Which statement about metering devices is true?

• A. Only gas refrigerant should enter the metering device
• B. Either liquid or gas can enter the metering device
• C. The metering device is not related to refrigerant state
• D. Only liquid refrigerant should enter the metering device

Answer: (D)

Metering devices are designed to throttle liquid refrigerant before it enters the evaporator. They rely on the liquid’s incompressible nature to create a controlled pressure drop and a predictable flow rate. If gas were allowed to enter, the device wouldn’t regulate flow properly—the mass flow would become erratic, leading to improper evaporator cooling and unstable superheat, which can stress the compressor. That’s why the correct idea is that only liquid refrigerant should enter the metering device. The system is built around throttling liquid, not gas, and any gas entering the metering device would disrupt this regulation.