Where is refrigerant added during the charging process of a low-pressure system?

Refrigerant is added during the charging process of a low-pressure system at the evaporator charging valve. This is because the evaporator is where the refrigerant absorbs heat and changes from liquid to vapor, making it crucial for the vaporization process to be initiated properly.

Charging through the evaporator allows the technician to ensure that the refrigerant flows correctly through the system and fully fills the evaporator coils, optimizing the heat exchange process and ensuring efficient cooling performance. By adding refrigerant at the evaporator charging valve, any necessary adjustments can be made to ensure that the system is adequately charged for optimal operation.

The other options, while they might be related to various aspects of system maintenance or operation, do not facilitate the effective charging of the low-pressure system in the same manner as the evaporator charging valve does.