Final answer:
A system with a fixed orifice metering device should be charged using the subcooling method to ensure optimal efficiency and performance.
Step-by-step explanation:
A system equipped with a fixed orifice metering device should be charged using the subcooling method. This is because such systems do not adjust to the refrigerant flow based on system conditions, relying on the proper charge to maintain efficiency and performance. In the subcooling method, refrigerant is added until the temperature of the liquid refrigerant exiting the condenser coil is sufficiently below its saturation temperature. This process ensures that only liquid refrigerant enters the orifice to maximize the efficiency of the cooling process.