Need advice on ducting for new DC - mainly around fittings

[Matt Putnam]

I got the go-ahead on upgrading my shop DC from a Delta portable 1.5HP to a dedicated/installed DC. I'm leaning heavily towards the Oneida 3HP Dust Gorilla Pro. Regardless of the DC I select though, I'd think my ducting will be the same. I'm planning to use spiral duct and need some help on the transitions and fittings.

Shop/Tool info:

• Shop = 20' x 30' (10' ceiling) with additional 10' x 10' shoulder for storage
• DC will go in another 10' x 10' room on the outside of the 10' x 10' shoulder that's part of my shop (2x4 insulated wall between shop area and DC area)
• SawStop Professional (currently only collecting dust at base but plan to install over-blade collection as well)
• "Floating" tool. I have a 18-36" Performax sander currently and a Delta shaper. I'll eventually get a planer and jointer to add to the mix. All of these will be on mobile bases as "floating" tools and will be wheeled to a central area in the shop while in use.
• Miter saw (see below on questions)

Dust Collection Duct

• The main trunk line of the DC will run ~25' along ceiling before getting to table saw
• The trunk will extend beyond table saw another ~10' to where it will drop down for the "Floating" tool connectio

Questions:

• Best to transition from the DC cyclone input to 8" duct for the main trunk?
• If 8" trunk to table saw split, should the trunk extending beyond to the "Floating" tool be 8" (for the 10' run) or go ahead and run it as 6"?
• OK to transition from 8" to 6" for the drop to the table saw and the "floating" tool?
• OK to use non-spiral fittings? Local supplier said they can get spiral Wyes and elbows but very expensive, whereas a non-spiral fitting is more affordable
• Local supplier has 8" to 2 6" wyes (so I think it has 8" coming in and 2 6" arms coming out), but should I be looking for a fitting that's 8" with a 6" off-chute (I believe that's a wye as well)
• Is a 1 1/4" radius 90 elbow a no-no? A supplier has those but I know the larger the radius, the better
• Connect miter saw or not? I know it'd be good airflow to use the big DC but my use of the miter saw is often one or two quick cuts and that's it. Seems overkill to fire up a big cyclone for that. If I don't connect the big one, I'll likely use my Delta 1.5 for the miter saw.

I'm sure I'll have more questions but that's my starting point for now.

Thanks

[Hoang N Nguyen]

Conklin metal industries, they have a location in SC and have all the fittings for spiral pipes. I buy all my pipes and fittings from them at a very good price compared to other online vendors.

I have the Oneida V3000 and only run 6" main trucks, works fine. It won't hurt for you to run 8" with the Gorilla pro but I'm not sure if it'll make a huge difference given you're only running 1 tool at a time and your runs aren't that long.

If you run 8" to the TS then drop and reduce, I would still keep the run to the floating tool at 8" until you drop and reduce.

If you want larger radius, a cheaper option would be to connect (2) large radius 45* fittings together. It'll land you somewhere in the middle price wise.

I wouldn't connect to miter saw if it's only a few cuts here and there. Oneida doesn't recommend turning on and off the DC more than 5-6 times an hour. I usually just leave my DC running if I know I'll need to turn it on within a few minutes.

[Matt Putnam]

Thanks, Hoang.
After posting my thread I dug up an old reply you sent me a few months back recommending Conklin. I talked with them a bit ago and think they'll be a good source for much, if not all, of the duct.
Did you get large radius elbows from Conklin? The guy I talked with didn't seem very familiar with those.
Thanks for the other answers above.

[Hoang N Nguyen]

I reused all of the stamped elbows I had from the old shop. For the rest, I joined 2 of the 45* elbows together. It's not as clean of a look but it's cheaper than a large radius elbow but gives you the same benefits.

[glenn bradley]

I run PVC and also use dual 45's for the large 90 turns. I try to avoid 90's altogether but, sometimes you are stuck.

45-not-90.JPG

[Jim Finn]

You can use regular HVAC adjustable ells with spiral pipe if it is 26 gauge. Just seal the connections, and the adjustable seams, well. I have done a lot of that when I was a sheet metal worker, before I retired.

[Joe Jensen]

There is a ton of incorrect information on the web about duct sizing. Bill Pentz (google it) has a great spreadsheet to help you model. An 8" main branch will have too low of air speed to keep the dust suspended. The most important factor in moving air is enlarging to smallest opening. My Sawstop ICS had a 4" port on the bottom of the cabinet that connected to a rectangular opening at the bottom of the cast iron shroud under the blade inside the cabinet. No way to enlarge that port. A 5" main, a 6" main or an 8" main and you will get basically the same CFM through that small port. When you see large main branches that is for shops where more than one worker is running machines at the same time, like 5 workers. Your 3HP Oneida does not need more than a 6" main. The small ports on your tools is what will kill your CFM, not the main branch size.

See post number 32 at this link. http://www.sawmillcreek.org/showthre...ollector/page3

[Andy Giddings]

There is a ton of incorrect information on the web about duct sizing. Bill Pentz (google it) has a great spreadsheet to help you model. An 8" main branch will have too low of air speed to keep the dust suspended. The most important factor in moving air is enlarging to smallest opening. My Sawstop ICS had a 4" port on the bottom of the cabinet that connected to a rectangular opening at the bottom of the cast iron shroud under the blade inside the cabinet. No way to enlarge that port. A 5" main, a 6" main or an 8" main and you will get basically the same CFM through that small port. When you see large main branches that is for shops where more than one worker is running machines at the same time, like 5 workers. Your 3HP Oneida does not need more than a 6" main. The small ports on your tools is what will kill your CFM, not the main branch size.

