During charging, what is the primary reason for performing a thorough evacuation?

• A. Remove moisture and air and non-condensables
• B. Increase system pressure
• C. Lubricate moving parts
• D. Clean the refrigerant

Answer: (A)

Removing air, moisture, and non-condensables from the system before charging is essential to get an accurate refrigerant charge and efficient operation. Air and non-condensables raise head pressure and hinder heat transfer, which can skew readings and reduce performance. Moisture in the system can react with refrigerant and oil to form acids, and water can freeze in metering devices, causing blockages. A thorough evacuation pulls these unwanted gases and water out, allowing the system to be charged properly and operate reliably. This isn’t about increasing pressure, lubricating moving parts, or cleaning the refrigerant, so those outcomes aren’t achieved by evacuation.