these are mechanical A/C units usually an Air Handler Unit (AHU) or a Condensing Unit (CU) that are usually about 10.0'x7.5'x5.5'?
1. Should they be treated as an enclosed box and apply load on the windward, leeward and roof side of it?
2. Should it be treated as a sign structure with positive wind pressure on the windward side only?
I usually use option #1 but I have seen #2 being used. I would like to know if I am over designing here.