Dust Collection. Single stage vs cyclone

[Bryan Solomon]

I am in the process of building a new shop. Proposed size to be 30' x 27' with a loft above that measures 10' x 25'. The internal ceiling height will be 15'. This will be close to triple the size of my previous shop, which I am very excited about. I need some help with a dust collector, being the one I have been using is extremely undersized (1 hp bag type woodtek I bought when I was 13 years old). I called Oneida a few weeks back and was told I needed a 5 HP cyclone, which is about $4,000 along with a ballpark of another $4,000 worth of duct work. If I were a betting man, I would say whoever I spoke with must work on commission.

I started looking into this more and quickly realized the difference in CFM ratings between and single stage and cyclone collector. A single stage collector has almost double the CFM rating for round about half the price of a cyclone of the same horsepower. I don't quite understand the advantage of spending the extra money for a cyclone if it moves less air? If it moves less CFM, does that also mean that is has less suction? I see grizzly sells a 3 hp single stage dust collector with 1 micron filters on top for about $800. And if I really needed the 5 hp, I could get two of these for still about half the cost of a 5 hp cyclone. And to keep the floor space clear, I could put both of the single stage collectors on platforms high up on the wall (ceiling height will be 15'). Am I thinking about this correctly???

Here is a list of the machinery I have that need dust collection:
Powermatic 66 5hp table saw
Powermatic 100 12" planer
Delta 28-206 14" bandsaw
Oliver 4240 10" jointer
Mitersaw station
Router table
Would like 2 floor sweeps

Advice on this is much appreciated.

[David Walser]

Bryan -- I believe all of us who've gone down this road before would say you want a cyclone. There are lots of woodworkers who started with a single stage dust collector, grew dissatisfied with the performance, and switched to a cyclone. In my case, I 'converted' my single stage collector into a cyclone. The only part left from the DC is the blower and the upgraded filter (my first attempt at getting the DC to work better.) I really wish I'd started with a cyclone.

Before I take a stab at telling you why you want a cyclone rather than a single stage dust collector, let me address your concerns about CFM. The CFM ratings of single stage dust collectors are significantly overstated. The CFMs are measured at the inlet without any dust bags or filters attached. So, yes, if the marketing department hasn't 'improved' the numbers by rounding up, the blower can move that much air. But, that's hardly a real world number. What's important is how much air can the unit move through your ducts WITH the filter installed. Cyclones are measured differently. The CFMs are measured at the inlet to the cyclone -- usually with the filters attached. (And, yes, a cyclone reduces air flow. It takes energy to spin the air in the cyclone. That energy consumption reduces the amount of energy that can be used to move air through the machine. There is no free lunch. So, a cyclone with the same blower as a singe stage DC will have a slightly lower CFM rating.) This isn't a real world number, either. Again, your ducts aren't attached to the inlet. Obviously, the maker doesn't know what everyone's ducts will look like, so they just measure at the inlet.

So, why a cyclone rather than a single stage unit given that even a well-designed cyclone will reduce air flow? The issue isn't which unit will move the most air when the filters are clean. The issue is which one will move the most air after 15 minutes of use. With a DC, all the fine dust will be trapped by your filter. That very quickly reduces CFM! With a well designed cyclone, very little of the fine dust reaches the filter -- it's been removed by the cyclone. That means your cyclone will be working as well as it was right after the filters were cleaned after 15 minutes, 15 hours, or 15 days of use. And, when your cyclone is operating at 99% of its peak capacity, it will be moving a lot more air than your DC would be at 50% of peak capacity.

Obviously, the discussion above assumes the DC and cyclone have the same sized blower and motor. However, as you may have noticed, it's really hard to find a single stage dust collector with a 3hp (or larger) motor. Why is that? It's because large commercial shops and industrial plants don't use single stage dust collectors. Obviously, they could make really large single stage dust collectors. And, if the single stage design had material advantages over cyclones, they would be making them and that's what commercial shops and industry would be using. They're not making large DCs and industry isn't using them because the the filters would need to be cleaned constantly. When I worked at a furniture mill while I was going to college, the mill had two giant -- three story tall -- cyclones that served the entire mill. There was a railroad car parked underneath the cyclones to catch the shavings. We filled it up once a week. Two or three times each year, when we were milling wet wood, the chips and dust would cake the inside of the cyclones and they would quit working. One of us would need to climb inside the cyclone to knock the chips and dust off the walls of the cyclone. (Dangling from a rope inside a cyclone can be fun! Just don't let anyone turn the cyclones back on while you're in there...) The process of unclogging the cyclones took no more than 15 minutes. That was the only attention they required. How often would we have needed to clean the filters of a single stage DC of a similar capacity?

