Maximum Plenum Space Height

[masseng7911]

Hey Guys,

Is there a code for the maximum plenum height for a plenum return?

My celing height is 9'-0" and my building height is 18'-0". I'm afraid that on a really warm day it will take alot of coil to cool the office space down.

The location is Massachusetts

 

[LSA]

I am here in Los Angeles, CA and I have seen fresh air and exhaust plenums as high 18'-0" AFF. I do not believe there are any restrictions on height but if your plenum is above finish floor, you will need to provide sprinkler coverage underneath.

 

[stanlsimon]

What kind of insulation do you have in the roof or walls? As long as you don't have old windows or leaking roof vents up there the heat gain/loss won't be too signifigant. The Carrier load program lets you figure with or without the plenum.

In my opinion return plenums are like a giant overhead dust accumulation system. I would much rather pay for a little return duct. At least you can clean the ducts if they get dirty.

Sincerely
sls

 

[MintJulep]

With a plenum volume equal to your occupied volume it probably will prolong the pull-down time.

Stratification may also cause your operating conditions to be higher than expected, especially if the return to the unit is just a hole in the roof.