While wall air conditioning units vent the warm air only through the back of the unit, the window air conditioners vent through the back and sides. So if we try to fit them in the walls, the side vents would be blocked by the walls and cause overheating of the unit. So mostly, the two types of AC AC, A.C. or Ac may refer to: Air conditioning, technologies for altering the temperature and humidity of air; Alternating current, a type of electrical current in which the current repeatedly changes direction. " data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]">ac units are not interchangeable. However, select window ACs can be fitted in the walls only if they have a slide-out chassis wall sleeve.