Advice needed re dust collector duct size
Moved and setting up shop.
Need advice on size of duct for my Jet JCDC-3 dust collector. 3 hp. 230 volt. Single phase. Specs say the air flow – with filters installed – is 1240 CFM, air velocity is 3542 FPM. Has an 8 inch inlet.
Note – my ceiling height is 9 ft 9 inches.
My hope – and hence my questions – can I
a. start out with 8 inch duct pipe going (approx. 10 ft) from the DC up at an angle to ceiling and then, at the ceiling, turn 90 degrees,
b. and then reduce to 6 inch duct and go across the ceiling (approx. 17 ft),
c. with 5 drops to individual machines (approx. 7 to 9 ft counting elbows into machine)
d. Each drop to a machine would be a 4 inch duct, which is the port size of each machine.
OR should I, at the DC outlet reduce from 8 inch to 6 inch duct the full length of my trunk line (up and across the ceiling, totaling approx. 27 ft) with each drop to a machine using 4 inch ducts.
Any other sources I should ask these questions???
Thanks much!
Alan – planesaw
Replies
Here’s a start for you: https://www.ductingsystems.com/dust-collector-duct-design.php
https://www.google.com/amp/s/www.oneida-air.com/amp/blog/how-to-select-the-correct-duct-diameter
https://www.spiralmfg.com/designing-efficient-dust-collection-system/
Thanks much for your kindness and leads. Will spend some time with those links.
Do your own research, it's pretty simple math. The links provided above by eddo are excellent.
If you buy your duct work and fittings from Oneida they may do the design work for you, worth asking if you don't want to do it yourself.
“[Deleted]”
I'm a woodworker, not an air handling person too. But all I did was Google "dust collection duct sizing" to get the answers I shared with you, all in 20 seconds or so. It's something any woodworker could have done. :-) So yeah, "do your own research" was good advice, anyone can do it, even woodworkers.
Well, I'm going to have to spend a chunk of time looking through your links. The last one had some helpful info, but reading SP, CFM, FPM, et al, is like reading Greek to me. How do I know what those data points are for the particular tools I have? Well, like I said, I'll have to read and do some more googling. Again, thanks for the lead.
Reply #2 gave good advice, Oneida may help you size it, the other companies may as well.
First, I could not ask Oneida's help in planning when I won't be buying anything from them. Oneida costs are way higher than my non-income woodworking budget at this point. I have a good bit of used 4, 6, and some 8 inch duct from big box stores and purchased from other woodworkers. I'm not disputing Oneida quality, I'm just not sure a 5 ft section of duct is worth about 8 times the cost of new from a big box store. If I was earning a living as a woodworker, I might consider it, but not since I'm retired. Thanks for your links and thinkin'.
Alan
I don't know what you have from the big box store, but you may problems with your duct collapsing if it is the super thin stuff I see around me. Hopefully it won't be a problem.
Airflow=dust collection effiency. Any duct size has some friction loss which slows down your airflow. The smaller the duct size the higher friction loss. for those of us that run a single machine at a time, just run 8” up to your tool. Then try to modify the dust collection points on your tools to the biggest you can or the same open area as your 8” diameter pipe. Then you have the most available airflow/airspeed to collect the most dust at your tool. Also place gate valves at each tool to open when using otherwise keep closed. The tool modification is probably the hardest. Piping is dirt simple from that mindset
All that other splitting/resizing garbage is for those shops that are running many machines at once.
Thanks much!
Google Bill Pentz and look at his articles. Pretty clever guy but to boil it all down, the specs on the label are always unreliable. For a small shop and a 3HP collector, I would go with 6" or 8" horizontals with 4" drops and keep your hoses as short as possible. You need more velocity in the drops to lift.
Thanks much!
I asked the same question on another website. With the exception of references to Pentz, there was no overlap between the other comments and links and the comments and links here.
After I retired (from a human service organization, not woodworking related at all) I was recruited by a Woodcraft franchisee to work part time on the floor and part time teaching classes. One of the things I learned is that most woodworkers comprehend very little, if any, about the chemistry of finishes (just tell me the brand I should use), nor the air handling engineering aspects of dust collection. They can make some high end things out of wood, but then they are stuck as to how to finish the piece.
SO, on the other website, I was given the following link with a simple worksheet that will probably get me to within 95 percent of my duct size questions. This link, based on what little I know, will probably be my default answer for anyone in the future asking me about dust collection for the small (1,000 sq ft or less) one (1) person shop.
https://www.woodmagazine.com/figure-dust-collection-needs-by-the-numbers?fbclid=IwAR1ul8ieQjQDfaQXq1Fr1QoOPjQsrAsr-Y-hHNyUQ0YAFSRuktoc6ZK0sBc
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