| The time now is Oct 11, 2008 - 01:42 PM |
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Post subject:Question?air velocity on supply outlet registers (Grilles)
 Posted: Apr 24, 2008 - 04:02 AM #7527
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Joined: Apr 17, 2008
Posts: 5
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I'm curios about the air velocity for residential use recomended for the supply outlet registers on a typical bedroom or living room. Is there any kind of rule to follow, you know, if for example you need 500 cfm on a room, usin a ductculator yuo obtain at 1"SP you need 12X8 duct and at that mark the air velocity for 500 cfm marks 850 FPM, would that be correct or is necesary blow the duct size at the register to obtain diferent air velocity.
Also I'm curios about the velocity needed when using swamp cooler which handle bigger air volumes to feed areas. In other words I need to know what to do in both cases, normal ref. a/c and swamp cooler a/c used in dry areas like west Tx. |
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Post subject:RE: Question?air velocity on supply outlet registers (Grilles)
Posted: Apr 24, 2008 - 05:43 PM #7529
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Power User
Joined: Nov 01, 2006
Posts: 95
Location: McEwen,Tn.
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cacle70........I use .08 for s/a and .06 for r/a. Is this install clg,floor or wall?
You need to find a Hart&Cooley catalog.It's got the engineering data in it
for sizing your registers..We use for 7" pipe 140cfm @.08 with a 6x10 grille.
That'll give you about 600 fpm @ the grille..If it's a wall grille you have to consider the throw.FPM would be greater..Don't know about swamp coolers.
I'm sure the manufacturer has his recomendations..
bordontn2 |
_________________
"Old too soon/ smart too late"
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Post subject:RE: Question?air velocity on supply outlet registers (Grilles)
Posted: Sep 16, 2008 - 11:34 AM #7829
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Joined: May 02, 2004
Posts: 9
Location: Ohio, USA
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I was taught to use 0.5" S.P. for residential applications (your reference to bedrooms / living room).
Swamp coolers... Wikipedia has a nice article for you.
Also when a ductulator is not available the old "rule of thumb" helps.
6" round pipe = 110cfm
7" round pipe = 150cfm
duct sizing "rule" for 8" duct is: total 6" SA's times 2 plus 2.
example using seven (7) 6" SA's total:
7*2=14 plus 2 = 16
so an duct 16x8 will do.
return air duct = SA duct plus 2
so.. an 18 x 8 duct will do (though it's more common to use 20x8).
also stage your duct.
I seldom ever have more than an 8x8 duct at the end of a supply trunk.
10ft x 10ft room = 1 6" supply and 1 6x14 wall return.
smaller areas such as bathrooms *could* be reduced to 5" if there are no windows to an outside wall; otherwise stick with 6" supply.
7" SA's feed 2nd floor rooms equal to or larger than 10ft x10ft.
we use 4x10 floor SA for a 6" pipe and 4x12 floor SA for 7" pipe, in most cases.
Though I am starting to questin this old rule because it is old, and many newer equipment are coming through with variable drive motors. Also, the old 400CFM/ton is being reduced to 350CFM/ton which will require a slightly smaller duct size; but we don't want the system to sund like a vaccuum cleaner when it's at high speed. Maybe this should require it's own thread?
peace,
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