Dust collection expert

[dwacker]

Do we have a dust collection expert? Ive got some questions about the main run, branches and drops. Its seems that most use the largest possible main run for example 8" then drop to 6" branches then 4" drops. Is there a reason to drop to 6" branches" Would it do any good to leave them at 8"?

Thanks

Don

[dcustoms]

Don,

What type of DC do you have? It is best to leave the pipe as large as possible, as long as possible. I kept all of mine 6" all the way to the machine and just put on new ports. Doing this allows for the greatest CFM at the tool it self. As far as the 8" main to 6" branches if your DC can support that large of a main thats great and then you can go to 6" branches and drops or just the drops it all depends on how your DC is designed. If you can tell me the Make and Model along with the manufacture specs (which are no where near real life performance) I can answer your question a little better.

[VitalBodies]

You have to factor in where you plan to put your blast gates also.

There is ideal and there is real world. Real world usually includes the costs (8" duct is expensive) and the convenience of using the system such as where the gates are located.

If you have long runs of 8" duct with 8" branches and no gates in the 8" branches (4" gates at the tools instead) all that 8" dead space effects the performance somewhat. An ideal system would have blast gates at the 8" branches so only the part of the system in use is open. Real world might find that having the gates up high, and over yonder inconvenient.

[dwacker]

Don,

What type of DC do you have? It is best to leave the pipe as large as possible, as long as possible. I kept all of mine 6" all the way to the machine and just put on new ports. Doing this allows for the greatest CFM at the tool it self. As far as the 8" main to 6" branches if your DC can support that large of a main thats great and then you can go to 6" branches and drops or just the drops it all depends on how your DC is designed. If you can tell me the Make and Model along with the manufacture specs (which are no where near real life performance) I can answer your question a little better.

http://www.grizzly.com/products/3-HP-Cyclone-Dust-Collector/G0441 This is dust collector I ordered. It will be outside attached to the back wall of my building with no micron filter attached. I have a buddy (hvac guy) that is going to duct it however I see fit. It can be all 8" or what ever is needed. If you think 8" blast gates at the branches are needed then so be it. He was thinking a 8" main run and 4 8" branches with manual blast gates at each branch. The blast gates can be in the attic. We have found some normally open spring loaded gates with a pull string to open.

Don

[VitalBodies]

I have that same DC. I really like it : )

I would try to make use of the muffler if you do not need to take the port/fitting off the back like I did.

If you can you might like a flat/smoot floor under the barrel to roll the barrel on rather than say, gravel.

If this is a custom duct then consider that if and when you branch to 6", then both branches would be 6 (8/6/6).

On the other hand if you go to a 6" and carry on with the 8" (8/6/8) further across the shop then you would (in an ideal system) have a gate at the 6" to maintain the integrity of the 8" duct.

Real world might want that gate as a 4" at the tool.

I set up my system in zones. I do not open one port to use a tool I open a zone. Very few tools can be dust free with one 4" port and I try to keep close to 8" of duct open in that zone which is four 4" ports. In a sense you are creating a bubble of vacuum in and around that machine.

My system is not ideal but makes use of many of the techniques. I had to balance with real world quite a bit. But have 8" of duct means I can over compensate using zones.

[dcustoms]

With the specs on your system you should/could run the entire thing in 6 inch. I goal is to get 1000CFM at the machine itself. The DC is not powerful enough to run more that one machine at a time ( and maintain the 1000CFM) so running all 6inch would give you the 1000cfm while minimizing the risk of the airflow dropping down to low in the larger main line. As a side note 26ga in the lightest HVAC pipe I would run on a 3hp cyclone. For more information about duct design you can go to Bill pentz's website. There are a lot of good diagrams about how to make the proper hookups to your tools. Also by putting your DC outside and not having filters on it you are creating the best environment for the performance of that DC. The cyclone will operate much more efficiently the way you are doing it. It also pushes all the finest dust out side and not back into your shop, while also not clogging filters. Going back to the DC piping I really think the 6inch for the entire thing will be your best bet. Just like any DC system try to minimize anything that creates friction loss ( incredibly long runs of pipe, tight elbows etc.) Hope this helps

[VitalBodies]

I am not a ducting expert but I spent quite a bit of time reading up on ducting and dust collectors. Personally I would go with 8" where you can since this DC was designed to be used with an 8" duct. Consider each tool carefully and what it takes to pull both the chips and fine gas like dust from the tool and from the over spray that many tools have. The over spray is why I went with zones (3-4 four inch ports per tool). The classic way to do dust collection is to use only one port per tool. But as woodworkers get smarter that will change. Even the new grizzly band saws have two 4" ports and a table saw needs an extra port for the dust guard - at least.

