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Discussion Starter · #1 ·
Hi! I am upgrading my shop from a 1 car garage to a dedicated shop that will be 25' x 25'. I recently acquired a Laguna P Flux 1 https://860860.app.netsuite.com/cor...0902&c=860860&h=cd39892c7cb5220f58d9&_xt=.pdf (1.5hp, 18.8Amp, 1314CFM at 6" inlet per Laguna) and was hoping to get opinions on permanent duct work in the shop. I am planning on having the DC stationary in it's own closet and ducting into the shop itself using a main run for the TS/Joiner/Planer island that then branches of 45 degrees to router table/bandsaw/spindle sander against the wall. Neither run would be over 15' long and run along the ceiling.

So, here is my question: Would it be better to run a 6" main trunk that then reduces down to 4" at the tool blast gates or would it be better to just run all 4" ducting and upgrade later if I increase the HP of a future DC? While I understand that 6" ducting would almost double the volume of air in the system, which is usually great for impeller driven DCs, I am a little worried about the HP being strong enough to move the air efficiently.

Any advice or recommendations would be more than welcome!

Thanks!
Andrew
 

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I can tell you from experience using a 1 1/2HP blower with a cyclone 6” will definitely work better. My first set up was blower/bag/4” ducts. When I remodeled I went to blower/cyclone/6” ducts. It is important to note I exhaust outside and this is probably why I’m getting away with it. Put filters in my system and it’s a different ballgame. If you can exhaust outside, I would do it. If you heat your shop, I would consider that carefully. Assuming yours is similar rated CFM (1100] I assume you would get similar results.

I did 6” drops to within 4‘ of the machine, then reduce to 4” and flex.

No, it’s not the best set up, and I plan on getting a much bigger 5HP ClearVue, but it works for me. The only reason I have a 1.5 blower is I put it up temporarily while trying (unsuccessfully) to find a 3HP blower, it has been there 5 years and it “works”, even tho the gurus would say it’s not supposed to.

That said, much depends on what you’re collecting and where it’s located. Shavings producers are easier to collect, dust producers the hardest, so, for example, if you can locate your table saw closer, you’ll get better CFM’s at the machine.

My suggestion is use PVC, don’t glue anything, and give yourself some flexibility to see what works best.
 

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Agree completely with the good Dr's post. Just to add a few wonky comments, you're looking at a couple of factors: air flow (CFM) and air speed (FPM). As you know, the larger the duct, you'll get better air flow, so better overall performance.. Once dust enters the ducting, air speed has to be considered. According to the iconic Bill Pentz, air speed in the duct should be 3000 FPM for horizontal runs, to ensure good movement of dust particles and chips. Vertical drops need to be 4000 FPM for vertical drops (since you're also fighting gravity). FPM=CFM/duct cross sectional area (~0.2 ft^2 for 6" round duct), so at 1300 CFM, you're getting more than 6000 FPM. I suspect that the 1314 CFM quoted by Laguna is idealized and optimistic, but even dropped by a third, you still have plenty of air speed. Four inch ducts will increase air speed, but also increase resistance and diminish air flow. Go with 6" as much as practical. Just my $0.02
 

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yacht woodworker
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I just ran ductwork throughout my shop. I opted for the spiral metal pipe. I've got a 6000 CFM blower with an 8" inlet. I ran an 8" main line until I split a few lines off, dropped down to a 7" line that went across the shop, then reduced the size as I split off to different machines. Most machines I hard piped 4" drops as close as practical then connected with flex. For my planer/drum sander, I piped a 6" drop that I reduced to 5" and ran 5" flex to make the connection.

For you, I'd recommend that you go with larger trunk lines, not 4". I'd say a 6" trunk, 5" branches, and 4" drops. For your setup, put blast gates on everything so you can optimize all of the CFM at one machine.
 

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Discussion Starter · #5 ·
Wow, this is all great information. I understand that there is a higher associated price with 6" ducting vs 4" ducting, but it seems to be worth it when considering the increase in dust extraction efficiency. I suppose my next step is to price out the difference between metal pipe and sewer pipe. I am assuming that the frictional resistance between the two is negligible as they are both internally smooth sided? Also, any opinions on grounding the pipes? I have not yet heard about any extractor/dust collector catching fire due to static electricity but I understand that folks have gotten a shock at times due to static charge build-up. I obviously don't want to get shocked or have a fire, but is grounding the pipes worth it? What is the best way to ground if I choose to ground the system?

Again, thanks for all the great info!

-Andrew
 

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In my shop PVC can build static in winter low humidity. On time I got a pretty good zap from a blast gate so II grounded them but not the pipes. Since then most of the wires have been removed after clearing out the slots never replaced them. The most I’ve ever noticed around pipe is my arm hair standing.

but that doesn’t mean you couldn’t get a zap. Bottom line not a big issue.
 

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where's my table saw?
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Wow, this is all great information. I understand that there is a higher associated price with 6" ducting vs 4" ducting, but it seems to be worth it when considering the increase in dust extraction efficiency. I suppose my next step is to price out the difference between metal pipe and sewer pipe. I am assuming that the frictional resistance between the two is negligible as they are both internally smooth sided? Also, any opinions on grounding the pipes? I have not yet heard about any extractor/dust collector catching fire due to static electricity but I understand that folks have gotten a shock at times due to static charge build-up. I obviously don't want to get shocked or have a fire, but is grounding the pipes worth it? What is the best way to ground if I choose to ground the system?

Again, thanks for all the great info!