See post number 32 at this link. http://www.sawmillcreek.org/showthre...ollector/page3

Joe's info is very similar to what Clear Vue told me - no need to go above 6 inch even with a 5HP system unless you have multiple machines producing dust at the same time

[Ole Anderson]

I may sound like a broken record, but 7" ducting is the sweet spot for the main duct run on 2-5 hp cyclones. Your table saw may arguably be the most used machine and it has one of the larger demands for air if you have both top and bottom collection. Per Bill's website, you need 2800 fpm velocity for horizontal runs and 3800 fpm on vertical runs. Flow requirements for a TS are in the order of 800 cfm. So the maximum size horizontal run at 800 cfm and 2800 fps would be 7.28" and the maximum pipe size for a vertical run would be 6.25". Obviously you can juggle the flow and velocity requirements to achieve any result you want. As far as sizing ducts, the other factor is pipe loss and that is made up for with available static pressure (suction) which is largely a function of horsepower and an appropriately designed impeller to utilize that horsepower. You can go with smaller ducts, but the trade off is that static pressure loss increases due to friction in the pipes that increases by the square of velocity. So, yes, you can get by with smaller pipes if you have enough static suction available.

[Joe Jensen]

I may sound like a broken record, but 7" ducting is the sweet spot for the main duct run on 2-5 hp cyclones. Your table saw may arguably be the most used machine and it has one of the larger demands for air if you have both top and bottom collection. Per Bill's website, you need 2800 fpm velocity for horizontal runs and 3800 fpm on vertical runs. Flow requirements for a TS are in the order of 800 cfm. So the maximum size horizontal run at 800 cfm and 2800 fps would be 7.28" and the maximum pipe size for a vertical run would be 6.25". Obviously you can juggle the flow and velocity requirements to achieve any result you want. As far as sizing ducts, the other factor is pipe loss and that is made up for with available static pressure (suction) which is largely a function of horsepower and an appropriately designed impeller to utilize that horsepower. You can go with smaller ducts, but the trade off is that static pressure loss increases due to friction in the pipes that increases by the square of velocity. So, yes, you can get by with smaller pipes if you have enough static suction available.

I respectfully disagree. No standard 2-5HP system can pull 800CFM through a 4" port. Those systems cannot create enough suction pressure to move that much air. With a 3HP Super Dust Gorilla you will more likely get 350 CFM through the 4" port on the saw. The PDF paper I posted at the Sawmill Creek link above goes through the math. Take that 350 CFM and now do the math on your 7" duct and you will see that the velocity will be too low.

Please play with Bill Pentz's excel spreadsheet. You will see that the static pressure improvement from going to a 7" pipe from a 6" pipe is negligible. In the paper I show how with a 5HP Oneida Pro system you will be able to pull about 550 CFM through a 3.5" port (effective inside area of a 4" port outside diameter port).

[Ole Anderson]

I respectfully disagree. No standard 2-5HP system can pull 800CFM through a 4" port. Those systems cannot create enough suction pressure to move that much air. With a 3HP Super Dust Gorilla you will more likely get 350 CFM through the 4" port on the saw. The PDF paper I posted at the Sawmill Creek link above goes through the math. Take that 350 CFM and now do the math on your 7" duct and you will see that the velocity will be too low.

Please play with Bill Pentz's excel spreadsheet. You will see that the static pressure improvement from going to a 7" pipe from a 6" pipe is negligible. In the paper I show how with a 5HP Oneida Pro system you will be able to pull about 550 CFM through a 3.5" port (effective inside area of a 4" port outside diameter port).

I am sorry you misunderstood if you believe I was saying 800 cfm through a 4" port. However here is a pic showing my 2 hp SDG pulling 570 cfm through a 4.12" end of the hose, 6160 fpm. Empirical, not theoretical. 7" main to 5" overhead to 4" vertical/blast gate (3.5" orifice) and about 4 feet of slinky (10 feet if pulled out). My point was that at 800 cfm (typical 5" bottom, 3" top on a TS), you don't want to go bigger than 6" on a vertical run or bigger than 7" on a horizontal run in order to maintain minimum velocities. I have played around plenty with Bill's spreadsheet and found a few poor "misdirections" in some of the inputs at the top. Actually (and now I am saying it), there is no problem pulling 800 cfm through a 4" port (orifice) if it is directly attached to a 6" duct. Through a long 4" duct, yes there will be a problem. There is a substantial difference between the losses in an orifice and the losses through a duct. That is why I always challenge the misinformation which commonly states that if you choke a hood to a small diameter, say 4", you might as well size the duct leading to it at 4".

And to empirically verify my statement on vertical minimum velocities, my 5" bottom connection on my saw (which has a bell mouth adapter into the saw), I have one time had to clear a few offcuts at the bottom of the 6" vertical elbow. No problem with chips nor of course dust.

We agree that 550 cfm through a 4" duct is reasonable.