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Refrigeration & Air Conditioning Mechanic Red Seal · Question

Which of the following scenarios is most likely to lead to poor oil return in a refrigeration system?

Multiple large diameter P-traps in a vertical suction riser would collect excessive amounts of oil, and the lower refrigerant velocity in oversized traps would

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Question: Which of the following scenarios is most likely to lead to poor oil return in a refrigeration system?

Answer options:

  • A suction line sized for excessively high refrigerant velocity
  • A horizontal suction line pitched towards the compressor ✅ A vertical suction riser with multiple large diameter P-traps
  • A system operating at a consistently high evaporator superheat

Correct answer: A vertical suction riser with multiple large diameter P-traps

Explanation: Multiple large diameter P-traps in a vertical suction riser would collect excessive amounts of oil, and the lower refrigerant velocity in oversized traps would be insufficient to entrain and lift the oil back to the compressor, leading to oil logging in the evaporator and poor oil return.

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