[dcustoms]

Here is a quote from Bill Pentz that I think will help with the main duct size conversation. "Always use the largest diameter duct that your blower can use with the least number of restrictions. If your ducting is too small, then it instead of your blower defines the CFM that your system can provide at your machines to pick up the dust. If your ducting is too large you might not maintain the airspeed needed to keep sawdust and chips from building up and blocking your ducting. You need about 3000 feet per minute (FPM) airspeed to keep light sawdust moving horizontally and about 3700 FPM to move it vertically. Air engineers target their designs to maintain about 4000 FPM to keep the dust entrained (moving). FPM is simply CFM divided by the area of the duct in square feet instead of inches (144/sq. in.). If you do the math for the 1000 CFM we need at our larger tools and the 4000 FPM airspeed we need to keep our vertical runs clear, most small shops should run at least 7” duct. This sized duct is rare and the more commonly available 8” duct is so large we end up with the airspeed falling so low our vertical runs plug. My personal solution has been to use 6” duct which will normally only carry about 790 CFM, and to get that to over 1000 CFM by using an oversized impeller of at least 15” diameter running at 3450 RPM. This makes for more noise but results in great fine dust collection. It also means my whole system of mains and down drops ends up using 6” duct."

[dwacker]

So basically 8" branches with drops to match the machine are as good as Im going to get unless I go out and buy the equipment to measure air flow. Sounds as if you have to use the fake it method unless you have the ability to test, since the manufacturers fudge on the numbers.

Don

[dcustoms]

IMO a 3hp motor with a 15.5inch impeller cannot support an 8 inch main line in real world application I think the min DC configuration for an 8 inch main line would be a cyclone with a 5hp motor and a 16 + inch impeller that's just my opinion. Also all you have to do is modify the machines to a larger port. For example a TS with an over arm blade guard with dust collection you would put a 5 inch port on the TS and 4 inch on the blade guard. A jointer or planer would get 6inch ports and so on.

[dwacker]

IMO a 3hp motor with a 15.5inch impeller cannot support an 8 inch main line in real world application I think the min DC configuration for an 8 inch main line would be a cyclone with a 5hp motor and a 16 + inch impeller that's just my opinion. Also all you have to do is modify the machines to a larger port. For example a TS with an over arm blade guard with dust collection you would put a 5 inch port on the TS and 4 inch on the blade guard. A jointer or planer would get 6inch ports and so on.

Are you saying I really should downsize the main line and branches to 6" and the make all the drops 6" if possible? Im pretty open to anything at this point as long as it works. Cant go 5hp already ran a 30a dedicated circuit.

Don

[dcustoms]

How big is your shop? How many tools and what type are they? I think your DC should work well without filters direct venting outside with all 6 inch lines. A 5hp cyclone only requires a 30a circuit, they pull anywhere between 18 to 24 amps depending on motor and configuration.

[dwacker]

How big is your shop? How many tools and what type are they? I think your DC should work well without filters direct venting outside with all 6 inch lines. A 5hp cyclone only requires a 30a circuit, they pull anywhere between 18 to 24 amps depending on motor and configuration.

PM2000 Table saw with 3.25hp router

PM 20" planer

PM 12 Jointer

PM 24" Bandsaw

PM 18" Drill press

PM 5hp Shaper

PM 25" Double Drum or PM 16/32 Open end wide belt

The main line will only need to run 20ft the branches will be about 15 max either direction off the main. Drops will end up about 9.5 since its all going in the attic with 8'6" ceilings.

Don

[VitalBodies]

Be aware that Bill Pentz started designing DCs quite some time ago and publishing his finding on the WWW. Back in those days things were different and his work helped to change them. Many of the modern DCs likely made use of that information. Grizzly and Onieda and others have designed systems since then and have the ability to do testing, like matching the correct impeller to the duct sizing.

http://cdn0.grizzly.com/pdf/Cyclone_Dust_Collectors.pdf

There is also the differences in the impeller designs, housings, back pressure and cyclones that all over time get refined. I have the Grizzly 3HP DC and it does a great job with fine dust and shavings using even a home made 8" duct.

I can not imagine going down to 6" duct when 8" is what it made for and works great. I can imagine that Bill did back when he wrote what was quoted.

