R-Pro › Field cases › Air conditioning
AC New Install — Flaring and Torque Tightening Procedure
Likely causes
Step 1 — Cut, ream copper tube and flare (45° standard)
Check: Cut tube square with tube cutter — never use saw/file (deforms cross-section). Remove internal burrs with reamer — but never over-ream (thins copper wall). Tube end extension in flaring tool must match gauge (typically 1–1.5 mm). Flare face must be free of cracks, oval distortion, or rough surface.
What to do: Use ratchet or clutch-type flaring tool — ensures consistent flaring pressure. R-32/R-410A requires slightly thicker flare wall vs R-22 — use A2L-compatible newer tool. Inspect flare visually after forming — if defects found, cut and redo (never try to fix existing flare).
Step 2 — Tighten by torque table (both over- and under-torque cause leaks)
Check: Use torque wrench + 90° crowfoot. Standard torque: 1/4" (liquid) 17.6–24.5 N·m (13–18 ft·lb, sweet spot 15 ft·lb), 3/8" (suction) 33.3–41.2 N·m (25–30 ft·lb), 1/2" 49.0–61.8 N·m, 5/8" 63–78 N·m. R-410A/R-32 use separate spec (never cross-reference). Manufacturer manual takes priority.
What to do: Apply small amount of Nylog Blue or refrigerant oil to flare face before tightening — distributes friction, ensures seal. With sealant applied, use lower end of torque (below 15 ft·lb risks leak). Hold tube with one hand so flare nut rotation does not turn the tube. Re-check torque within 24 hours of installation (settling can lose ~5% torque).
Common leak causes — installation defect self-diagnosis
Check: 10 leak causes (ACServiceTech): ① over-torque (flare crack) ② under-torque (no seat) ③ tube rotation (scratched seat) ④ over-reaming (thin copper) ⑤ flare end cracks/debris ⑥ wrong angle (not 45°) ⑦ no lubricant ⑧ ends not held during torque ⑨ aged copper tube ⑩ R-22 torque chart applied to R-32.
What to do: Immediately after tightening, pass both vacuum decay test (separate case) and nitrogen leak test (separate case) before charging refrigerant. If leak found, cut and re-flare that joint — never re-tighten over an existing flare. Accept 5–10% copper tube waste per meter — repair-visit cost far exceeds material cost.
Flare leaks are the #1 cause of new-installation defects. Torque wrench + Nylog Blue + ratchet flaring tool = 90% reduction in leak rate. Apply protective sleeve to copper at exposed flare areas vulnerable to outdoor-unit vibration. R-32 mildly flammable — leaks pose fire/explosion risk; use A2L-compatible leak detector.
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