This is a typical older roof top unit.all the aspects of infrared are used with HVAC .This unit had too hot and too cold at the same time and energy loss and condensation problems.the HVAC tech doesn't need IR to troubleshhot problems but the customers sure like a visual explanation.The use for IR is imeasurable and endless.
I'm an Infraholic

Thats a great picture. I have run across the same thing with explanations. A picture really does say a 1000 words. Pretty much just hand them the picture and walk away.