Quick dust collection piping question

[George Werner]

I've tried searching but couldn't find a specific answer to this one. I'll be running 6", 26ga snap lock pipe across the ceiling all the way back to my 2HP Laguna cyclone. My question is where is the preferred location to transition to the 4" connection to the machines. Would I be better off transitioning to 4" pipe at the ceiling when I start my vertical drop to the machine, or is it better to carry the 6" as close to the machine as possible and make the transition to 4" at the flex duct connection?

[Don Kondra]

As close as possible and make the transition to 5" hose.

It is not a lot of work to change the ports to 5" and will make a significant difference in final CFM.

Cheers, Don

[Wade Lippman]

I made mine at the ceiling. Well, 8" to 2 6" branches to 8 4" drops.
I just measured a drop at 500cfm, which is adequate for most things.
Mine is 3hp, but that is probably only an advantage with more than one port open.

[Dan Friedrichs]

The preferred location is "nowhere". Necking down to 4" pipe will severely limit airflow in the entire system. Like a garden hose - if you have a small nozzle, it doesn't matter if you have a 1/2" garden hose or a fire hose connected - the nozzle is the primary driver of the total system flow.

Technically, 6" ducting will exhibit slightly less resistance than 4" ducting, but it's a negligible difference.

If you are dead set on 4" connections to the machines, then save yourself the hassle and just run 4" ducting throughout - you'll have a severely inadequate system, though.

The best performance will be achieved if you maintain 6" all the way through the entire system. That may mean multiple ports per machine, if a machine isn't amenable to a 6" port.

(Usual disclaimer: this advice is overly-generalized, for a one-man shop with only one blast gate at a time open, <5HP blower, etc)

[George Werner]

Thanks everyone, I really appreciate the help!

[Don Kondra]

One final word(s)

I've recently converted my 2 HP two bagger to a Super Dust Deputy with Wynn filter.

All lines are 5".

Anemometer readings are 460 - 520 CFM.

With a short length of 4" hose at the end the readings drop to 350 CFM.

Cyclone install done.jpg

Why would you not want to achieve your collectors potential ?

Cheers, Don

[Ole Anderson]

I am not sure how to be nice about this, but pretty much ignore most everything you read in post #4 as much of it is incorrect. Although I hope it is a great exaggeration to make a point. I would agree with paragraph 4. If you have a short run of 4" at the end you will be much better served by the balance of the duct being 6". The hose analogy is good only if the nozzle is much smaller than the hose, which is not the case with 4" vs 6" duct. To verify, just plug your numbers into the spreadsheet on the BillPentz dot com website.

To answer your question, do what I did: reduce from 6" to 5" at your main, run 5" horizontal then to a vertical elbow then a reducer to 4" vertical snaplock to your blast gate where you attach your 4" hose,(keeping the hose as short as possible). That way you will keep velocity high enough in the vertical to carry chips and small offcuts and a short 5" horizontal run will not choke your system. Bump it to 6" if it more than, say, 5 feet.

Vertical duct runs: 4000 fpm minimum: 6"=785 cfm, 5"=545 cfm, 4"=349 cfm
Horizontal duct runs: 2800 fpm minimum: 6"=550 cfm, 5"=382 cfm, 4"=244 cfm

See paragraph B.5 under Ducting in Bill Pentz's write up regarding minimum velocities.

As far as available cfm on a 4" hose, I measured my setup at 570 cfm (6,160 fpm) at the end of a 4.12" quick connect with about 4 feet of slinky hose. 2 HP Oneida SDG. That makes over 4000 fpm in the 5" run and more than 2800 in the 6" main horizontal run. I have a 7" horizontal main and have not had any problem with buildup in the main run with less than 2800 fpm, although I do occasionally open up two end runs to clean it out as a precaution.

[Robert Engel]

I think the previous poster is spot on. Also what Don^ said.

I've done a couple systems and found the bottom line is not CFM's but is the collector collecting??

Also, keeping the dust producers like drum sander, band saw and TS closest to the DC is huge.

[Dan Friedrichs]

I am not sure how to be nice about this, but pretty much ignore most everything you read in post #4 as much of it is incorrect. Although I hope it is a great exaggeration to make a point.

Obviously it is both an exaggeration and an over-simplification, but my point is: if you're going to bother installing SOME 6" ducting, why not install ALL 6" ducting?

When people see diagrams showing a 6" trunk branching to 5" then down to 4" drops, they assume that's optimal. I think people see HVAC systems built that way and assume a DC system should be done the same. But if you're a 1 man shop with only 1 gate open at a time, the 6-5-4 system is restricting airflow (relative to a system done entirely in 6"), and now you're dealing with reducer couplings, different sizes of ductwork, etc, for no benefit at all.

I agree that there are tertiary issues (like the ability to suck small chips up a vertical run), but I don't think I'd design a system around those requirements. I'd design a system around the idea of getting maximum air moved, which will be achieved with larger ducting.

[Hoang N Nguyen]

I'm no expert in this field but like others have said, I run my 6" mains as close to my machines as possible, then I dropped in a 6 to 4 reducer, blast gate and finally flex hose.

[glenn bradley]

I reduce as close to the machine as possible and not at all if possible.

[Mike Heidrick]

Also, keeping the dust producers like drum sander, band saw and TS closest to the DC is huge.

Wouldn't you want larger chip collectors like planer/jointer closer than the TS and sander?

[John Donhowe]

why not install ALL 6" ducting?

The main reason for reducing from 6" to 4" or 5" on vertical drops is to make sure you have enough air speed to pull chips and dust upward to the main trunk. According to the venerable Mr. Pentz, you need 3000 fpm air speed for horizontal runs, but close to 4000 fpm for vertical runs (since you're fighting gravity). If you're DC is powerful enough to supply 4000 fpm in 6" ducts, you're all set- but if not, the only way to increase air speed in a given section of the system is to reduce the duct size there.

[Bill McNiel]

George,
"I know nothing" about the Mr Pentz and even less about the numbers but.....I have the same Laguna as you so FWIW this is what I did and it has worked really well.

• I put a 6" Wye, with blast gates, at the inlet (one run goes up to the ceiling, across the shop and serves the majority of my toys while the other drops to the floor and handles my main bench, chop saw and router sled). Used 26 ga Snap Lock ducting from the BORGs. Sealed all seams and connections with HVAC gunk and Duct Tape. Purchased self cleaning alum Blast Gates from LV.
• I ran 6" to as close to each machine as possible (TS, Re-Saw and 12" planner all have 6" connections).
• Some of the machines have flexible connections, primarily so they can be moved or angled 1'-2' to facilitate long runouts.
• TS has 24' of 6" with a 6"x4"x12" HVAC vent connector at the machine. No above the table DC.
• Jointer/planner has 22' of 6" with 2 1/2' of 6" Alum Flex to the Planner and 4' of ribbed 4" plastic hose to the Jointer.
• 25/50 Supermax has 16' of 6" with 3' of ribbed 4" plastic hose to the machine.

I have virtually no dust/chips uncollected and am very happy. I still need to provide collection at the Oscillating Spindle Sander, the SCMS, Drill Press and Lathe but it keeps getting put off until "after the next project is done". No technical info for you but thought this might help a bit. Undoubtedly someone will come up with the math that proves that my system isn't really working and I will go back to making stuff and stop offering my uninformed opinion.

[Jim Andrew]

I have changed the 4" ports on some of my machines to 6". Some machines are not hard to change, others are more difficult. The one machine I find that works well with 4" is my go453 planer. I used a 6" hose, and a 6 to 4 reducer at the machine.