What steps should be taken before using a recovery unit to remove a charge?

Before using a recovery unit to remove a charge, it is essential to check the service valve positions and recovery oil level. This step is crucial as it ensures that the system is properly prepared for the recovery process. Correctly positioned service valves prevent refrigerant from entering or leaving the system at unintended points, which can lead to system contamination or improper recovery.

Additionally, ensuring the recovery oil level is appropriate is vital for the unit's functionality. Low oil levels can damage the recovery unit and affect its performance, while too much oil may lead to inefficiency or a malfunction in the recovery process.

While checking the refrigerant type, inspecting the hoses, and checking the weight of the cylinder are all important steps in the recovery process, they relate more to ensuring safety, proper handling, and efficient recovery rather than pre-usage checks of the recovery unit itself. Thus, prioritizing the service valve positions and recovery oil level directly impacts the successful and safe operation of the recovery unit.