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Refrigeration & Air Conditioning Mechanic Red Seal · Question

A service technician is commissioning a new walk-in cooler. The hot gas bypass valve is chattering during low load conditions. What is the most likely cause?

Chattering in a hot gas bypass valve often indicates unstable operation due to issues like an incorrect pressure signal to the valve diaphragm, which can be cau

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Question: A service technician is commissioning a new walk-in cooler. The hot gas bypass valve is chattering during low load conditions. What is the most likely cause?

Answer options:

  • The bypass valve is incorrectly sized and is too large for the application.
  • Insufficient head pressure causing unstable gas flow to the valve. ✅ The valve's external equalizer line is clogged or restricted.
  • Incorrect superheat setting on the thermostatic expansion valve.

Correct answer: The valve's external equalizer line is clogged or restricted.

Explanation: Chattering in a hot gas bypass valve often indicates unstable operation due to issues like an incorrect pressure signal to the valve diaphragm, which can be caused by a clogged or restricted external equalizer line reacting to fluctuating evaporator pressure.

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