# Thread: Residential Duct traversing

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## Residential Duct traversing

What is best practice on placing ports in rectangular duct for air flow traversin. How many, how far a part?

2. Hi Adamf79,
What are the duct dimensions?
That information is needed to determine traverse layout.

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Originally Posted by Allen
Hi Adamf79,
What are the duct dimensions?
That information is needed to determine traverse layout.
Currently working on 16x8, 14x8, 12x8 and 24x14

Can you tell me how to calculate layout for rectangular duct traversing.

Thank you

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The ducts you referenced require a 16 point traverse. This is the equal area traverse. Drill four holes equally spaced starting with the holes at the edge of the duct which are 1/2 the calculated spacing from the edge. On the 24" duct the edge holes are placed 3" from the edge of the duct then two holes at 6 from the edge holes and 6" apart. Traverse points are the same spacing.
Residential duct traverse is rarely possible because there is normally little straight run that allows a good flow profile.

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Originally Posted by WAYNE3298
The ducts you referenced require a 16 point traverse. This is the equal area traverse. Drill four holes equally spaced starting with the holes at the edge of the duct which are 1/2 the calculated spacing from the edge. On the 24" duct the edge holes are placed 3" from the edge of the duct then two holes at 6 from the edge holes and 6" apart. Traverse points are the same spacing.
Residential duct traverse is rarely possible because there is normally little straight run that allows a good flow profile.
Thank you,

Is there a chart that I can get somewhere that I can know for future reference? Or any online reference?

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Just type in "Equal Area Duct Traverse" online and several sites will come up.

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Originally Posted by WAYNE3298
Just type in "Equal Area Duct Traverse" online and several sites will come up.
Thanks Wayne. I found few one by fkuke and one by dwayer, and others. That is why I finally ask here. As most of them point to at list 5 points. None of them explain exectly.

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The method I gave you is the equal area method which is easy to understand and very accurate. The Log Tchebycheff method is generally considered to be more accurate but takes a lot more time and requires more test points. I have run thousands of duct traverses and there is not enough difference in the two methods to state the log method is better. The results of the traverse meaning the relative closeness of the readings compared to each other is a lot more important than anything else. The quality of the readings determines the accuracy of the traverse. I have a post in this forum that has more info if you are interested.
Large ducts require more test points but in resi you probably don't need to worry about that.

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Originally Posted by WAYNE3298
The method I gave you is the equal area method which is easy to understand and very accurate. The Log Tchebycheff method is generally considered to be more accurate but takes a lot more time and requires more test points. I have run thousands of duct traverses and there is not enough difference in the two methods to state the log method is better. The results of the traverse meaning the relative closeness of the readings compared to each other is a lot more important than anything else. The quality of the readings determines the accuracy of the traverse. I have a post in this forum that has more info if you are interested.
Large ducts require more test points but in resi you probably don't need to worry about that.
That is what I look up equal area method, and fluke and the other came up. If you can point me to some good reading material that I can get better understanding that would be great.

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If you are union get the TABB manual. It is as good as any other. You can buy the NEBB or ASHRAE books on tab work. I rely on NEBB and AMCA for most info I need.

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Originally Posted by WAYNE3298
If you are union get the TABB manual. It is as good as any other. You can buy the NEBB or ASHRAE books on tab work. I rely on NEBB and AMCA for most info I need.
Great, I will look one of them up. do they all explain how to calculate spacing. Did you say that you did a write up on it on this forum as well?

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I have a couple posts in this forum but don't remember what is in them. The books I mentioned give spacing and a lot more info. Everything you need is in them.

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Originally Posted by WAYNE3298
I have a couple posts in this forum but don't remember what is in them. The books I mentioned give spacing and a lot more info. Everything you need is in them.
Great thank you!

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