As for whether or not Oneida is giving you good advice, I suggest you compare their answer to what you hear from ClearVue. A lot of this will depend on the layout of your shop and your ductwork layout. The more branches and drops you have, the more capacity the cyclone will need. For that reason, I suggest you don't use floor sweeps. I get the attraction. I loved the floor sweeps we had at the mill. However, the two sweeps are two additional sources of leaks and add to the overall length of the ducts in your system. Instead, I suggest you use flex hose quick connects at a couple of your machine drops. You can then use a length of flex hose and a 4' length of 4" PVC to act like a vacuum hose to clean up your shop. I uses something similar to this from Rockler (my version is no longer made): https://www.rockler.com/rockler-dust...ge-floor-sweep. With Rockler's 21' collapsable 4" flex hose, I can clean my entire shop. I use it to vacuum off my workbenches and to sweep the floor. It works great and I find it more convenient than the floor sweeps we had in the furniture mill.

[james manutes]

Great response David ! Very few guys remain w/ single stage collectors . Keeping the filter clean is the key . Bill Pentz suggests 800 CFM to capture all the finest , smallest dust , and that is not cheap to achieve . I'd say the first step is to try to settle on the basic duct layout , w/ the focus on it being leak free . Leaks will set you back , so do what you can to eliminate them . Cluster tools if possible , keeping the system smaller . I think in a shop less than 900 sq. ft. , a 3HP Clear Vue or Onieda system will be enough . You are probably at the limit of a shop built cyclone , but a well thought out one could get you close . Some tools will benefit from changing the ports on them . Four inch ports will choke the system , try to avoid that . I also like the Rockler expandable hose , no longer use a floor sweep . Bottom line , I don't think you need a 5 HP system .

[james manutes]

My mistake , the CV 1800 is a 5 HP motor . It is priced like a 3 HP Onieda , but I thought it was 3 HP .

[Jim Becker]

Bryan...CFM ratings. Not something to rely upon on mass market machines and their advertising. They will never come even close to that level of performance in the real world. They are generally bogus and those "big" numbers can only happen if the unit is running unrestricted by ductwork right to the point of motor failure. If you cannot get a fan curve for the unit you are considering, then you will not know what the capability of the collector will be when hooked up to a ductwork network. The specialty dust collector companies generally provide fan curves which clearly indicate what the expected CFM will be over the possible conditions it will be employed.

The advantage to a cyclone is the pre-separation which allows for easier handling of collected debris and helps to improve filtration.

I'm a very happy Oneida customer. They know what they are talking about. (there are more economical sources for the duct work, however) I feel the same about Clearview. Grizzly's long cone cyclones also seem to be good products...you may or may not be able to get fan curves from them...I don't know.

[John K Jordan]

Brian,

It's been a while since I researched this for my new shop (2012 or '13), but at the time I decided on the 5hp ClearVue cyclone for some of the reasons David W mentioned in his excellent post. I've been quite happy with the performance. I see the cost now is under $1800. You do have to assemble it but that was trivial - much easier than installing all the duct work!
I used 6" PVC pipe for the main ducts and drops. I put my main ducts above the ceiling in the trusses.

One thing about a cyclone - the longer the cone the better the separation. The cone on the ClearVue is fairly long. Mine passes almost nothing to the filters - even powder-fine dust is dropped into the can.

My ceilings are 9' and the cyclone barely fit with a 30gal metal trash can as a bin. When sizing a bin, consider the weight of a bin full of fine sawdust and the path from the cyclone to the outside. I wouldn't want to handle a bin much heavier than the 30gal can, at least not by myself. I use a hand truck to move the bin outside where I lift it to the back of a truck to take it where I dump it in the woods. Most of the sawdust I collect is from the bandsaw, lathe, and sanders. Planer/jointer shavings will fill up the bin a lot quicker but with much less weight.

You DON'T want to overflow the bin under a cyclone - that can send sawdust to the filters and cause a mess to clean up. I haven't done this but I've read reports of others who have. One advantage to the ClearVue is you can see inside as it's operating and even see if the bin is full (but I occasionally pull off the lid to check if it's almost full).

A big cyclone can be deafeningly loud. I put mine plus a 5hp air compressor in a 4x8' sound insulated closet.

I have no experience with a conventional single-stage dust collector. Before I built this shop I used a big shop vac which didn't collect much.

