Dust Collection Overload

I think you’ll be just fine, blast gates at each tool and 4 inch tubes to connect the whole thing. No reason you can’t connect a trash can in line with the tube as long as all the connections are fairly tight you should get plenty of suck from the system. Let us know how it works out.

-- Paul, La Center, Washington

Permanent 15’ away? I suppose it depends on what you mean by sufficient. I have a 1.5 hp Delta dust collector. if its not sitting within a few feet of whatever its hooked up to, i might as well not hook it up and just use it like a shop vac when Im done. I’ve been pretty disappointed by it, Im saving for an upgrade, a big clearvue or an Oneida within the next year.

-- "Democracy is by far the worst system of government. Except all the others that have been tried." ~ Winston Churchill

Coincidentally I poked around on the Bill Pentz site last night for a few hours, and my head is still spinning Based on my understanding of his general principles, I’d say that you are asking for problems as follows:

1. Downsizing to 4 inch from 6 inch at the machines is not good because the air velocity in the 6 inch pipe would be too slow.

2. Four inch header is too small

3. Changing the dust collector 4 inch wye to 6 inch might overload the motor and cause it to burn out/overheat.

4. It seems like he doesn’t like any hobbiest dust collectors and only recommends a Clearview.

5. The dust collector should be in the middle of everything, not at the end – and vented to the outside after collecting the “big stuff.”

I was all set to plan on adding a DC to my shop, but now I’m in a reset mode due to the cost if it is to be done using his methodology.

My main bjective was to get rid of the small particles that zap your lungs. After reading his blog it would seem the only practical way for most hobbiest woodworkers is to wear an appropriate mask (the little paper jobs with rubber bands won’t cut it either) or powered respirator.

-- Joe

1 1/2 hp SC dust collector will work fine on the tools that you mentioned, though I would try to get closer to the tablesaw. The tablesaw, portable planer and the jointer are your largest makers of dust and the DC should be as close as it can be to those machines. The 4” pipe should work fine ( a 6” system w/6” outlets would be better), and I would recommend a Thien ( http://www.cgallery.com/jpthien/cy.htm ) seperator before the DC. Pleated filters work much better than bags for filtering the fines. Bill Pentz is very knowledgable, but don’t let him stop you from building a DC because you can’t afford one, even his systems allow fines back into the shop air. The only way to stop all fines is to exhaust outside your shop.

Good luck with the system.

-- -JimmyC...Clayton,NC- "Just smile and wave boys, smile and wave"

go to reviews and check on ‘dust collectors. I have a 1&1/2 hp with a vortex separator and its great.

-- RTB. "dumb animals are not stupid they simply can't talk "

Sounds like it would almost be better to just have a small fan blowing the fines away from the work station and sweep it all up when you’re done.

-- Debt is nothing more than the 21st Century's form of slavery.

I was a early adopter of dust collection in my workshop, the main reason being, I hated to sweep. So, the more sawdust that was picked up at the time of creation, the better it be. So my first dust collector was 1HP import, main reason being, there weren’t a lot of affordable choices at the time.

Then, all of a sudden, everybody jumped on the bandwagon. So I bought one of Delta’s first 1-1/2HP units. I plumbed it in to all my machines using 4” PVC (I ran a 6ga bare ground wire throughout it) with blast gates at each station. It did ok, but I wanted better.

So I bought one of Oneida’s first cyclones with the internal filter and re-plumbed everything with 5” steel and blast gates. Still in use today, but I’m in the process of upgrading it to one with an external filter units that has a filter 3 times the size of the internal filter.

My point in sharing this is, been there, done that. Don’t get caught up by all the new fangled ours is better then their’s and don’t ever believe advertised CFM ratings. Ask the manufacturer for a CFM verses static pressure graph and use that to compare the real performance.

And if they can’t or won’t provide you with that graph, say bye, no matter what excuse they give you for not being able to provide it, because that graph will show real performance and if they don’t want to provide it there’s a reason for that.

And if you really want a good dust collection system, look at Oneida, now. Not after you buy your first dust collector, or your second (like I did) and waste(d) your money, do it now. They will help you design your system and your ductwork free of charge. I’ve been there, done that, came full circle. Penn State or all these others are playing catch up to Oneida. Oneida does one thing, dust collection, that is their specialty. And I do believe they sport the Made in USA emblem.

Ask Oneida for comparisons of their equipment to all the rest, you’ll get them. Ask all the rest for comparisons of their equipment to Oneida and…

All I can say, is I ran the route, and I’m just passing that on.

-- -Curt, Milwaukee, WI

Curt
Thanks for your input, this is good advice, I’ll definately check Oneida out.

