Can Mini Split Lines Run Up: A Comprehensive Guide

Mini split systems have become increasingly popular in recent years due to their energy efficiency, flexibility, and ease of installation. One common question that arises is whether the refrigerant and condensate lines can be run up and inside the walls. In this comprehensive guide, we will explore the technical details, best practices, and critical considerations for running mini split lines up and within the walls.

Avoiding Oil Build-up and Proper Line Positioning

As mentioned in the initial answer, it is crucial to avoid coiling or leaving the mini split lines in a vertical position, as this can lead to oil build-up and negatively impact the system’s performance. Instead, the lines should be laid horizontally to prevent oil accumulation.

When running the line set up above the indoor unit, even a couple of feet, the same problem can occur. To mitigate this, it is recommended to cut the lines to the exact length required and avoid any unnecessary coiling or vertical positioning.

Protecting Insulation and Preventing Condensation

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When running the mini split lines inside the walls, it is essential to ensure that the insulation surrounding the lines is not damaged. Damage to the insulation can lead to condensation, which can cause water damage and other issues.

To prevent this, the installer should take great care when routing the lines through the wall cavities. They should use protective sleeves or conduits to shield the insulation and maintain its integrity. Additionally, the lines should be secured in place to prevent any movement or shifting that could compromise the insulation.

Avoiding Low Spots and Ensuring Proper Drainage

Another critical consideration when running mini split lines up and inside the walls is the avoidance of low spots. Low spots in the line set can trap condensed refrigerant oil, which can negatively impact the system’s performance and efficiency.

To prevent this, the lines should be installed with a slight upward slope, ensuring that any condensate can drain back to the outdoor unit. If necessary, the use of a condensate pump may be required to ensure proper drainage, especially in cases where the lines are run horizontally within the building.

Technical Specifications and Manufacturer Guidelines

The mini split line set typically consists of two copper pipes: a larger diameter pipe for the refrigerant and a smaller diameter pipe for the condensate drain. The specific dimensions of these pipes will vary depending on the make and model of the mini split system, as well as the distance between the indoor and outdoor units.

It is crucial to consult the manufacturer’s instructions and guidelines for the proper line set specifications, including the recommended pipe diameter, length, and lift. Failure to follow these guidelines can lead to issues with system performance, efficiency, and even potential safety concerns.

Tools and Equipment for Running Mini Split Lines

To successfully run mini split lines up and inside the walls, installers will need a variety of tools and equipment, including:

  • Copper tubing cutter
  • Flaring tool
  • Refrigerant manifold and gauges
  • Vacuum pump
  • Torque wrench
  • Insulation sleeves or conduits
  • Mounting brackets and fasteners
  • Sealants and adhesives

It is important to ensure that all tools and equipment are properly maintained and calibrated to ensure a successful and safe installation.

Step-by-Step Guide for Running Mini Split Lines Up

  1. Carefully measure the distance between the indoor and outdoor units, and determine the required line set length.
  2. Cut the copper tubing to the appropriate length, ensuring that there are no low spots or unnecessary coils.
  3. Use the flaring tool to create flared ends on the copper tubing, allowing for a secure connection to the mini split system.
  4. Insulate the refrigerant and condensate lines using the appropriate insulation sleeves or conduits.
  5. Secure the insulated lines to the wall using mounting brackets and fasteners, ensuring a slight upward slope for proper drainage.
  6. Carefully route the lines through the wall cavities, taking care not to damage the surrounding insulation.
  7. Connect the lines to the indoor and outdoor units, following the manufacturer’s instructions for proper torque and sealing.
  8. Perform a thorough leak test and vacuum the system to remove any air or moisture.
  9. Charge the system with the appropriate refrigerant, again following the manufacturer’s guidelines.
  10. Test the system’s operation and make any necessary adjustments to ensure optimal performance.


Running mini split lines up and inside the walls is a viable option, but it requires careful planning, attention to detail, and adherence to manufacturer guidelines. By following the best practices and technical specifications outlined in this guide, DIY enthusiasts and professional installers can successfully navigate the process and ensure a safe, efficient, and long-lasting mini split system installation.