Recovery removes refrigerant from the system into a certified cylinder, evacuation pulls a deep vacuum to remove air and moisture, and recharge adds the correct amount of refrigerant by weight. Together they restore a system after repair. Skipping steps causes moisture damage, poor performance and repeat failures.
If a technician says they need to open the sealed system, these three steps are the standard. Knowing them helps you judge whether work was done properly.
Step 1: Recovery
Refrigerant should not be vented. A recovery machine draws it out of the system into an approved cylinder so it can be reused, recycled or disposed of properly. Recovery is required before opening the sealed circuit for most repairs. The technician records how much was recovered, which helps check for leaks.
Step 2: Repair and prepare
- The failed part is replaced or the leak is repaired.
- Joints are brazed with nitrogen flowing to prevent scale inside the pipes.
- The filter drier is replaced.
- The system is pressure tested with nitrogen to confirm there are no leaks.
Step 3: Evacuation
A vacuum pump removes air and moisture. Moisture in a system can freeze at the expansion valve, form acid with oil and damage the compressor. A deep vacuum is measured with a micron gauge, and the system is held to check that it does not rise, which would show a leak or remaining moisture. Quick evacuation to save time is a common shortcut that causes trouble later.
Step 4: Recharge by weight
The technician adds refrigerant by weight from a scale, following the nameplate or the calculated charge for the system and line lengths. Charging by weight is more accurate than charging by gauge pressure alone, especially on systems with receivers and head pressure controls. The technician then checks superheat, subcooling, pressures, temperatures and amp draw.
Why each step matters
| Skipped step | Likely result |
|---|---|
| Recovery | Refrigerant vented, breaks rules and wastes money |
| Nitrogen while brazing | Scale and debris clog valves |
| Drier replacement | Moisture and acid remain |
| Deep evacuation | Air and moisture cause icing and acid |
| Charge by weight | Over or under charge, poor performance |
Questions to ask your technician
- How much refrigerant was recovered and how much was added?
- Was the drier replaced?
- What vacuum level was reached and held?
- Was the system leak tested after the repair?
- Where is the record kept?
Refrigerant rules are set by the EPA and depend on the refrigerant type and system, so confirm the current requirements with your technician. See the filter drier, topping off a leaking system and compressor and refrigerant repair pages.
What to expect on the day
A proper job takes time, and a visit that includes evacuation may leave the box off for a few hours. Plan for that by moving perishable food to another cold space beforehand. Ask how long the box will be down and what the technician will do after charging to confirm it is cooling correctly, such as watching temperatures and defrost operation. A quick job that skips the wait is a warning sign.
Questions about this topic
How long does evacuation take?
From a short time to a few hours, depending on system size and moisture. Rushing it is not wise.
Why charge by weight?
It is more accurate than pressure alone, especially with receivers and head pressure controls.
Can I ask for the paperwork?
Yes. Reputable technicians record recovered and added refrigerant and can share it.