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How to Get Air Out of an AC System?

Published in HVAC Repair 3 mins read

The primary method for removing air from an AC system involves vacuuming the interior of the refrigeration system. Often, incomplete vacuuming leads to residual air within the system.

Here's a breakdown of the process:

  • Vacuuming the System: This is the most important step. A vacuum pump is connected to the AC system to remove all air and moisture. This process lowers the pressure inside the system. A deep vacuum is crucial for optimal performance.

  • Why Air is Problematic: Air contains moisture and non-condensable gases. Moisture can react with the refrigerant and oil, creating acids that damage the system. Non-condensable gases reduce the system's efficiency and increase pressure.

  • Checking for Leaks: Before vacuuming, it's a good idea to check for leaks. If there's a leak, the system will draw in more air after vacuuming, defeating the purpose. Leaks can be detected using electronic leak detectors or soap-and-water solutions.

  • Using a Vacuum Pump and Manifold Gauges:

    • Connect the manifold gauge set to the AC system's service ports.
    • Attach the vacuum pump to the center port of the manifold gauge set.
    • Open the manifold valves to allow the vacuum pump to pull a vacuum on both the high and low sides of the system.
    • Run the vacuum pump until the system reaches the desired vacuum level (typically around 500 microns).

  • Holding Vacuum: After vacuuming, close the manifold valves and turn off the vacuum pump. Monitor the vacuum gauge to see if the vacuum holds steady. If the vacuum drops, it indicates a leak in the system.

  • Triple Evacuation (For Systems with Significant Contamination): In cases where a system has been opened to the atmosphere for an extended period or has significant contamination, a triple evacuation process may be necessary. This involves:

    1. Vacuuming the system down to a certain pressure (e.g., 500 microns).
    2. Breaking the vacuum with a small amount of refrigerant.
    3. Vacuuming the system down again.
    4. Repeating steps 2 and 3 one more time.
    5. Finally, vacuuming to the target micron level and holding the vacuum.

  • Considerations:

    • Always use the correct type of refrigerant for your AC system.
    • Wear safety glasses and gloves when working with refrigerants and vacuum pumps.
    • If you are not comfortable working on AC systems, consult a qualified technician.

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