System Dehydration, Evacuation Standard and Moisture Acceptance Criteria Before Charging

System Dehydration, Evacuation Standard and Moisture Acceptance Criteria Before Charging

Poor evacuation leaves residual moisture, which triggers acid and copper plating; Xiteliduo defines vacuum standards and testing for new or rebuilt systems. Cold storage refrigeration compressor moisture inside the circuit reacts with POE oil to form acid, corrode metal and create copper plating. Semi‑hermetic piston compressor deep evacuation target is 500 microns absolute pressure, holding stable for minimum 4 hours after pump isolation. Refrigeration compressor for food cold room must pass moisture validation before charging, especially after piping modification or compressor replacement. R404A piston refrigeration compressor evacuation requires two-stage vacuum pumping; single-stage pumps cannot reach the required deep vacuum level. Low temperature cold storage compressor and 2‑stage piston refrigeration compressor circuits have larger internal volume and require longer hold time. Chinese refrigeration compressor manufacturer data shows incomplete evacuation is the root cause of 41% of premature oil acidification failures. Semi‑hermetic compressor price comparison does not include vacuum pump, vacuum gauge and moisture testing; this is commissioning service content. Refrigeration compressor fault troubleshooting for early acid formation always reviews whether evacuation and dehydration were performed correctly. Cold chain refrigeration unit compressor skids are evacuated before leaving factory; field work only needs re-evacuation if piping joints are opened. Rising vacuum pressure after pump shutdown means leaks or desorbing moisture; you must not proceed with refrigerant charging. Xiteliduo prohibits using refrigerant purge as a substitute for deep vacuum; purging cannot remove dissolved moisture from pipe walls. After evacuation, moisture test sample should show oil moisture below 50 ppm before system charging. If moisture fails, repeat evacuation and add temporary filter driers with high water capacity to remove residual moisture.

FAQ

1. What target vacuum level and hold time for system dehydration? 500 microns absolute pressure, stable hold for minimum 4 hours.
2. What percentage of early oil acidification failures come from bad evacuation? 41% of premature acid failures are caused by incomplete evacuation.
3. What pump type is required to achieve deep vacuum? Two-stage vacuum pump is mandatory for proper dehydration.
4. What signal shows residual moisture or leaks during evacuation? Vacuum pressure rises after the vacuum pump is isolated.
5. Can refrigerant purging replace deep vacuum evacuation? No, refrigerant purging cannot remove adsorbed moisture.
6. What is the oil moisture acceptance limit before charging? Oil moisture content must be below 50 ppm before charging refrigerant.