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Refrigeration & Air Conditioning Mechanic Red Seal · Question

During a system diagnostic, you find that the suction pressure is abnormally high, and the superheat is very low, sometimes fluctuating close to 0°C. What is a probable cause related to the TXV operation?

Excessive refrigerant flow (overfeeding) by the TXV can lead to high suction pressure, as the evaporator is flooded with liquid, reducing the surface area for l

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Question: During a system diagnostic, you find that the suction pressure is abnormally high, and the superheat is very low, sometimes fluctuating close to 0°C. What is a probable cause related to the TXV operation?

Answer options:

  • The TXV has lost its charge. ✅ The TXV is significantly overfeeding the evaporator.
  • There is a restriction in the liquid line leading to the TXV.
  • The external equalizer line is clogged.

Correct answer: The TXV is significantly overfeeding the evaporator.

Explanation: Excessive refrigerant flow (overfeeding) by the TXV can lead to high suction pressure, as the evaporator is flooded with liquid, reducing the surface area for latent heat transfer, and causing very low superheat, potentially allowing liquid refrigerant to return to the compressor. This is a common TXV troubleshooting scenario.

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