[OP]
Contributor
Im near ready to order duct work for a central DC system. My plans were to run 6 drops off the main line.
With 6 drops, is there any sense in spending the dollars for a main line larger than 6 diameter? Im not running more than one machine at a time.
My DC has a 8 intake. Its an old 3hp old Dayton short cone cyclone (industrial variety I picked up for cheap).
Member
I would go 8" for horizontal run. Only about$4 more for five foot section. Depending on shop size that is only a few bucks. The fittings are what will cost you more.
Contributor
Will his dust collector handle 8" ducts and keep the velocity up? Would need to know specs to figure out.
Moderator
That was my question too. Seems like the calculations would need to be done considering the specs (or tests) and the design. It would be discouraging to install 8" ducts then discover dust accumulating inside due to insufficient air speed. If that occurred the ducts or the cyclone might need to be replaced.Originally Posted by Larry Frank
The fact that the machine comes with an 8" port would lead you to think that was correct. What we don't know is if that unit was designed for wood spoil or some lighter dust collection job. With 3HP and an 8" port it is in line with several currently available woodworking cyclones.
"A hen is only an egg's way of making another egg".
Samuel Butler
[OP]
Contributor
The model Dayton 5E817A.
It reportedly moves air at 1800 CFM. The fan is only 12", straight blades...and lots of them.
The unit sits at the front corner of my garage and my plans were to run the main 20' to the back. The branches off the main line wouldn't be more than 6-7' and my wall drops would be 5'.
Machines:
- 8" jointer (4" port that needs expanded...Grizzly)
- TS (4" port that needs expanded if possible...PM66)
- 18" BS (with two 4" ports that cannot be expanded)
- Planer (Dewalt)
- router, miter, sanding station...etc.
My question comes from an article I read online stating there is no purpose to running a main line larger than your drops, IF only one drop (one machine) will be running at a time. That was news to me, but it did make some sense.
Have you read this in more than one article? A sample of one is no sample at all ;-) It does sound sensible though. My machine has a 7" port and due to my short runs I reduce to 6" right at the DC entry.
I placed my 2HP cyclone DC (rated at 1350 CFM) as close to my main spoil maker as possible. My tablesaw at about 10' will suck up my safety glasses if I am not careful. The planer is just a bit farther lineally.
Still my longest 6" run is about 20' (bandsaw). I consider collection at that port reasonable but, nothing to write home about. With runs of 30' I think you may be setting yourself up for disappointment. Just food for thought.
It is not uncommon to perceive a new dust collector as awesome by waving your hand in front of a port while it is running. Even sprinkling sawdust near the port or 'vacuuming' sawdust out of a barrel is a poor simulation of spoil being launched off a cutterhead at 9000 Surface Feet per Minute.
We are all challenged by the shape and space we have available. It may be fine but, integrating the DC into your layout could give you better results. Your spoil generation will vary with how you use your tools but, the heavy hitters in my shop are the planer, jointer and tablesaw in that order.
Due to my layout I actually run a separate DC for the jointer and edge sander. I lost too much air volume/speed to meet my needs by the time I plumbed ducting to those machines.
Like lighting, a DC is not always a single complete solution; special tasks may need targeted help. I run two shop vacs with Dust Deputies on them. One for powered hand tools and typical vac use. One for the DP and smaller bandsaw. The task specific setup cost about what running large ducting to those areas would have cost and works better for these small machines.
Last edited by glenn bradley; 08-14-2018 at 11:51 AM.
"A hen is only an egg's way of making another egg".
Samuel Butler
Member
I disagree with this.
Both diameter & length of run determine CFM drops. So it makes perfect sense to maintain larger ducts especially on longer runs. Keep the 4" drops as short as possible.
Contributor
Just my opinion but the 12" impeller is only going to provide about 1200 cfm. Based upon my calculations this will give around 3500 fpm and below the 4000 fpm recommended by Pentz.
If it were me, I would go with 6" duct due to velocity concerns and cost of fittings. But that is just me...
[OP]
Contributor
I'll have to pull up that article when I return home and post the link, assuming that's not against forum rules?
I need to cross reference Bill Pentz's site again. He has a "Layout and Ducting Design" illustration with what he describes to be a well laid out design: 3hp unit, 8" main, 6" drops. But then he goes on to say (in "pipe sizing" section) that he recommends most small shops to use the same size main as the drops. He supported that statement by citing the 4,000 FPM required to move dust vertically, which would seem to imply some systems cannot move at that rate with a main larger than 6"...unless you use the "oversized" blowers like in his designs.
To be sure, I'm NOT criticizing Bill Pentz's writing or knowledge. More likely I just need to read it again from my PC. The first go around was on my iPad and his site didn't format correctly. The last words of every line were cut out of view.
[OP]
Contributor
I bought this through an auction, and when I went to the warehouse to pick it up I was really surprised to find that it only had a 12" impeller. It's a beefy steel impeller that I won't worry about chipping, but given the size of the housing, weight, and footprint of the machine..I was as disappointed as all the women who have been in my life
Contributor
The fact is that reducing the main is going to drop the CFM. How much will depend on the length of the run. Do the calculations for your particular shop to decide if you can afford the reduction. It's not hard to do. There are several sites that have calculators to do that.
My main run is 8" because it's longish (about 30') & has 3 90* elbows. But you gotta watch that your air velocity doesn't drop to the point where the solids start to fall out of the air stream.
Member
Patrick, when I redid my DC system after a shop expansion, I wanted to "do it right".
The first place I went is to Bill Pentz. All I can say is my brain quickly turned to oatmeal, OK? But I did get some understanding of the basics. Just keep in mind Pentz is designing a very efficient system. There's a reason why the only blowers Clear Vue sells are 5HP.
I came across a source that really put in layman's terms. That may have been somewhere on Pentz's site, but I doubt it. If I can remember I'll post that.
My longest run is 20' to my table saw.
Now here's what's interesting to me. My old blower was a 1 1/2HP Jet 1100. My assumption is it wouldn't work, so I began an (unfruitful) search for a 3HP blower (just a blower) - not to be found. Penn State Industries used to carry one, but d'c'd it. So I was down to finding a used 3HP DC and scavenging the blower off - no luck, either.
So, for the heck of it, I mounted that Jet blower in a stand, hooked up the ducts and - well- its still there, doing its job good enough for me, and that's with a Super Dust Deputy cyclone & 6" PVC ducts.
How good is it? Probably not the greatest, but it collects my table saw and I installed a floor sweep at the fartherst point of the run and I have to watch because it will suck up a steel screw!
That's why I think you'll be fine with the system you've got.
Contributor
http://www.freecalc.com/ductloss.htm
Why don't you play with the calculator above with what if scenarios? Try with 6" all the way and then with 8" and see what the losses are. Use Larry's 1,200 cfm (or even 1,000 cfm with the short cone cyclone) as it is much closer to what the impeller will produce. You'll get better performance if you can vent outside without filters, subject to proximity of the neighbours.
Contributor
The common question is always what goal do you have.
Do you want to get the larger dust particles or do you want to collect more of the fine particles.
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