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How to triple-evacuate a refrigeration system
Triple evacuation uses three vacuum pulls and two breaks with dry nitrogen. It helps remove air and moisture before charging, after the circuit has passed its leak test.
- Evacuate
- Break with nitrogen
- Evacuate
- Break with nitrogen
- Final vacuum
Prepare the circuit and tools
Work on a refrigerant-free circuit that has passed its leak test. Use clean vacuum pump oil, short vacuum-rated hoses and a micron gauge placed on the system away from the pump. Confirm which valves must be open so every section can be evacuated.
Run the three evacuations
Pull to the manufacturer’s first-stage target. Isolate the pump and break the vacuum with regulated dry nitrogen to the level in the procedure. Repeat the evacuation and nitrogen break. On the third pull, reach the specified final vacuum, isolate the pump and record how pressure changes over the specified hold period.
Read the result before charging
If pressure keeps climbing after isolation, check the gauge setup and circuit for leaks. Residual moisture and outgassing can also raise the reading. Verify tightness separately if in doubt. Record the initial reading, final reading and hold time. Follow the manufacturer’s charging procedure once the result passes.
Guide for trained technicians. Follow the manufacturer’s procedure and limits for the refrigerant and equipment model being serviced.
Technical references
- Copeland · VSMC Compressor Unit, Installation, Operation and Maintenance Manual · 35391VC Rev. 0 · “Evacuating the System”
- Daikin · Three-Phase Installation Instructions · IO-D-4045A · “Brazing”, “Leak Testing”, “Evacuation”