Your’s is one more example on why it is better to buy quality and performance the first time. Everytime that I have compromised and bought something based only on advertising hype and price I have been burned. It’s a false economy to buy something cheap now with the idea to replace it later when you have more money.

-- Joe

indeed it’s a lot of info. since I read Bill Pentz articles I have been holding off till I figure out my ‘final’ setup… in the mean time I use my Jet 1.5 1100CFM dust collector one tool at a time with a flex hose.

I think you’ll do fine with the 1.5 SteelCity collector in a garage shop your size, but for best performance, move it closet to the big chip makers – Tablesaw/Planer/Jointer. 4” pipes would work ok, but 6” would be a better choice, and in the long run will give you a better base (plumbing) to work with if you ever do choose to upgrade the collector.

PS. Oneida definitely has their hold in the market, but I’ve read some rave reviews on the smaller JDS cyclones well

-- When in doubt - There is no doubt - Go the safer route.

Thanks for all the advice, since I have already purchased the dust collector I am going to install the permanent dust collection system. With your suggestions I am going to install the 6” main run up to each machine the necking down to the port size. I will also install blast gates as close to the main header as possible. For right now I think I will for go the seperator due to the fact I would have to reduce size to 4” the increase back up.

After reading your responces and making the above decision I decided to call Steel City’s tech support and get there advice on the performance of the DC (knowing that they would also want to sell their equipment). They stated that normally you would want to run a cyclone (like Larry stated) but due to the short runs the DC will work fine and yes to go ahead and run 6” duct. I also asked if this would overload the motor, they stated no.

Thanks for the help, I’ll post pics when I get it all complete and find out how the performance is.

As you can see from my picture, I’m an Oneida fan. Its my second upgrade, and worth every penny.
If you’re trying to get the most bang for your buck and don’t want to upgrade to a cyclone, then
1. make sure you upgrade to a fine filter bag instead of the junk that comes with most DCs. I bought them from Oneida in my first system, and they greatly improved airflow and cut way down on the dust layer around the shop. http://store.oneida-air.com/retrofitfilterbags.aspx
2. yes, you should retro fit a 6” connection for 6” duct header then downsize to 4” right at the machines? Its not ideal to downsize to 4”, but frequently its all you can do.

-- Its a HOBBY...I already have a job.

Hey angelis, before you run 6” duct check it out, that might be too big When you increase duct size, or use too big of duct size, air velocity decreases. When air velocity decreases the stream is no longer capable of keeping material suspended in the air stream and it will settle in the duct work. Don’t increase to 6” if the dust collector has a 4” or 5” inlet. Even if it has a 6” inlet (or even bigger) you might want to still use 5” Unless you want to clean out your ducts periodically..

When I got my Oneida cyclone I was buying my duct work from Oneida, it has a 6” inlet so I was inclined to use 6” duct work. I was talking with an engineer there and was told to reduce the runs to 5” it increases air velocity,. So at the fist major junction, within 3’ of the cyclone, I used a 6” to 5” to 5” reducer. Then at each machine reduce to what you need, My table saw stayed at 5”, my jointer, RAS, chop saw, router table, drum sander, and planer all have 4”, oscillating spindle sander 3”.

Also, don’t use HVAC duct you can get at you home improvement stores, it’s typically too thin and can collapse if the duct collector is powerful enough. Use duct work that is designed for dust collection. I’ve seen pictures where the duct actually collapsed, flattened like a pancake, looked like a stream roller rolled over it.

-- -Curt, Milwaukee, WI

I too have seen the pictures of collapsed 6” duct and would like to know how they really crushed it. I personally think that it’s some sort of urban legend kind of like how pvc pipe can cause explosions in conjunction with DC with less than 3 hp, which is another fallacy. I took three lentghs of 6” hvac pipe and connected it to the inlet of my Grizzly 2 hp DC and then put a piece of 2” foam insulation over the inlet toact like a stoppage and glory be there was no collapse of the pipe. not scientific, but it worked.

Remember, “Only believe half of what you see, and none of what you hear.”

-- -JimmyC...Clayton,NC- "Just smile and wave boys, smile and wave"

When I purchased my first Delta 1-1/2HP dust collector I too used 4” PVC pipe, but I was aware of the explosion risk and ran a 6ga bare wire throughout it and grounded it to my electric service panel ground. Wood dust is just as volatile as grain dust and I’m sure you’ve heard of grain silo explosions, or is that something we’re only half supposed to believe?