The challenge (I see) in these times is not the DC or the duct but getting the tools modified to actually collect the dust at the location the dust is created.

Having a well designed duct is worth the time it takes for sure.

My shop made wooden duct (main line) is only 20' long also.

[dwacker]

The challenge (I see) in these times is not the DC or the duct but getting the tools modified to actually collect the dust at the location the dust is created.

Having a well designed duct is worth the time it takes for sure.

My shop made wooden duct (main line) is only 20' long also.

I was just talking to another shop owner about this. I do find it odd that a manufacturer recommends a certain CFM for a tool then puts a duct size on that is to small to handle the CFM. So what I'm wondering are we just using to small dust collectors and would a larger collector do a better job because it may have a higher velocity. The guy I was talking to just upgraded or downgraded depending on how you look at it to a 5hp bag system vs his 5hp cyclone. The bag system is rated at more than double the CFM. He says it was the best change he made to date. He made no changes to any duct work except where the collector connects to the main line for obvious reasons and says the factory sizes now perform the way they were intended. Makes me wonder if a big bag system stuck in a garden shed would have been a better choice for my shop. Granted the shed would have to have a ten foot ceiling.

Don

[VitalBodies]

Interesting. Do you know what machines he went to and from?

[dwacker]

Interesting. Do you know what machines he went to and from?

I know the cyclone was Grizzly but dont know what the new one is, didn't ask. Not Griz its grey not green. I did check the specs on the Griz and the bag ones are 1000 cfm higher.

Don

[dcustoms]

Be aware that Bill Pentz started designing DCs quite some time ago and publishing his finding on the WWW. Back in those days things were different and his work helped to change them. Many of the modern DCs likely made use of that information. Grizzly and Onieda and others have designed systems since then and have the ability to do testing, like matching the correct impeller to the duct sizing. http://cdn0.grizzly...._Collectors.pdf There is also the differences in the impeller designs, housings, back pressure and cyclones that all over time get refined. I have the Grizzly 3HP DC and it does a great job with fine dust and shavings using even a home made 8" duct. I can not imagine going down to 6" duct when 8" is what it made for and works great. I can imagine that Bill did back when he wrote what was quoted. The challenge (I see) in these times is not the DC or the duct but getting the tools modified to actually collect the dust at the location the dust is created. Having a well designed duct is worth the time it takes for sure. My shop made wooden duct (main line) is only 20' long also.

Grizzly actually hired Bill Pentz as a consultant when they were designing their new line of Cyclone DCs long story short they screwed him out of his commission, tried to discredit him and then sent his plans to their engineers who then completely bastardized them into what they are today. Not saying that their cyclones are all bad just that they are not what a Bill pentz/ Clear Vue cyclones are...no other cyclone is. With that being said you take a Grizzly or an Onieda and remove the filters and allow them to freely vent outside you are going to get a solid performance out of them. The problem being for those of us who don't have the option of venting outside these other cyclone options end up pushing the finest of dust back into the shop.

Also the bag style collectors have their advantages if they are put outside with a relatively open filter. Because there is not a cyclone to create that large amount of friction loss they can operate at a higher CFM. Some of the disadvantages however are the filters can clog quickly depending on how fine they are and anything that is collected goes through the impeller...so a piece of metal flying through the impeller and sparking then sitting hot in a bag of saw dust can cause problems.

As a side note Marc piped his entire shop with 6inch DC pipe out of his Clear Vue cyclone that has a 5hp motor and a 15inch impeller.

[VitalBodies]

I always had the impression (not the facts as I do not know Bill) that he was somewhat taken advantage of in the sense that he learned and developed things and others made use of that in ways that might not have seemed quite right at least to him and perhaps others. On the other hand the laws around inventions/designs are very well established. If one discloses such information, does not get a design or utility patent and such then that is highly likely to happen. Not to say that is moral/ethical/correct/honorable/etc or I agree/not agree with either school of thought but it seems to be how the game out there is played. Bill is not alone in that I am sure. I am not even sure that has happened it is just the impression I got - your story about him adds to that.

On 6" vs 8" I personally do not agree with the idea of going with 6" on the Grizzly but perhaps I fail to see the logic - and I LIKE that you have voiced/written your ideas, as it adds to the pool of choices (for Don) and is interesting to me personally too.

