Velocity-based ACR copper tube sizing for suction, discharge, and liquid lines. Supports R-410A, R-22, R-32, and R-134a.
| Line | Min Velocity (FPM) | Max Velocity (FPM) | Purpose |
|---|---|---|---|
| Suction (horizontal) | 500 | 4,000 | Oil return to compressor |
| Suction (vertical riser) | 1,000 | 4,000 | Must entrain oil upward |
| Discharge (hot gas) | 1,000 | 3,500 | Oil return; sound control |
| Liquid line | 75 | 300 | Prevent flashing; low pressure drop |
This refrigerant line sizer recommends ACR copper tube sizes for the suction, discharge, and liquid lines of a DX system using a velocity-based method. Enter the system tonnage, refrigerant (R-410A, R-22, R-32, or R-134a), and the suction and discharge saturation temperatures; the tool estimates mass flow, sizes each line to land within its velocity band, and reports the resulting tube size and actual velocity.
The suction and discharge (vapor) lines are sized to keep velocity high enough to return compressor oil, while the liquid line is kept slow to limit pressure drop and prevent flashing. Use the result as a preliminary check, then confirm against the equipment manufacturer's line-sizing tables.
Mass flow is approximated at about 0.6 lb/min per ton on the suction side; ρline is the vapor density for suction and discharge and the liquid density for the liquid line. The target velocity is the midpoint of each line's recommended band, and the tool rounds up to the next standard ACR copper size. Velocity limits — oil-return minimums on vapor lines and a low maximum on the liquid line — follow ASHRAE Refrigeration and manufacturer line-sizing practice, where velocity governs oil return and pressure drop sets the saturation-temperature penalty.
This calculator handles one step. AIM Works runs the complete MEP design workflow — thermal load calculations, duct & pipe networks, equipment selection, code compliance, and an AI design assistant — in one tool.
Results are design estimates for preliminary sizing. Verify final designs against applicable codes and standards — engineering judgment and a licensed professional engineer’s review are required.