How to Install a Split System Air Conditioner

Co-authored by Victor Belavus and Sophia Bell

Last Updated: October 27, 2024 Fact Checked

A split system air conditioner is a great option for keeping your home cool and comfortable in the summer months. These units are also quieter, easier to install, and more energy efficient than central air conditioning. This type of A/C is ductless, so all you have to do is install the cooling unit inside and the compressor and condenser unit outside, then run piping and a power cable between the units. If you don’t want to hire a professional to install a split system air conditioner and you have some experience with plumbing and electrical work, you can install the unit on your own. Each air conditioning unit is unique to its manufacturer, but the general installation process is the same.

Part 1

Part 1 of 3:

Setting up the Indoor Unit

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1
Select an unobstructed location on your interior wall to mount the indoor unit. You'll need to cut a hole through the wall to feed the pipes from the indoor unit to the outdoor unit, so make sure the location you choose will allow you to do so. Choose a spot away from direct sunlight and heat sources for the best results. Mount the unit 7 feet (2.1 m) off the floor and ensure there’s at least 6–12 inches (15–30 cm) of open space on every side of the unit to allow for proper airflow.^{[1]
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- Choose a location with studs to ensure the wall is strong enough to hold the weight of the unit.
- Install the unit at least 3.3 feet (1.0 m) away from antennas and power or connecting lines that are used for television, radio, home security systems, intercoms, or telephones. The electrical noise from these sources could cause operational problems for your air conditioner.
- Avoid locations where gas may leak or where oil mist or sulfur exists.
- Most of these units have remote controls so that you can easily turn them on or off and adjust the temperature even if they’re mounted high on the wall.
Tip: Choose a central location for the indoor unit where the cool air can easily flow through your home, such as in the living room.
2
Secure the mounting plate to the interior wall. Hold the mounting plate against the wall where you want to install the indoor unit. Use a level to make sure it is both horizontally and vertically level. Use a pencil to mark the locations of the screw holes, remove the plate, then drill a hole into the wall where each screw will go.
- Position the plate so it matches up with the holes, insert plastic anchors into the holes, and secure the plate to the wall with tapping screws.
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3
Drill a 3 in (7.6 cm) hole through the wall so you can feed the pipes outside. Make a mark in the center of the hole in the mounting plate. Use a keyhole saw or a drill with a hole-cutting attachment to create a circular 3 in (7.6 cm) opening through the wall that slopes slightly downward toward the ground to ensure adequate drainage.^{[2]
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- Make sure there are no pipes or wires behind the wall before drilling or cutting the hole.
Lift the A/C unit’s front panel and remove the cover. Make sure the cable wires are connected to the screw terminals and that the wiring matches the diagram that came with the unit.
5
Run the pipes and cables through the hole in the wall, then connect them to the unit. Secure the included copper pipes, power cable, and drain pipe together with electrical tape. Place the drain pipe on the bottom to ensure a free flow of water. Run the pipes and cable through the hole in the wall, then secure them to the designated spots on the indoor unit as directed by the instruction manual.
- Each line comes pre-insulated, so you don’t have to worry about adding extra insulation.
- Do your best to minimize how much the pipes and cable bend to ensure that the unit performs well.
- Make sure that the drainage pipe allows water to drain in an appropriate place. See the instruction manual included with your kit for more information.
6
Secure the indoor unit to the mounting plate. To attach the air conditioner to the wall, simply align the female connections on the back of the unit with the male connections on the mounting plate and press firmly to secure the unit in place. Make sure the unit tilts backward 2-3 degrees so that water can flow out of the drain pipe.^{[3]
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- It may help to have a friend hold the unit in place while you secure the connections.

