pressurization with exhaust louvers
pressurization with exhaust louvers
(OP)
I am modifying an existing HVAC system serving a pump station in a waste water treatment plant. It has to be maintained at 0.1" WC positive pressure relative to the atmosphere. The room has existing exhaust louvers at exterior wall, and the client would like us to re-use them. Is it possible to maintain the sapce at 0.1" wc positive pressure with exhaust louvers, and supply fans?
Thanks for advise...
Thanks for advise...





RE: pressurization with exhaust louvers
Louver seal-edges deteriorate with time and may need replacement to be tight, but you won't know until you measure.
Call a balancing contractor and find out if you are 0.1" wc positive now with existing fan/louver/control equipment.
RE: pressurization with exhaust louvers
The existing room is not pressurized, and the existing louvers are for air intake. My design approach is to add new supply fans and convert the intake louvers (48"x24") to exhaust type. The pressure drop through the new louvers will be designed at 0.1" wc. Would like to doube check if my concept is right - Can the room be pressurized with big louver opening...
Thanks in advance for help.
RE: pressurization with exhaust louvers
So yes, it is possible to maintain positive pressure in a space with exhaust louvers. At least until the wind blows, or the door opens, or a seal around a wall penitration deteriorates, or....
RE: pressurization with exhaust louvers
As the seals age and caulking dries out, change the rpm of the fan until you have the correct delta P again.
As Mint Julep points out, all bets are off if you operating personnel aren't the standard fool and leave the door open, remove the door seals and etc.....nothing is fool-proof because there is no standard fool.
RE: pressurization with exhaust louvers
Willards,
Good idea to provide the fan with VFD, which is controlled by the pressure sensor inside the space.. In this project, the space is relatively big though, over 200,000 cubic ft, (with two levels open to each other). May need to provide several sensors and get some average reading...Any good suggestion?
Thanks again...
RE: pressurization with exhaust louvers
Depending on which direction the wind was blowing you could ensure that the 'least' differential pressure in the space is 0.1".
One other concern would be estimating the volume of air required. Search the site and you'll find several discussions about the difficulty in predicting the amount of air required to pressurize a building.
* It isn't that you can't make something foolproof, the problem is that they keep making better fools....*
RE: pressurization with exhaust louvers
0.1" (or 25-30Pa in my money) across the louvre is a very typical design figure for what were originally inlet louvres. Unless there is some specific requirement for the 0.1" to be maintained, I wouldn't worry about VFD controls. In the middle of a ww plant after all. Use the louvre manu design chart for reverse use - Inlet louvres usually have special rainwater channels and don't flow like exhaust louvres.
If you are worried about switchgear corrosion, enclose it and separately ventilate.
RE: pressurization with exhaust louvers
RE: pressurization with exhaust louvers