# Wood Turning Club - Confusing Duct Layout



## DarcyW (May 11, 2017)

Hi guys,

I'm based down in New Zealand and have been tasked with _trying_ to design our workshop dust collection layout - For a woodturners guild. I've done a bit of this for at home, but I only had a few bits of equipment connected up to my 2Hp DC. Easy, and very forgiving...

This is all being installed in to our new club-rooms which are currently on-site and being joined to our existing club rooms - more than doubling the footprint. The existing rooms will become used for general wood-working, while the lathes are moved in to the building with the reinforced floor 

But... I've been given this task to do, with one main restriction. In NZ, to get more than 2.2kW (3Hp) you need to bring all three phases in to your building, and pay an increased per month meter rate. We're a non-profit (registered charitable entity) club, so that's not appealing. On the flip side, the dust collection setup up-front cost is paid by charitable grants... so in theory we can get a pretty decent DC up-front. In short, I'm limited to a single phase. And a single phase motor is limited to 2.2kW on a dedicated 15A 230V socket. Fine, so be it...

Up until I took this over, the plan had been to rely upon six air cleaners, and four mobile 1Hp DC's that get dragged around. That meant that we either had to give up all hope of storage (the white shelving in the pictures), or have less than 15 lathes - which is already a bit short. Because I didn't like that idea, fairly enough, I've now got to put together the alternative. The downsides of the prior proposal were: A lot of noise, obstructed walk-ways, no room for storage - we're already quite pressed for storage, and non what-so-ever had been allowed for in the new building!

Anyway... So, a typical usage scenario is that _any_ 3-5 pieces of equipment may be collecting dust at any one time (usually only 1-3). In our current club-rooms we don't have anything... at all... we open the windows and doors, and power-sanding (drill + sanding mandrel) is frowned upon.

My limitations are as follows:
- The DC needs to stay in that location
- The duct going through the walls can move vertically, but not sideways (due to bracing wall restrictions)
- The duct should ideally stay at head height (2.7m stud) - except for the bandsaw outlet
- The dust collector is limited to 3Hp!!!
- In NZ, anything bigger than a 5" blast gate isn't financially viable. Blast gates of 4" diameter are common, and cheap enough

Other considerations:
- The DC will be used for *fine dust collection only*. There is no intention to gather shavings of any sort (except the inadvertent kind...)
- The DC will have wireless remotes fitted for on/off
- Every lathe will have 5-6" duct running to it, dropping down to a vertical, with a 4" reducer, a blast-gate, then at most 1.2m (4ft) of 100mm flexi-duct

Other points of interest:
- The DC will be in an enclosed semi-sealed room, except for at least 2x 8" vents out through the floor, to underneath the building. This is done in an attempt to deaden sound and avoid the use of ear-protection when operating
- The band-saw is used infrequently and has a recommended 800CFM collection from a single 4" port (still not sure how that's supposed to work!)

I've tried a variety of different ducting layouts, but this seemed to be the best method of reducing bends, and having no more than two points of collection on any branch. It uses a bit more duct, but I think it simplifies the calculations

I'm just a bit stumped on how to calculate from here! I have a full spread of duct to chose from, I'll chose smooth wall duct wherever possible, and wide radius bends wherever I can. The duct sizes are from 100 - 200mm, 4 - 8", in 25mm steps. So, I can go nuts when it comes to choosing specific diameters... but I'm a bit of a loss on how to calculate for this setup! I'm pretty certain I now have enough information to begin calculations, but where to begin? I've allowed for 200mm ducting coming out of the DC and in to the main trunk... but what happens if only one blast gate is open? So many considerations I don't know where to start.

After a bit of research, I'm pretty much limited to one of two DC's. The retailer was very helpful and spent a couple days chasing up specifications for me. I really need to recommend Carbatec in NZ for their service!
3Hp Two Stage Cyclone CDC-2200C (UB-3100ECK)
Volume - 2200 CFM
Impeller - 15.8"
Static Pressure - Attached as file










3Hp Twin Bag DC-2200C-3P (CT-003VB-1PH)
Volume - 2200 CFM
Impeller - 14.5"
Static Pressure - Attached as file
The attached spec is from the 3 phase version of the same product. Supplier has stated the only difference is the 3 phase power requirement, and that performance is identical.










Each Lathe will have something like this dust-chute, for collecting fine dust (10" x 4" with 4" port)










Any help in this would be greatly appreciated... It looks to me like the Cyclone DC is the more powerful unit. But I still need to work out duct diameters.


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## Carl10 (Feb 3, 2017)

Darcy,

Sounds like a big project and you are doing your homework first. There are a couple of things that might help. You may already know or have considered this but I will assume you have not. First for the duct calculation, the easiest tool I have found is on Bill Pentz site. He has an excel spreadsheet already created just for this calculation http://www.billpentz.com/Woodworking/Cyclone/staticcalc_faqs.cfm under the ducting tab there is a spreadsheet choice that you can download and use. You only need the ducting section for your SP total. The other reference is the this article https://www.oneida-air.com/pdf/AWW article jan 2006.pdf , which shows your machine listed as the JDS cyclone (same machine different label). The impeller design is more radial/airfoil type and produces more CFM over higher SP. You will notice that the real world curve is not as flattering as the manufacturers curve (typical). Which brings me to your second choice of system and that is the 4 bag unit. That CFM stated is usually the blower only curve and the system performance curve will be a fraction of that curve. So the cyclone will give you better performance.

To capture fine dust you will need more airflow, so try and design close to 800CFM at each station. Even at 600 CFM you probably will not be able to support 2 open ports yet alone 3. Since you are using wide open ports versus directed collection ports (like a hood or a shroud) you really need to move more air. Is it possible to get two machines and split up the room?

If you are limited to one, start with the furthest three ports and work back distance and fittings into the spreadsheet. Ideally you would match the main trunk to the cyclone inlet (7"?) but if you have multiple ports open the velocity may drop below what is need to keep debris airborne in that size duct and will have to downsize. Start with the biggest and ideal CFM and work back.

Another more realistic choice is to expect the DC will only collect chips (lower CFM requirement) and provide small shop air cleaners at each station. My dad did this when he started carving with a Dremmel. He would put the air filter right on the bench in front of his work. This will pick up the fine dust right next to the machine and will allow more ports to be open on the DC.

Hope this helps,

Carl


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## DarcyW (May 11, 2017)

Giday Carl,

Thanks for the help. If we can remove more than 80% of the dust created by sanding we'll be happy... Ideally we can collect from three sources at once. My thoughts were that each branch would be 5-6" in diameter. But I couldn't work out what size to make the main trunk (6-8").

It's not really viable to split up the duct systems as we're limited to where the ducting can come through the walls - there's not enough room for two 7-8" side by side. Also, we're trying to keep the DC's in that small room so-as to reduce noise levels.

On my 2Hp at home (1200cfm) I've recently had about 4m of 4" flexi-tube and even that provides enough collection power. To be fair, there's only one device connected... but at 4m of ribbed ducting I'd be lucky to be getting 350cfm out of that - that's my understanding anyway.

I hadn't seen the oneida link before. Thanks. Bill's calculator just started getting complicate as I didn't know how to accommodate 'any three' vents being open.

Each lathe will use a small hood on an arm... Either that or we use those Big Gulp units, but they disperse the collection quite a bit and your air velocity drops.

Individual points of collection requires us to either reduce the number of lathes, or lose a significant amount of storage. The cupboards/shelves are only 300mm deep, so we'd probably need to remove all the storage in order to keep walk-ways clear while DC's were being used. It's hard! The lack of space makes it difficult...

Thanks for the help


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