High velocity air produces static electricity, if not grounded properly that static electricity can find a path and discharge in an arc, if there’s wood dust in that arc’s path that wood dust can ignite. As an example, take a handful of sawdust and throw it in a fire, you’ll see how easily and fast it ignites. Now, consider much finer wood dust, the sort that is created by woodworking machines and processes, definitively a recipe for disaster. Just running my shop vac with a long hose I can feel the static charge when it builds up on the hose. It is real, not imagined.

Also, because wood dust does have the risk of explosion, the National Fire Protection Association takes it very seriously and I would suspect insurance companies that provide homeowners insurance take that seriously too and follow it.

NFPA (National Fire Protection Association) Code 664; Prevention of Fires and Explosions In Wood Processing and Woodworking Facilities, which states “The collection equipment shall be designed and constructed entirely of noncombustible material suitable for the use intended.” “Non conductive material such as PVC shall not be permitted.”

As for duct work collapsing, take look at this:

http://www.oneida-air.com/activekb/?q=69

JimmyC, there’s a good explanation at the above link of what it took to collapse it.

Here’s an excellent guide for designing a dust collection system:

http://www.oneida-air.com/design/ductguide.pdf

But I guess I should only believe half of any of that eh? Oneida may not be a reputable company and may have staged that eh?

-- -Curt, Milwaukee, WI

blankman that pipe collapse image is not PVC, thats A/C metal duct… it’s very thin gauge metal and I’m surprised someone actually used that for dust collection purposes… PCV ASTM2729 should be suitable for dust collection on the ‘cheap’ side. 4” or 6”

I used to install that type of plumbing for central vacuum systems in homes/businesses (although the 2” version) it’s a lightweight ridgid material that performs well.

oneida does have a good resource of info on their site, def. worth checking out. thanks for the reminder

-- When in doubt - There is no doubt - Go the safer route.

PurpLev, yeah I know, exactly what I said, HVAC pipe used in a dust collection system may collapse, I never said PVC would collapse, I’d like to know what it would take to do it, a heck of a lot I bet. In my mind collapse is always synonymous with metal pipe so that’s what was thinking as for the material.

“PCV ASTM2729” is that PVC pipe? Being one that went that route myself, I would not recommend using PVC pipe for dust collection period. And I have to wonder, due to the NFPA specifically stating it is not to be used, what a insurance company would do if your house burned down and the cause was traced to your PVC dust collection system. Could they refuse to pay if you violated a code?

When I changed my homeowners policy to a different company a bunch of years back they were extremely concerned about my wood burning stove in the basement, so I would think anything that could be a fire related risk they seem to pay special attention to.

Heck, I’ve seen a lot of homemade vacuum pump setups for vacuum presses use PVC for their storage tanks and typically they’re pulling 25” Hg and not the 8” H2O that dust collection systems do. I’ve never heard of those PVC tanks imploding.

-- -Curt, Milwaukee, WI

BlankMan has introduced a very important point that needs to have significant consideration here.

A dust collection system has to do just two basic things; keep the air velocity in the pipe/hose above 3500 feet per minute (in order to keep dust particles suspended in the air stream), and have enough cfm capacity to take away dust and chips as fast as the tool generates them.

A technical concept that is difficult for some to understand is the fact that the velocity in the piping system is inversly proportional to the cross sectional area of the pipe. In other words, if you go from a 4” to a 6” piping system, the velocity in the pipe will decrease by a ratio of 4/9. If this causes the velocity to fall below 3500 feet per minute, the dust will not make it to the dust collector.

Thus as you go to a larger diameter duictwork, you’ll need to have a dust collector with a much larger cfm rating, which means much more HP, and unfortunately a higher noise level as well. Yes. You can put something like this in your garage, but the bulky piping system will take up valuable space, the electrical system will require an expensive upgrade, and the noise level will be a subject of intense interest for everyone in the family. In otherwords, why overkill if you don’t have to.

Believe it or not, I have a 1/2 HP single stage dust collector, that for a small, or very small garage shop, satisfies the two above requiremnets very well. It sucks up virtually every single spec of dust and chips from my 12” planer, even when I’m planing boards almost that wide. I have this same dust collector here in Gainesville, where I only have 250 sq ft to work in, as well as in my 24’x28’ “workshop in the Woods” up North. I’ll grant you that my tools are designed to be efficient with this type of system, which uses 2 1/2” diameter flexible hoses.

As an experiment, using your present 1 1/2 HP dust collector, obtain a 4” to 2 1/2” reducer, and an 8’ or 10’ length of flexible hose, and connect it to your tools and see how well the system works. I think you will be surprised.

-- "Heaven is North of the Bridge"

6 inch, 26 gauge ducting should be just fine. You won’t overload the motor with the bag or filter on it.