-Andrew
I used to get static shocked all the time. Then I realized that the clear spiral wound 6" connector hose between the blower and the separator was not "electrically" connecting the two units. I ran a bare copper wire between them connecting them and the static shock syndrome disappeared!
There's not enough volume of dust nor a a great enough static spark to ignite it according the Rick C our electrical engineer here:
 

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The metal ductwork you get from home stores is much higher drag than pvc. The good stuff is really expensive. PvC effectively cannot be grounded, but that is not a hazard.
 

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The metal ductwork you get from home stores is much higher drag than pvc. The good stuff is really expensive. PvC effectively cannot be grounded, but that is not a hazard.
Nothing scientific just opinion from experience; My first shop we had regular metal pipe. My shop now is sch 40 PVC. Completely different designs but metal seemed to move dust better than the PVC. When I do it again, my HVAC contractor has convinced me that spiral dust is the way to go. In an HVAC system the best duct system is spiral since air creates a spinning vortex as it travels through duct and the ribs inside the spiral duct help keep the air "organized"
 

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I'm not an aero engineer (I do work with them). The dryer vent style of ducting is what I was talking about. I don't see spiral ducting at home depot.
 

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I'm not an aero engineer (I do work with them). The dryer vent style of ducting is what I was talking about. I don't see spiral ducting at home depot.
You won't find spiral ducting at home depot. They carry the snap lock ducting and swivel fittings. I don't care for this style pipe. I ordered spiral pipe online. I can say I'm real happy with it.
 

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where's my table saw?
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Hi! I am upgrading my shop from a 1 car garage to a dedicated shop that will be 25' x 25'. I recently acquired a Laguna P Flux 1 https://860860.app.netsuite.com/cor...0902&c=860860&h=cd39892c7cb5220f58d9&_xt=.pdf (1.5hp, 18.8Amp, 1314CFM at 6" inlet per Laguna) and was hoping to get opinions on permanent duct work in the shop. I am planning on having the DC stationary in it's own closet and ducting into the shop itself using a main run for the TS/Joiner/Planer island that then branches of 45 degrees to router table/bandsaw/spindle sander against the wall. Neither run would be over 15' long and run along the ceiling.

So, here is my question: Would it be better to run a 6" main trunk that then reduces down to 4" at the tool blast gates or would it be better to just run all 4" ducting and upgrade later if I increase the HP of a future DC? While I understand that 6" ducting would almost double the volume of air in the system, which is usually great for impeller driven DCs, I am a little worried about the HP being strong enough to move the air efficiently.

Any advice or recommendations would be more than welcome!

Thanks!
Andrew
I don't don't know how Laguna rates their dust collectors, but this article explains that there are many factors involved:

My older Jet 1100's are rated at 1100 CFms, but how much is actually present at the end of 6ft of flex hose? I donno? I do know that only dust that is suspended in the air in the cabinet under my saw actually get sucked down the 4" port. There is a considerable build up in the corners of the cabinet that does not get collected. There's just not enough suction to capture it all.
 

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I have a large main with 4" drops. If your system can handle say 2-4" drops at once, you don't want to reduce it till it gets there..
 

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I have a large main with 4" drops. If your system can handle say 2-4" drops at once, you don't want to reduce it till it gets there..
How large is your main?
 

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The main is 4" reducing to 3" at the machine. Im only running a 1.5..dust collector..

You get too big on that main and the price skyrockets...

Product Tap Plumbing fixture Interior design Wood
 

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I remember hooking the dual Grizzly dust collector at the commercial shop. I needed a three way 12" pvc connector. It was about $180

I could use 6" on mine but wasn't worth tge additional cost. See the gray pipe from the motor to the bag on the left? Your not going to go bigger than that on this collector..
 

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I do know that only dust that is suspended in the air in the cabinet under my saw actually get sucked down the 4" port. There is a considerable build up in the corners of the cabinet that does not get collected. There's just not enough suction to capture it all.
I think this is more a result of the geometry of a box, rather than poor DC performance, and see it as a non-issue. The dust collecting in corners are contained and stable- by definition, it's not going anywhere- so I let sleeping dogs lie. I figure that designing a base that scrubs all interior dust would add complexity and cost to the saw, and make access to under table components more difficult than it already is.
 

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The collection on the SawStop is very good. But on my old saws, I had the same issue, and I agree it is the geometry of the box.

I taped all the gaps between the bottom and the sides, and put a ramp on the door. Helped a little, but I think you need way more than the recommended 350CFM to really collect a cabinet saw.
 

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The geometry of the box/cabinet? A cube is a cube, the saw cabinet is a rectangular 3 D shape. To me, it's about air flow in and out of the cabinet though the dust port. IF there is no blade cover to direct the dust spun off by the blade to a dust port, like modern saws IE. the Saw Stop, then dust collection will be a matter of dust in suspension. If you seal the cabinet too well there will be no way for new air to enter and you have essentially created a vacuum chamber. The dust fills the corners on it's own because that's the smoothest transition and easiest for it to flow out.
The 350 CFM flow is some theoretical figure arrived at by who know's how? The real number is how is it working or performance based CFMs. All saws are slightly different and some have blade covers, others do not. I own a Bosch 4000 with a blade shroud that I use outdoors and the dust really exits out that 2 1/2" port and if I used it indoors I could collect 90% + of the dust. The old Craftsman contractor saws have no such blade cover and gaps all over the place so the dust is just spun downward off the blade in no controlled manner. Mine are all direct drive, so there's no motor and belt to deal with and an open back. The floor of the cabinet has a 4" port in a piece of 16 GA sheet metal I screwed to the bottom. I works well enough, but a blade cover with a port would be ideal.
 

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I guess I'm lucky . I threw out mathematical numbers a long time ago.
 
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