Dust Collection "Drops"

[Bob Borzelleri]

Lately I've noticed more than a few references on duct suppliers websites to the notion that "drops" as in "Y's" should not actually drop but rather go out from the run they are "dropping" from on the horizontal and then turn down (presumably with an elbow) rather than simply head south from the line they are "dropping" from.

I don't think this is a universally held view as many diagrams still show drops dropping. I haven't yet thought through just why this horizontal suggestion has merit over a straight drop to the tool, but it does have me thinking as I am about to "refine" my plumbing in the near future.

Any thoughts on this or does what I have tried to describe even make sense?

[johnny means]

Seems to me anything that adds another turn on the way to the DC is less than ideal. Exactly what good would the added horizontal run do?

[Jason Beam]

Sweeping turns hurt airflow less than abrupt ones. The longer you can make that turn, the smoother the airflow will be and thus keeps the static pressure lower. This all translates into better airflow. If you use a T, the air must make a very abrupt 90 degree turn, this puts drag on the system and can affect your performance.

Consider it one way to maximize the performance of a duct system.

[Bob Borzelleri]

Usually when someone fails to make himself clear (as in me), it's because he probably wasn't all that clear in his own head in the first place.

So before restating what I thought I had read in a manner that is as foggy as the first time I did it, I thought it better to actually quote the info that got me to wondering in the first place.

This is a quote from "www.Kencraftstore.com" and it sez what I was wondering about. Note the last sentence.

"When selecting your wye branches, you should use wyes whose branches enter the main line at 45 degrees. It helps minimize turbulance and the chance for dust and wood chips to settle in your ductwork. The branch of your wyes should not point straight up or straight down, however should come in to your pipe from the side."

There is a graphic on the site that shows a bunch of Wye branches coming out of the side of the main line.

Just wondering if this is new thinking or what.

[Bill Arnold]

My system, as specified by Oneida for my SDG, has a wye at each drop location with an elbow to take the run straight down the wall to the machine. Seems to me that adding a horizontal run after the wye before heading down will add unnecessary length to the run.

On which websites did you see that recommendation?

[Bill Arnold]

... There is a graphic on the site that shows a bunch of Wye branches coming out of the side of the main line.

Just wondering if this is new thinking or what.

Not new thinking. It's the only thinking I've ever seen. That's not to say I've heard someone say on this forum recently that they used tees and their system works. It might work but can't be as efficient as using wyes.

[glenn bradley]

All my branches and "drops" are at 45* with a wye or a 45* elbow or a combination of 45* fittings to achieve various angles. I run my DC for a period of time following the dust making activity to clear the lines. I also run clear hose at the last step before the machine so I can monitor any debris build up (haven't had any yet).

http://www.sawmillcreek.org/attachme...1&d=1251762990

[Rich Aldrich]

It seems like they are worried about dust and debris dropping into the y if it points down. I have not experienced this issue nor any other issue once I got a dust collector that works (enough air flow and suction). Otherwise, it seems like another cost, air flow loss, place to get clogged.....

[Bob Borzelleri]

My system, as specified by Oneida for my SDG, has a wye at each drop location with an elbow to take the run straight down the wall to the machine. Seems to me that adding a horizontal run after the wye before heading down will add unnecessary length to the run.

On which websites did you see that recommendation?

Hi Bill...

I guess the link didn't activate 'cause I put it in quotes. Here it is:

www.kencraftstore.com

I saw that same graphic on a couple of other suppliers sites, but can't recall where at the moment.

[Lewis Cobb]

I've read the same thing - if the drop branches off the run straight down - or even at an angle, you run the risk of debris that is going by that drop falling down and building up in the bottom. Particularly if it's a drop that's seldom used. Then when the day comes and you fire up that drop, you have a huge plug of stuff racing through the system that could cause trouble at the other end when it "slams home". This is not my experience - just stuff I have read as I plan my DC ducting system. I can see the logic in it, but it might be more trouble for marginal systems that are not moving air fast enough to keep the dust entrained in the air, and it "tumbles" along the horzontal runs.

[Bill Arnold]

Hi Bill...

I guess the link didn't activate 'cause I put it in quotes. Here it is:

www.kencraftstore.com

I saw that same graphic on a couple of other suppliers sites, but can't recall where at the moment.

I copied the reference and saw the diagram. It shows wye connections as they should be used. There's nothing magical going on here. A properly designed system will use wyes NOT tees for proper air control.

[John Keeton]

I've read the same thing - if the drop branches off the run straight down - or even at an angle, you run the risk of debris that is going by that drop falling down and building up in the bottom.

Depending on how many gates I have open, which machines, and a variety of factors I have never assimilated I get this situation occasionally, but it is less than half a cup of debris and hardly enough to matter. My lines are metal hvac, and the drops come off like this -


When I plug in my hose, and open the gate, the debris drops down into the hose and gets sucked out the second the DC is kicked on.

[Bob Borzelleri]

I copied the reference and saw the diagram. It shows wye connections as they should be used. There's nothing magical going on here. A properly designed system will use wyes NOT tees for proper air control.

Bill...

I wasn't thinking they were using "T"s. They are wyes but in the graphic, the issue is that the Y comes of the main line to the side and then comes down with an elbow. I don't think this is the norm; at least not on any duct system I've seen.

...Bob

[Clay Crocker]

I don't think the OP was asking about wyes vs. tees, I think the question is how the wyes should be oriented in the main line; horizontal or vertical? To keep my main line as short as possible I designed it to run through the center of my equipment setup with wyes radiating out horizontally (see picture). If your main line runs directly over your equipment then I don't see a big problem with your wyes dropping out of the bottom of your main line in a vertical fashion. You will get a little bit of dust dropping down into the unused drops down stream of the drop you are currently using, but IMHO it would not be a big problem.