height of ductwork above floor

[mark mcfarlane]

Most of the shop pics I have seen have vertical runs at each machine, tied into an 'overhead' main duct.

Any reason to not run the main duct down low nearer the floor, or say 3' above the floor (other than the 8" or so of lost space along the wall)? I've heard people want a large horizontal dict coming out of the collector, but is that really that important, i.e. does it matter if the single vertical run is right by the collector versus many vertical runs at each machine...

Moving the main down to 3' off the floor would eliminate the need for vertical runs, reducing pipe, and, in my case, not block the windows,...

Here's the wall where the windows get in the way of ducting. I'll have an awesome view out these windows (golf course, lake, island, lots of purty trees) and would like to take the windows even lower, but it probably wouldn't work great having them below 'machine height'. I've sketched in some ducting about 3' above the floor (in green)

[Mike Heidrick]

I am thinking I want mine high to go above windows and not to trip over the runs to the machines and high enoughso that material can easily pass under the line to the machine. Ill have the drop by the tool out of the way from the material. 3' up would be very trippy possibly.

[mark mcfarlane]

I am thinking I want mine high to go above windows and not to trip over the runs to the machines and high enoughso that material can easily pass under the line to the machine. Ill have the drop by the tool out of the way from the material. 3' up would be very trippy possibly.

Mike, I am proposing against the wall, 3' off the floor, so I don't see any trip hazard. You'd just have to move the machines 8" away from the wall, the diameter of the ducting, which in my current room design is actually a good thing to get away from the wall to open up infeed and outfeed space because the wall bumps out about 3' by the doorway (far right of pic).

[Andy Giddings]

Mark, I think the advice is to have a min 4ft straight run into the DC/cyclone inlet. I believe this is to improve efficiency but I've not noticed a significant difference myself. Regarding the duct at 3ft from the floor - is your main goal to get a better view doing this or some other reason? As you state, the view is going to be limited by the machine height. What about a different scenario where you have the duct at ceiling height but put one tall window (almost floor to ceiling) and two from machine height to ceiling? That way you can be confident the duct won't get in the way and you can max your outlook?

[mark mcfarlane]

Mark, I think the advice is to have a min 4ft straight run into the DC/cyclone inlet. I believe this is to improve efficiency but I've not noticed a significant difference myself. Regarding the duct at 3ft from the floor - is your main goal to get a better view doing this or some other reason? As you state, the view is going to be limited by the machine height. What about a different scenario where you have the duct at ceiling height but put one tall window (almost floor to ceiling) and two from machine height to ceiling? That way you can be confident the duct won't get in the way and you can max your outlook?

Hi Andy, My main goal is to get as much window space as possible and preserve the view. 'Gently turning' vertical drops from the ceiling will take maybe 2.5' of vertical space with 8" pipe???, so not only do I have to look at the ductwork, but I may need to lower the top of the windows. Mostly, I don't want to look at the duct work.

Theoretically I can put the windows anywhere I desire, but the existing windows along the back of the house are all 6' tall and start @ 24" above the floor. Almost the entire back of the house is glass, so I have some architectural considerations to deal with.

[Malcolm McLeod]

Recommendations of straight pipe run prior to a critical point (collector) are typically specified relative to pipe diameter. If you were installing a flow meter, you would want something on the order of 10+ pipe diameters of straight run upstream of the metering point. An elbow or obstruction in the pipe induces turbulence in the flow and the straight run allows it to become more laminar (smooth) - and so improve dust separation or the accuracy of the meter.

You're talking cyclone, not meter, but principle still applies.... You can expect some loss of efficiency as you shorten the straight run into the cyclone. I would be guessing to try to estimate it, but if your performance expectation is as grand as your planning efforts (yes, I'm jealous), you may want 4-5 feet minimum. Once past the inlet run, you can yank it and bank it as much as you can stand.

Good luck and welcome to Texas! ...It's like a whole other country.

[mike mcilroy]

I have about 4' long drops of 6" flex hose under my run that goes under my garage door and they do give some flexibility to the planer and jointer I have hooked to them so I can move the machines just enough if I am working with extra long stock.
Also in my shop the wall space at that level is at a higher premium for storage and general functions than the higher area.
You wouldn't be the first or the last to try something and then change it later. Good luck with it.

[mark mcfarlane]

Anyone ever paint their ductwork? I'm thinking Norfab. Maybe I can go retro-industrial...

[Jim Becker]

Mark, duct work design is both objective and subjective. The former has to do with providing the best air flow characteristics and performance and the latter has to do with aesthetics and accommodating the needs of the individual shop and shop owner. If you are comfortable with the lines being at that three foot mark and you can route efficiently to your cyclone, then there's nothing wrong with that. However, you may be forcing longer duct runs to accomplish that...the most efficient duct designs often traverse a shop diagonally for a good portion of the design and that's easiest to do overhead.

As to painting...have at it! Nothing wrong with that outside of the extra work. And of course the paint chipping over time as things "move"...

[Larry Frank]

I think that preserving window view is great. I wish I had some Windows in my shop.

Painting would be great but look into the right prep for galvanized steel.

[James Biddle]

I have the ducts in my basement shop space 2' off of the floor and I regret it. Everything now has to be stored that distance away from the wall, effectively reducing your floor space. Also, the duct tends to collect a lot of sawdust that settles on it, making it look terrible.

[Alan Schaffter]

Running duct work along the walls means the runs are all orthogonal at right angles, requiring one or more 90° bends and a long run to the tools near the end. Bends and long runs mean resistance. To avoid both vertical runs, 90's, and long runs, run the duct below the floor. If that is not possible the next best is overhead in a XMAS tree design with 45° bends, shorter runs, and no 90's.

[Randy Rizzo]

image.jpegDid something similar, except my pipe is close to floor supported on "chairs", and either screwed to floor or cabinet. It is exposed, but it's on the opposite side of where I'm usually working. For the short time I've had installed not a problem tripping over it. From the miter hood to the DC is a straight 6' run. Previously I just had it connected via flex to the TS. Maybe it's just wishful thinking, but I think it's improved the collection.

[John K Jordan]

...duct work design is both objective and subjective. The former has to do with providing the best air flow characteristics and performance and the latter has to do with aesthetics and accommodating the needs of the individual shop and shop owner. ...the most efficient duct designs often traverse a shop diagonally for a good portion of the design and that's easiest to do overhead.

Well stated. I put my duct work in diagonal and straight lines down the shop to minimize runs and bends for performance. For aesthetics and to preserve wall space for shelves and such I ran all the (6") horizontal ducts in the trusses above the ceiling.

This was an exercise in careful planning (on tool positioning), a major engineering effort (to avoid even a single cut into any truss) and an incredible amount of extra work for my construction crew (of one, me.)

It was also the best thing I ever did for the shop (except perhaps for putting in heat and air.) All runs to the tools are completely out of the way except for vertical drops through the ceiling. This minimizes wasted wall space. Ducts cannot collect dust on the top (I have shelves for that). Connections and support hangers and ducts could be uglier than ugly. The extra cost was zero.

During construction:
DC_duct_IMG_20141228_195036.jpg
Beginning of run from DC closet off-camera to the right.

Drop at lathe:
lathe_PM_IMG_20160331_18501.jpg
I make use of nearly all the wall space.

I did install attic access panels to reach inspection and clean-out plugs at the ends of the longest runs. Also, the ceiling is 4x8 plywood put up with screws, removable for repairs if necessary.

[John K Jordan]

...with 45° bends...

Instead of two 45 deg elbows to make a 90, in several places I used 22.5 deg elbows for an even gentler radius.

JKJ