totally confused re: 4" & 6" ductwork - help!!!

[rickd]

hi,

i just got a Grizzly 1029z 2hp dc and am in the process of planning the installation of a collection system. i have a 6" Jointer, 13" Planer, router table, 10" bandsaw, orbit sanders and, of course, a BT3100. up until now, i have been using a ridgid shopvac but it just couldn't keep up with my jointer and planer.

Originally, i had just planned to just install a 4" clear flex hose setup(main line and branches with blast gates) in my workshop which is 10' x 20'. my jointer and planer are along the same wall as my dc so that's good i guess!

After reading Bill Pentz' site and other info, i am now pretty much confused about what to do re size of ducts. cfm, static pressure, air velocity etc. has made me feel pretty inadequate as far as figuring all this out. is 4" flex hose ducting all around not good enough? do i need 6" duct everywhere with reducers to my 4" and 2.5" equipment ports? or, should i install a 6" main line with 4" branche lines? my dc has a 6" port, or 2 x 4" ports. Also, because of cost and hassle, i don't really want to go to metal or pvc ductwork(except for wyes, gates etc.).

So, enough for theory and engineering specs, once again i want to turn to the bt3 forum for "real world" user experience and advice. What size ducts do you use in your dust collection system and how does it work? right now, i am sort of leaning towards installing a 6" main line with 4" branches(although to keep it really simple, i guess i would prefer all 4") - but, before i get into buying anything i would really like to hear what others on this forum have used re duct size and how it works for you.

hope this explains my problem and i appreciate any advice you might have.

[stewchi]

I am not familiar with the Grizzly put if it is the same strength or stronger than the HF with a canister than I would go for 5” ducts for horizontal, 4” vertical up runs (against gravity) and 6” for vertical down runs (with gravity). I plumbed my HF 2HP DC this way, actually I used 6” horizontal and when I moved I noticed a about a Ό” of saw dust on in pipe, so 5” is probably better. This configuration should optimize your CFM.
I used metal because the size for 4”,5” and 6” are very common, it was cheaper than PVC, no static electricity (I don’t think that matters though) and it fit right onto my blast gates , my DC and my 4” flex hose with no special adapters or reducers or anything (I used 4” flex for my vertical down runs). It was not very expensive, but I did by a crimper (about $10) to crimp the ends of a straight piece or fitting so it would slide into the next piece.
I connected to a lot of machines so I needed a lot of fittings, I found PVC was about ½ the price for a straight length of pipe but the fittings were twice the price of HVAC. And I only needed 2 straight pieces but lots of fittings (Tees, 90s etc). So the HVAC turned out to be much cheaper. I think the real advantage was how well the sizes fit with the blast gates, and flex hose.

[JimD]

I have a 1 hp Delta DC. I used 4 inch plastic pipe - the thin stuff sold for drainage outside, not the schedule 40 stuff sold for drain connections within the house. I am curious about the comment that metal could be cheaper. I looked at it briefly and thought it went the other way but maybe I didn't look hard enough. With your bigger DC, maybe you need or could use bigger pipe. The only place where my DC struggles sometimes is the jointer which is also my planner (with a planner attachment). Mine is an old hand feed INCA which is 8 5/8 wide. A 4 inch pipe will take the chips away but seems to be at about it's limit. A 12 inch planner might be a bit much. I think a 4 inch connection to other machines should be OK.

If you tee your hard lines close to the DC, you can have two blast gates open at the same time to reduce the backpressure on the DC. Even my little DC pulls OK for the BT3100 with one other gate open. You thus do not have to have big lines to let the DC pull against acceptable back pressure - you can in effect let it pull on two 4 inch lines.

another recommendation is to look hard at just making your own blast gates. I used some that came in a kit that were plastic and was pretty dissatisfied. They never fully opened and tended to fill up with dust making movement difficult. It is easy to make wooden gates that never plug up and fully open. In principle, it is just a plywood slider with a couple of plywood end pieces that have holes the right size for either the pipe you are using or for a coupling for the pipe (the way I have done it for the last couple). I have an old magazine article that started me doing this and I have been very satisfied with the results.

You want to use as much hard pipe and as little flexible pipe as possible in making your connections. The resistance of the flexible is much greater than the hard. The hard pipe is also much cheaper. I taped my connections initially (aluminum tape is best but duct tape will work for awhile) and then went back and glued them when I was sure I was happy with the setup.

Jim

[Tom Miller]

quote:Originally posted by rickd

After reading Bill Pentz' site and other info, i am now pretty much confused....

That's how most people come away from that site. It's definitely an extreme. The other extreme is the place I just went to over lunch to pick up some 5/4 maple boards. Good Lord, those people are going to be dead in 2 weeks! An 1/8" of fine dust covered everything, including me by the time I was done picking out my boards.

Oh, where were we...
The biggest improvement you can (and I think you should) make, is to switch from flex to anything with a smooth wall. I chose 4" pvc (sewer and drain, or schedule 35) for its relatively low cost, availability of fittings, and ease of swapping around fittings. (I've used HVAC, but prefer pvc, others prefer HVAC, YMMV.) If I could find 6" pvc and 6" to 4" reducers, I'd probably have a 6" main by now, but I can't so I don't. That's the beauty of HVAC, BTW; the availabilty of sizes and reducers.

Did I mention I also have the 1029z? I currently have the "0.3 micron" bag on top, and a plastic bag on bottom.

Do get rid of the flex as much as possible.

Regards,
Tom

[LCHIEN]

I think you have to take Bill Pentz with a grain of salt. He's a perfecdtionist but with his repiratory problems I guess he has to.
I think he is striving for 99.9% capture in everything and the engineering is therefore ultimate. I do like reading it to see what the problems and tradeoffs are.

I think his recommendation IIRC is to use 6" everywhere and don't step up and down in sizes due to the resctrictions it causes. And the 6" is to guarantee that all material is "entrained" in the air stream even when going vertical. And you need minimum 800 cfm actual air flow.

I've dreamed up a couple of ways to hook up a permanent shop but I'm not there yet.

I don't have a permanent system yet, just 4" flex hoses 10' long going to my machine that I move as needed. I'm working on improving it but still a long way from a permanent 6" straight wall or even 5" dust system.
I don't seem to have any piles of stuff, and I don't have 8' vertical runs, so I'll assume I'm at 90+% and be happy with that.
For now.

[rickd]

thanks to each of you for your response to my questions! the info you provided helped me to make sense of some of the things i read on bill pentz' site. Good thing i asked because i sure looked to be heading off on the wrong track.

i am going to take your advice and keep the flex ducts to an absolute minimum and use as much pvc pipe as i can instead. i think with my grizzly dc it should work out o.k.

[maxparot]

I have the HF 2hp w/ filter cartrige conversion. I keep a trash can separator in line which keeps the real heavy stuff from going through the DC impeller. I (like Jim) use 4" drain pipe. I have blast gates at each machine. Could I get better performance from my DC with larger pipes probably but how much better and at what cost. The machines that have small ports Like the BT won't see a difference. My planer pushes the sawdust into the pipes and the DC works fine with it.
The place I wish I had better flow is at the lathe and as we all know turning is messy so I can't complain about what the DC doesn't catch. Ther is no such thing as a perfectly clean workshop while the work is going on. I just like to limit how much clean up is needed during and at the end of a project.

[Tom Slick]

this site may help you
http://www.airhand.com/designing.asp