MRCOOL® DIY50-3858C-O — R-454B 50ft 3/8″ + 5/8″ Lineset for DIY 24K & 36K Indoor w/ DIY Pro Cable

MRCOOL® DIY50-3858C-O — 50 ft R-454B Quick-Connect Line Set with DIY Pro Cable

The DIY50-3858C-O is MRCOOL’s 50-foot pre-charged quick-connect line set for DIY 24K and 36K indoor units. It pairs 3/8″ liquid and 5/8″ suction copper lines with the 75-foot DIY Pro Cable, so a single part number covers both the refrigerant and the electrical run between your indoor and outdoor units.

Key features

• 50-foot length — for installations where the indoor and outdoor units sit far apart
• Line sizes 3/8″ + 5/8″ — the correct diameters for DIY 24K and 36K indoor units
• R-454B compatible — matches MRCOOL’s current refrigerant standard, and also works with earlier R-410A DIY equipment
• Pre-flared quick-connect ends — thread on by hand and torque; no flaring tool, no nitrogen purge, no vacuum pump
• 75 ft DIY Pro Cable included — factory-terminated communication and power cable, no wire stripping
• Foam insulation on both lines — limits heat gain and surface condensation

Compatibility

Designed for MRCOOL DIY 4th and 5th Generation 24,000 BTU and 36,000 BTU indoor units that call for a 3/8″ x 5/8″ line set. Always confirm the line sizes listed in your indoor unit’s installation manual before ordering — 9K, 12K and 18K heads normally use 1/4″ x 1/2″ instead.

What is in the box

• 1 × 50 ft insulated pre-flared line set, 3/8″ and 5/8″
• 1 × 75 ft MRCOOL DIY Pro Cable

Installation notes

Route the line set with sweeping bends and avoid kinking the copper. Tighten the quick-connect fittings to the torque values in the MRCOOL manual, then check the connections with leak detection solution. Refrigerant work and final commissioning should be performed or verified by a licensed HVAC technician where local code requires it.

Frequently asked questions

Does this line set come pre-charged with refrigerant?

Yes. MRCOOL DIY quick-connect line sets ship pre-charged, which is what allows the system to be commissioned without a vacuum pump.

Will DIY50-3858C-O work with my 12K indoor unit?

No. MRCOOL 9K, 12K and 18K indoor units use 1/4″ x 1/2″ lines. This set is sized for 24K and 36K units.

Do I still need a separate communication cable?

No. The “C” in the part number means the 75 ft DIY Pro Cable is included, replacing the shorter cable supplied with the condenser.

Is R-454B backward compatible with my older R-410A DIY system?

The line set hardware itself fits both generations. The refrigerant charge is matched to current 5th Gen equipment, so confirm your model’s requirements in the MRCOOL documentation before mixing generations.

Can I shorten the line set?

No. Quick-connect line sets are sealed and pre-charged at the factory and must not be cut.

Why buy from Cedars HVAC

• Genuine MRCOOL OEM parts — never aftermarket substitutes
• Contractor-friendly pricing on every line set and accessory
• Fast nationwide shipping direct from the distribution center
• Financing available at checkout

Shipping and returns

Most orders ship the same or next business day direct from the distribution center. Standard ground shipping covers the continental United States, and expedited options are available at checkout. Returns are accepted within 30 days on unopened, uninstalled parts — see our return policy for full details.