Best approach to provide Coil Protection would be to install equipment protection pre-filters (commonly called cottonwood filters, air intake screens, coil filters rooftop unit filters) directly over the front and back coil and extending down to the top of the roofing curb. One end would require an air intake screen over the bottom and extending down to the roof while the control panel end would require an air intake screen below the chiller base rail and extending down to the roof deck. Recommended grade of filter is the HD Commercial Grade with quick release twist lock fasteners.