conflicting DC information

[Tom Jones III]

I have become a believer in the utility of a good DC system. I am still deciding about the importance of sub 2 micron filtering. Here is the conflicting information I am receiving.

Bill Pentz's site, which I hold in high regard, indicates that 4" pipe is never going to generate enough suction to keep a planer clean under reasonable power.

The local woodworking shop has the 1200 cfm Jet canister DC. They are doing everything wrong. They have a really short run coming out of the DC, then a 90* up to the ceiling then another 90*. There is some flex hose to get to the ceiling. After the ceiling runs, there are more 90*'s and lots of flex hose. Every piece of pipe and flex hose is 4". They have a PowerMatic planer, it looks to be in the 15" or 16" range. I asked several very direct questions about their setup, and they say that when running the planer it is absolutely clean, every piece of dust gets sucked up.

So what is going on? I'm sure Bill wouldn't make his claims without reason. I am also confident in the local shop, they are very reliable.

The reason for this post, I'm trying to decide between a 1200 cfm delta bag DC, the Jet 1200 cfm canister and the Oneida Dust Gorilla. Will there be any functional difference between these three other than filtering capabilities?

[Keith Outten]

There are always exceptions, even to a good rule of thumb...I use all 4" PVC and my 15" planer is always clean. My DC is a Grizzly one horse unit which isn't anything special. The only thing unique about my setup is that I exhaust directly outside into a box so there is no filter, bags or other line restrictions.

[Donnie Raines]

I have always used 4inch PVC with some flex pipe at the unit. Never had any real issues doing it this way either.

[Jeff Sudmeier]

I only have a 12 inch planer, with a blower, but I hook up to mine using a 4 inch to 2 1/2 reducer. I have never had a problem with chips collecting.

It is all about how far you want to go. Bill's site is probably correct in saying that you are not going to get the super fine dust (the most harmful) with the 4 inch pipe. That said, you aren't going to see much dust collecting around the planer that is that size. It produces mainly bigger chips.

There are many ways to skin the cat and many varying degrees of safety. With my set up, am I protecting myself from all of the dust I could? No. Is my shop a lot cleaner? Yeppers!

[Andy London]

I can't really comment on their setup but can offer a few words based on my own setup...which is my 4th go around.

I started with a shop vac, upgraded to a 1 h.p. bag unit and moved tool to tool, then ran 4" to the tools...didn't work well, bought a 2 h.p. Delta better but not great, changed the pipe to 6" worked great but only for a short time, Bought a second 2 h.p., used one for fine dust, one for larger dust....worked good...just fustrating and time consuming now have the Gorilla and am very pleased.

At the time I had the first 2 h.p. Delta, I also had a 20" General planer, with 4" from the DC I probably picked up 60% of the chips, with 6" I picked up over 95%. This is planing 2 to 8 wide boards, taking no more than 1/8th per pass.

The issue all along was maintaining the performance (CFM) at the hood. In short, due to some of the work/tools we do in the shop that creates fine dust, the filters load, CFM goes down the drain and I am stuck with a large amount of dust in the air again.

Cleaning the bags, sometimes every day became to fustrating for me and made a mess outside the shop, sometimes even covering me should the wind change direction.

Based on my experience Cyclones put a tiny fraction of the total dust into the filter which is why they make so much sense for woodworking operations and why their performance remains so linear as compared to a single stage unit.

I guess it boils down to how much dust you create and whether or not you mind keeping your filters clean.

As for the different sized pipes, in my own experience, everytime I have put bigger pipe on, the performance has been a "Wow", even if I did not change the hood, running a larger pipe as close to the tool in question, then reducing to say 4" has shown a big difference in my shop.

Andy

[Tim Morton]

There are folks who say you can't enjoy music or dvd's on less than a $20k system too.

[David Fried]

There are folks who say you can't enjoy music or dvd's on less than a $20k system too.

That's just so you can hear it with the DC running!

My cyclone is temporarily mounted so I hook it up to my 15" Grizzly planer using a 5" to 4" reducer at the DC and run 15 feet of 4" flex hose. It seems to get everything! I was surprised at what was in the garbage can. Like Jeff said, it's not sawdust but rather shavings appropriate for a hamster cage!

