AC Cooling Fault — Non-Condensable Gas (Air/Moisture) Contamination

Identify non-condensable — compare pressure vs P-T chart

Check: After OFF, measure condensing temperature → compare with P-T chart. Pressure 1.5–2× chart value = non-condensable contamination. With system OFF, check top of condenser (high side) — non-condensables collect at top. After vacuum, if pressure doesn't match P-T chart = leak or non-condensable.

What to do: Full recovery → vacuum (≤500 μm) → recharge by weight from fresh cylinder. Only after passing leak check (nitrogen + electronic detector). Inadequate vacuum = #1 cause of non-condensables. Below 5°C ambient = triple evacuation mandatory. Use dedicated cylinder; avoid season/cross-charging (contamination).