Under Floor Dust Collection

[Morey St. Denis]

"Flow testing done in Australia that shows long curves flow worse than short curves"?..

Agreed, that statement is bound to be highly controversial. Chris, could you kindly provide some science and further documentation behind that assertion? Not only does it go against what "seems logical"; you're also implying that nearly two centuries of scientific research into fluid mechanics and our resulting textbooks on fluid mechanics and fluid dynamics that we learned from at university were wrong... Surely there has got to be another explanation to whatever might have been empirically observed. The flow coefficient of two 45 degree fittings back-to-back and added together always is better than a single 90 of equivalent radius and the longer the curve radius getting from vector A to right angle vector B, the better the flow coefficient, remains my thinking until proven otherwise. Simple conservation of momentum and energy, even within a fluid media of mixed densities .

[Jon Snider]

I think my underfloor duct question is about to get derailed....

[Peter Christensen]

Morey here is a link with engineering data for air handling systems. On page 54 the duct losses for ninety degree and three piece ninety (i.e. two forty-five's) degree elbows are shown. The 3 piece ninety is almost double that of the smooth ninety degree elbows. Does it challenge your thinking? Even if you take in the value of the two forty-fives added together and not counting the straight section between they only best the smooth ninety with a .75R.

[Peter Christensen]

I think my underfloor duct question is about to get derailed....

Maybe a little. Sorry.

If I had a crawlspace and a strong floor I'd put the ducts below. Any future changes would be only a little harder in sitting room rather than from a ladder. You would just have to plug the old floor holes.

[Carlos Alvarez]

"Flow testing done in Australia that shows long curves flow worse than short curves"?..

The curve was upside down.

[Chris Parks]

Let me clarify what I mean before everyone starts jumping to conclusions because maybe I have jumped to a conclusion. The conventional method of using two 45's instead of a single 90 bend is what I am referring to and not a manufactured bend in a pipe. Also the tests were done in PVC, we in Oz do very little metal ducting simply because it basically does not exist due to no HVAC industry as you guys have. Go to the Ubeaut woodworking forum and have a search through the dust extraction sub forum for the tests. There is a lot of work done in that forum looking for ways to improve flow and also looking at dust monitoring, more than anywhere else I know of. There is hours of reading there for anyone who is interested.

[Joe Jensen]

Chris would you pm me the link if you can find it? I know two forty-five degree corners are worse than a large radius ninety but had seen nothing about a long sweep being worse than a short one. Thanks

I too would love to see the link, pretty hard to believe

[Chris Parks]

I can't link here but do the search, it isn't hard to find the forum or the sub forum. Sending a private link is just as restrictive as only one person gets it and everyone really should read some of the stuff on that site. Don't blame me I would love to put the link up.

[Peter Christensen]

No sweat Chris. I’ve been a member there and the DC forum is usually the first I check. QC Inspector

[Chris Parks]

I think it has the most up to date stuff available for anyone looking at DE in a serious way. BobL did the tests sometime in the last twelve months (I think) with full graphical results as he always does.

[Robert Engel]

I think my underfloor duct question is about to get derailed....

Surprised? DC threads are like sharpening and dovetail threads......LOL

I do not have an underfloor system, but I've never once clogged a DC duct (mine are 6" w/ 4" drops).

There won't be an issue going overhead I think you will find the vertical drops not an issue.

To your question, with a unit that big, I can't see a vertical rise will be an issue.

I don't know about Clear Vue but Oneida will help you plan your system if you purchase a unit.

[Chris Parks]

Go underfloor if you can and want too, part of mine is underfloor. The only provisos I would put on doing it is a very good dust extractor such as Oneida or Clearview, nothing less, a good design that can be accessed for any blockages and I have outlined that above where the main ducts can be accessed from the boundaries of the slab or floor. I certainly have never had any clogging in my overhead or underfloor system using a CV1800 and would not expect any to occur in a well designed system. I hate overhead drops unless they are directly over the machine as they just interfere with me getting around the workshop so I went to extreme lengths to design the ducting to drop straight onto the machines. The problem I see with going underfloor is no matter how well I plan it always seems to need design changes and most people find the same thing. I mentioned above my system is on its fifth iteration at least, new machines, new cabinets and benches etc. Even the way we work changes as we gain more experience etc.

[Carlos Alvarez]

WHAT?? Why can't the link be posted?

[Alan Schaffter]

The big advantage of underfloor is that you can make the most direct runs, avoid 90° bends, and not worry about overhead beams, pipes, lights, etc. Remember, however, that unless your DC is under the floor too, the duct will need to go up and you'll need a horizontal section before it enters the cyclone (if using a cyclone.) My shop is on the second floor of my garage so most ducting runs along the garage ceiling. My "push-through" cyclone is at garage level also. The duct penetrates the floor for machines in the center of my shop and for machines along the wall it runs up to and behind the knee walls. It has worked great for over 14 years!

[Carlos Alvarez]

I am SOOO jealous.