How Far Can You Run a Mini Split Line: A Comprehensive Guide for DIY Enthusiasts

A mini split line, also known as a line set, is a crucial component of a mini split air conditioning or heating system, connecting the indoor and outdoor units. The length of this line can significantly impact the system’s performance and efficiency. In this comprehensive guide, we will delve into the technical details and provide expert-level insights on how far you can run a mini split line, catering to the needs of DIY enthusiasts.

Understanding Mini Split Line Length Limitations

The maximum length of a mini split line can vary depending on the brand and model of the system. Most manufacturers recommend a maximum line length of around 100 feet, with some exceptions like Mitsubishi and Fujitsu, which may allow for longer line lengths of up to 200 feet or more.

It’s important to note that running a mini split line beyond the manufacturer’s recommended length can have several implications:

  1. Refrigerant Charge Adjustment: Longer line sets may require additional refrigerant to be added to the system, as the efficiency of the system can decrease with longer lines.
  2. System Performance: Exceeding the recommended line length can impact the system’s overall performance, potentially leading to reduced cooling or heating capacity, decreased energy efficiency, and increased operating costs.
  3. Warranty Implications: Running a mini split line beyond the manufacturer’s specifications may void the system’s warranty, so it’s crucial to adhere to the guidelines provided by the manufacturer.

Factors to Consider When Determining Line Length

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When planning the installation of a mini split system, several factors should be taken into account to determine the appropriate line length:

  1. Manufacturer Recommendations: Always refer to the specific guidelines provided by the manufacturer of your mini split system. These recommendations are based on extensive testing and engineering to ensure optimal performance and reliability.
  2. System Capacity: The capacity of the mini split system, measured in BTUs (British Thermal Units), can influence the recommended line length. Larger capacity systems may have more flexibility in terms of line length.
  3. Elevation Changes: If the indoor and outdoor units are installed at different elevations, the line length may need to be adjusted to account for the vertical distance between them.
  4. Ambient Conditions: Environmental factors, such as temperature and humidity, can impact the performance of the mini split system and may require adjustments to the line length.
  5. Installation Complexity: The complexity of the installation, including the number of bends, elbows, and other fittings required, can also affect the maximum recommended line length.

Purchasing and Handling Long Line Sets

Finding sources for long or bulk line sets can be a challenge, as they are not as commonly available as shorter line sets. When purchasing a long line set, consider the following:

  1. Manufacturer-Approved Line Sets: Opt for line sets that are specifically designed and approved by the manufacturer of your mini split system. These line sets are engineered to work seamlessly with the system and are more likely to meet the manufacturer’s specifications.
  2. Refrigerant Line Diameter: Ensure that the line set you purchase has the correct refrigerant line diameter, as specified by the manufacturer. Using the wrong diameter can lead to performance issues and potential system damage.
  3. Insulation Quality: The line set should be well-insulated to prevent heat transfer and maintain the system’s efficiency. Look for line sets with high-quality insulation that meets or exceeds the manufacturer’s recommendations.
  4. Brazing Considerations: It is generally not recommended to braze two pieces of line set together, as this can affect the performance of the system. If you need to extend the line set, consider using a manufacturer-approved line set coupler or splice kit.

Hands-On Approach for DIY Mini Split Line Installation

For DIY enthusiasts with advanced hands-on skills, it is possible to run a mini split line set of up to 100 feet or more, depending on the specific requirements of the installation and the manufacturer’s recommendations. Here’s a step-by-step guide to help you through the process:

  1. Measure and Plan: Carefully measure the distance between the indoor and outdoor units, taking into account any elevation changes or obstacles. Refer to the manufacturer’s guidelines to determine the maximum recommended line length for your specific system.
  2. Line Set Selection: Choose a line set that meets the manufacturer’s specifications, including the correct refrigerant line diameter and insulation quality. Ensure that the line set is long enough to reach the desired location without the need for splicing or brazing.
  3. Routing and Securing: Plan the route for the line set, ensuring that it is as straight and level as possible, with minimal bends and elbows. Secure the line set using appropriate hangers or supports to prevent sagging or damage.
  4. Insulation and Weatherproofing: Properly insulate the line set to prevent heat transfer and maintain the system’s efficiency. Ensure that the insulation is sealed and protected from the elements, especially in outdoor or exposed areas.
  5. Refrigerant Charge Adjustment: If the line set length exceeds the manufacturer’s recommended length, you may need to adjust the refrigerant charge. Consult the manufacturer’s instructions or seek the assistance of a professional HVAC technician to ensure the proper refrigerant charge.
  6. Testing and Commissioning: Once the line set is installed, perform a thorough system test to ensure proper operation and identify any potential issues. Follow the manufacturer’s guidelines for system commissioning and troubleshooting.

Remember, running a mini split line beyond the recommended length can have significant implications on the system’s performance and efficiency. It’s crucial to carefully consider the manufacturer’s guidelines and seek professional assistance if you have any doubts or concerns.


The length of a mini split line is a critical factor in the performance and efficiency of a mini split air conditioning or heating system. By understanding the technical details, manufacturer recommendations, and hands-on installation considerations, DIY enthusiasts can successfully navigate the process of running a mini split line, ensuring optimal system performance and longevity.

References: Thread on Long Mini Split Line Sets
Garage Journal Forum Thread on Long Mini Split Line Sets
YouTube Video: How Long Line Set for Mini Split? (Ask Expert Episode 118) Resource: How Long Line Set for Mini Split? (Ask Expert Episode 118) Blog Post: How Far Can You Run Mini Split Lines?