JKJ

[Justin Rapp]

Bryan,

I just went through an upgrade to my DC system, going from a single stage 1hp bag unit that I rolled from machine to machine to a cyclone. So the above posts already provide the benefit of going to a cyclone, and now that I have a cyclone, having the benefit of 2 stage collection really helps keep the air flowing rather than deal with a clogged machine.

In your research you will find that the claim is the longer the cyclone the better the separation. This is well known and if you do ultimately go with a shorter there are some tricks to getting better separation. What I mean about a shorter cyclone, those are typically the models mounted on a base with wheels, such as Jet, Laguna, some of the Grizzly models, etc.

So, what determines your HP needs. Honestly, the primary reason is how many tools you will be running at the same time. If you are a 1 person shop and have blast gates at each tool, your going to focus the suction to the one tool in use. If you are going to be running 2 or 3 of those tools at the same time, than you will need to step up your hp.

The second need to step up to more HP is to the length of your duct runs. If you can put your DC in a location that would have the shortest duct runs to your machines, the less HP you will require. Duct planning is just as, if not more important than the actually dust collection machine.

So, to give you an idea, my shop is a little smaller than yours and I run:

10" contactor saw (blocked up to get as good of dust collection as I can)
13" planer
6" jointer
14" DC (with two dc ports)
router table
miter saw
drill press

I am using a 3hp Laguna and have been very satisfied with the DC I am getting from it. All of my ducting is 26G smoke (aka vent) pipe (some call it 26G hvac ducting but it's actually for the venting side not hvac air supply) and holds up well and cost me under $400 including tape, hangers, duct mastic etc. I would suspect it would hold up to a 5hp unit as long as you keep 1 blast gate open. I did do a collapse test and my dc didn't collapse my ductwork.

Also, why do you want 2 floor sweeps? Sweeping the floor causes fine dust to get airborne and with good dust collection your big chips should mostly get pulled into the cyclone. A much healthier option to get floor dust is to use a wet dry vac with a hepa filter in it to suck up and trap the sawdust that does make it to the ground.

So you do have options before dropping $8000+ on a unit and the ducting. Do your research and planning before dropping the $$$.

[glenn bradley]

A single stage collector has almost double the CFM rating for round about half the price of a cyclone of the same horsepower. I don't quite understand the advantage of spending the extra money for a cyclone if it moves less air?

I need to jot this down so I can just cut and paste this response ;-) Not that your thread is trivial, it is not. The question comes up a lot. A single stage will move more air due to the cyclone or other separator not being in the path. Separation takes effort. If you can vent all of your spoil outside a single stage is the way to go. If you have to return your air into your work area . . . the reasoning becomes clear.

- If you have to breathe your return air, you need really good filtration.
- A cyclone keeps your really good filter from clogging annoyingly often.

So there you go, easy-peasy. If your air comes back into your shop, you want a cyclone and very good filtering. If you can vent all your spoil, you want a single stage.

To the 5HP recommendation, yes a 5HP cyclone with the proper fan and filters will give you the performance you should have in a home shop in order to protect your health at our current state of technology. This is just science and math, not a philosophical discussion. As we move away from that model to what we can afford, fit or otherwise deal with we must augment our dust collection with personal protective gear to varying degrees. I am going to try to milk a few more years out of my 2HP cyclone by super-tuning my duct path in the new (not yet built) shop. I am going in knowing I may not succeed or that the required add-ons of mask, fans, ambient cleaners, whatever may be more than I want to deal with. The out-building for the DC will be physically and electrically adequate for a 5HP upgrade should it come to that.

This does not mean "5HP or else". That is the current healthy recommendation. How close you have to get to that model is up to you, what you do, how often you do it, if you have kids, if you're a Capricorn and who knows what else. My point is, you want the best dust collection you can afford but, I would cut back a bit rather than go without a jointer if you get my drift ;-)

[David Walser]

Glenn -- I agree with everything you said. I just want to caveat your conclusion that, "If you can vent all your spoil, you want a single stage." Few of us can vent all our spoil if that includes the chips and larger pieces of sawdust. Quickly, we'd have a large pile of chips on the outside of the shop. Single stage collectors generally have a type of separator that allows the chips and larger particles of dust to fall into the collector bag while the air flows out the filter (and the smaller particles are trapped by the filter). However, for these separators to work as designed, something needs to slow the air steam, allowing the larger particles to fall out of the air and into the bag. The filter performs part of this function. So, venting a single stage DC will, almost inevitably, result in a lot of chips and sawdust being dumped outside the shop. So, yes, you can do it. And if you can, it will work well. Just be prepared for a mess.

