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How to Install a Window AC Unit in a Horizontal Sliding Window


If you’re looking for a way to beat the heat this summer without breaking the bank, then installing a window AC unit in a horizontal sliding window may be the way to go. 

Assuming you’ve already measured your window and know what size air conditioner you need, installing the unit is actually pretty straightforward. 

If you haven’t yet, it’s a fairly easy process that anyone can do. Just follow the steps below and you’ll have cool air circulating in no time!

Measure the Window Opening

window AC unit

Before you purchase a window AC unit, you’ll need to measure the window opening to ensure that the unit will fit. Once you know the dimensions of the window, you can narrow down your choices and select a unit that will fit comfortably. 

To measure the window, start by measuring the width at the top, middle and bottom. Then, measure the height at the left, middle and right. Use the smallest width and height measurements to find a unit that will fit comfortably. 

If possible, it’s also a good idea to measure the depth of the window sill. This will give you an idea of how much space you have to work with and whether you need to install accordion-style side panels. 

Once you have the measurements of the window, you can start shopping for an air conditioner.

Choosing a Window AC Unit With the Proper BTUs

When choosing a window AC unit, it’s important to select one with the proper BTUs for the square footage of the room. Most units will have an energy efficiency rating (EER) that can help you determine the appropriate BTUs for your needs. Generally speaking, you’ll want 20 BTUs for every square foot of living space. 

If you’re unsure of the square footage of the room, you can measure it by multiplying the length and width of the room by feet. For example, if the room is 10 feet wide by 12 feet long, the square footage would be 120. Therefore, you would need a unit with at least 2,400 BTUs. 

It’s also important to consider the ceiling height of the room when selecting a unit. For every foot above 8 feet, you’ll need to add 600 BTUs. So, if the ceiling in the room is 9 feet, you would need to add 600 BTUs to the 2,400 BTUs, for a total of 3,000 BTUs. 

Finally, you’ll need to take into account any heat-generating appliances in the room, such as a TV or space heater. For every 100 watts of power these appliances use, you’ll need to add an additional 40 BTUs. Knowing these will help you save more money and electricity while using a window AC unit.

Install Accordion-Style Side Panels

Accordion-style side panels are available for most window AC units and can be installed if necessary. To install the side panels, first, remove the front grille of the unit. Then, insert the side panels into the slots on the sides of the unit. 

Be sure that the side panels are properly aligned before pushing them all the way in. Finally, replace the front grille.

Position and Secure the AC Unit

Now, it’s time to secure the unit in place. Most units come with a bracket that you can screw into the window frame.

In order to secure the window AC unit, you will need to screw the provided bracket into the window frame. Begin by lining up the bracket with the holes in the window frame. If necessary, use a drill to create pilot holes in the frame. 

Once the bracket is in place, use screws to secure it to the frame. Be sure to use screws that are long enough to penetrate the frame and reach the bracket, but not so long that they protrude out the other side of the frame.

Plug It In

Now that the air conditioner is installed, it’s time to plug it in and turn it on. Make sure that the exhaust hose is not kinked or blocked in any way, as this could cause the unit to overheat and shut down. Also, be sure to check the manufacturer’s instructions to see if there are any special considerations for your particular model.

Once the unit is plugged in and turned on, you should feel cool air coming from the vents. If the unit doesn’t seem to be cooling the room properly, check the thermostat to make sure it is set to the correct temperature. Also, be sure to check the air filter and clean or replace it if necessary.

Final Thoughts

In conclusion, installing a window AC unit in a horizontal sliding window is not difficult, but there are a few things you need to do to ensure that it is done correctly. 

First, measure the window opening to make sure that the unit will fit. Then, choose a window AC unit with the proper BTUs for the square footage of the room. Next up is installing the accordion-style side panels that come with the unit, if necessary. 

Afterward, lift the AC unit into the window opening and position it so that the exhaust hose is facing outside. Once that’s done, simply secure the unit in place by screwing the provided bracket into the window frame. 

Finally, plug in the unit and turn it on, making sure that the exhaust hose is not kinked or blocked in any way. And with that, you now have a brand new window AC unit to keep you cool!

JP Reyes

JP has been in the aircon industry for almost as long as he has been alive. As a child JP would help his tatay fix aircon units at their junk shop in Cavite. After graduating UP in the early 2000's, JP then started his own Aircon servicing business and within 5 years had 10 shops in 8 different cities. Fast forward to today and JP brings all his experience and expertise online to give readers trustworthy advice and reviews about Air-conditioning buying, servicing, cleaning and repair in the Philippines.

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