HEPA Filters..

[Badbird2000]

Ok guys, i need to design some new HEPA filters into an existing duct system. Having trouble finding information on what size filter box i would need. My existing supply ductwork is 30x22 and carries 5,000 cfm. Also, i need to determine what the static pressure drop will be, because i am pretty sure the existing fan in the rooftop unit won't cover it.

I love Fridays....

 

[cdxx139]

Talk to the manufacturer.

I believe they require a certain velocity (500 fpm?), which will increase your velocity to enter the box, then after the box you can decrease back to the existing ductwork.

This adds static to the system, maybe at least an inch, and most systems do not have an extra inch lying around, you may also need to replace the fan.

If you are adding a HEPA to the system, it may be prudent to clean the ductwork first.

knowledge is power

 

[ChasBean1]

Keep standard sizes. Standard size is 24" by 24" by 12" deep filters. The duct should flare (at no more than a 30° angle) to a 48" x 48" enclosure to house 4 filters. The velocity would be 313 fpm, which is well below the typically accepted limit of 500 fpm.

 

[MechEngNCPE]

300 FPM is ideal for typical 12" HEPAs