“6 inch, 26 gauge ducting should be just fine” What is that based on? The 6” part. As 8iowa said it’s all about air velocity. I would be very surprised if that Steel City unit could support 6” pipe. I looked at that DC, no performance graphs anywhere, not even in the manual. I had the Delta 1-1/2HP version, no way would it do the air flow necessary to keep the material in the stream using 6” duct work.

When I had it plumbed with 4” duct work and used a Dwyer Mark II Manometer to determine air velocity and volume, it didn’t make the grade, not even close. And like 8iowa said, increasing the pipe diameter decreases the air velocity by 4/9, I doubt very much that 6” duct work would be “just fine”.

What I’d be more wiling to bet will happen if he uses 6” duct work is he’ll be disappointed that the ducts have sawdust laying in them (something that should never happen in a properly designed system but did with my Delta 1-1/2HP DC and 4” pipe) and then complain what a piece of junk that Steel City DC is because it’s not working as claimed when the crux of the matter is system design. (angelis, I don’t know that you would complain just making an example reference of what people do.)

There is engineering involved to get a dust collection system running well and seat of the pants engineering does not qualify. It’s a shame people ignore publications and advice on the matter and have to find out the hard way. At one time I too thought I knew, then I sought advice from a professional in the business that really did know, and I learned and now have a much better performing system.

-- -Curt, Milwaukee, WI

Excuse me Blankman, Angelis stated that Steel City said it was ok to use 6”, you can argue with Steel City on that one if you want to. I was just suggesting that 6”, 26 gauge metal ducting shouldn’t colapse.

Woodchuck, sorry, I missed the fact that the emphasis was on the 26ga of which I totally agree.

But I really question Steel City’s advice that 6” ductwork will be just fine.I wonder if that’s from a Level 1 support person or somebody with a engineering background in fluid dynamics.

I’d really be interested to see the results of testing that system with a manometer when it’s running to see what the air velocity and volume is..

-- -Curt, Milwaukee, WI

Blankman, I went to Steel City’s website to see what size the intake is without the WYE, ofcourse they don’t say, or somehow I missed it, so that was a waste of time. If it’s 6” then he MIGHT have got ok info, if it’s 5” forget it. It’s really hard to say what anyone can use. He MAY be able to use 6”, but if he uses too many elbows, or tight radius 90’s, or gawd knows what, that can hinder performance also. I’m staying out of the layout.

I pulled a favor and picked up the ductwork last friday. 6” spiral wound duct necking down to 4” at the machines. I have not installed it since my dust collector is on backorder for a couple of weeks. I did ask the steel city tech if it would be better to run with the 4” since it had the (2) 4” wye. They stated no, that I would have a better performance with the 6”. I also told him there would be two main branches going to my tools, one for my smaller tools and one that would hit the planer, table saw and jointer. He advised to install blast gates off each two main branches and if would also help with the are the DC was pullling from.

Take a look at this:

http://www.deltaportercable.com/uploads/PCD/Documents/News/182DustCollectors.pdf

It’s not Delta hype, it’s actually a review by Wood magazine. Interestingly enough they have graphs that shows the Static Pressure verses CFM for both 4” and 6” ductwork.

If using 6” ductwork and the static pressure due to ductwork length, elbows. etc. rises above 2.5” that Steel City DC will not be able to support the airflow (700 CFM) that using 6” ducting requires. 2.5” of static pressure is not that much when dealing with duct work.

Doing some rough calculations using 2.5” for that DC, that means that DC can support ~55’ of 6” duct, BUT, each 90 degree bend is equivalent to 12’ of duct, so it disappears fast.

If using 4” ductwork that DC can sustain 400 CFM (required CFM for 4” duct) to just over 7” of static pressure. That then means it can support a bit over 100’ of duct and 90 degree elbows are only equivalent to 6’ of duct.

5” ductwork would be someplace in between there and was probably why Oneida recommended that size.

The inlet size of the DC should not be the factor that determines duct size, it’s all about air velocity and volume.

(Length calculations based on information from that article.)

Bigger, in this case, is not necessarily better.

angelis, I see your runs are short, but does that mean you’re going to have 6 branches, one for each machine coming back to the DC in the center? If you’re putting up permanent ductwork that sort of implies it’ll be a run and I know you said 2 runs so those distances stated 2’, 4’, 15’ is a run, 15’ being the total for that one? That includes up and down or down and up, because I’m sure you want it somewhat out of the way.

-- -Curt, Milwaukee, WI

I would think that how well you keep the dust bag clean is also going to be a determining factor on how well everything works.

