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An experienced novice
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Discussion Starter · #1 · (Edited by Moderator)
3 years ago I decided I needed dust collection in my shop and purchased one of the Harbor Freight "2 HP" dust collectors for $150. I quickly realized that the flannel bag filter was filling my shop with very fine dust, so I found the after-market pleated paper filter that fits the HF collector and all was well. Except that the HF collector is noisy and doesn't really produce enough suction for big tools like my hybrid table saw. So I did some research on this forum and found that a repair part impeller from Rikon would fit the HF impeller housing and provide lots more volume. Then I discovered the 36" Dust Deputy and decided that I would build a 2-stage system with the HF blower sucking through the Dust Deputy cyclone and exhausting into the existing HF bag and filter combo.

To make a loooong story short, I finally got the room built onto the side of my shop building to contain the Dust Sucker and contain the noise. And I got the Dust Sucker built, and hung on the wall in the new Dust Room. And yesterday, I finished installing 4" galvanized duct work on the ceiling to the four major tools. It's all 4" to the table saw and planer, the miter saw has a 1-1/2" dust port, so I reduced from 4" to 2-1/2" at the blast gate, and 2-1/2" to 1-1/2" at the tool. And the shop built router table was built around 2-1/2" DC components, so it reduces from 4" to 2-1/2" at the blast gate.

Some photos
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Jack of too many trades..
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Nice big space! I wish I had the headroom to run my DC trunk overhead.

Couple questions:
  • Are those 45-degree bends impacting your suction?
  • If that's HVAC pipe and fittings, did you do something to reverse the direction of the flanges at the1 junctions and seal the "seam" on the long pipe sections?
-Edit-
Sorry, meant to say 90 degree bends
 

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An experienced novice
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Discussion Starter · #3 ·
Nice big space! I wish I had the headroom to run my DC trunk overhead.

Couple questions:
  • Are those 45-degree bends impacting your suction?
I don't know, because the only thing I have to compare it to is 12 feet of flexible hose laying on the floor.
  • If that's HVAC pipe and fittings, did you do something to reverse the direction of the flanges at the junctions and seal the "seam" on the long pipe sections?
No, I ran the ducting in the conventional direction, because otherwise the Wyes would not face upstream, and no, I did nothing to seal the seams. I might have to. I have a bunch of small leaks at the blast gates that need fixing, then I'll see if those are leaking enough to worry about.
 

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Egg Spurt
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Stumpy Nubs has a whole video on the downsides of ducting.. He suggests PVC.. I might tend to agree if I had experience with any kind of dust collection other than the floor and broom.. I did purchase a Delta DC from a guy in CL recently.. We'll see how it works out. I'm not so worried about the super fine dust as I am having to sweep and vacuum for hours at a time..
 

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Jack of too many trades..
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Stumpy Nubs has a whole video on the downsides of ducting.. He suggests PVC.. I might tend to agree if I had experience with any kind of dust collection other than the floor and broom.. I did purchase a Delta DC from a guy in CL recently.. We'll see how it works out. I'm not so worried about the super fine dust as I am having to sweep and vacuum for hours at a time..
I watched that video (and several others). He makes a number of good points - including about how the flanges point the wrong direction for suction - and I noticed that as I was assembling my own DC trunk. The stumpynubs video is not especially comprehensive about HVAC pipe. I picked up Sandor Nagyszalanczy's "Woodshop Dust Control" as a reference and he specifically recommends metal HVAC pipe for a small shop as long as it's at least 27 Gauge or thicker, but he does recommend that you not go under 30 ga as it will collapse under high suction. I used aluminum sealing tape (after regular duct tape proved inadequate) to seal all my junctions, and I flared out the metal "Y" fittings to install blast gates.

Now that I have a powermatic PM1300 with 6" inlet, I will probably upgrade my trunk to 5" and invest in the quality spiral pipe... when I can afford it. Sandor N. says that even 27 ga. is too thin for a 5" pipe.
 

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An experienced novice
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Discussion Starter · #6 ·
I chose galvanized over PVC because of the ease of connecting pipes to tools and gates. I couldn't find adapters to fit the 4" PVC that I could get. And wyes and corners were much more expensive in PVC.
 

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Jack of too many trades..
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had the same issue. no thin-walled 4" PVC around here without finding a specialty shop. I actually use both galvanized "Y"s and ABS Ys from my local woodcraft shop.

 

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I doubt that small section of ABS is generating a lot of static electricity, but there could be some buildup in the flex hoses. This trunk is all galavnized steel - except for that junction for the Tablesaw. That said, The section to the left of the ABS before the collector is grounded to the 20-amp conduit you see running above the trunk.
 

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There's a couple of YouTube video woodworkers who've produced articles about static in DC systems. Pretty much an "old wife's tale", with very little, if any, proof it's ever caused an explosion in a woodshop.

Dust in factories has cause terrible and deadly explosions. Dust in DC systems just doesn't reach the saturation levels found in factory settings.
 

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There an article from an MIT scientist in a Fine Woodworking back issue about how remote the risk is for any sort of home DC system, but hey, why take a chance. when I only have to bridge a few inches with a wire.
 

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Sandor Nagyszalanczy's "Woodshop Dust Control" does explicitly recommend grounding PVC and metal systems. He goes so far as to say that you should ensure that the bodies of all of your stationary machines are also grounded. That might be overkill, but worth considering.

He (SN), agrees that the risk of static spark causing a fire or explosion is very low and typically associated with large and very dry shops. He also mentions that the consequence if you happen to be that extremely remote instance could be death and/or complete loss of the shop.

I guess I'd think of it more like a risk mitigation where Risk = Likelihood x Impact and the liklihood is very low, but impact is very high. A few inches of copper wire from my trunk to my conduit is a negligible cost compared to my shop and home being consumed in a fire.

The Fine Woodworking article on the topic is this:
PVC Pipe Dangers Debunked. 4-in.-dia. plastic duct is unlikely to cause a static-induced blast in a home shop By Rod Cole from issue #153–Tools & Shops 2002 Issue. I have a deluxe membership so I can read back issues, but the findings are based on scientific literature from the Journal of Electrostatics where experiements and various tests have been performed.

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Setting the fire risk aside (and I originally did when I set up my mostly PVC system) a fellow woodworker mentioned that static build up can also make dust cling to your collection pipes and thus reduce the effectiveness of the system. For that reason alone, it maybe be worth grounding your collection pipes.
 

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Jack of too many trades..
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I used some 14 ga. copper wire to both attach my ground and to bridge the sections where I don't have conituous metal-to-metal contact. SN (referenced earlier) suggests using cheap speaker wire from "Radio Shack" which kinda "dates" the book, but still represents a cheaper solution than today's pricey Romex.

I also use aluminum foil tape for all my junctions which (i assume) is also conductive. Which reminds me that I wanted to perform a continuity test on the system...
 
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