## Coach, can you check my rationale?

Building Section Vignette and Multiple Choice

### Coach, can you check my rationale?

Hi Coach,

I am taking CDS on this saturday and would like to have my rationale on determining the duct space depth with you.

I usually choose the deepest duct size on the same ceiling surface. Then add 8" for lighting..
Please see the images and let me know. Thank you!

http://u.cubeupload.com/salmonx/DUCTSPACE2.jpg ---> this is how I drew to determine the total depth for 1st floor ceiling
http://u.cubeupload.com/salmonx/Rationale01copy.png ----> this is the number I found "the deepest"
http://u.cubeupload.com/salmonx/Rationale02copy.png ---> this is the number I found "the deeepest" for 2nd floor
salmonx

Posts: 17
Joined: Thu Mar 21, 2013 1:28 pm

### Re: Coach, can you check my rationale?

You don't necessarily use the deepest duct.
You must use the largest joist/duct combination within each space having the same ceiling height.

Example

Within the first floor area that has a 9' ceiling, the following exist:

1) A 18" duct under a 24" joist
2) A 10" duct under a 30" joist
3) A 16" duct under a 28" joist

The governing combination is #3 and neither the largest duct nor the largest joist is used.

Coach

Posts: 13235
Joined: Wed May 23, 2012 2:08 am

### Re: Coach, can you check my rationale?

thank you
salmonx

Posts: 17
Joined: Thu Mar 21, 2013 1:28 pm