In window AC installation, first the outer case is securely fixed in the window with the help of screws. The inner unit of window AC is then firmly fixed inside the outer case with the help of screws. After the inner unit of window AC is properly fixed in the outer case, the window AC is switched on to check if it is starts properly. Then the front screen or the cover is gently fixed on the inner unit. Finally the air filter of window AC is inserted in place and the front cover is closed.