[Hugh R]

Wayne, certainly no expert here, but if your pulling already cooled air in, you compressor works less. Icing up is on the evaporator occurs from a less than 32 degree temp at the evaporator. Cooler air has less moisture than warm air. So less moisture from cooled air = less icing. One of the ways A/C works best is to recirculate already cooled air. The question is "Is the air from the server room warmer than the air outside?" Given where you are located, you should have a "smart" system that will pull makeup air from the coolest place. Winter outdoors, summer maybe from the server room.