A system with a TXV metering device is field charged using which charging method, with the aid of a charging chart?

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When a system uses a TXV, you charge by subcooling. The TXV regulates the evaporator’s superheat, so measuring and targeting a specific superheat isn’t a stable indicator of overall charge. Instead, the charging chart provides the expected refrigerant amount based on how much the liquid refrigerant in the condenser outlet is subcooled below its saturation temperature. By achieving the recommended subcooling, the system lies at the correct charge level and the liquid entering the TXV is fully condensed, ensuring proper metering and operation.

Charging by superheat, pressure, or weighing is less reliable here because these methods don’t consistently reflect the actual charge in a TXV-equipped system—the TXV will adjust to maintain evaporator conditions, masking the true amount of refrigerant in the system.