Refrigeration (ACR) copper tube sizes from 1/4 to 2 1/8 inch OD with metric equivalents, standard wall thicknesses, allowable working pressures, and when K65 high-pressure alloy replaces plain copper for CO2 and R410A plants.
Refrigeration pipework is specified by tube outside diameter — unlike plumbing tube named by nominal bore. The standard soft/hard-drawn ACR sizes:
| OD (in) | OD (mm) | Typical wall (mm) | Working pressure* (bar) | Common duty |
|---|---|---|---|---|
| 1/4" | 6.35 | 0.8 | ~140 | Gauge lines, cap tubes out |
| 3/8" | 9.52 | 0.8 | ~95 | Liquid lines small splits |
| 1/2" | 12.7 | 0.8 | ~70 | Liquid/suction small systems |
| 5/8" | 15.88 | 1.0 | ~70 | Suction lines, heat pumps |
| 3/4" | 19.05 | 1.0 | ~58 | Suction/discharge |
| 7/8" | 22.22 | 1.14 | ~57 | Suction medium plants |
| 1 1/8" | 28.58 | 1.27 | ~49 | Suction/liquid headers |
| 1 3/8" | 34.92 | 1.4 | ~44 | Suction risers |
| 1 5/8" | 41.28 | 1.52 | ~41 | Large suction |
| 2 1/8" | 53.98 | 1.78 | ~36 | Rack suction mains |
*Order-of-magnitude allowable pressures for hard-drawn Cu-DHP at 50 °C with standard ACR walls — derate brazed joints at higher temperatures; the system standard (EN 378 / EN 14276) and the tube producer's tables govern design.
R410A condensing at 43 bar and transcritical CO2 at 90–130 bar exceed what larger plain-copper sizes allow. For R410A, thicker-wall copper covers common line sets; for CO2 above ~52 bar the industry answer is the copper-iron alloy K65 (CuFe2P) with matching fittings, rated 120 bar in the standard programme: see K65 couplings, K65 blanking caps and the full jointing walkthrough in the K65 CO2 pipework guide. Never braze a plain-copper fitting into a K65 line — the fitting, not the tube, sets the joint rating.
Continental drawings sometimes call metric copper (6, 10, 12, 15, 18, 22, 28 mm OD); couplings between the systems exist but each joint must use a fitting made for the two actual ODs — 15.88 mm tube does not seal in a 16 mm compression fitting. Suction lines are insulated to prevent condensation and capacity loss: wall thickness per line temperature and ambient humidity, closed-cell elastomeric as standard — matching sizes are listed under HVAC & Refrigeration together with impulse tubes and brazing consumables (silver-alloy guide).