Part 2

Part 2 of 3:

Installing the Outdoor Condenser

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1
Position the outdoor unit away from any heavily trafficked, dusty, or hot areas. Find the hole you drilled through the mounting plate for the interior unit and position the exterior unit within 50 feet (15 m) so the piping and cable can easily be attached.^{[4]
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Research source} Choose a location with at least 12 inches (30 cm) of space surrounding its perimeter to ensure proper functioning. If possible, select a shady location that’s sheltered from the wind in addition to dust and traffic to keep your unit functioning at its best.
- Make sure that no antenna of a radio or television is within 10 feet (3.0 m) of the outdoor condenser.
Don’t place the outdoor unit directly on the ground, as it’s heavy and can shift around on dirt or rocks. It’s necessary to install the condenser on a concrete pad, which you can find at home improvement stores. Position the pad where you want to install the unit and use a level to make sure it’s flat and even.^{[5]
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Tip: Situate the concrete pad so that it’s high enough to keep the unit out of any water that may puddle on the ground due to rain or snow.
Lay a rubber cushion on top of the pad to minimize vibration, then set the outdoor condenser unit on top of the pad. Secure the unit to the concrete with anchor bolts.^{[6]
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4
Check the electrical wiring in the outdoor unit. Remove the cover on the condenser. Refer to the unit’s wiring diagram in the instruction manual and make sure the wires are connected as the diagram suggests. Make any adjustments as necessary.
- Fasten the cables with a cable clamp and replace the cover.
5
Connect the piping and cable to the outdoor unit. Use flare nuts to secure the 2 copper pipes from the indoor unit to the outdoor unit as per the instruction manual. Connect the power cable that runs from the indoor unit to the outdoor unit as well.
- Finally, connect the power supply to a designated outlet.
- If necessary, you can trim the copper pipes to eliminate excess.

Part 3

Part 3 of 3:

Completing the Project

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1
Bleed the air and humidity from the refrigerant circuit. Remove the caps from the 2-way and 3-way valves and from the service port and connect a vacuum pump hose to the service port. Turn the vacuum on until it reaches an absolute vacuum of 10mm Hg. Close the low pressure knob and then turn off the vacuum.
- Test all of the valves and joints for leaks, then disconnect the vacuum. Replace the service port and caps.
To ensure the pipes and cables don’t move around or become disconnected, attach them to the exterior wall of your home using the clamps that came with the kit. Follow the directions in the manual to ensure the clamps are spaced adequately.
3
Seal up the hole in the wall using expanding polyurethane foam. Spray expanding polyurethane foam into the hole you drilled to feed the cable and piping through the wall. Make sure the hole is completely sealed to prevent hot air or insects from getting through.
- Let the foam dry as per the instructions on the label before turning on your air conditioning.
4
Turn on the unit and enjoy the cool air! All that’s left to do is to start the A/C, which you can do from the indoor unit. It should only take a minute or 2 for cool air to start blowing into your home.^{[7]
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- Refer to the instruction manual if you have any trouble operating your new air conditioner.

Expert Q&A

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Question

How should I maintain my AC unit?

Victor Belavus
Air Conditioning Specialist
Victor Belavus is an Air Conditioning Specialist and the Owner of 212 HVAC, an air condition repair and installation company based in Brooklyn, New York. In addition to HVAC and air conditioning units, Victor also specializes in furnace repair and air duct cleaning. He has over 10 years of experience working with HVAC systems.

Victor Belavus

Air Conditioning Specialist

Expert Answer

Most homeowners shouldn't do extensive maintenance themselves—hire a professional for that. However, you should be replacing your filters at least every 3 months, and inspect your outdoor condenser for any debris, as well. I would also recommend covering your AC condenser for the winter to protect it from snow.

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Since a split system AC is ductless, it's less susceptible to air leaks, which means it's often a more energy-efficient solution.^{[8]
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Victor Belavus
Air Conditioning Specialist

Expert Interview. 1 April 2020.}

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Make sure to choose the proper size air conditioner for your home to ensure it's energy efficient.^{[9]
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Victor Belavus
Air Conditioning Specialist

Expert Interview. 1 April 2020.}

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Check your outdoor condenser for debris and replace your air conditioner filter regularly—at least every 3 months.^{[10]
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Victor Belavus
Air Conditioning Specialist

Expert Interview. 1 April 2020.}

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Warnings

If you are based in the European Union, you must have your split system air conditioning unit installed by a qualified F-Gas engineer in accordance with EC/517/2014. It is illegal to install these systems without the appropriate qualifications.

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Do not allow any wiring to touch the compressor, refrigerant tubing, or any moving fan parts.

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If you live in a country where it is legal to install a split system air conditioning unit without professional qualifications, you must still follow all municipal codes for electrical wiring and other aspects of the installation.

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Some split system air conditioner manufacturers void the unit’s warranty if it is not installed by a licensed tradesman.

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