'Trane with Power Ehaust' found this in Missouri~ (not one of our customer's) I just wonder what the pressure issue was and what they were trying to achieve... do they want it in negative pressure? I don't know, I wouldn't touch their machine, maybe they're running it with the O.A. damper open 100percent??? Sure catches your eye though
Are you sure it wasn't just an exhaust fan that may have been ducted elsewhere? Seems like a mall that this store was in, consider that this store is open to mall during operating hours. Who knows...overkill if just used for power exhaust on such a small RTU.