MRCOOL® DIYCOUPLER-3858K75C — DIY 4th/5th Gen Coupler Set (3/8″ + 5/8″) with 75ft DIY Pro Cable for 24K & 36K

MRCOOL® DIYCOUPLER-3858K75C — 3/8″ and 5/8″ Coupler Set with 75 ft DIY Pro Cable

DIYCOUPLER-3858K75C joins two MRCOOL DIY quick-connect line sets on a 24K or 36K zone and includes the 75-foot DIY Pro Cable for the longer electrical run. The Pro Cable is factory-terminated, so there is no wire stripping at either end.

Key features

• Two machined brass couplers — 3/8″ liquid line and 5/8″ suction line
• 75 ft DIY Pro Cable included — pre-terminated plug-and-play cable, replaces the 25 ft cable shipped with the condenser
• Quick-connect design — mates to MRCOOL DIY flare fittings, no brazing and no vacuum pump
• For 24K and 36K indoor units — the capacities that use 3/8″ x 5/8″ lines
• Both generations supported — compatible with 4th Gen R-410A and 5th Gen R-454B DIY systems

Pro Cable versus standard wire

This kit includes the MRCOOL DIY Pro Cable, which plugs directly into both units. If you would rather field-terminate plain communication wire and save on the kit, order DIYCOUPLER-3858K75 instead. The couplers are identical in both versions.

Line length limit

MRCOOL specifies a maximum of 75 feet of total line length per zone across the two coupled line sets. Plan the run before ordering.

What is in the box

• 1 × DIYCOUPLER-38 (3/8″ coupler)
• 1 × DIYCOUPLER-58 (5/8″ coupler)
• 1 × 75 ft MRCOOL DIY Pro Cable

Frequently asked questions

What does the C at the end of the part number mean?

It indicates the DIY Pro Cable is included rather than plain communication wire.

Can I use this on a 12K or 18K indoor unit?

No. Those units use 1/4″ x 1/2″ lines and need DIYCOUPLER-1412K75C.

Do I still use the 25 ft cable that came with my condenser?

No. The 75 ft Pro Cable replaces it once the refrigerant run is extended.

Will this work with my 4th Gen R-410A system?

Yes. This coupler kit is listed as compatible with both 4th Gen R-410A and 5th Gen R-454B DIY equipment.

Can I join three line sets on one zone?

No. MRCOOL supports a single coupled joint per zone, within the 75 ft total length limit.

Why buy from Cedars HVAC

• Genuine MRCOOL OEM parts — never aftermarket substitutes
• Contractor-friendly pricing on every line set and accessory
• Fast nationwide shipping from our Miami, Florida warehouse
• Financing available at checkout

Shipping and returns

Most orders ship the same or next business day from Cedars HVAC in Miami, Florida. 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.