw, 14" bandsaw, and floor model drill press. In addition I have 4" brand x belt sander, home made 12" disk sander, and a year old Rigid 10" miter saw. I don't see any of these creating unusual problems.

Thanks again,
Jim

[jim bradley]

Hi Brian,
Thanks for the lead. I checked it out briefly---it looks good. I will pursue it in detail tomorrow when I have some time.

Enjoy,
Jim

[jim bradley]

Hi Ken,
I read an article of several pages by Bill Pentz. Boy was that an eye opener (should I say lung opener?). At this point my DC has a 4" flex tube that I put next to the machine in use. After reading his article the garage doors stay open and I put on a mask and I get the heck out of there ASAP.
My shop is in very early planning stages and DC has become a major priority since reading the article. My lungs and I say thanks to Bill. Anyway that was why I made my original posting. I'm sure it is easier to do it correctly now than to patch later.
Tomorrow I am going to pursue Brian's URL in more detail. I have already scrapped plans for a 6" main with 4" laterals to go to all 6". I'm glad I had not purchased ducting yet. At least I didn't waste money on the 4" stuff.
I was concerned that I did not have or know how to get flow meters, etc. Jeff put my mind to ease on that---just go 6" and don't worry.
Thanks for your response and
Enjoy,
Jim

[Steve Clardy]

Welcome Jim