Quick pressure-drop ACR copper sizing for refrigerant lines.
| Line | Max friction loss | Velocity check (FPM) | Purpose |
|---|---|---|---|
| Suction (horizontal) | 2 °F | ≥ ~500, ≤ 4,000 | Capacity penalty; oil return |
| Suction (vertical riser) | — | ≥ ~1,000 | Carry oil upward (large risers need more) |
| Discharge (hot gas) | 1 °F | ≥ ~500 horizontal, ~1,000 riser; ≤ 3,500 | Oil return; sound control |
| Liquid line | 1 °F | ≤ 300 | Stay subcooled; limit liquid hammer |
Friction limits are over the entered equivalent length — the basis of the ASHRAE Refrigeration Handbook line-capacity tables (per 100 ft). Velocity figures are common rules of thumb.
Doing this for a whole building? See this step inside a connected AIM Works project — loads, ventilation, equipment, and Design Review in one place.
Book a Demo →This refrigerant line sizer recommends ACR copper tube sizes for the suction, discharge, and liquid lines of a DX system. Enter the system tonnage, refrigerant (R-410A, R-454B, R-32, R-134a, R-407C, or legacy R-22), the suction and discharge saturation temperatures, and the equivalent length; the tool finds the mass flow from the refrigerating effect, sizes each line for pressure drop, and reports the tube size, velocity, and friction loss. It shares its engine with the Refrigerant Pipe Sizer, which adds superheat, subcooling, and a full capacity table.
The suction and discharge (vapor) lines are sized for pressure drop and then checked for enough velocity to return compressor oil, while the liquid line is sized so its loss stays well inside the subcooling. Use the result as a preliminary check, then confirm against the equipment manufacturer's line-sizing tables.
The refrigerating effect h1 – h4 is taken at your suction temperature plus 10 °F superheat and your condensing temperature less 10 °F subcooling (for R-410A at 40/110 °F it is about 72 Btu/lb, or roughly 2.8 lb/min per ton). Densities, enthalpies, viscosities, and dP/dT come from the CoolProp reference equations of state — the REFPROP-equivalent data ASHRAE Handbook—Fundamentals Ch. 30 tabulates; for blends the temperatures are dew points and the liquid uses the bubble point, and discharge gas assumes 70% isentropic compression. The friction factor is Colebrook’s with drawn-copper roughness, and tube IDs are ASTM B280 ACR. The friction limits are the ASHRAE Refrigeration Handbook line-capacity-table basis applied to your equivalent length; the velocity checks are rules of thumb, made at full load (check staged or inverter equipment at minimum capacity). Use the Refrigerant Pipe Sizer to change superheat or subcooling.
AIM Works brings peak loads, ASHRAE 62.1 ventilation, equipment and plant sizing, compliance checks, Design Review, and engineering deliverables into one connected mechanical design workspace.
Duct and pipe distribution sizing is planned for V2 — at launch, keep using this calculator for that step.
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.