What are Line Sets? And why do you need them for your Mini Split and HVAC Split System?

Line sets might not sound very exciting, but they are an essential component to your HVAC system. So, if you like retreating to the coolness of your home on an especially sweltering and humid afternoon, you’ll want to choose a line set you can depend on. Line sets are in fact a necessary part of any cooling system. 


When you’re purchasing a new HVAC system, it is always better to get the line sets and other important accessories right away. That’s especially important as local vendors may not have the correct size or configuration that you need. 

What are Line Sets?

MRCOOL 50 Ft. Pre-Charged No-Vac 3/8-Inch x 3/4-Inch Line Set for Universal Series (NV50-3834)

Basically, line sets are not advanced technology. They are composed of a few copper pipes that connect the condenser to the evaporator. This also applies to mini splits where the line set works by connecting the indoor unit (air handler) to the outdoor unit (condenser). The line set is responsible for creating a secure passageway that can allow the condenser to supply refrigerant to the evaporator across a span of many feet. 


As you examine these sets, you'll observe that one of the lines is bigger than the other. This difference is intentional. The smaller tube is called the discharge line. This line links the compressor to the condenser.  It transports the dense liquid refrigerant over to the evaporator, where heat can be dispersed. The larger tube is the suction line and its job is to carry lighter gas refrigerant back to the condenser to eliminate heat.


The refrigerant and vapor within the tubes continuously circulates in a loop, directing either heat air from outside or the cooled air where it needs to go. If your system includes a heat pump, then this flow process is reversed, in order to move heat into the home.


The line set also includes insulation around the copper tubes to prevent heat loss or gain during the refrigerant transfer process. This insulation helps maintain the efficiency of the HVAC system by reducing the amount of energy required to cool or heat the indoor air.

Line Set Sizing

MRCOOL DIY 4th Generation 66 Ft. 3/8-Inch x 5/8-Inch Line Set Kit for DIY 24K, & 36K Indoor (DIY66-3858C)

The size of the line set needed for an HVAC system depends on several factors. These include: 

  • The size of the unit 
  • The distance between the indoor and outdoor units
  • The height difference between the units.

The two copper tubes that make up the line set are typically sized based on the tonnage of the HVAC system, which is a measure of its cooling capacity. Generally, a 1.5-ton system will require a 3/8-inch line set, and a 2-ton system will require a 3/8-inch or 1/2-inch line set. The specific sizing may vary depending on the manufacturer's specifications and local codes.


It's essential to ensure that the line set is properly sized and installed to maintain the efficiency and effectiveness of the HVAC system. Improperly sized line sets can lead to increased energy consumption, reduced cooling capacity, and other operational issues. 


In summary, line sets are crucial for HVAC systems because they allow for the transfer of refrigerant between the indoor and outdoor units, which is necessary for the system to operate efficiently and provide heating or cooling to the indoor environment.

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