# Dust Collection Ductwork Question



## KimR (Nov 22, 2016)

I just installed a ClearVue CV 1800 cyclone. PVC drainage pipe is not available except in Schedule 40 in my area. I contacted Oneida but they declined to help with designing the ductwork system. I contacted NordFab. They referred me to a regional dealer, EAS. The designer there designed a system that runs a 6"duct from the cyclone about 6' to a 6" drop to my lathe. After that she necked the trunk line down to 4". She claims the trunk should match the size of the dropd and, since all the other machines have 4"ports, the trunkline should be 4". The internet gurus, e.g., The Wood Whisperer, Jay Bates, et al., all seem to say to maximize the duct diameter until you reach the tool port. This would mean the trunkline should be 6". The designer is adamant that that's just a waste of money. What say you, LJs?


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## papadan (Mar 6, 2009)

I used all 4" for years and never had a dust problem. That was with a 2 hp Grizzly DC and nothing else.


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## pmayer (Jan 3, 2010)

You are getting terrible advice, and you'll be wasting a lot of your investment in a 5 HP cyclone if you do that. The only reason to drop down to 4" is if you cannot keep your air velocity up over 4000 FPM. Otherwise you are just introducing static pressure for no reason. It would take a very long run of 6" hard pipe to introduce enough static pressure to pull the air velocity below 4000 FPM with your dust collector. With that machine you should run 6" all the way to your tool, and replace the 4" ports on the tool in many cases.


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## RobS888 (May 7, 2013)

> You are getting terrible advice, and you ll be wasting a lot of your investment in a 5 HP cyclone if you do that. The only reason to drop down to 4" is if you cannot keep your air velocity up over 4000 FPM. Otherwise you are just introducing static pressure for no reason. It would take a very long run of 6" hard pipe to introduce enough static pressure to pull the air velocity below 4000 FPM with your dust collector. With that machine you should run 6" all the way to your tool, and replace the 4" ports on the tool in many cases.
> 
> - pmayer


I agree, ignore any idiots recommending 4" pipe! You can and should use pipe diameters matched to your DC size.


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## AZWoody (Jan 18, 2015)

Why not change the diameter at the tool to use 6". If that's possible, that's the best way to get your best collection at the source.

I have the clearvue 1800 with the larger impeller and ran all S&D 6" for mainlines and have either a 6" dust port or dual 4" ports at pretty much every tool.


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## TungOil (Jan 16, 2017)

Paul is right, you need to maintain duct velocity to keep the particles suspended. Ductwork design is a compromise between keeping velocities high (smaller pipe) and minimizing friction (bigger pipe). Bigger is not alway better and it is more complicated that simply matching the port on the DC.

This is a good primer: https://www.airhand.com/designing/


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## Manitario (Jul 4, 2010)

That's really bad advice from the Nordfab dealer. As others have mentioned, 4" duct introduces a large amount of static pressure compared to 6" duct. If you had huge, long runs of 6" pipe you theoretically would have to worry about FPM, but in most non-industrial shops (for which a Clearvue would be inadequate anyways) your main concern is CFM. I've had a Clearvue in 3 workshops with runs ranging from 20' to 50' of 6" pipe and have never had to deal with clogging from due to shavings dropping out of the airflow from low FPM. I reduce right at the machine when needed. 
Having set up the DC for 3 shops in the past 5 years, would be happy to help with your design if you PM me.

Also, consider K+B ductwork instead of Nordfab; the parts (and clamps) are interchangeable with Nordfab and are cheaper!


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## wapakfred (Jul 29, 2011)

Another vote to scrap that advice. Run the 6" all the way to the tool, even if you have to modify the tool port. It really peeves me that tool makers are giving DC just a glancing blow with the puny ports they put on tools. Some tools can't be easily modified, so with them you just have to go with what you have.


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## papadan (Mar 6, 2009)

> You are getting terrible advice, and you ll be wasting a lot of your investment in a 5 HP cyclone if you do that. The only reason to drop down to 4" is if you cannot keep your *air velocity up over 4000 FPM.* Otherwise you are just introducing static pressure for no reason. It would take a very long run of 6" hard pipe to introduce enough static pressure to pull the air velocity below 4000 FPM with your dust collector. With that machine you should run 6" all the way to your tool, and replace the 4" ports on the tool in many cases.
> - pmayer


*Air velocity at 4" is more than double the velocity of 6"* All idiots know this!


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## Manitario (Jul 4, 2010)

papadan: FPM=CFM/area so technically you're correct, however as you can see from the formula, as CFM decreases, FPM also decreases. Given that a run of 4" pipe increases the static pressure of the system and will decrease CFM, this will somewhat negate the increase in FPM from the decreased pipe area.


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## pmayer (Jan 3, 2010)

> *Air velocity at 4" is more than double the velocity of 6"* All idiots know this!


Yikes. I'm not sure what your point is, papadan, or why you are using such an aggressive tone toward me. My comment was not directed toward you, and I'm sorry if I offended you. I was responding to the original post; not yours, and was simply suggesting that KimR shouldn't move down to 4" pipe with this machine unless it was necessary in order to increase the air velocity in the pipe. The point that you made about higher velocity air movement in smaller point is consistent with what I was saying.