Exactly. And if 6” duct is used 3 90’s and 15’ of pipe will put it pretty close to the limit, 92% to be exact, thus if the bags start to clog from use, and they will, performance will degrade and by the fact it that it’s so close to the maximum, that degradation will be more noticeable.

Whereas using 4” duct. 3 90’s and 15’ of pipe will be running it at 33% of maximum, lot of wiggle room there. I’m not advocating using 4” ductwork but I strongly recommend using 5”, probably be in the 60% to 70% range.

It sure sounds like andelis is dead set on using 6” thus ignoring sound engineering in designing an efficient system. I was there, I did that, and I learned the hard way and I was extremely disappointed in the performance of the system. That’s the only reason I’m spending the time to post this information here, I hate to see others make the same mistakes.

-- -Curt, Milwaukee, WI

Thanks blankman… there are also others, other than the OP that are reading and taking notes… so your words are not lost…

-- When in doubt - There is no doubt - Go the safer route.

Thanks PurpLev.

-- -Curt, Milwaukee, WI

Blankman, don’t take my statement that I had 6” duct as a dissmissal of your comments, first take a look at when you made your replies and the fact that I noted I picked up the duct work on Friday. Since the duct is already here I will hook it up per Steel City’s recomendation and tweak if needed.

I am curious on who you are blankman, I noticed on your website that you sell tools including onieda systems? I am curious if your replies come from an engineering background or from Oneida’s technical data?

Thanks everyone for the advise and input, reading through the replies there are as many conflicting view points here as the information available on the web. And those viewpoints can get heated.

In the last few points there are arguments on why 4” duct will perform better, but in Pentz’s he discusses the issue of duct size and gives the following statement:

“For instance a 1.5 hp dust collector that can move a maximum of 1100 CFM moves far less air than that maximum depending upon what sized ducting we use. This typical small shop dust collector blower only generates 4” to 6” of pressure when working. With the added overhead of our filter and minimum ducting, that pressure is only ample to move about 800 CFM when hooked up with a short piece of 6” flex hose. That pressure will only pull about 550 CFM when connected with 5” flex hose and only about 450 CFM when hooked up with 4” flex hose.” – Bill Pentz

And the following under duct resistance:

“Ducting resistance is known as static pressure. Even a short run of duct that is too small for a blower will cut the airflow down to the highest speed that pipe can sustain. The impact on most hobbyist blowers is terrible. A 3/4 HP blower with a maximum airflow of about 600 CFM will rarely provide more than about 300 CFM real air flow when connected to a 4” pipe. On that same 4” ducting a 1 HP unit that gives 650 CFM maximum rarely will maintain 350 CFM. A 1.5 HP rated at 1100 CFM barely gives 450 CFM. And a 2 HP capable of 1200 CFM is lucky to provide 500 CFM. Bumping up to 5” pipe adds about 100 CFM to each of these configurations. Bumping up to 6” pipe causes problems for the under 1.5 HP units because the air speed (FPM) can fall too far and make dust block the pipes, but with this bigger pipe, the bigger units end up going to 800 and 900 CFM. As a result, you need to use at least 5” duct for any hobbyist blower rated up to 1100 CFM and 6” duct for blowers rated 1100 CFM to 1800 CFM. ” – Bill Pentz

After reading the above and also reading other’s views on this topic you can understand why I noted the title as Dust Collection Overload.

Beyond numbers and calculations, is their anyone using a 1 1/2 HP DC with a permanent ductwork? If so, what are your runs in length and size? How many turns?

My day job is as an IT Professional, my hobby, at least one of them, is woodworking. I went to an engineering college in which 4 years of Calculus, Statics & Strength of Materials and Fluid Dynamics were all required courses, even for Electronics and Computer Science, two of my three majors, and both courses were very hard courses, but that was pretty long ago now. Fluid dynamics is the study of liquid and gases in motion.

I do not sell tools or machines with the exception of my tools I replace. That link on the web page is for three things, a edge sander I used three times and got tired of it taking up space, an air compressor that I replaced because it was too noisy in my shop, and a T-Fence that I replaced with a Biesemeyer. I do not sell Oneida, but I am in the process of upgrading my Oneida cyclone and will be selling my current one.

I had a Delta 1-1/2 HP 1200 CFM DC permanently plumbed with 4” PVC, exactly what you asked. It did not do well. If you took notice, it is listed under Former Tools on my web site, exactly for that reason, that’s why I sold it. It had an 18’ run that picked up the planer, chop saw, & RAS. The RAS was the farthest in that run at 10’, the pipe ran farther for future expansion which never developed. It had a second 16’ run that picked up the Unisaw. router, & 8” jointer. Both runs met at the DC. There were 2 90’s that brought the run up then over for the planer, chop saw, & RAS, and the second run went down and 90’d along the floor and went pretty much straight then for the Unisaw. router. & 8” jointer. It didn’t cut it. There was always sawdust in the bottom of the Unisaw cabinet even though it is sloped to the output port. And sawdust usually accumulated in the pipes. That 1200 CFM DC did not cut it.

