Line set size by brand
Pick your mini-split's brand and capacity to get the right line set size — then shop it. Prefer to go by run length too? Use the size calculator.
How brands size line sets
Here's the part most people get wrong: line set diameter is set by your system's capacity, not the brand. A 12,000 BTU head needs the same line sizes whether it's a Pioneer, a Senville, or a Daikin — the manufacturer engineers every unit of that capacity for the same refrigerant flow.
What actually changes between brands is the connection:
- Quick-connect / pre-charged (e.g. MrCool DIY) — proprietary line sets with sealed couplings that twist together. No vacuum, no flaring. Buy the matching brand line set in the right length.
- Field-flared (Pioneer, Senville, Daikin, Mitsubishi and most others) — standard copper line sets you flare and torque on site, or buy pre-flared.
Line set size by capacity
| System size | Typical line set (liquid × suction) |
|---|---|
| 9,000 BTU | 1/4" × 3/8" |
| 12,000 BTU | 1/4" × 1/2" |
| 18,000 BTU | 1/4" × 1/2" |
| 24,000 BTU | 3/8" × 5/8" |
| 36,000 BTU | 3/8" × 5/8" |
| 48,000 BTU | 3/8" × 5/8" (some 3/8" × 3/4") |
These are the most common pairings. Exact diameters and the maximum line length are printed in your unit's installation manual — treat it as the final word.
Brand sizing guides
In-depth line set size guides for specific mini-split brands. Tap any brand for its full sizing chart:
Guide: how to verify a DIY mini-split in the AHRI Directory before you buy →
Common questions
What size line set does a MrCool DIY use?
MrCool DIY systems use proprietary pre-charged, pre-flared line sets. A 12,000–18,000 BTU DIY typically uses 1/4" × 1/2" and a 24,000–36,000 BTU DIY uses 3/8" × 5/8", in fixed lengths of 16, 25, 35, or 50 ft. Replace like-for-like with a MrCool DIY line set, and confirm against your unit's manual.
Does line set size depend on the brand?
The diameter is set by the system's capacity, not the brand — a 12,000 BTU unit uses the same line size across most brands. What varies is the connection type (quick-connect vs field-flared) and whether the line set is proprietary and pre-charged.
Can I reuse my existing line set?
Often yes, if the diameters match your new system, the run length works, and the lines are clean and leak-free. Existing R-410A line sets can frequently be reused. Always pressure-test and verify against the new unit's installation manual.
This tool provides general guidance based on common mini-split line set sizing by capacity. Exact line diameters, connection types, and maximum line lengths vary by model — always verify against the manufacturer's installation manual before purchasing or installing.