In order for a refrigerant to become superheated it must be heated in a section of the low-side refrigerant line:

• A. Where no liquid refrigerant is present
• B. In the high pressure line
• C. In the condenser
• D. In the receiver

Answer: (A)

Superheat means heating the vapor above its saturation temperature, which only happens when there is no liquid present. After the liquid refrigerant has fully evaporated in the evaporator, the vapor travels through the suction (low-pressure) line toward the compressor. If you heat in a section where liquid can still be present, the heat goes into vaporizing that liquid and you get a two-phase mixture rather than vapor that’s hotter than its saturated temperature. To actually raise the temperature above the saturation point, you must heat only the dry vapor, which is found in the low-side portion of the line after the evaporator and before the compressor. Heating on the high side, in the condenser, or in the receiver would involve liquid or high-pressure conditions that don’t produce true superheat in the same way.