A:Answer Inside every refrigeration unit (i.e.: air conditioner) there is a compressor. The compressor circulates refrigerant and compresses it from a gas to a liquid continually. The compressor is lubricated by oil which sits in the bottom of the cylindrical can containing the compressor itself. If you install it in any other position than horizontal/flat, the oil inside that can will move to a position where it will do no good. Also, the liquid refrigerant in the evaporator (the "radiator of cold") will not flow correctly.
In short, you will bring the unit back to the store because it "stopped working" within a few days--if not hours. Try one of those indoor coolers with the plastic duct that hangs out the window. That should work better for a vertical application.
