What should be checked before using a recovery unit to remove a charge from a system?

Before using a recovery unit to remove a charge from a system, it is essential to check the service valve positions and the recovery oil level. Ensuring that the service valves are properly positioned is crucial because it establishes the correct pathway for refrigerant to flow into the recovery unit. Any improper valve position could lead to inefficient recovery or even damage to the unit.

Additionally, checking the recovery oil level is important because the recovery unit relies on this oil to function properly and safely. If the oil level is low, it may result in inadequate lubrication, which could lead to mechanical failure of the recovery unit during operation. This step not only helps ensure the success of the recovery process but also promotes safety and the longevity of the equipment.

The other options, while relevant to the general operation of a refrigeration system, do not directly pertain to the immediate preparations for utilizing a recovery unit.