[martyphee]

A planer generally creates big chips. In order to suck those up you really don't need a ton of CFM, but to get the small stuff like from a sander you need it. Checkout Bill's site again. He does mention something to this effect.

[Allan Johanson]

Lots of great info in this thread.

Here are some more bits:

- The Jet DC1200 is a fantastic 2HP machine. It will outperform pretty much any other 2HP single-stage machine out there.

- As I said in a different thread, I think some folks worry too much about 90* bends. Some machines can handle them fairly well and in this case, the Jet seems strong enough to handle that particular duct run.

- Some folks have said over and over again that 4" hose can't flow any more than 350cfm. Well, I've tested my cyclone flowing 750cfm in 4" hose. That Jet DC on a shorter run can easily exceed 500cfm through 4" hose. With a good hood, that's great for any hobbyist power tool with the potential exception of 2 hoods on a TS and 2 hoods on a BS (the SCMS is tough for any DC). But you can easily design around that to still have great collection at those machines with this 2HP DC.

- Each person is different and will react differently to dust in the air. My wife has asthma and dust really bugs her. For someone else they might not notice it as much and to them the air might be "clean" (while my wife is laying on the floor, unable to breathe).

- For those three machines you are considering, I'd go for the cyclone for Andy's reasons. I'm not a fan of a cannister on a single-stage DC because I think it might clog too often. I had an annoying enough time with the two bag DCs I owned prior to the cyclone.

Cheers,

Allan

[JayStPeter]

Lots of great info in this thread.

Here are some more bits:

- The Jet DC1200 is a fantastic 2HP machine. It will outperform pretty much any other 2HP single-stage machine out there.

- As I said in a different thread, I think some folks worry too much about 90* bends. Some machines can handle them fairly well and in this case, the Jet seems strong enough to handle that particular duct run.

- Some folks have said over and over again that 4" hose can't flow any more than 350cfm. Well, I've tested my cyclone flowing 750cfm in 4" hose. That Jet DC on a shorter run can easily exceed 500cfm through 4" hose. With a good hood, that's great for any hobbyist power tool with the potential exception of 2 hoods on a TS and 2 hoods on a BS (the SCMS is tough for any DC). But you can easily design around that to still have great collection at those machines with this 2HP DC.

- Each person is different and will react differently to dust in the air. My wife has asthma and dust really bugs her. For someone else they might not notice it as much and to them the air might be "clean" (while my wife is laying on the floor, unable to breathe).

- For those three machines you are considering, I'd go for the cyclone for Andy's reasons. I'm not a fan of a cannister on a single-stage DC because I think it might clog too often. I had an annoying enough time with the two bag DCs I owned prior to the cyclone.

Cheers,

Allan

- I agree that the Jet is a nice machine. But, I've never used any others so don't know how they compare.

- 90* bends aren't bad things, just make them large radius. As I said in same thread, it's cheap in terms of time and money to do large radius so why not. There's plenty of other places to compromise that will save real money or time.

- Generally accepted number is 400 CFM to collect chips. Bill Penz says 800 is necessary to capture small particles. I believe the argument is that 4" is difficult to hit the magic 800 number. 400 is easy and will keep a planer clean. It depends if you want a chip collector or dust collector.

- True, each person reacts differently. But, I think that can change if you spend too much time sucking small particles. For a hobbiest such as myself who averages less than 10 hrs. in the shop per week, my system is probably overkill. I'm just not a fan of dust boogers.

- I too like the cyclone for ease of use. I wouldn't go back to a 2-bag system. The cartridge systems would be my second choice, modified with a bin instead of lower bag. I think it would be much easier to use even though you have to knock the dust out of the filter occasionally.


Jay

[Dan Forman]

One of the main points that I got out of the Bill Pentz page, was that with a machine like the Jet, without a cyclone separator, the filter will ulitmately suffer damage from chips being sucked up into it, puncturing it, and letting dust through. You would need to construct some sort of proctective device out of windowscreen or something similar to keep chips from getting embedded into the filter medium. Keep in mind that the cleaning mechanism, that rotating beater bar thingy, would only worsen any damage caused by an embedded chip. The other thing to remember, as that the most damaging dust is so small as to be invisible, so you wouldn't see it.

