How to Install a Mini-Split AC Heat Pump

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Mini-split HVAC systems offer a convenient way to heat and cool a space while avoiding significant ductwork. For this reason, they’re a popular HVAC solution for many businesses and homeowners. However, the process of installing a mini-split is complicated for most people to install on their own, and requires an HVAC technician’s help. While it’s a fairly easy process for a certified technician, there are some key steps that need to be followed when installing these systems. Learn how to correctly install a mini-split AC and heat pump system with our guide below.

Installation Prep

Before you begin the installation, you need to make sure that the right unit and supplies are at-the-ready. This can take some preparation prior to the installation of the actual mini split unit. Here are some key preparation items that need to be checked:

Condenser—A condenser is required for the installation of a mini-split unit. If one isn’t present on the property, it will also need to be installed.
Electrical Power—A mini-split unit requires its own circuit to be powered. Check that there is sufficient power on the property before installation. If not, a dedicated disconnect box may need to be installed. Depending on your training and the installation booking, you may be tasked with performing this installation.
Proper Condensate Drainage—This is crucial for long term performance of the mini-split unit. Additional installation of a drainage system may be required.
Refrigerant—Refrigerant lines and charged refrigerant are required for a mini-split. Have these present and ready to go for a mini-split installation.

Choosing an Installation Location

You will need to choose two location spots to install a mini-split HVAC system: one indoor and one outdoor (if a condensing unit needs to be installed). The location for this system is crucial, so make sure to take these tips into consideration:

Indoor Unit

The indoor air handler needs to be mounted on an exterior or perimeter wall
Allow 6-7 feet of space between the bottom of the unit to the floor
The space also needs to be large enough to accommodate the air handler unit
Avoid direct sunlight and heat sources

Outdoor Unit

Choose a level, flat surface that will provide adequate airflow to the condenser (at least 4” of clearance behind the unit and 20” above and in front of it)
Avoid an area that have considerable debris accumulation
The area needs to be free from direct sunlight
If installing in a snowy climate, a platform may need to be installed to keep the condenser off the ground

Indoor Unit Installation

Step 1—Locate wall studs to use for installing the mounting brackets into.
Step 2—Install the mounting brackets into the wall studs with appropriate fasteners, making sure they’re level.
- NOTE—If a wall stud cannot be found for the mounting location, use hollow wall anchors that are appropriate for the wall’s material.
Step 3—Drill a hole around 2-3” in diameter through the wall at a slight downward angle. This will be used to feed the electrical cables, refrigerant lines and condensate drain through.
Step 4—Drill another hole to provide an exit to the exterior of the property that’s angled slightly downward. This will allow you to connect the various lines and cables to the condensing unit outside.
Step 5—Run all refrigerant lines, power cords and drain through the holes to the outside. Have an assistant on the outside to take these lines and ready to connect them to the condenser unit.
Step 6—Mount the air handling unit of the mini-split system to the bracket. Depending on the size of the unit, you may need assistance from another technician. Secure the air handler onto the mounting bracket.

Outdoor Unit Installation

Step 1—Install a platform or wall brackets for the condensing unit, depending on the type of unit itself.
Step 2—Mount the condenser on its appropriate platform.
Step 3—Connect all the refrigerant lines, power cords and drainage to the condenser unit.
Step 4—Once connected, secure the lines and cables to the wall next to the condenser. Use covers to protect them from the elements.
Step 5—If needed, install a disconnect box near the condensing unit.

Post-Installation Testing & Charging

After installing the mini-split system, it’s vital that you perform certain tests to check that the system is working as it should.

Charge Refrigerant—Charge the refrigerant through the system, making sure to follow all manufacturer specifications.
Check for Leaks—Using a vacuum pump and gauge manifold, check for any leaks that may be present. This also removes moisture from the lines.

Test System Operation—Turn on the mini-split system and check that it’s operating correctly. Change heating and cooling settings and check for any possible issues.

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