Another reason to go with a cyclone over a single stage machine is the cyclone separates out the larger items before they can hit the impeller. Impellers are pretty durable, so generally there is no harm done by allowing something large -- or metal -- to hit the fan. However, the large bang it makes can be startling! No damage may have been done the the machine, but you might need to change your pants...

[Bryan Solomon]

Wow! What a huge amount of advice in such a short period of time. Thanks so much.

Sounds like you guys have me sold on the cyclone. The clearvue seems to be the most power for the money. I will be calling them and asking the same questions that I asked Oneida a few weeks back. Now for the next question...putting the cyclone in a closet or a neighboring structure: I plan to have room to build another storage room connected to the garage on the back side of it (maybe 10' x 7'). It will have separate door to the outside and will be separated by the exterior wall of the garage. This will be room to store my yard tools, lawn mower, and potentially dust collector. My question is in regards to the suction from the dust collector. If the cyclone is located in this room, do I need to put a large transfer grille between the garage and this room? How much air needs to be available for the cyclone to run?

[Jim Becker]

My cyclone (and compressor) are in a sound abated closet and I wouldn't have it any other way. It makes a significant difference in overall sound level. And yes, you do need to return air back to the shop if you are not venting outside. But...it should not be a "grill". It needs to be an indirect path or you'll just be dumping the noise back into the shop. A baffled hard path like I use up between the joists or even some of the flexible HVAC duct that meanders a little (like John Jordan uses) will do the trick. And the overall area of the return to the shop needs to be equal to or preferably larger than the outlet from the cyclone to the filters.

[John K Jordan]

My cyclone (and compressor) are in a sound abated closet and I wouldn't have it any other way. It makes a significant difference in overall sound level. And yes, you do need to return air back to the shop if you are not venting outside. But...it should not be a "grill". It needs to be an indirect path or you'll just be dumping the noise back into the shop. A baffled hard path like I use up between the joists or even some of the flexible HVAC duct that meanders a little (like John Jordan uses) will do the trick. And the overall area of the return to the shop needs to be equal to or preferably larger than the outlet from the cyclone to the filters.

I've read reports from people who said they used the insulated flexible HVAC duct for exhaust but I've never tried it. The insulation is supposed to work like a muffler to reduce the noise.

I built a baffled return duct with the bulk up above the ceiling between two trusses from my closet. I did put a grill and HVAC filters on both ends of the duct but after maybe 6 years of use haven't seen any dust collected on those. This was my working design sketch of the duct, built from 1/2" plywood, sprayed with rubber inside, insulation stuffed around it in the ceiling:

Dust_collector_baffle_small.jpg

Putting it in an outside closet attached to the shop might be even quieter than mine, which is pretty quiet. I'd hang the cyclone on a non-shared wall to reduce direct sound transmission.

JKJ

[John C Bush]

Hi Bryan,
Congrats on the new shop. A cyclone in an attached structure is a great way to go. I have a 2ph Griz cyclone in an attached shed--vent outside with no return air-- and it has worked very well for me. Main 7" run is 30' with 6" branching to 4" drops. HVAC snaplock with brush-on duct sealer on pop-riveted joints and fittings. I had floor sweeps but never used them. I'll send you mine if you want to try them. The 2hp handles a 20" planer, 12" jointer, 25" drum sander, TS, BS, etc , just fine so not sure if 3hp is needed. Maybe with the HEPA filters 3hp would be better/needed. Noise level is fine for conversation and managing chip barrel from an outside door is easy as well. Good luck shopping.

[Tom Dixon]

Hi Bryan,

My shop is similar in size to yours. Mine is 24'x36' with 10' Ceilings. I ended up buying a Grizzly G0442 5 HP Cyclone Dust Collector and put in Spiral Pipe. I used an an 8" main and 6" branches which I reduced to 4" or 5" at the machine if necessary. I built a separate 5'x8' insulated exterior shed for the cyclone with filtered returns. Not including the shed I spent about 6K, 3K for the cyclone and 3K for the spiral pipe and fittings, with the majority of the piping cost being the number and types of fittings. The shed allowed me to raise up the cyclone so that the 8" pipe is about 2 " from the ceiling so it's out of the way. I am very pleased with the result. Regardless of what brand you choose, go with the cyclone and if you can put it in a closet or a shed it will definitely reduce your noise. A shed saves on internal floor space as well.

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[Jim Becker]

I've read reports from people who said they used the insulated flexible HVAC duct for exhaust but I've never tried it. The insulation is supposed to work like a muffler to reduce the noise.

Did I "mis-remember" what you were using? If so, my apologies. I thought you did the flexible stuff snaking around your rafters for your return...