In my dealings with Oneida, they said that 5 inch drops should be sufficient for a home shop. That is at odds with the Pentz site, but then they have been at this a while too. Sometimes it's hard to sort out what is adequate and what is overzealous. Wish I had the answer!

Dan

[Dev Emch]

Tom...
Not to worry. Here are some facts to help you out.

First of all, there are two places I can think of where you do not want 90 degree bends. Dust collection runs and the pipe leading from the house into the septic tanks!

First the technical stuff. When liquid like air enters a 90 degree elbow, it experiences a radical and abrupt change of direction. This creates vortex flow and turbulence. It takes 3 pipe diameters downstream of the elbow to correct this and to reestablish laminar flow. Kinetic energy is what keeps chips and dust in suspension during the flow to the DC. Some of this is lost during this change. You also experience pressure drops in the regions affected. To high a pressure drop and you loose suspended dust particles. As long as you allow the flow to reestablish laminar flow and to reenergize any particles that have droped out, you will be O.K. But, these elbows can clog at a moments notice and very fast. For me this is the bigger issue. If you put two 90 degree elbows very close to each other such that the flow cannot recover in time for the next elbow, you will have issues.

I think if you have smaller machines and short runs, the scheme you eluded to will work for the most part. A 15 inch jet planer is a small machine. This system would be hopelessly lost when a 30 inch newman is taking a 3/8 inch cut. So it is a matter of perspective. At any rate, it does not take much more effort to use inline angle connections.

Now, how large a tube do I need? Good question. First you have to look at the run your making *AND* the CFM of your DC. Increase the tube size too much and your velocity will drop off badly. NOT GOOD. Yes, your looking at CFM but if I run X CFM through two different tubes, one will have a higher velocity to compensate for the reduction in cross sectional area.

Also, you may need to increase your tube size if your run is a bit long. This is to reduce the pressure drop from ramming to much flow through to narrow a passage over too long a distance. But this increase will not be much and in most cases, proves secondary.

Next question. How many machines do you plan to hook up to your DC? For most of you guys, you will be running one machine at a time. So any machines attached to your DC tube network should have blast gates on them. Home made blast gates will do just fine. Now if you will never run more than one machine and you got a good deal on one type of pipe, you can do the whole run sequence in one diameter. But this is not normally how its done.

Often you will find a single main plenum of 6 inch or 8 inch tube. This is the backbone of your system and connects into the DC vortex intake in as straight a run as possible. Avoid 90 degree turns. This plenum will run about 1/2 to 2/3 the length of your shop: NO MORE! Along the plenum will be 22.5 or 45 degree straight run elbows with one shunt being a smaller diameter. So for example, if my main plenum is 6 inches, the shunt diameter may be say 4 inches. These form the branches. Also note that as each elbow dumps its load into the plenum, the direction of flow is always toward the DC. NEVER ORIENTATE these elbows opposite the flow or you may get clogging of unused shunts.

The last branch will consist of a reducer on the main plenum and the main now drops to 4 inches as well. Afterall, this is the last branch even though its also the tip of the main plenum.

By doing this, I get an increase in my velocity within the branch lines. I also avoid any opportunities for the flow to drop unwanted material within the plenum stucture.

Each machine is unique in how much of a dust collection tube it needs in terms of diameter. The dust collector on my tenoner is, as I recall, 8 inches in diameter. That is because you have 5 cutter heads working in open space and you will experience a huge loss of efficiency here. Planers are more effiecient because they have a tight and effective hood over the high energy chip exit region of the cutter. Many older large table saws have 6 inch collectors because they too leak like heck. The more leakage, the more CFM you need and the larger diameter tube you will need.

The mainstay of all DC systems is its vortex separator. By deliberate intent, this thing creates a huge vortex flow which takes kinetic energy out of the suspension and drops the heavier particles out. Its an air brake for your air flow squeezed into a small package.