For KimR's system, I disagree with the advice that was given by the EAS design consultant. I had the same CV machine as KimR for years and the difference in CFM when using a 4" duct vs. a 6" duct was dramatic, and strongly favored the larger duct. In your case, with a 2HP system, chances are good that you are better off with 4" pipes as you used, because that system would likely have a difficult time maintaining adequate air velocity in a 6" duct over any significant length. Prior to my CV I had a 1.5 HP single stage DC and ran 6" main duct. Big mistake. I thought it was collecting ok until I took apart one of the ducts and I found that a large amount of dust had settled in the pipe over the years. When I hooked up the CV, it pulled many gallons of debris from the pipes when I first turned it on.

Respectfully,

Paul


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## ssnvet (Jan 10, 2012)

did you download the static calculator spread sheet that Clear View links on their web site?

Think of it this way…. it doesn't matter how much "suck" power your lungs can produce, if you try to drink a super sized Coke through a coffee stir stick tube… you're not going to move a lot of fluid.


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## papadan (Mar 6, 2009)

Paul, my sarcasm is aimed at RobS88 the fool, he's the one that thinks it's necessary to call someone an idiot. If your DC has a 6" inlet then by all means use 6" and if it has a 4" than all you need for proper operation is 4"unless you are planning on sucking up 5" pieces of wood. And just to add one other thing, All DC manufacturers say to ground your system, even though all the experts here say no.


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## them700project (Aug 12, 2015)

Also Nordfab is wonderful stuff but you can save 2 metric ******************** tons of $$$ if you run spiral instead. it goes in easy and I ran a bunch of it for under 600 with gates. My fan is in the attic with filter, cyclone in corner of shop all 6" on ceiling I have 2) 4" drops and 1) 6" with room for a couple more drops


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## pintodeluxe (Sep 12, 2010)

You can special order 26 gauge 6" metal pipe from Home Depot at a significant savings over other options. 
Much less expensive than specialty retailers.


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## jmos (Nov 30, 2011)

I've got a ClearVue 1800 also and I used 6" where ever I could; all the mains and as many of the drops as possible (including replacing stock ports where possible.) When the tools couldn't be modified I went to 4" as close to the tool as possible. Also minimize the use of flew hose as it has a high pressure drop.

Around me I had a heck of a time finding thin walled PVC. I finally ended up at an irrigation supply house that served the landscape irrigation business. No plumbing houses carried it. Just a thought.


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## RobS888 (May 7, 2013)

> Paul, my sarcasm is aimed at RobS88 the fool, he s the one that thinks it s necessary to call someone an idiot. If your DC has a 6" inlet then by all means use 6" and if it has a 4" than all you need for proper operation is 4"unless you are planning on sucking up 5" pieces of wood. And just to add one other thing, All DC manufacturers say to ground your system, even though all the experts here say no.
> 
> - papadan


Here I thought people used larger diameter pipes to move more air. Now I know it is to accommodate 6, 8 or even 10 inch diameter pieces of wood. Amazing! DKV at his best.


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## Rayne (Mar 9, 2014)

Another vote to run 6" all the way to the tool. Check your local HVAC dealers/wholesalers. They normally will sell to the public if you ask. That's how I got my 5" 28 gauge metal ductwork for much cheaper than any of the PVC pipes HD/Lowes carries. I only had to find the Wyes.


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## JBrow (Nov 18, 2015)

KimR,

I tend to follow the manufacturer's recommendations wherever possible. According to ClearVue, 4" duct work will effectively evacuate large chips, but can leave a lot of the fine dust uncaptured. Most certainly, 4" duct work will save money, but fails to take full advantage of the system you have.

I am surprised you did not turn to Clear Vue for your duct work design. While I did not avail myself of their duct work design service, I found their technical support extremely helpful and responsive to my questions. For example, when I mentioned duct work, the tech service agent was concerned that if I went with metal, that I should avoid light gauge HVAC metal pipe. Their concern was that light gauge metal could collapse under the pressures that the CV1800 is capable of producing. I ended up using SRD35 PVC 6" duct work mainly because it was locally available and less expensive than the heavy gauge metal piping and fittings. I did notice the Clear Vue is a Norfab dealer, but I do not know how well they price this piping.

http://www.clearvuecyclones.com/content/6-duct-design


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## Redoak49 (Dec 15, 2012)

Interesting thread….but the bottom line is how much cfm you get at the tool. For most of the tools, 600-800 cfm with 4000 fpm velocity is what is needed. If you can get that flow with a 2", 4" , 6" or 8" duct who cares.

Based upon your dust collector, you can reach the requirements in different ways. With mine, I can achieve this with the 4" ports on my cabinet saw, 15" Planer, and other tools. If you have a 2 HP unit, you will need 6" as long as you get sufficient velocity.

The decision on duct size needs to be made with knowledge of your performance curve.


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