Indicative sizes for common R410A/R32 single-split systems on pipe runs up to about 15m. Always follow the manufacturer's line-size and maximum-length tables, derate for long or high runs, and add trim charge where required. Not for VRF/VRV or long-line applications.
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This calculator suggests the liquid and suction line sizes for a split air conditioning system from its cooling capacity. Enter the capacity in kilowatts and it returns indicative pipe sizes for a common R410A or R32 single-split installation.
It is a quick reference for air conditioning engineers pricing or planning a split-system install, where the interconnecting pipework has to be the right size for the unit. Undersized pipes throttle performance and can damage the compressor; oversized ones waste money and refrigerant.
The suggestion comes from the typical line sizes manufacturers specify across capacity bands. It is a starting point for a standard run — the manufacturer's own tables are always the final word, especially on longer or taller pipe runs.
Cooling capacity → matched liquid and suction line sizes (typical R410A/R32 split, run ≤ ~15m)
Split-system line sizes step up with cooling capacity: a small unit might use a 1/4" liquid line and 3/8" suction line, rising to 1/2" liquid and 7/8" suction on larger units. The suction (gas) line is always larger than the liquid line, and long or high runs need the sizes checking against the manufacturer's maximum-length tables.
Type the system's cooling capacity in kW — the figure from the unit's specification, for example 3.5 kW or 5 kW.
The calculator shows an indicative liquid line and suction line size for a typical single-split system in that capacity band.
Confirm the sizes against the specific unit's installation manual, which gives the exact line sizes and the maximum permitted run and height.
For long or tall runs, follow the manufacturer's guidance to upsize the suction line and add trim charge as required.
The suction line is the one that matters most for performance. It carries low-pressure gas back to the compressor, and undersizing it causes excessive pressure drop, lost capacity and poor oil return — so never drop below the manufacturer's suction size to save on copper. The liquid line is less sensitive but still specified.
Long and tall runs change the sizing. Beyond the standard run length, manufacturers often require a larger suction line, additional refrigerant charge, and oil traps on vertical rises. This calculator covers a typical run of up to around 15 m; anything longer or with significant height must be taken from the manufacturer's line-length tables.
These are indicative sizes for common R410A and R32 single-split systems, not a design for VRF/VRV or long-line applications, which have their own sizing rules. Always size the actual job from the specific unit's installation manual — this tool is a quick sanity check, not a substitute for it.
Indicative sizes for common R410A/R32 single-split systems on pipe runs up to about 15m. Always follow the manufacturer's line-size and maximum-length tables, derate for long or high runs, and add trim charge where required. Not for VRF/VRV or long-line applications.
It depends on the cooling capacity. A typical 3.5 kW split uses a 1/4" liquid line and 1/2" suction line, while a 5 kW unit often steps the suction line up to 5/8". Enter the capacity above for an indicative pair of sizes, then confirm against the unit's installation manual.
Because it carries low-pressure refrigerant gas, which takes up far more volume than the high-pressure liquid in the liquid line. A larger suction line keeps the gas velocity and pressure drop within limits so the system does not lose capacity or fail to return oil to the compressor.
Yes. Longer runs increase pressure drop, so beyond the standard length manufacturers often require a larger suction line and additional refrigerant charge, plus oil traps on tall vertical runs. This calculator assumes a typical run up to about 15 m; longer runs must be sized from the manufacturer's tables.
The sizes shown are for common R410A and R32 single-split systems, which cover most modern domestic and light commercial air conditioning. Other refrigerants, VRF/VRV systems and long-line installations have different sizing rules, so always work from the specific manufacturer's data for those.
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