But not all of the particles are large enough to drop out nor does the vortex separator brake the air flow to zero. The smaller the particle, the less kinetic energy is needed to keep it suspended. So all the tiny stuff remains and passes into the DC's blower blades. These are often plastic or aluminium because a steel blade can create a spark and this does not sit well with fine wood dust in an oxygen rich environment!

This flow then exits the DC blower stage and enters the bag house. The bag house is the last opportunity you have to catch everything you wish to catch before its released again into the environment. Often you may see two or three stages of filters in the really fine extraction units. Its pointless to use a 2 micron filter to try to clean up a flow in which your average particle size is 20 microns. The bigger the particle size the cheaper the filter. So you may have a 20 micron filter feeding a 10 micron filter fedding a 2 micron filter. At the end, particles of 2 microns and smaller are all that is being released.

In some cases, its just easier to just exhust your DC blower stage to the outside. There are two disadvantages here. First, in environments where you have to heat or cool the shop, your going to loose a huge amount of heating and cooling dollars to the wasted energy being exhusted. Second if your shop has a wood stove, then the DC may have a huge negative affect on your stove's draft. It will suck smoke into the shop and in no time, your shop looks like the inside of a texas roadside bar-b-que emporium.

The new health studies being released are ironic. Its not the dust you can see that is hurting you. Even sander dust that you can hold in your hand is not that bad. Breath it in and the tiny little hairs inside your nose and throat go to work moving this stuff out. A couple of hours later you are hacking up sawdust luggies. Its the super fine particles that are an issue. Particles the size of those found in cigarette smoke. These are often so small you can barely see them and so small that the tiny guard hairs in your body cannot detect or move them out. They sail right by your defenses and lodge in the deepest regions of your lungs. The avoli sacks.

So, how small should you go on your filter system if you are not exhusting to the outside? Well, if it were up to me, I would enclose the bag house in a box structure with a glass panel front door. Put a rod in there that you can push to shake the bags every once in a while. A drawer at the bottom of this box collects the larger fine dust and you can empty this with ease. This box then exhusts to a finer filter. This would be your optional 2 or 1 micron filter. Be careful here to make sure this filter does not put to much back pressure on the whole system. You may need a few of these.

Of course this example is over kill for most folks. I would then turn to Onieda to see what innovations they have come up with. These final filters are called final filters or polishing filters and Onieda has released some nice innovative ideas in this area lately. For the size, performance and space needed, I have to say that I do like the Onieda solution.

[Ken Waag]

The reason for this post, I'm trying to decide between a 1200 cfm delta bag DC, the Jet 1200 cfm canister and the Oneida Dust Gorilla. Will there be any functional difference between these three other than filtering capabilities?

Tom,

I leave the duct sizing alone as I've read Pentzke's and Oneida's info, and I'm still confused. And it's not a perfect world when we have 4" ports on most of our machines.

But as to the options above, I'd have to throw in a strong recommendation for a cyclone one way or another. With the prices dropping, Grizzly, Oneida and others it hard to justify not having a cyclone system. I have the Delta 1200, built a cyclone, and put the Delta motor/fan housing on top. I exhaust thru high efficiency cartridge filters. If I were doing it today, I'd buy one of the 2 or 3 hp prebuilt units.

Pay attention to the filter ratings and get the best (higest rated) one you can. As dicussed elswhere on the forum, if you use a mediocre filter you can actually be filtering out the least hazardous stuff, and recycling the most hazardous dust back into your air.

And if you're using good filters, there is no sense throwing all the debris at them. Let the cyclone spin 98% of it into a cannister. That way your filters stay efficient for a long time. I think clean air is worth doing right. Look at it this way whatever your DC efforts don't filter, your lungs will.

Good luck,
Ken

[Jerry Olexa]

One man's meat is another man's poison. Take your pick and then you use your old gut instinct and go forward!!

[Jeff A. Smith]

I removed my bag completely on my 2-stage, and routed a piece of 6" pipe through the wall of my shop with a giant "dryer-like" flap over the exhaust port to keep out rain. The barrel still collects the big stuff, but the difference in suction is enormous (without that 2 micron bag slowing the airflow). Of course, I live in a rural area away from other houses... so the small amount of sawdust that gets blown out doesn't bother anyone as far as I can tell.


Jeff Smith
Athens, AL