Change of fan in HVAC system

[Ryeep]

Hello. We have an HVAC system originally aimed for thermal comfort only, and would like to use it for rooms that require HEPA filters.
The original fan is not suited for the higher static pressure required, so the idea is to install a limit-load in its place.
My question is: if I maintain the same flow through the evaporator (different operation point, higher static pressure), should I have any other worries concerning the system performance/integrity? Apart from noise.

 

[moideen]

what is the evaporator operating point? if it is higher, i thing, it may not affect the system performance. but you should modify the electrical side according to the high static fan.

 

[willard3]

Horsepower of the fan will increase if the pressure increases

 

[Ryeep]

Operating point stays the same, we are swapping only the fan for the higher static. About the electrical requirements, we are also redoing all the power supply, so I guess that's covered.
Might be trivial, but my concern was if the higher static pressure could, somehow, damage the coil or submit the AHU structure to more stress (maintaining the flow).

 

[willard3]

You might check the poressure rating of the ductwork and air handling unit, I don't think you'll effect the coil.

 

[GT-EGR]

If all else is staying the same except for adding the additional pressure drop at the end of all runs via HEPA filters - the only issue you will have is due to the increased static pressure downstream of the fan. So this will increase duct leakage out of the ductwork and AHU (may not be significant if it was sealed well to begin with), and if your duct or AHU casing isn’t rated at the new pressure it may deflect their shape. The coils will be fine, but you may have some existing pressure control components in your AHU or ductwork that now don’t work in your new increased pressure range. Depending on the new fan you get it may change the sound profile coming out of your unit. As discussed previously you’ll also need more power.

 

[SAK9]

What you need are Fan Filter Units ie. HEPA filter unit with its own integral fan.Then you would not need to upgrade your AHU fan

https://www.terrauniversal.com/cleanrooms/clean-rooms-fan-filter-units.php

 

[Ryeep]

Thank you all very much for the input, it was of great help.

 

[chicopee]

Using the fan performance curve (Static pressure vs CFM), the(HP vs CFM)curve and the upgraded system characteristic curve that include the HEPA filters pressure drop, and AC specifications, you can make a decent educated guess into the electrical requirement, duct size and AC equipment adequacy.