Can Mini Split Lines Run Inside Walls: A Comprehensive DIY Guide

Running mini split lines inside walls is a viable option for homeowners and DIY enthusiasts, but it requires careful planning and execution to ensure a successful installation. This comprehensive guide will provide you with the necessary technical details and hands-on expertise to tackle this project with confidence.

Line-Set Installation

The line set, which consists of the refrigerant lines, is the critical component that connects the indoor and outdoor units of a mini split system. When running the line set inside the walls, it is essential to ensure that the lines are installed without any bends or kinks, as these can restrict the flow of refrigerant and compromise the system’s efficiency.

To achieve this, you will need to use 3/4″ or 5/8″ OD (Outer Diameter) copper tubing for the line set. Copper is the preferred material due to its durability, flexibility, and ability to withstand the high pressures and temperatures associated with the refrigerant flow. When selecting the tubing, make sure to choose a type that is specifically designed for mini split systems, as it will have the necessary insulation and protective coatings.

The length of the line set should not exceed the manufacturer’s recommended limit, which is typically around 50 feet for most mini split systems. Exceeding this limit can lead to reduced system performance and increased energy consumption.

Condensate Line Installation

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The condensate line is responsible for removing the moisture that accumulates in the indoor unit during the cooling process. When running the mini split lines inside the walls, it is crucial to ensure that the condensate line is installed separately from the refrigerant lines.

The condensate line should be installed with a downward slope towards the outdoor unit, allowing the water to drain efficiently. A typical condensate line is made of 3/4″ PVC or CPVC piping, which is readily available and easy to work with. It is important to avoid running the condensate line inside the wall alongside the refrigerant lines, as this can lead to water damage or clogging issues.

Accessibility for Future Maintenance

One of the key considerations when running mini split lines inside the walls is the accessibility for future maintenance or replacement. Since the lines will be hidden from view, it is essential to plan for easy access in case any repairs or adjustments are needed.

To ensure accessibility, you can create an access panel or a chase (a recessed space within the wall) that allows you to reach the line set and the condensate line. This will make it easier to inspect, service, or replace the components if necessary, without having to tear down the entire wall.


Proper insulation of the line set is crucial to maintain the system’s efficiency and prevent heat loss or gain. The refrigerant lines should be insulated with foam insulation tubing, with a thickness that matches the manufacturer’s recommendations, typically ranging from 1/2″ to 5/8″.

The insulation helps to minimize heat transfer, which can impact the system’s cooling or heating performance. It is important to ensure that the insulation is continuous and without any gaps or breaks, as this can compromise its effectiveness.

Wall Thickness and Stud Spacing

The thickness of the wall and the spacing of the wall studs are important factors to consider when running mini split lines inside the walls. A typical 2×4 stud wall with 16″ on-center spacing is generally suitable for accommodating the line set.

However, if the wall thickness is greater or the stud spacing is different, you may need to adjust the installation process accordingly. This may involve using longer screws or anchors to secure the line set, or finding alternative routing paths to navigate around obstacles.

Safety Considerations

When running mini split lines inside the walls, it is crucial to prioritize safety and avoid damaging any existing electrical wiring or plumbing lines. Before starting the installation, use a stud finder to locate the position of the studs and any other hidden utilities within the wall.

Additionally, use a fish tape or a similar tool to carefully route the line set through the wall, ensuring that it does not interfere with or compromise the integrity of any other building systems. Take the necessary precautions to protect yourself and the existing infrastructure during the installation process.

By following these technical guidelines and hands-on best practices, you can successfully run mini split lines inside the walls of your home or building. Remember to always consult the manufacturer’s instructions, local building codes, and safety regulations to ensure a safe and compliant installation.