🔍 Key Concepts

• Refrigeration cycle flow: compressor → condenser → receiver → expansion device → evaporator → back to compressor • Difference between liquid line and vapor (suction/discharge) lines in a refrigeration system • Why a sight glass must see mainly liquid, not vapor, to judge proper charging

💭 Think About

• First, trace where in the cycle the refrigerant should be a high‑pressure liquid rather than a vapor or low‑pressure mixture. • Ask yourself: in which part of the system would bubbles in the flow tell you that the system is undercharged or flashing off instead of being solid liquid? • Consider whether you’d want the sight glass before or after the expansion device, and whether pressure there is normally high or low.

✅ Before You Answer

• Confirm that a sight glass for charge indication must be located where refrigerant is intended to be subcooled liquid. • Verify which line between the condenser/receiver and the expansion valve carries high‑pressure liquid. • Eliminate any line where refrigerant is normally vapor (suction or discharge) rather than liquid, since a charge‑checking sight glass would not function correctly there.