Those CFM ratings on all the DC’s are exaggerated to say the least. It might get that at 0” static pressure, but 0” static pressure can only be attained by not connecting anything to it. Not very useful. The manufacturers test their DC’s in the way that gives them the best numbers. Somebody did a review that showed a graph of the manufacturers ratings right next to a graph that showed the same DC’s all tested in the same controlled, accepted way. Not a single one’s test results matched the manufacturers claimed performance, all were worse. I’m going to see if I can find that again. And on the flip side, when they stated it has 11” of static pressure that’s at 0 CFM, again not very useful. And it’s not linear a transform, that’s why it’s called a curve and testing in a controlled, accepted method, is the best way to determine that curve.

You’re second quoted paragraph of Bill Pentz pretty much says the same thing that I’ve been saying. That Oneida document that I referenced has a section on why if 4” is good and 5” is better, and then why 6” is NOT even better. 8iowa said it too. It’s not guess work, it’s engineering to make a system perform. Bill Pentz is dead on in saying that a 1200 CFM DC might only pull 500 CFM. I’ve never seen one pull what the manufacturer claimed.

Steel City said 6” will work. Did they ask you how many elbows are in the run, how long the run is? The take off for the machine, wye or what ever, counts too. And that last foot or two (or more) of flexible hose counts too and flexible hose is really bad. None of mine on stationary machines are longer then 6”. If they didn’t ask you these questions there’s no way they can say 6” duct is going to work. Do you know how many elbows there will be? Do you have a sketch or a drawing of your runs with elbows and exact measurements? I’m not nitpicking but if you don’t things have a way of changing, growing, etc. when you actually do the installation.

I am very meticulous and thorough in anything I do, be it work, be it hobby, because I don’t like doing things twice. I did not do that with the 1-1/2HP DC and the 4” pipe, I was naive and I landed up doing it over. Mostly because I believed that it was a 1200 CFM DC, the manufacturer wouldn’t lie, right? And I thought that this wasn’t rocket science. Well I was wrong and paid the price and should have paid more attention to fluid dynamics. But, before I did it a second time I bought books, I researched, I read everything I could, reminded me of fluid dynamics (doh), I contacted experts, I then understood from an engineering standpoint what it took, and I won’t have to do it a third time.

So you have the 6” duct. You can’t return it? What if everyone here is right and you find out later? You either live with it or you replace it and eat the cost of that 6” duct.

You asked for advice but you don’t seem to be really listening. Call Oneida, tell them you’re going to use 6” duct on a Steel City 1-1/2HP DC, see what they say, they’ll probably try and sell you a cyclone, but I’d be willing to bet they’d recommend not using 6” duct. Maybe they will sell you one if this doesn’t pan out. They’re experts in the field and have a number of patents, dust collection is all they do, not, oh by the way, we sell dust collectors too. They have years of expertise, not yesterday I designed a table saw, today I’m working on a dust collector. You have to realize once the product hits the market a machine company isn’t going to keep an expert around if they don’t need their services designing something, assuming they had an expert to start with.

Remember. you asked.

-- -Curt, Milwaukee, WI

I’m going to review Bill Pentz’s site, those two paragraphs seem to be out of context and I want to see them in context.

-- -Curt, Milwaukee, WI

Just to make sure that the explosion capabilities are pretty much nil, read about Explosion and PVC tests done by MIT, which by the way, is not hearsay.

http://www.sacramentoareawoodworkers.com/Articles/DustCollectionandPVCPipeDangersDebunked.pdf

The metal duct (hvac) that I have is not smooth sided ( has ridges for strength), so I do not know where they got their’s from. Mine has not collapsed.

PVC will cause static shock, but not explosions when used with DC with less than 3 hp motors. The bigger problem with dust collectors is picking up a loose screw, or piece of metal, which can cause a spark while going through the impeller and start a fire in your dust bin, which is why dust bins should be made of metal and not of cardboard like the ones that Oneida sells.

Oh by the way the NFPA 664 code states, as I quote you BlankMan, “Use of non- conductive material shall not be permitted” so is cardboard conductive ? Lol.

Those NFPA codes are for businesses, not home use, and yes I checked with my insurance company to see if I was still covered if I used PVC and my agent (State Farm) said I was.

