The famous website on dust collection is adamant that you should use 6"
ducts from the collector all the way up to your tools, then reduce down to
4" to get into the tool. He says this allows you to get the full capacity
of a dust collector, if its 1.5 hp or greater. My dealer swears I should
use all 4" ducts and it will be fine with a Jet DC1100 or greater. My shop
is 3 car garage and he's been out here and has some idea of the pipe network
I would need for dust collection.
The jet book on dust collection recommends a 6" main pipe with 4" branches
going to the tools.
I'd like to hear the real-world experience from some of you that are running
1.5 - 2 hp dust collectors.
By the way, can anyone tell me what difference I might observe between the
jet 1.5 hp and 2 hp collectors? The published specs are 1100 cfm and 1200
cfm. I would suspect the larger collector could achieve its capacity
through a more complex or restrictive pipe system.
Are there any other brands you might recommend? The Jet models seem to be
the most for the money in the $400-$500 price range. Others that use
cartridges seem to be in the $800 up price range.
I've got 4 inch DWV PVC clear to the 1100 DC in my big 'ole garage, with a few
90 degree bends thrown in. Total run from the furthest machine is better than
60 feet. Plus the garbage can cyclone. It sucks just fine in my one-man
shop.Tom>Subject: 6" dust collection pipes
I use the Penn State 2HP cyclone, with 6" thinwall PVC everywhere
right to my blast gates,at which point I drop to 4" flex for the last
4 feet or so to my machines. I am totally happy with the performance
of my system, although I just eyeballed the design and have never
taken any performance measurements. I also took the trouble to do each
of my 90 degree bends as a pair of 45's. After living with the thing
for a couple of years, I never get clogs and the system seems to work
really well, with plenty of airflow to occasionally send chunks of
wood and such back to the cyclone for my musical entertainment.
Take a look at the spreadsheet on that site, then do some computations
with your setup. Be sure to use the dust collector volume vs. static
pressure drop curve for your dust collector. I have a 2 HP system, and
5" pipe is the optimal size for the pipes, 4" has too much static
pressure drop, 6" doesn't get the flow rate up high enough. I used to
have the system hooked up with 4" flex duct -- I never had a clog and it
always sucked up the chips, but... When testing my 5" system, I
understand now what static pressure drop really does to a system;
although my 4" system on the table saw would clean up the chips, I could
actually see the system pulling in dust through the blade insert with
the 5" system -- it looked like one of those Jenn-aire range hood
commercials. When you use the curve I indicated above, the process on
that spreadsheet will be iterative, you will have to find flow volume,
check the pressure drop, then adjust the volume input until the volume
and drop intersect on the chart.
Thanks for the feedback. The site is much better organized than when I
first looked at it. I've printed out the whole site, downloaded the
spreadsheet, and I'm reading and learning tonight.
Your qualitative description of the differences is inspiring to do it right.
2HP is rather on the borderline. I'd go with 4" though, because 6" on
an underpowered DC fails more drastically than 4" suffers through
friction. If your workshop is big enough that you need 6" because of
run lengths, then make sure then fan is big enough !
If I was plumbing in a whole workshop from scratch, then I might do a
shared roof-level backbone in 6", but I'd certainly do the drops to
each machine in 4". Sucking vertically in 6" just doesn't work if
you're at all marginal.
Die Gotterspammerung - Junkmail of the Gods
Thanks for the comments, Andy. I've done more reading and looked at the
charts and I am beginning to understand the give and take. I had a course
in fluid mechanics in college and its slowly coming back to me.
Me too. I also designed hydrocyclones used in the paper/pulp
industry. The knowledge and experience helped me to build my shop
cyclone for cheap. With pipes, the smoother, the less turbulance and
I never had that opportunity (EE's didn't need to take that). My
nighmares come from suppressed memories of Statistical Thermodynamics.
The course was taught by a professor who was mad at the world because he
hadn't won the Nobel prize. Straight 90, 80, 70 grading scale with
tests that were designed and had a class average of 60.
That reminds me of the professor I had for Differential Calculus. He has never
taught the class before and could not solve the
problems himself Then the entire class failed the test (actually, high score
was a C) he stated that he would not grade on a curve
and that the whole class was stupid. Ah, the good ole days.
"It ain't what you don't know that gets you into trouble. It's what you know
for sure that just ain't so." --- Mark Twain
Yep, our linear systems class was that way also. Same average on the
first test,except one guy got either a 96 or 100. I knew him and talked
to him afterwards -- turns out he had failed the class the semester
before so had the pre-requisite for the class (a full working knowledge
of all material to be presented in the class).
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