| OD Size | ID (in.) | Suction cap. (tons) | Suc. vel. (fpm) | Discharge cap. (tons) | Liquid cap. (tons) |
|---|
This refrigerant pipe sizer recommends suction, discharge, and liquid line sizes for a direct-expansion (DX) system. Choose the refrigerant — R-410A, R-22, R-32, R-407C, or R-134a — and enter the system tonnage, evaporating and condensing temperatures, superheat, and subcooling. The tool computes mass flow from the refrigerant's cooling effect, converts it to a volume flow in each line, and selects ACR copper tubing that holds velocity within accepted limits.
Each line has a different job: the suction and discharge (vapor) lines must move fast enough to return compressor oil, while the liquid line stays slow to limit pressure drop and prevent flashing. The capacity table shows every tube size at a glance, so you can trade one size up or down with the velocity and oil-return consequences in view.
Volume flow: V̇ (ft³/min) = ṁ ÷ 60 ÷ ρline
Velocity: v (fpm) = V̇ ÷ A where A = π · (ID ÷ 24)²
The cooling effect (hg – hf) is the saturated-vapor enthalpy at the evaporating temperature minus the saturated-liquid enthalpy at the condensing temperature; 12,000 BTU/h equals one ton. Density ρline is the vapor density for suction and discharge and the liquid density for the liquid line. Recommended velocity bands — roughly 700–4,000 fpm suction, 1,000–3,500 fpm discharge, and 50–300 fpm liquid — follow ASHRAE Refrigeration and manufacturer line-sizing tables, where velocity governs oil return and pressure drop sets the saturation-temperature penalty. Properties here are simplified; confirm against published data.