Originally Posted by jinxed
... does the system come charged from the factory or does the installer have to charge it?
Most home air conditioning system components are pre-charged at the factory -- the condenser, evaporator coils and insulated refrigerant lines. Metal membranes seal the openings and the act of screwing the lines onto the condenser or evaporator pierces the membranes and allows refrigerant to flow. However, if one doesn't mate the parts properly, it is possible to have the refrigerant leak away, requiring a recharge. Installers typically check the pressures with an HVAC manifold gauge set right after the system is assembled and add refrigerant as needed. They also perform leak tests to make sure all the joints are tight.