In your quote: Always use the largest diameter duct that your blower can use with the least number of restrictions. If your ducting is too small, then it instead of your blower defines the CFM that your system can provide at your machines to pick up the dust. If your ducting is too large you might not maintain the airspeed needed to keep sawdust and chips from building up and blocking your ducting.

I tend to lean in that direction in general and can see the logic of that and would suggest that to Don - he will make the final decision of course but will decide from what info/opinion/etc he gathers.

The rest of the quote seems to be "details" that may or may not apply to a give situation or system.

I have not measured the CFM or the FPM but it is very observable that the system is sufficient to pull fine dust and chips and shavings no problem.

But again, the details - how long the run, how many chips, how many elbows, how many tools and high the lift and on and on - could make a difference.

You also have to study the dead areas (branches with gates way down the line) in a system as they could contribute to clogging.

I have clear panel in my main line so I can see the performance of the duct and DC.

I can not even imagine this clogging from what I have seen. I can imagine chips gathering in the dead areas and thus I suggested blast gates to shut off the dead areas and maintain the integrity of the main line that is in use.

dcustons: As to your thoughts on going with 6", what is the logic/reasons/symptoms/etc as to why one would risk possibly choking the system with a 6" duct. That alone would add a huge amount of resistance into the line.

[VitalBodies]

I was just talking to another shop owner about this. I do find it odd that a manufacturer recommends a certain CFM for a tool then puts a duct size on that is to small to handle the CFM. So what I'm wondering are we just using to small dust collectors and would a larger collector do a better job because it may have a higher velocity. The guy I was talking to just upgraded or downgraded depending on how you look at it to a 5hp bag system vs his 5hp cyclone. The bag system is rated at more than double the CFM. He says it was the best change he made to date. He made no changes to any duct work except where the collector connects to the main line for obvious reasons and says the factory sizes now perform the way they were intended. Makes me wonder if a big bag system stuck in a garden shed would have been a better choice for my shop. Granted the shed would have to have a ten foot ceiling.

Don

Velocity. I read once that someone said (in a forum) that you can not just hook up a DC to a central vac duct and expect it to work. "They are totally different" he went on to say. The impression I got was the velocity of vac was way higher, but the amount air the DC moves is way higher than the vac. I saw elsewhere some other tid bit of info that seemed to agree.

I personally think the factory sizes are from yesteryear and that dust collection (currently) is in the early stages - there is a lot of room for growth. My Jet band saw has an oddball two inch port but the actual smallest opening in the port (if you eyeball down it) is something like 1/2" by 3/4" or so?

[dcustoms]

VitalBodies,

I must say I have enjoyed this back and forth we have had. questioning each others thoughts and opinions about a topic like this creates an environment where we can constructively hone our knowledge. You have brought up a lot of good points and I respect your opinions, as it seems you do mine.

The reason I say 6 inch main line and 6 inch the hole way is for a lot of reasons.

First, in my experience with dust collectors of all types including my most current, as you probability guessed is a Clear Vue, I have messed with many different duct sizes and had many "failures" in my DC setups which led me to do a lot of research, a lot, which brought me to my current setup. I have all 6 inch S & D pipe running into my Clear Vue which is a 5hp with a 15in impeller. My shop set up is similar to what it sounds like Don's is, and my system works great.

Now the reasoning behind the 6 inch was I only use one tool at a time and I wanted really good fine dust collection, not just chip collection. And since the grizzly does not have the capacity to run more than one tool at a time and still have sufficient fine dust collection there is no need to try and run larger pipe. The 6 inch pipe has the capacity to deliver the right amount of CFM's at the equipment to provide really good fine dust collection. Also with a DC putting out 1400ish CFM's I felt from research, that there might not be sufficient velocity in the 8 inch pipe when all the friction loss was factored in. Another reason is simply that 6 inch pipe is cheaper. I also had a concern that even though the grizzly DC has a good size impeller that it would fall short of hp to keep the velocity up.

I made these recommendations off what I know will work. It seems as though we come from two different schools of thought on dust collector setup. It is just like anything else though, We have all setup our shops dozens of times and have figured out a lot of different ways to make everything work a little better.

I could talk all day about Dust collection but that won't get my customers jobs built. Hopefully my condensed answer helped you see where I am coming from.

Dustin

[VitalBodies]

I thought about what you wrote Dustin, while in the shop and I have also enjoyed this discussion. Having done a lot of research there still seemed to be some holes and I wondered why that is. It is as if there are still enough variables, that getting things down to a hard and fast approach is not that easy - although some things seem solid.

