R-Pro › Field cases › Air conditioning
AC New Install — Pre-Charge / Purge / Service Valve Opening
Likely causes
Step 1 — Verify outdoor pre-charge then open service valves
Check: Outdoor pre-charged at factory for standard line length (R-32/R-410A). Verify pre-charge weight + default line length on nameplate/manual. Open valves only after passing both vacuum decay and nitrogen leak tests. Service valves = separate ones for liquid (small) and gas (large) lines.
What to do: Open with allen key: gas line first, then liquid line, fully (stem to stop). Immediately depress core on gas-line service port → brief vent (purge) → system pressurized. Single leak check (soap foam). Additional length charge = (actual length − default) × g/m → add by weight from cylinder.
Incomplete valve opening = abnormally low suction → compressor damage. Opening liquid first = liquid hammer from precharged refrigerant slamming into evacuated line. Open gas first = safe. Verify pre-charge weight on nameplate exactly — varies by BTU within model lineup.
All 565 cases work offline in R-Pro, with error codes for 62 brands and P-T data for 108 refrigerants.
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