A line set change is the process of replacing the copper tubing and insulation that connects the indoor and outdoor components of an air conditioning or heat pump system. Here are the general steps involved in a line set change:

1. If the system is still charged with refrigerant, the refrigerant needs to be safely removed and recovered by technician. This is necessary to prevent environmental damage and potential legal violations.

2. The old line set needs to be cut and removed from the system. 

3. Once the old line set has been removed, the new line set can be installed. This involves connecting the tubing between the indoor and outdoor units and insulating the lines to prevent condensation.

4. The system needs to be pressure tested to make sure there are no leaks in the new line set.

5. After the pressure test has been completed, the system needs to be vacuumed to remove any air and moisture. Then, the system can be recharged with the appropriate amount of refrigerant.