How Far Can You Run An AC Line Set?

Installing a refrigerated AC system always comes with some challenges. One of the greatest is finding the optimum place to set the condensing unit. Many small residential lots limit the places that a condensing unit may reside. Many times, these locations may be far from the HVAC unit and the condensing coil. The question of how far you can run an AC line set is critical to a proper installation.

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In general, seventy-five feet is considered the maximum distance a line set can be run. However, there is no absolute rule about the length of an AC line set. The variables that affect the maximum line set length are numerous. The recommendations and requirements of the manufacturer must also be considered. Local building codes can also figure into the equation.

In any case, the first reference to consider is the manufacturer’s specifications. Other factors may affect your decision, such as the type of HVAC system and condenser, the elevation changes in the system, and requirements for additional equipment required for proper operation of the HVAC system.

When you start to locate the condensing unit for your new HVAC system, it is important to consider the AC line set length. Several factors must be considered to ensure the proper operation of your HVAC system. Some factors are more subtle than many people realize.

Even the smallest detail can be the difference between an efficient and effective installation. Failing to attend to the details is a mistake many do-it-yourselfers make with their HVAC project. There are no shortcuts to performing a proper AC line set in your home.

Some homeowners make a critical mistake when selecting the site for their refrigerant condenser is the actual length of the AC line run. The term used by HVAC professionals is “total equivalent length.”

The length of your AC line set is not a linear measurement from the HVAC unit to the condensing unit. No AC line set runs directly to the HVAC unit. The AC line set must negotiate through the house, often following walls or attic spaces to reach its destination.

This necessitates numerous bends, ups, and downs. Rather than measure the direct linear distance, you must calculate the “total Equivalent length” of the line set run. This measurement considers the total length of the AC line set needed to negotiate the route from the condensing unit to the HVAC unit.

The best and most accurate information about the AC line set length for your HVAC system is the Manufacturers specifications and recommendations. All HVAC manufacturers provide this information with the user and installation manuals that come with the HVAC systems.

The information in the installation guide should be the rule and guide for your installation. If you deviate from the manufacturer’s recommendations and specifications, you risk voiding the warranty. An improper AC line set may damage the condenser and require extensive repairs or replacement.

The major problem with long AC line sets is friction loss in the lines. As the liquid refrigerant moves through the refrigerant line, it encounters friction from the tubing walls. The longer the refrigerant line, the more friction loss affects how much refrigerant gets to the evaporator coil.

The friction loss effects may be offset by using larger diameter refrigerant lines. However, some compressors may not be able to deliver enough flow rate through the larger diameter lines. The overall operation and efficiency of the HVAC system will suffer if the installation is not precisely calculated.

Determining the proper size of refrigerant lines for a given length of AC line set is a complicated issue. If the line size, size of the condensing unit, and the length of the run are not carefully calculated, the system may not operate at peak efficiency. Poorly made decisions about the AC line set size can damage the condensing unit.

Most HVAC manufacturers offer considerable information about sizing refrigerant lines based on the size of the condensing unit and the length of the AC line set. The manufacturer has the best information in all cases, and their recommendations should be followed closely.

Some situations may require the condensing unit to be mounted above the evaporator coil on your HVAC system. The length of the line set must always be considered. In installations where the Condensing unit is above the evaporator coil, most manufacturers suggest the installation of an oil trap.

If the height difference is 15 to 25 feet, one oil trap is usually adequate to protect the system. Where the height difference is 25 – 50 feet, most manufacturers recommend installing two oil traps. If the height difference exceeds 50-feet, three oil traps should be installed in the system.

The question is not the height of the AC line set but the position of the Condensing Unit in relation to the evaporator coil. If the compressor is below the evaporator coil, you can see less efficiency from your HVAC system.

In a horizontal AC line set run, the overriding issue is friction loss in the lines. The longer the AC line is set, the greater the flow rate is reduced in the line. For example, a compressor on the same level as the evaporator may deliver 100 units of flow. The evaporator will only see 90 units of flow because of friction loss.

When the compressor is below the evaporator unit, the flow rate can be reduced enough to lower the unit’s efficiency. In addition, the flow rate in the refrigerant lines may not be sufficient to carry the lubricating oil through the system.