Copper Line Sets

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Copper Line Sets

What Are Copper Line Sets?

Line sets are the copper tubes used to connect the condenser to an evaporator in an AC unit. For mini-split systems, these line sets connect the indoor unit with the outdoor unit to enable the outdoor unit (condenser) to supply refrigerant to the indoor unit (evaporator).

The set comes with two lines - a smaller and a larger one. The smaller tube,  also called the liquid or discharge line, carries dense liquid refrigerant to the evaporator, where it can absorb heat. The larger tube, also called the suction line, carries lighter gaseous refrigerant back to the condenser where the heat can be rejected.

The refrigerant and vapour in the lines are continually recirculated in a loop to provide either heating or cooling, depending on the direction of the flow. If your system has a heat pump feature, the flow is simply reversed to provide heating.

Single-Zone vs Multi-Zone

For most residential applications, only one line set is needed as these systems have single indoor units. Whereas for multi-zone systems, one line set per indoor unit is required. And to ensure that the system functions properly, you'll need to make additional considerations such as distance, total line length, and diameter. Furthermore, some multi-zone systems also require a branch box, and it needs its own line set to connect to the outdoor unit.

The diameter of the line would depend on your application. In case there are any changes needed in the size of the line, you will need to use a port adaptor to make those connections.

Line Set Sizing

Based on different factors, line sets come in different sizes. These factors include the brand of the mini split, condenser size, number of indoor units, and distance between units. To get the proper sizing requirements for your particular system, you should always check your installation manual.


The diameter of the line depends on the BTUs of the unit. The greater the BTUs, the larger the diameter line set will be required by the system.

Line sets are available in multiple sizes. For instance, a small (diameter) set contains a 3/8" suction line with a 1/4" liquid line. While a larger line set contains a 3/4" suction line with a 3/8" liquid line. The first number indicates the diameter of the suction line, and the second number indicates the diameter of the liquid line.


While determining the total maximum line set length required for your system, you need to consider the allowed length by your specific system, bends and corners, vertical rise, and thickness of the walls.

Ignoring the allowed length of your system can leave you with a system that doesn't work properly.


The two factors that are closely related to the refrigerant in the line set are; the distance between units and the number of units. All new mini-split systems come charged with refrigerant from the factory. Although this charge is often sufficient for the majority of installations, yet in case of longer line sets, additional refrigerant is needed to ensure that the mini-split operates properly.

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We are a leading Maintenance, Repair, And Operations (MRO) Supplier, providing exceptional experiences to businesses. Check out our extensive range of Perfect Aire Copper Line Sets.