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Refrigeration & Air Conditioning Mechanic Red Seal · Question

A walk-in freezer operating on R-404A exhibits low box temperature, frosted suction line back to the compressor, and excessively high suction pressure. The TXV has a sensing bulb securely attached to the suction line. What is the most probable issue with the TXV setting?

Low superheat (overfeeding) means the valve is allowing too much liquid refrigerant into the evaporator, leading to a flooded evaporator, frosted suction line,

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Question: A walk-in freezer operating on R-404A exhibits low box temperature, frosted suction line back to the compressor, and excessively high suction pressure. The TXV has a sensing bulb securely attached to the suction line. What is the most probable issue with the TXV setting?

Answer options:

  • The TXV is set for excessively high superheat. ✅ The TXV is set for excessively low superheat (overfeeding).
  • The TXV's equalizer line is plugged.
  • The TXV's sensing bulb has lost its charge.

Correct answer: The TXV is set for excessively low superheat (overfeeding).

Explanation: Low superheat (overfeeding) means the valve is allowing too much liquid refrigerant into the evaporator, leading to a flooded evaporator, frosted suction line, and high suction pressure.

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