Casement Window Air Conditioner Installation

The installation of an air conditioner for a casement window is similar to installing one for a double hung window. However, there are specific steps that are unique to this type of air conditioner.  Because of the shape of the window, these units are also called vertical window air conditioners and are taller than the typical window air conditioners.  In this article, we will discuss how to install an air conditioner window unit for a casement window or a sliding window.

How to Install a Casement Window Air Conditioner

The instructions below are for a typical slide-by window made of wood or a metal casement window. You may need to make modifications if installing in a different type of window other than the ones referred to here. Also, be aware of your city or state’s codes for electricity. Keep in mind that you may need a professional electrician to determine if you have the proper grounding for the air conditioner.

casement window air conditioner

Casement Window Air Conditioner

Preparing for Installation

If installing on a wood-frame casement window, there may be a need to build a wood frame using at least 1-inch (2.54 cm) thick wood, with a 15-1/2-inch (39.37 cm) wide opening. For mounting purposes, if the material is brick or cement, it may be necessary to put a wood stool strip under the air conditioner. 

Tools Required

Flat-head screwdriver

Phillips-head screwdriver

Carpenter’s level

Tape measure

Fine tooth saw

Electric or hand drill

Knife and scissors


Because the unit weights between 88 (39.92 kg) to 105 (47.63 kg) pounds, it is recommended that you have someone help you with the installation. Also, be sure to inspect the condition of the window to ensure that it can hold the weight of the unit. 

When selecting a location for the air conditioner, keep in mind that corners do not allow air to flow properly, so a centralized location is recommended. Typically, the casement window must be at most 16 ¼ inches wide (41.27 cm) and at least 21 ¼ in in height (53.97 cm) with a maximum height of 39 7/16 in. (100.2 cm). Please refer to your owner’s manual for specific dimensions for your unit. Also, the window must be within 6 ft (1.83 m) of an electrical outlet. You should not use an extension chord.

After selecting the window for the unit, you will need to find the proper location for the support base.

When installing an air conditioner in a sliding casement window, you also have to install a support bracket on the outside wall that braces the outer part of the unit. To prevent damage to the outside wall, you may want to use a siding protection board, which needs to be long enough to span 2 wall studs.

The following steps will explain how to install the air conditioner on the slide-by window:

  1. Attach the support brace platform. There should be a 45° angle between the support brace and the platform. There should also be a slope of 3/16 of an inch (0.4762 cm) on the platform to allow for proper condensation drainage. 

    Casement Window Air Conditioner Support Platform

    Casement Window Air Conditioner Support Platform

  2. Measure and mark a line 8-11/16 in from the window jam. This will be used as a marker for the support platform.

  3. Install the support platform assembly. You will drill holes in the window frame that correspond to the holes in the platform. Refer to owner’s manual for specifics.

  4. Your unit should include a track seal that is placed on the room side of the window track. Install the track seal. If installed correctly, the two holes drilled in step 3 should be directly the seal strip in the inner track.

  5. If using a siding-protection board, install to the side of the outer wall of the home.

  6. With platform tab against the inside of the window track, attach the support platform assembly to the window jam.

  7. Adjust the platform so that the outside edge is 3/16 inch (0.4762 cm) lower that the inside edge.

  8. Level the platform so that it is balanced from side to side.

  9. Measure the height of the window opening and subtract the height of your AC Unit. This will be used to cut the window frame included with the unit.

  10. If your unit includes an additional decorative frame, cut to specified height measured in step 9.

  11. Attach support side panels to AC unit using included screws.

  12. If your unit includes a plastic window panel, cut to match the plastic window frame prepared in step 10.

  13. Slide plastic window panel into window frame with smooth side facing the interior of the room.

  14. Attach the window panel and frame to the air conditioner. Add any weather stripping included to the side of the AC and plastic frame.

  15. Remove the front assembly of the unit. Take care not to push or pull the direction louvers.

  16. Now, place the casement air conditioner in the window opening. It should fit into the window opening so that the side channels and window panel frame are against the side and top window jams.

  17. Slide the window sash against the side of the air conditioner. It should fit snugly against the AC. If it does not, you many need to use screws to attach the panel frames to the sash. (Refer to your owner’s manual).

  18. To secure the unit, attach the safety bracket over the base of the air conditioner and attach to the from of the support platform. This will prevent the unit from moving.

  19. Insert the foam seal strip/sash between the window glass and the vertical sash.

  20. Install the locking bracket to the inner window sash to the base of the outer window sash.

  21. Replace the front cover. Again, take care not to push or pull the front panel louvers.

The above instructions can be adjusted based on the size of your window. Please refer to your owner’s manual for specific details regarding your unit.  

Posted in Casement Window Air Conditioner Installation, Window Air Conditioner Installation.

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