-- -JimmyC...Clayton,NC- "Just smile and wave boys, smile and wave"

I guess this is the way I see it, nobody knows what size the intake is on the dc, if it’s a 5” or 6 ”, or they aren’t telling, I wouldn’t go bigger than it is. I think the main should be exactly that, and branched off to 4” at the main to the machine, like a tree, and it should be kept at a minimum legnth. The next issue is that your system was designed as a portable system and the intake is low to the ground, cyclones are permanent and more suited for cieling mounted ducting systems, their intakes are close to the cieling. My suggestion if your dead set on useing the dc you ordered would be to disassemble the blower assmbly from the mobile base and mount it up on the wall, close to the cieling. It would be less ducting and less elbows.

JimmyC, that’s a good point, I had to laugh too when I read what you wrote, a cardboard barrel… Never gave that any thought before…

BTW Did your insurance agent give you that in writing…. Not that he’d ever deny having had said that….

Yeah I’ve seen articles/reports that PVC is bad, PVC is ok, just like eggs are bad for you eggs are good for you, all depends on the week and the phase of the moon. I don’t know who’s really right, but I have felt static electricity build up on plastic pipe when air is moving through it so I’ll error on the side of caution and not use it.

-- -Curt, Milwaukee, WI

Ok, after further review, I’m starting to understand wherein the confusion lies. And in doing so I’m remembering this stuff from when I did my installation the second time with the cyclone some 10 or more years ago.

People are using different numbers for velocity needed to keep the material entrained in the stream. Bill uses 3000 FPM for horizontal runs, 3700 FPM for vertical runs, and a design target of 4000 FPM. Wood magazine used 700 CFM for 6” duct which works out to be 3565 FPM. Using Bill’s 3000 FPM for horizontal duct it works out that 589 CFM is the magic number. Using Bill’s 3700 for vertical duct that number is 726 CFM. 8iowa suggested 3500 FPM. Which one is right? Closer? Best? Don’t know.

But depending what number you use you can come up with all kinds of results. Yes it will work. No it won’t work. I see the confusion and the overload.

If you have vertical duct and the airflow direction is up and you use Bill’s 3700 FPM value, that says you need 726 CFM. According the Static Pressure vs CFM graph for 6” duct in the Wood magazine article that Steel City DC can only do that at 2” of static pressure (resistance to air flow caused by the duct). That then says you’re limited to 44’ of duct. That’s 2 90’s and 15’ of straight, or 3 90’s and 15’ of straight, depending on who’s numbers for the elbows you use. Add in the 45 degree branch to the machine and any additional duct and/or any flexible hose you’ll probably exceed that.

If you don’t have any vertical sections pulling up and you use Bill’s 3000 FPM value (which I personally think is low) that says you need 589 CFM which puts you around 4.5” static pressure (a bit hard to tell on the graph) that would indicate it can support 100’ for 6” duct. I personally would not gamble on this because the result is dust accumulating in the ducts.

If you use 3500 FPM, which a lot of people seem to use, that says you need 687 CFM getting you back to the 2.5” static pressure and 55’ of duct and pretty much corroborates Wood magazines 700 CFM value.

If you use the design target that Bill mentioned, 4000 FPM, that requires 785 CFM and which exceeds the maximum performance of that Steel City DC by ~40 CFM according to the Wood magazine testing. That’s why I think by using 6” duct you’re putting yourself way too close to the upper limit of performance that that DC is capable of, and IMO there’s no reason to do that, there’s not that much to gain but quite a bit to lose by doing that.

After giving this a lot of thought, here’s what I came up with

If you use 4” duct you’ll have good air velocity (FPM) but not great volume (CFM), possibly not enough volume to pull all of the dust from the machine but it probably won’t accumulate in the ducts. (Although based on personal experience using a DC pretty close to this one, dust did accumulate in the pipes.)

If you use 6” duct you’ll have good volume (CFM) but low air velocity (FPM) which may lead to sawdust accumulating in the ducts.

If you use 5” duct you’ll be at some point in between those two with enough volume (CFM) to remove the dust from the machines and enough air velocity (FPM) to keep the dust entrained in the air stream thus not accumulating in the ducts. Now I remember why Oneida recommended 5” after running the numbers and refers to it as the sweet spot.

Using 6” will put you at the upper limit of what it can do, using 4” would restrict what it could do, 5” is that happy medium.

-- -Curt, Milwaukee, WI

I think this thread is overloaded.

