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Refrigeration & Air Conditioning Mechanic Red Seal · Question

A refrigeration system with a thermostatic expansion valve (TXV) is operating with a low suction pressure, high superheat, and a noisy compressor. What is the most likely cause?

A restricted liquid line filter-drier reduces refrigerant flow to the TXV, causing low evaporator pressure (low suction), the TXV to starve, and high superheat.

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Question: A refrigeration system with a thermostatic expansion valve (TXV) is operating with a low suction pressure, high superheat, and a noisy compressor. What is the most likely cause?

Answer options:

  • Refrigerant overcharge ✅ Restricted liquid line filter-drier
  • Worn compressor valves
  • Slightly undersized condenser

Correct answer: Restricted liquid line filter-drier

Explanation: A restricted liquid line filter-drier reduces refrigerant flow to the TXV, causing low evaporator pressure (low suction), the TXV to starve, and high superheat. The compressor may operate noisily due to gas slugging or high pressure differential.

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