Hi,

I have several AHU's that serve a big office building. On the propose building, some of these AHU's have installed MERV 9 + MERV 13 and the others are installed with MERV 13 for both outdoor air and supply air.

My doubt is whether to account for both the filters for pressure drop adjustment in the baseline case.

Example:
Am I to account for 125 Pa (MERV 9) + 225 Pa (MERV13) for the first type and 225 Pa x 2 (2 x MERV 13) for the second? Or should I only consider 1 x 225 Pa (1 x MERV 13, being the most demanding filter) per AHU?

I know that the "A" is calculated based on pressure drop adjustment and air flow that actually goes through the device. The real issue is whether to account for 2 or only 1 MERV filter per AHU.

Please advise!

Thank you in advance!