BlankMan, I didn’t need my agents approval in writing because I am now using metal ducting. But as far as completely trusting an insurance agent…... I don’t think so. I worked for insurance companies years ago and compare insurance to legalized gambling, first the odds are set on whether you are going to have a tragedy or not, then year after year you put down a fresh bet on it HAPPENING while they are betting that it won’t, only they always seem to skew the odds in their favor. Lol.

BTW, I do agree with what you say on the whole, but it’s better for health to do what you can afford at the moment, then upgrade when you can.

-- -JimmyC...Clayton,NC- "Just smile and wave boys, smile and wave"

JimmyC, and I do agree with you that doing what you can afford now is a good way to go. It’s just the calculations indicate that using 5” duct would allow it to perform better then 6” duct and I would think that would as you say provide for a better health benefit. And I would think save some money in the process too on the duct.

I wonder what he paid for that Steel City DC, I see Woodcraft and others are selling it for $299. In looking at the Wood magazine review it looks like the Grizzly 2HP is a significantly better performer and only $44 more (with shipping) then what WC sells the SC for. The testing indicates the Grizzly could do near twice as much as the Steel City.

-- -Curt, Milwaukee, WI

Woodchuck, really? Or are you joking? I see no wink indicating such. I’m spending the time and looking up the information that pertains and doing the calculations and that’s not appreciated?

You think the main should be 6” and the branches should be 4”. Is that based on engineering calculations or gut feel?

-- -Curt, Milwaukee, WI

I don’t remember saying that the main should be 6”, no one knows what fits the blower, 5” or 6”. Aparently you missed my next to last reply, or you ignored it, like what I’m going to do with your last sentence. Goodluck.

Yeah I stand corrected, I misinterpreted that.

I’ve been doing more digging, pulled out my Woodshop Dust Control by Sandor Nagyszalanczy and my Design of Industrial Ventilation Systems Fifth Edition by Alden/Kane books, everything is now as clear as mud. No wonder I forgot all this stuff, it’s so convoluted my subconscious felt the need to purge it from my brain.

Surprisingly though, I found my ductwork sketch with elbows and dimensions and air velocity and velocity pressure and static pressure calculations. I think this one was for my first system though.

I’ve seen recommendations that the main should be at 3500 FPM and then the branches at 4000 FPM, and then the main should be at 4000 FPM and the branches at 4500 FPM in various articles. And these books are the same way, they’re close but they don’t match exactly for the same thing.

But it did jog my memory on another thing, that the equivalent length of straight duct for an elbow is based on the radius of the elbow to the diameter of the duct ratio. So that explains why some say 12’ and some say 8’, they should qualify that with the R/D ratio though so it be clear. I think all the elbows I used were 1.5’s.

It’d be nice to have s set number. Is it 3500 for the main? Is it 4000 for the main? All depends who you talk to. I was hoping I could find some study by a University, OSHA, the EPA, the Foresty Department, etc., but nada.

I guess all the experts have agreed to disagree. Makes it tough to know the right way.

-- -Curt, Milwaukee, WI

Blankman, I think you are starting to see my comment on “Overload” all the reaserch I have found is contradictory to some degree. Yes you are right I asked the question and in the replies there are still differences in views.

Woodchuck, the reason I was going with six inch was the fact that when the wye is removed it leaves a 6” port.

I have also been concerned with the 90 degree sharp turn and know about the issues it can cause in the flow of materials. My job is the construction of water treatment facilities (150 million dollar facilities producing 20 – 30 million gallons per day)and am heaviliy involved in the piping of these facilities. I have cadded up the piping of the system and have minimized all changes in direction as this increades the total dynamic head the machine is required to pull, simular situation to the piping I have done professionally. I have also not purchase any 90 degree fittings and have either purchased wyes or put two 45 degree fitting to mimic a long radius bend. One of the main trunks will handle the smaller machines (router, band saw and drill press). The other branch handles the larger machines ( planer, jointer table saw). This routing where I would have most of my concern has a double 45 fitting to go vertical, 5’ of pipe, then a double 45 fitting to go into the header, the 8 feet straight run to the 6’ drop of for the table saw which will include another two double 45 fittings. I have the ability to put a 6” x 4” reducer in the run to the dust collector if it increases performance. This is my longest run out of the whole system it makes about 19 feet of run with 4 double 45 fittings. I did discuss the setup with steel city and they noted that I would receive better performance with the 6” piping, will this end up true, that can only be seen, as real life application is the true test. As I have experienced in my field, their is a point to be made of the saying “Well, it looked good on paper”. Unfortunately I have never been able to get an engineer to agree to this statement, maybe someday.

Woodchuck, thanks for the idea on mounting the intake higher, I’ll definately look into that. Steel angle and blots are cheap for a increase in performance.