The DIY Guide on How to Install a Mini Split

Installing a mini split system yourself can be a rewarding project that saves you money and gives you greater control over your home's comfort. That being said, choosing the right location for both the indoor and outdoor units is key to performance and efficiency. In this guide, we’ll walk you through how to select the best spots for installation and break down the essential steps to properly mount and connect your mini split system. Let’s dive in and get your space feeling just right.

How to Pick the Location

Choosing the right location indoor and outdoor for your ductless mini-split system is essential to maximize efficiency, performance, and longevity. Proper placement ensures optimal airflow, minimal energy loss, and easier maintenance.

Indoor Unit Placement

When selecting a location for your indoor unit, aim for both functionality and efficiency:

• Wide Coverage: Pick a position for the unit so that it can blow air freely across the largest open area. Avoid corners or dead zones where airflow may be blocked.
• Accessible Location: Choose a spot that’s easy to reach for routine maintenance, such as cleaning filters or checking settings.
• Unobstructed Airflow: Ensure the area around the unit is clear of furniture, curtains, or other obstacles. Good airflow is critical to efficient heating and cooling.
• Pro Tip: Installing the unit higher on the wall helps cool or heat the room more evenly, as air naturally circulates downward.

Outdoor Unit Placement

The outdoor compressor unit requires careful placement to ensure safety, performance, and durability:

• Check Distance and Line Limits: Place the outdoor unit within the allowable distance for the refrigerant lines and electrical cables to reach the indoor unit without exceeding manufacturer limits.
• Keep It Unobstructed: Avoid placing the unit near walls, fences, plants, or other objects that could block airflow. Leave at least 12–24 inches of clearance on all sides.
• Solid, Safe Foundation: Install the unit on a stable, level base—like a concrete pad or wall bracket—that provides good drainage and vibration control.
• Ensure Proper Grounding: Make sure the mounting surface is grounded and secure to prevent safety risks and equipment damage.
• Pro Tip: Avoid placing the outdoor unit where it’s exposed to direct sun all day or where snow and ice can fall from the roof onto it.
• Quick Check: Make sure the outdoor unit isn’t exposed to direct sunlight all day or vulnerable to falling ice/snow from a roof above. Partial shade and weather protection can extend its life.

Installation Steps

Installing a ductless mini-split system requires precision, preparation, and attention to detail. Below is a step-by-step guide covering both indoor and outdoor unit installation. Whether you're doing it yourself or supervising a professional, understanding the process helps ensure everything is done correctly.
 

Indoor Unit Installation

Choose the Best Location

• Select a central spot on an exterior wall where airflow can reach the most area in the room.
• Avoid placing the unit near heat sources, direct sunlight, or high-traffic areas.
• Ensure there's at least 6 inches of clearance above the unit and 12 inches to each side for proper air circulation.
  
  

Check Wall Integrity and Locate Studs

• Use a stud finder to locate secure anchor points for the mounting bracket.
• The wall must support the unit’s weight. If it's drywall or plaster, anchor into studs or use wall anchors rated for the load.
  

Install the Mounting Bracket

• Mark and level the mounting bracket according to the manufacturer’s template.
• Secure it firmly into studs using the provided screws and anchors.
• Double-check that it’s perfectly level to ensure condensate drains correctly.

Drill the Wall Hole

• Drill a 2.5"–3" hole through the wall at a slight downward angle (typically 5–10°) from inside to outside.
• This hole will carry the refrigerant lines, electrical cables, and drain hose to the outdoor unit.
  

Prepare and Route Line Set, Wiring, and Drain Hose

• Bundle the refrigerant line set, electrical wires, and drain hose together using tape or insulation wrap.
• Carefully feed the bundle through the wall hole.
• Ensure the drain hose runs downhill the entire way to prevent water backup.

Connect the Line Set and Wiring

• Use a torque wrench to tighten flare nuts on the refrigerant lines to manufacturer specifications.
• Connect the control wire to the terminal block inside the indoor unit following the color-coded diagram in the manual.

Secure the Drain Hose

• Route the drain hose to a proper discharge point. Avoid kinks, loops, or upward slopes.
• If necessary, use a condensate pump for vertical drainage.

Mount the Indoor Unit

• Lift the unit onto the mounting bracket, making sure the hooks align and the unit locks into place.
• Ensure the unit is level and stable.

Test Fit and Insulate Connections (Optional for DIY)

•  If you're not connecting refrigerant lines yourself, a technician will do this later.

 

Outdoor Unit Installation

Choose an Appropriate Location

• The outdoor unit should be within the manufacturer’s maximum and minimum line length from the indoor unit.
• Avoid direct sunlight, snow accumulation zones, or areas under dripping roofs.
• Ensure a minimum of 12–24 inches of clearance around the unit for airflow and maintenance access.
  

Prepare a Solid Base or Mount

• Install a concrete pad, paver base, or wall bracket that is level and stable.
• Use anti-vibration pads or rubber feet to reduce noise and movement.

Mount the Outdoor Unit

• Position the unit on the prepared surface or bracket.
• Secure it with bolts or mounting screws, ensuring it's level and clear of obstructions.

Connect Refrigerant Lines

• Carefully uncoil and route the line set from the indoor unit.
• Remove caps, align the flare fittings, and use a torque wrench to tighten them to spec.
• Use pipe insulation and weatherproof tape to wrap exposed lines.

Connect Electrical Wiring

• Open the service panel and connect the power and communication cables from the indoor unit according to the wiring diagram.
• Connect the power supply (typically 240V) from the disconnect box, ensuring the breaker is off during work.
• Use proper wire gauges and conduit as required by local electrical code.

Ensure Proper Drainage

• Check the slope of the surface and ensure water can drain away from the base.
• If using a mounting bracket, make sure it doesn’t block water flow or cause pooling.

Vacuum and Charge the System (Pro Required)

• A professional HVAC technician must connect a vacuum pump to the service ports to evacuate air and moisture from the refrigerant lines.
• Once vacuumed, the system is either charged with refrigerant from the unit’s pre-charged lines or manually charged to the correct level.

 

System Start-Up and Test

Once all connections are secure and power is restored, turn on the system and monitor for:

• Proper startup of both units
• Quiet operation and no unusual sounds
• Good airflow and temperature control
• No refrigerant or condensate leaks

 

One last word of advice
If you feel lost at some point during the process, don’t hesitate to outsource some of the steps, especially when it comes to electrical components. Make sure to leave the refrigerant balancing to a professional as it can affect the warranty and the overall performance of the unit. 

Remember: refrigerant balancing isn’t a DIY step—leave it to the pros to keep your system running safely and efficiently.

On that note, we hope you enjoy your new mini split for the years to come!