MRCOOL® DIY® Quick Connect Pre-Charged Line Sets: Tested for Perfection

  • April 13, 2023
  • By MR COOL

The Quick Connect® line sets from MRCOOL® are a critical component of our DIY® Ductless Mini-Split Systems as they simplify the installation process. Without these essential parts, one would need costly HVAC tools to connect, braze, and charge the line set, making the acquisition of a new HVAC system considerably more expensive. Our DIY® Quick Connect line sets have proven to be remarkably dependable throughout our initial development and continued use, earning a patent for their importance and ease of use in the installation of the MRCOOL® DIY® Ductless Mini-Split.

Given the uniqueness of our Quick Connect® pre-charged line set connections within the industry, we entrusted 360º Product Testing, a highly trusted resource for product testing, to perform a series of quality assurance tests to evaluate and ensure their leak resistance. 360º Product Testing has worked with corporations and organizations like the Department of Homeland Security, LG, PepsiCo, and the U.S. Air Force, Army, and Navy. Through this product testing session, we can guarantee that we consistently provide products of the highest quality, ensuring the best possible comfort experience for our customers.

In October 2022, we sent 360º Product Testing eight coupler assemblies, and testing began promptly. 

Before any connections were made, 360º recorded data. As they assembled the Quick Connect® couplers, they observed that the design of the fittings, with each connecting part having a spring-loaded valve to seal the fitting once connected, allowed for corrections and alignment to prevent cross-threading before connecting. 360º Product Testing characterized the fitting process as “an easy connection unlikely to be improperly done.”

Once the couplings were connected, 360º Product Testing determined the leak-free functionality of our pre-charged line set. To accomplish this, the connected fitting assemblies were subjected to hydrostatic pressure testing at a minimum of 400 PSI for at least eight hours. To obtain the most accurate readings and minimize temperature swings that may affect pressure, the tests were conducted in an environmental chamber. At this pressure, which is comparable to normal operating pressure, the couplers did not leak.

One last obstacle the couplers overcame was a pull test to evaluate the strength of the connection. One coupler was randomly selected to undergo a pull test, where it was placed in a test stand fitted with a force gauge. One end of the coupler was secured to the test stand, while the other end was attached to the force gauge, and tension was applied to confirm if the connection held. The tension was then increased to just over 500 pounds of force, and the coupler passed with flying colors.

We appreciate 360º Product Testing for the opportunity to have our line set connections tested by such a trusted company, and we are thrilled to announce that their findings confirm that our pre-charged line sets are as reliable and easy-to-use as we claim.

If you are interested in evaluating the MRCOOL® DIY® Ductless Mini-Split and its DIY® Quick Connect® Pre-Charged Line Sets, please visit our Where to Purchase page at or take a look at

For dependable innovation and substantial savings, choose MRCOOL®.

22 thoughts on “MRCOOL® DIY® Quick Connect Pre-Charged Line Sets: Tested for Perfection”

  1. What line lengths are available? I have one room through the wall from the outside until and one that is 30 feet away.

    1. The typical line set length that comes with the single-zone DIY Ductless Mini-Split is 25′, but you can purchase longer line sets at our retailer, as well as couplers to link additional line sets.

      1. Can I purchase a ceiling cassette? My Home Depot doesn’t seem to find it in their catalog. It is on your website. I prefer to have a ceiling unit as one of my zones. Can I purchase it directly from you or is there a retailer in my area that I can purchase the ceiling cassette DYII unit from.? I need a 9000 BTU capacity. Thank you.

        1. We don’t sell direct, so you’ll need to purchase one from a retailer. Here’s the model number for the 9k BTU DIY Ceiling Cassette:

  2. I have a 12,000 mr Cool U shape new this season.
    What should the output temperature be on this unit?
    Thanks Ray

  3. I’m installing a 4th Gen 18,000 Btu two air handler system. I have connected the line sets to valves A and B and I am ready to turn them on but the manual also refers to two “King Valves” which my outside unit does not have. Is the manual referring to a different system or am I missing something. I don’t want to proceed with turning on the refrigerant until I’m clear on this.

  4. Are the line sets designed to be positioned vertically or horizontally?
    I noticed your MRCOOL DIY mini split product videos show them positioned vertically so just curious if MRCOOL recommends one over the other?

    1. The line sets can be run essentially however you need, as long as the condensate drain line is on a downward slope or has a condensate pump. If you mean storage of excess line set, we recommend that excess line set remain coiled and stored horizontally near the condenser.

  5. I have been reading conflicting opinions on coiling the access line.

    I just installed a MRCOOL mini split in my basement. The outside unit is right outside and about 3 feet higher. I coiled the access line in the basement vertically against the wall so it won’t be in the weather. Is this a problem long term?

    I have tested the unit in both heating and cooling. It works perfectly.

    1. If by access line, you’re talking about the refrigerant line, then coiling it horizontally is ideal, but how you have it coiled should also work.

  6. When the connections are made between the compressor and the coolant lines as well as the inside unit and the coolant lines before the king valve is opened, if you subsequently disconnect them will there be loss of refrigerant?

    1. We can’t guarantee that there will not be refrigerant loss if the lines are disconnected. Because of this, the lines should not be disconnected, and the DIY® Ductless Mini-Split is considered a permanent installation.

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