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Old 06-20-2009, 06:03 PM   #1
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Duct and reducers


Hi new to the site and have a question.

I did a complete room by room manual J My trunk will be strait
one trunk line is 12 foot the other is 36 foot long should there be any
reducers as the trunk nears the end? Or somewhere in the middle?

Thanks in advance.

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Old 06-20-2009, 09:56 PM   #2
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For the 36; long run, yes. Location depends on where the takeoffs are and what size they are.

The 12' run I think would be fine.

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Old 06-20-2009, 10:22 PM   #3
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Reduce when ever the velocity drops too low.
Too low varies with what velocity you had at teh first piece of trunk line.

The 12' section may need to be reduced, depending on how much air, the first supplies on it take. The more air they take, the lower your velocity will be.
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Old 06-21-2009, 02:14 AM   #4
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Ok cool that's understandable.

Tho one thing that intrigues me is a some of my rooms (example) 13 x 11 and a ceiling height of 7' 3" called out 2 5inch round ducts I would have thought it would have called for 2 6inch 2 windows in the room one on east wall and one on north. Two 5inch sound right?

Room came out to be a heat gain of 4,077.

Thanks again.
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Old 06-21-2009, 07:20 AM   #5
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5" is queationable.

What CFM did it say.
What static pressue?
And what are you using, hard pipe or flex?

5" flex is equivelant to 4" hard pipe.
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Old 06-21-2009, 02:55 PM   #6
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The air handler puts out about 1200 cfm.

Calc for that room was 173 cfm

Its going to be hard pipe trying to stay away from flex.
Now the speed of air shows a recommended 900 but I thought it was supposed to be 600?
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Old 06-21-2009, 04:56 PM   #7
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Your not going to get 173 out of 2-5" supplies too easiliy.
It will be loud.

Either needs to be 1-7" and a 5", or 2-6".
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Old 06-21-2009, 05:31 PM   #8
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Quote:
Originally Posted by beenthere View Post
Your not going to get 173 out of 2-5" supplies too easiliy.
It will be loud.

Either needs to be 1-7" and a 5", or 2-6".
Had a feeling it was 2-6" 2-5"s just did not look right

And no matter what ill be using dampers like normal Thanks.
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Old 06-21-2009, 05:33 PM   #9
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You have an e-mail I could send you a PDF of the load calcs?
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Old 06-21-2009, 05:41 PM   #10
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You can't recieve PMs yet.

I was going ot PM it to you.
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Old 06-21-2009, 05:47 PM   #11
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yeah i noticed lol and I dont know how many posts i need before i can PM

mine is

k1518n69 AT hotmail dot com

sorry about the goofy way i did it trying to make it so spam bots cant recognize it
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Old 06-22-2009, 06:23 AM   #12
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Keep getting delivery notifications when I email you.
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Old 06-22-2009, 03:54 PM   #13
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Do not know why I got 2 emails from you and did reply

Thanks
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Old 06-22-2009, 04:20 PM   #14
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kept getting non delivery notices.


What size A/C did you select again.

According ot my charts. At your design conditions. You need a 3 ton unit, to meet the cooling load of your sensible load.
And will nee to move 1400CFM.
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Old 06-22-2009, 05:04 PM   #15
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I take it you got my email.
And Wow that thing was totally off?

eventually im going to install double pane windows will the 3ton be over sized then?

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