How To Install a Mini-Split Air Conditioner

Installing a mini-split air conditioner can significantly improve your home’s comfort and energy efficiency. These versatile systems offer cooling and heating without requiring ductwork installation, making them an excellent choice for many homeowners. In this article, we’ll guide you through the installation process, from selecting the right location to making the final connections. This Old House plumbing and heating expert Richard Trethewey shows the key steps for installing a mini-split air conditioner in the video above.

Choosing the Right Location for a Mini-Split Air Conditioner

The right placement of both indoor and outdoor units determines the performance and efficiency of your mini-split system.

Outdoor Unit Placement

When selecting a location for the outdoor condenser unit, consider the following factors:

• Adequate airflow: Give it at least 12 inches of clearance on all sides of the unit.
• Accessibility: Choose a spot that allows for easy maintenance and repairs.
• Noise considerations: Place the unit away from bedrooms or quiet areas of your home.
• Protection from the elements: Install the unit on a level surface, preferably on a concrete pad.

Indoor Unit Placement

Install the indoor air handler in a location that maximizes cooling efficiency. If possible, choose an exterior wall for easy connection to the outdoor unit. That said, you can install it on an interior wall by snaking the cables and tubing under the floor joists and up a wall cavity, as Trethewey does in the video.

Place the unit high on the wall for optimal air distribution. Avoid placing the unit near heat sources or in direct sunlight. Don’t forget to give it enough space for proper airflow and maintenance access.

Preparing for Air Conditioner Installation

Before beginning the installation process, gather all necessary tools and materials and prepare for a safe installation.

Tools and Materials Needed

• Concrete pad for outdoor unit (if not already in place)
• Drill/driver with a 1-1/2-inch hole saw bit
• Drywall saw
• Electrical wiring
• Hammer
• Indoor and outdoor mini-split units
• Level
• Mounting bracket for indoor unit
• Pliers
• PVC pipe and fittings for drainage
• Refrigerant line set
• Wire stripper

Safety Precautions

Installing a mini-split air conditioner involves working with electricity and refrigerants, so safety should be a top priority. Follow these precautions:

• Turn off power to the area where you’ll be working.
• Wear appropriate personal protective equipment, including gloves and safety glasses.
• Follow all local building codes and obtain necessary permits.
• If you’re not comfortable with any aspect of the installation, hire a professional HVAC technician.

Installing the Outdoor Air Conditioner Unit

The first step in the installation process is setting up the outdoor condenser unit. This component is responsible for releasing heat from the refrigerant that it removes from the inside of your home.

1. Place the concrete pad on level ground, ensuring it’s stable and even.
2. Set the condenser unit on top of the pad, checking for level placement.
3. Secure the unit to the pad according to the manufacturer’s instructions.

Running the Refrigerant Lines for the Mini-Split Air Conditioner

Connecting the indoor and outdoor units requires running refrigerant lines through your home’s exterior wall. Here’s how.

1. Use a 1-1/2-inch hole saw to drill through the exterior wall where the lines will enter the house.
2. Feed the refrigerant line set through the hole and into the building.
3. Run the lines from the outdoor unit to the location of the indoor unit, typically through the basement or crawl space.

Installing the Indoor Air Conditioner Unit

With the outdoor unit in place and the lines run, it’s time to install the indoor air handler. Installing the indoor unit involves more than just connecting the lines—it also means securely mounting the unit to the wall. Prepare the wall where you’ll install the indoor unit by checking that it’s solid and free of obstructions. This prevents any potential issues later.

Screw the metal mounting bracket to the wall at the manufacturer’s recommended height. Then, mount the bracket on the wall, using a level to get it straight. This will facilitate easier installation of the indoor unit and let the condensate drain properly. Attach the indoor unit to the bracket by aligning it carefully, making sure it clicks or locks into place. This keeps it secure and allows it to operate without creating undue noise or vibration.

Making the Connections for Your Mini-Split Air Conditioner

The final step involves connecting all the components of your mini-split system.

1. Connect the refrigerant lines from the outdoor unit to the indoor unit. Check that all connections are tight and properly insulated to prevent leaks.
2. Assemble the PVC drain line according to local codes.
3. Run the drain line from the indoor unit to an appropriate drainage point outside your home.
4. Pull electrical cable and low-voltage wire from the condenser to the indoor unit.
5. Make all necessary electrical connections according to the manufacturer’s instructions and local electrical codes.

Testing and Finishing Up Your Air Conditioner Installation

Once you make all the connections, it’s time to test the system and complete the installation.

1. Turn on the power to the mini-split system.
2. Test the unit and check that it’s functioning properly and cooling effectively.
3. Install the air conditioner’s cover to complete the indoor unit installation.
4. Clean up the work area and dispose of any debris properly.

Air Conditioner Maintenance Tips

Perform regular maintenance to keep your mini-split air conditioner running efficiently. Clean or replace air filters monthly during peak usage. Keep the outdoor unit free from debris and vegetation and schedule annual HVAC maintenance to maintain optimal performance.

Our Conclusion

Installing a mini-split air conditioner can be a rewarding DIY project for experienced homeowners. However, it requires careful planning, attention to detail, and a good understanding of HVAC systems. If you’re unsure about any aspect of the installation, consult an HVAC contractor to safely and efficiently install your system.

Learn More: Ductless Mini-Split Pro Installation Steps