Little Advice on Ducting size.

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Forum topic by Bieser posted 03-09-2013 11:09 PM 1121 views 0 times favorited 8 replies Add to Favorites Watch
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176 posts in 2237 days

03-09-2013 11:09 PM

I have read a bunch on duct size for dust collection, Im just looking for a little further Advice. My shop is 14×24 I am going to run a main line across the ceiling down the wall to three tools, The other line will run approximately 20’ down the wall to table saw, jointer, shaper and planer. All tools will have their own blast gate. The two main lines will have their own blast gate as well. I have a HF dust collector that I have hot rodded with a cyclone. My question is the main impeller (I know its on the small side) has a 5 inch diameter inlet. Could I or should I run 5” diameter on my mains with 4 inch drops to the tools or bump up to 6 inch. I am concerned the HF main not have enough pull for 6” lines. I would run 6” if some of you that run something similar are still able to collect dust.


8 replies so far

View Jim Finn's profile

Jim Finn

2687 posts in 3124 days

#1 posted 03-09-2013 11:43 PM

I have a shop the same size as yours and I have a Grizzly 2 HP 220 volt dust collector and I ran 6” metal duct all the way to each 6” flex at the tool. I arranged my shop so that all tools except the table saw are on outside walls so I ran the 6” duct along the floor. This saved going up to the ceiling and back down with the duct. (Saves about 16 feet of duct.)

-- No PHD just a DD214 Website>

View Shawn Masterson's profile

Shawn Masterson

1325 posts in 2151 days

#2 posted 03-10-2013 12:50 AM

go for 6” and mod the DC so it is 6” and the impeller. check out Bill Pentz's page he has all the info you need

View pmayer's profile


1032 posts in 3267 days

#3 posted 03-10-2013 01:40 AM

I think you you might be pushing your luck with that configuration. I ran a similar setup for a few years and while I thought I was getting adequate suction I found a lot of dust built up in the ducts when I reconfigured. When I upgraded to a 5 HP cyclone and turned it on for the first time I was amazed by how much debris I cleared out of the duct work, reminding me that my setup was “sort of” working, but not really keeping up, and probably leaving a lot of the fine dust behind.

I ran my ducts like Jim did and it helped a lot, but wasn’t quite enough with my DC. If you can keep the ducts on the floor rather than the ceiling it would be a good idea.

The trade-off is air speed vs. air volume movement. 6” improves your air volume movement, but it slows down the FPM compared to 4”, and if it dips too low it will be inadequate to capture fine dust that is suspended in the air, and can cause problems like dust buildup in the ducts like I experienced.

Shawn’s suggestion to go to Bill’s site is a good one. If you end up doing this I would suggest using no flex, or if you need to, keep it to an absolute minimum, because any length of flex hose at all will pull your CFM below an safe level given that you will be living on the edge.

-- PaulMayer,

View Bieser's profile


176 posts in 2237 days

#4 posted 03-10-2013 02:09 AM

I know at some point I will probably up grade my dust collection…(If only money wasn’t an issue!) I would like to run 6” so that when I do upgrade I will be good with new collector, I just want to make sure that current one will work for a little while couple years I would guess.

View pmayer's profile


1032 posts in 3267 days

#5 posted 03-12-2013 05:12 PM

Your approach is pretty much the same as what I did. I ducted with 6”, knowing that I was underpowered on the DC side, with the intention of upgrading soon. With the HF collector you will not be out too much when you go to upgrade.

-- PaulMayer,

View Cole Tallerman's profile

Cole Tallerman

392 posts in 2387 days

#6 posted 03-12-2013 05:26 PM

Look on Craigslist for a used 3 hp dust collector and take the impeller. I looked at your shop and I would say if you moved the DC closer to your tools then you would be totally fine with 4” duct. Just make sure you dont use any t’s or 90 degree elbows!

View Bieser's profile


176 posts in 2237 days

#7 posted 03-12-2013 05:29 PM

The collector is just sitting there for now. I plan moving it into a shed on outside of shop

View crank49's profile


4032 posts in 3173 days

#8 posted 03-12-2013 06:03 PM

I think you should throw the cyclone away and replace the filter bag with a cartridge. Then put a simple drop out box at machines where heavy chip loads will be generated, i.e. jointer or planer. A Cyclone will rob you of the main thing you need to pull crap through a long bunch of pipe; static pressure.

There is nothing about a cyclone that makes it a better filter than a cartridge unless it is a high efficiency cyclone design and those require at least 9” static pressure drop across the cyclone. About all the pressure the HF can muster is 11 inches and that is with severely restricted flow and even at 100 CFM would only leave about 2” static to overcome all your hood entry losses and duct friction losses. Just not enough.

A low efficiency cyclone will only cost you about 2 1/2” static, but it only catches the big particles, like over 30 microns. And, the fine stuff still goes through to plug up the secondary filter, so why bother?

A drop out box, on the other hand, drops the heavy stuff out at the source so the dust collector doesn’t have to pull it through 20 ft of duct.

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