What is the first step required before recovering refrigerant from an R-410A unit using a recovery machine with R-22 refrigerant?

The correct answer is based on the importance of maintaining the integrity and functionality of the recovery system when transitioning between different refrigerants. Before recovering refrigerant from an R-410A unit with a recovery machine that previously contained R-22, it is crucial to remove the R-22 from the recovery unit and change the filter.

This is necessary because refrigerants have different properties and mixtures that can negatively impact the performance of the recovery equipment and the purity of the collected refrigerant. R-22 and R-410A have different chemical compositions and physical characteristics. If R-22 remains in the recovery machine while attempting to recover R-410A, it could lead to an improper recovery process and potential contamination of the recovered refrigerant, which would not meet the standards for recovery and could complicate recycling or disposal.

In addition, changing the filter is essential to prevent any residue from the R-22 from contaminating the new recovery process. This process ensures that the recovery machine is clean and ready to handle R-410A effectively, promoting safe and efficient refrigerant recovery.