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Old 07-22-2008, 06:17 PM   #1
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Need help Duct Sizing.


This is the first and last time I'll have to do this and I have no clue how. All I need is for these 2 forms to be filled out.

System 1 Form:
Constant Velocity Method
Please Size Duct Work Using Velocity Rate of:
Trunk @ 800, Branch @ 400, Return @ 600, Filter Grill @ 300FPM
Construction Data
Equip CFM 1200
| Duct ........ | CFM | Width | Length | FPM |
|A.) Unit
Supply
| B.) ......... | ___ |. (12") .| ______ | ___ |
| C.) ......... | ___ | _____ | ______ | ___ |
| D.) ......... | ___ | _____ | ______ | ___ |
| E.) ......... | ___ | _____ | ______ | ___ |
| F.) ......... | ___ | _____ | ______ | ___ |
| G.) ......... | ___ | _____ | ______ | ___ |
| H.) ......... | ___ | _____ | ______ | ___ |
| I.) .......... | ___ | _____ | ______ | ___ |
| J.) ........... | ___ | _____ | ______ | ___ |
All-Branches: | ___ | _____ | ______ | ___ |
Floor Reg: ... | ___ | _____ | ______ | ___ |
Return
K.) ............. | ___ | _____ | ______ | ___ |
Filter Gr .......| ___ | _____ | ______ | ___ |

System 2 Form:
Equal Friction Rate Method
Please Size Duct Work Using Equal Friction,
Ignore All Velocity Over Rides Except Filter Grill @ 300FPM
Construction Data
CFM ........................... (1500)
Avail Ext Pres Drop......... (.35)
Subtract;
Wet Coil ...................... (.09)
Filter Grill ..................... (.06)
Flr Register ................... (.03)
Heat Strip ..................... (.01)
Tot .............................. _____
Lgt Supply Run ............... _____
Plus Ret Run .................. _____
Tot Run ........................ _____
Conv to Friction Rate....... _____
| Duct ........ | CFM | Width | Length | FPM |
|A.) Unit
Supply
| B.) ......... | ___ |. (14") .| ______ | ___ |
| C.) ......... | ___ | _____ | ______ | ___ |
| D.) ......... | ___ | _____ | ______ | ___ |
| E.) ......... | ___ | _____ | ______ | ___ |
| F.) ......... | ___ | _____ | ______ | ___ |
| G.) ......... | ___ | _____ | ______ | ___ |
| H.) ......... | ___ | _____ | ______ | ___ |
| I.) .......... | ___ | _____ | ______ | ___ |
| J.) ........... | ___ | _____ | ______ | ___ |
All-Branches: | ___ | _____ | ______ | ___ |
Floor Reg: ... | ___ | _____ | ______ | ___ |
Return
K.) ............. | ___ | _____ | ______ | ___ |
L.) ............. | ___ | _____ | ______ | ___ |
M.) ............. | ___ | _____ | ______ | ___ |
N.) ............. | ___ | _____ | ______ | ___ |
O.) ............. | ___ | _____ | ______ | ___ |
Filter Gr ........| ___ | _____ | ______ | ___ |

Attached Thumbnails
Need help Duct Sizing.-system1layout.jpg   Need help Duct Sizing.-system2layout.jpg  

Cyon is offline   Reply With Quote
Old 07-23-2008, 07:59 PM   #2
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Need help Duct Sizing.


go to your local hvac supply house and by a ductulator
I would love to help but the slide chart will cost you like $3 and I hate paper work

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Old 07-23-2008, 08:15 PM   #3
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Need help Duct Sizing.


Here's some stuff to get you started.

http://www.designmaster.biz/Products/HVAC/LearnMore/Features/ductsize.html

http://www.engineeringtoolbox.com/equal-friction-method-d_1028.html

Searching this second website more thoroughly might turn up some constant velocity stuff.

The procedures look pretty tedious so I'd put them on a spreadsheet if you can.

ASHRAE is probably the ultimate authority on this but it's hard to get their books through interlibrary loan.

Last edited by Yoyizit; 07-23-2008 at 08:29 PM.
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