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Forum topic by Dj1225 posted 03-25-2018 10:33 PM 836 views 0 times favorited 11 replies Add to Favorites Watch
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Dj1225

75 posts in 2643 days


03-25-2018 10:33 PM

Topic tags/keywords: dust collection ducting motor size

Hi All,

I am building a new shop and would like a little advise in regards to dust collection.

I have a L shape building with two sections. The build and assemble section is 24X60, and a finishing area which is 24X30.

The property sets up naturally to just exhaust the chips and dust directly out the rear of the building. I have total flexibility to put in whatever is needed duct wise.

Basically I plan to keep all the heavy chip/dust producing tools isolated in a 24×30 section of the shop.

I have a couple planers, Table saw, shaper, route, lathe and chop saw, that I would consider the biggest producers of saw duct and chips.

My plan is to run a 6 or 8 inch trunk line down to both some stationary tools, plus a few ducts I can just roll tools to, and a couple floor ducts for clean up.

I want to exhaust everything outside where I can watch it pile up and then push it down a big gully to let it rot. This area is pretty large it would take me decades to even make a dent in the gully.

My main question is what size motor should I use. I was thinking a 5 HP would be large enough to have several ports open at one time. Also is 8 inch trunk too large, is 6 optimal?

At the machines it will have to fit into 4” ports.

To say I am excited would be an understatement. I just want to do this properly.

Any advice would be appreciated.

Thanks,

-- Dave


11 replies so far

View GR8HUNTER's profile

GR8HUNTER

6236 posts in 1135 days


#1 posted 03-25-2018 10:43 PM

HP should not be a concern and you will need to transition down size after you have some take offs and you will also need blast gates to open and close :<)) start with 6 inch

-- Tony---- Reinholds,Pa.------ REMEMBER TO ALWAYS HAVE FUN

View TungOil's profile

TungOil

1274 posts in 917 days


#2 posted 03-26-2018 02:24 AM

Start here.

https://airhand.com/designing/

Size your ductwork to the machinery, then select your DC to provide the flow and pressure drop you need.

-- The optimist says "the glass is half full". The pessimist says "the glass is half empty". The engineer says "the glass is twice as big as it needs to be"

View Redoak49's profile

Redoak49

4052 posts in 2411 days


#3 posted 03-26-2018 11:24 AM

For the size of building and more than one gate open, I would go with a 5 hp.

I run a 5 hp with 6” main duct. I use the 4” ports and get very good cfm with them. I am certain you will get people saying 8” duct and open the machine ports to 6”. However, the bottom line is if you can get adequate flow with whatever you chose. I did actual measurements with my setup and the 4” ports work well. The actual numbers and details are in my blogs.

View Fred Hargis's profile

Fred Hargis

5595 posts in 2916 days


#4 posted 03-26-2018 01:33 PM

I think a difference between what you want to do and most of the rest of us is keeping several ports open at one time. Just a swag, bit I’d bet that would take a lot or air flow and you might need the 8” (but that is a swag). I have 5 HP with a lot of 6” duct and while I haven’t measured the air flow yet, it seems to do OK. If I get to the point where I can measure it, I guess I could try to do so with several gates open and see what happens.

-- Our village hasn't lost it's idiot, he was elected to congress.

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GR8HUNTER

6236 posts in 1135 days


#5 posted 03-26-2018 01:39 PM



Start here. https://airhand.com/designing/

Size your ductwork to the machinery, then select your DC to provide the flow and pressure drop you need.

- TungOil


good advise …i just couldn’t remember that name :<))

-- Tony---- Reinholds,Pa.------ REMEMBER TO ALWAYS HAVE FUN

View Dj1225's profile

Dj1225

75 posts in 2643 days


#6 posted 03-27-2018 03:14 PM

Thank’s everyone for your comments, I assume direct venting vs bag capture makes no difference?

-- Dave

View TungOil's profile

TungOil

1274 posts in 917 days


#7 posted 03-27-2018 04:00 PM



Thank s everyone for your comments, I assume direct venting vs bag capture makes no difference?

- Dj1225


No, it will make a difference in at least a few ways:

1) the DC will have better performance without the resistance of a bag on the discharge of the blower.

2) you will move a lot of air through your shop, which means bringing in outside air as makeup air. If you are located somewhere that gets very cold or hot this is a big consideration as you will be exhausting all of your expensive conditioned air out the wall

3) you will quickly create a big mess outside where your discharge exits the building

In my

-- The optimist says "the glass is half full". The pessimist says "the glass is half empty". The engineer says "the glass is twice as big as it needs to be"

View EarlS's profile

EarlS

2892 posts in 2770 days


#8 posted 03-27-2018 05:29 PM

Tung – great site for sizing a DC system. I’m thinking I might go through all of the calculations and see what the math tells me and compare it to how things are performing in the shop. I have a strong suspicion that my main trunk is undersized but I haven’t bothered to run the numbers to see what science will tell me.

-- Earl "I'm a pessamist - generally that increases the chance that things will turn out better than expected"

View TungOil's profile

TungOil

1274 posts in 917 days


#9 posted 03-27-2018 06:31 PM

Earl-

I think I have posted that link at least 50 times on LJ alone and you might be the first person to actually look at it, so thanks for that. Curt at Air Handling Systems has done a very good job of simplifying the process of designing ductwork for dust collection systems. I use their duct and fittings, but there are other suppliers as well.

The mistake most folks make is buying the DC first, then trying to size ductwork ‘to fit the dust collector’. This is backwards- the duct and DC should be sized together as a system. Start with the CFM requirements of the tools you have (and I would suggest the ones you want to buy!) and a layout of your shop. Design the ductwork to deliver the CFM and velocities needed (they are different and competing things) and figure out the pressure drops in each leg. Then and only then can you select a DC unit that will deliver the CFM you need for your particular system.

This question seems to come up quite often and there is a lot of confusion around designing these systems. I’ve replaced several pieces of equipment recently so I should probably run back through the calculations for my shop as well. Perhaps I’ll do a detailed blog on how to do these calculations using my shop as an example after I finish building my chairs. Unless you beat me to it….

-- The optimist says "the glass is half full". The pessimist says "the glass is half empty". The engineer says "the glass is twice as big as it needs to be"

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EarlS

2892 posts in 2770 days


#10 posted 03-27-2018 07:49 PM

If I get my 2018 Box Swap finished early I will definitely take a swing at writing a DC calculation blog. Unless you finish your chairs first and beat ME to it….

-- Earl "I'm a pessamist - generally that increases the chance that things will turn out better than expected"

View TungOil's profile

TungOil

1274 posts in 917 days


#11 posted 03-27-2018 10:57 PM

That is NOT likely!

-- The optimist says "the glass is half full". The pessimist says "the glass is half empty". The engineer says "the glass is twice as big as it needs to be"

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