For data center air conditioning systems (especially precision air conditioners or CRAC units), the vacuum level requirement mainly depends on whether the system has a compressor (with refrigerant) and the manufacturer’s specifications. Here are the industry-standard guidelines:
General Standard
Target vacuum level: 500 microns or lower (≈0.66 mbar, ≈66 Pa)
This is the common HVAC and data center standard to ensure the system is almost free of moisture and air.
High Standard / Best Practice: 300 microns or lower
Recommended for large refrigeration systems or those sensitive to moisture (e.g., low-temperature systems, long piping).
Why 500 microns?
A refrigeration system must be free of moisture and air; otherwise, it can cause:
Freeze-up (ice blockages)
Acid formation leading to compressor damage
Reduced heat transfer efficiency
Below 500 microns means the system pressure is close to a true vacuum, and most residual moisture has been removed.
Vacuum Procedure Recommendation
Pull down to about 1500 microns first, hold for a few minutes to check for leaks.
Then pull down to 500 microns or lower, and hold for 10–15 minutes without rising.
If the pressure rises quickly after stopping the pump, there’s likely a leak or residual moisture.
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