Stairwell Pressurization system

[Jamsith]

Which is the correct method to sizing the duct for the STAIRWELL Pressurization system, by constant friction or constant velocity? if by velocity what is the normal sizing values for this? please help me. I am in the mid of sizing.

 

[willard3]

Either method is good.

Get a Trane wheel and learn to read it.

Q (*flow in cfm) = velocity (feet per minute) x area (square feet)

 

[Jamsith]

Hi Guys......
Still I am struggle on this.... Please somebody help me

 

[GT-EGR]

Size your duct either way, it's really not the critical selection to pressurize a stairwell, the duct sizing only matters since smaller ducts will then require more fan horsepower to operate. Make it a low pressure system, around 800 fpm, no more than 0.1"/100'. But really the velocity number matters if you are worried about someone hearing the duct noise, otherwise if you exceed both those numbers I have you for whatever reason, you'll just need more fan horsepower since your duct will impose a higher static pressure loss.

Hopefully you are aware that your stairwell pressurization fan main purpose it to pressurize the stairwell, so you have to do a calc based upon all the door openings, window cracks, etc - to determine the amount of air you need to deliver into your stairwell to get the pressure you want. Then you add that pressure to your duct loss pressure and that's your fan's pressure and CFM.