A couple of things came to mind.

Your statements:

1) My shop set up is similar to what it sounds like Don's is, and my system works great.

2) And since the grizzly does not have the capacity to run more than one tool at a time and still have sufficient fine dust collection there is no need to try and run larger pipe.

3) I also had a concern that even though the grizzly DC has a good size impeller that it would fall short of hp to keep the velocity up.

On number 1 you say your system works great. It would be nice to come up with a standard test we could all use on our systems to see how the systems are doing. Everyone might think their system is fine, but they might not be as, Bill figured out the hard way. I am not questioning your judgment/assessment, but this is more in an effort to have some kind of standard that everyone could use to see how they are doing and have a goal to work towards. Also, when you say your system works great what does that mean to you? You have seen the full spectrum from what you have said so you would have first hand observation.

On 2, are you sure that is true, and how could one test that? I leave four 4" ports open most of the time (implying that more tools could be being used) and the only tool that like me to shut one extra gate is the Woodmaster 718 when it is moving massive quantities of shavings. I personally think the hood needs a redesign to support 2-3 ports for a planer that large.

On 3 you mention velocity. This is something I have pondered a bit. Most people (I have seen on youtube - often with a big DC and automatic gates) seem to open one gate and work a tool. That to me was counter intuitive as they were opening a 4" port ONLY on an 8" DC.

That has to put some kind of load on the machine and restrict something somewhere. There would be some gain of velocity at the port opening however but a theoretical loss of CFM in the duct. The Grizzly is made for running more than one tool. That would imply more than one gate open. So the question remains, should one have four 4" gates open on an 8" duct or not. The high velocity seems to help suck up big stuff (bigger than needed - which the average user would notice) but the large CFM of four gates open would move MUCH more air and fine dust which not everyone might not notice from casual observation - but would make the most difference to the lungs.

[dcustoms]

Number 1,

I am working on ideas for testing DC efficiency in a small shop but with out buying expensive equipment for testing I think it is going to be hard since the dust we are worried about is microscopic. Bill Pentz does have some really good stuff on his website about testing DC systems and air quality. When I say my system works great that means that I have the largest amount of CFM's at the dust producing tools as possible which is around a 1000. However the way my DC is set up there is a possibility I have a little more. The goal is the 1000cfm at the tool to collect the finest dust a number that can not be achieved with a 4 inch port.

Number 2,

Keeping that magic number in mind of 1000CFM the grizzly cannot achieve 1000 cfm at more that one tool at a time. So that is what I mean by saying that it does not have the capacity to run more that one machine at a time.

Number 3,

That is why I recommend 6 inch pipe all the way to the machine because the air velocity will remain at an appropriate level the entire way plus having a 6inch port on your machine (or a 4 and a 5) will give you the fine dust collection you are looking for.

I am not reinventing the wheel here, I have done a ton of research and have completely bought into Bill Pentz's DC research/findings/fixes. There is a ton of information on bill's website that can be very enlightening. Hope this all helps.

[dwacker]

I paid to get some real life info. The tech came out and showed me first hand that the 8" is going to provide more cfm to the tool provided that the tool has an 8" opening. That being said after laying out a few test pipes it was easy to see that the real limiting factor is port size. It boils down to the fact that for my shop the best is going to be 8" dropped down to the port size with no more that 2' of flex hose per port. Even at that the Griz is not going to provide the optimum CFM and in order to get that sort of flow I would have to step up to a 7,5 hp machine. Since that isnt going to happen it will be just what it will be. On a side note Vita the square and or rectangle duct according to the tech totally destroys any chance of getting the capabilities of the machine and further limits the flow. Why I dont truely understand but he showed me with a piece of 10' square hvac duct and the cfm fell on its face.

Don

[konkers]

Number 1,

I am working on ideas for testing DC efficiency in a small shop but with out buying expensive equipment for testing I think it is going to be hard since the dust we are worried about is microscopic. Bill Pentz does have some really good stuff on his website about testing DC systems and air quality. When I say my system works great that means that I have the largest amount of CFM's at the dust producing tools as possible which is around a 1000. However the way my DC is set up there is a possibility I have a little more. The goal is the 1000cfm at the tool to collect the finest dust a number that can not be achieved with a 4 inch port.

I'm setting up shop in my new house and just picked up the air quality meter Bill recommends from http://dylosproducts.com/ . At $200 it seemed like a good deal for being able to measure how effective my system is at fine dust collection instead of guessing.

-Erik