MRCOOL 25FT 3/8 x 5/8 Flared Line Set Kit for 24K Olympus and Advantage Mini Split, MC25-3858

MRCOOL 25FT 3/8" x 5/8" Flared Line Set Kit (MC25-3858)

The MRCOOL MC25-3858 represents a purpose-engineered refrigerant line set specifically designed to optimize performance in MRCOOL's 24K BTU (2-ton) Olympus and Advantage mini-split systems. This precision-manufactured copper line set provides the critical thermal connection between outdoor condensing units and indoor air handlers, ensuring proper refrigerant flow, system capacity, and operational efficiency.

This specialized line set features expanded dimensions necessary for proper operation of MRCOOL's mid-range mini-split systems:

• Increased Diameter Sizing: Features 3/8" liquid line and 5/8" suction line diameters, specifically calibrated for optimal refrigerant flow in 24K BTU (2-ton) applications
• Optimized Connection Fittings: Pre-flared ends with properly sized fittings (1/2" liquid line fitting, 3/4" suction line fitting) ensure secure, leak-resistant connections
• Strategic Length: 25-foot length provides sufficient reach for standard residential installations while staying within maximum recommended length specifications
• Premium-Grade Materials: Constructed from high-purity, dehydrated copper tubing that meets ASTM B280 standards for refrigeration applications
• Professional Preparation: Line set arrives factory-sealed, capped, and nitrogen-purged to maintain internal cleanliness

These enhanced specifications are critical for maintaining proper refrigerant velocity, oil return, and thermal transfer capacity in higher-BTU mini-split applications.

The MC25-3858 incorporates several features that streamline the installation process:

• Factory-Flared Connections: Precision machine-flared ends eliminate the need for field flaring, reducing the risk of leaks and connection failures
• Application-Specific Sizing: Correctly sized for 24K BTU applications, eliminating guesswork and ensuring compatibility with specified systems
• Optimized Handling Characteristics: 17-pound weight and flexible design facilitate routing through various structural elements
• Direct System Integration: Engineered for direct connection to MRCOOL Olympus and Advantage 24K system fittings
• Comprehensive Package: Contains all necessary line components in a single package for simplified project planning

These features significantly reduce installation time and specialized tool requirements while promoting proper system setup—valuable benefits for both professional contractors and experienced DIY installers.

The MC25-3858 line set is specifically designed for:

• MRCOOL Olympus 24K BTU Mini-Split Systems
• MRCOOL Advantage 24K BTU Mini-Split Systems

This precise sizing makes this line set incompatible with smaller (12K/18K) or larger (36K+) capacity mini-split systems that require different line diameters. This application specificity ensures optimal performance within the designed capacity range.

The proper selection and installation of this line set directly influences several operational characteristics:

• Thermal Capacity: Correctly sized lines ensure the system can deliver its full 24,000 BTU cooling/heating capacity
• System Efficiency: Proper line dimensions minimize pressure drops that can reduce SEER/HSPF ratings
• Oil Return: Optimized line sizing ensures proper refrigerant velocity for oil return to the compressor
• Operational Sound Levels: Correct sizing helps reduce refrigerant noise that can occur with under/oversized lines
• Compressor Protection: Proper oil return and refrigerant management extend compressor life

While the MC25-3858 simplifies installation, adhering to these best practices ensures optimal performance:

1. Proper Bend Technique: Use tube benders for any directional changes to maintain proper internal diameter
2. Structural Support: Secure lines every 4-6 feet (more frequently on vertical runs) to prevent vibration and stress
3. Thermal Insulation Integrity: Ensure insulation remains intact and sealed, particularly at connection points
4. Connection Preparation: Apply appropriate refrigeration oil to flare surfaces before connection
5. Correct Torque Application: Use calibrated torque wrenches when tightening flare nuts (typically 45-50 ft-lbs for these connection sizes)
6. Comprehensive Testing: Pressure test connections to at least 400 PSI with dry nitrogen before system evacuation

The MC25-3858 line set package includes:

• 25 feet of insulated, paired 3/8" liquid line and 5/8" suction line copper tubing with factory-flared ends
• UV-resistant, closed-cell foam insulation on the suction line to prevent condensation and energy loss
• Factory-installed protective caps to maintain internal cleanliness

The package dimensions (28-1/2"W x 3-1/2"H x 29"D) and 17-pound weight reflect the coiled configuration for shipping and storage.

This product carries a Proposition 65 warning and has shipping restrictions to certain U.S. territories (GU, PR, VI). Its freight class (125) indicates its handling requirements for shipping purposes. Unlike complete HVAC systems, the line set itself does not carry a separate registered warranty as it is considered an installation material.

The MRCOOL MC25-3858 line set serves as the vital thermal connection that enables MRCOOL's 24K BTU mini-split systems to deliver their rated performance. By providing precisely sized, pre-flared refrigerant lines manufactured to rigorous standards, this line set ensures proper refrigerant dynamics between indoor and outdoor units—preserving system efficiency, capacity, and long-term reliability.

For contractors and experienced DIY installers working with MRCOOL's mid-capacity systems, the MC25-3858 eliminates the specialized preparation and sizing considerations associated with refrigerant line installation, supporting both proper system function and installation efficiency. When properly installed, this line set helps ensure the complete 24K BTU mini-split system will deliver the comfort, efficiency, and performance expected from MRCOOL's Olympus and Advantage product lines.

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