Question 84Refrigeration/AC - 1st Asst/Chief70% to pass
An air-cooled refrigerated container unit using R-134a as a refrigerant has a box temperature set point of -15°F, but it is currently operating with a stable return air temperature of 0°F. The fresh air makeup vent is closed, the unit is operating at 460 VAC/60 Hz, and the unit is in full capacity cool (modulating valve 100% open). Using the illustrated troubleshooting guide, what would be the normal range of expected discharge pressures if the ambient air temperature is 90°F? Illustration GS-RA-52
AI Explanation
The correct answer is A) 150-190 psig.
1. Explanation:
Based on the given information and the refrigeration troubleshooting guide illustration GS-RA-52, the normal range of expected discharge pressures for an air-cooled refrigerated container unit using R-134a refrigerant, operating at a box temperature set point of -15°F with a stable return air temperature of 0°F, and an ambient air temperature of 90°F, would be 150-190 psig.
2. Reasoning:
The discharge pressure in a refrigeration system is primarily determined by the condensing temperature, which is affected by the ambient air temperature. With an ambient air temperature of 90°F and the unit operating in full capacity cool mode, the expected discharge pressure range would fall within 150-190 psig, as indicated in the troubleshooting guide.
3. Other options:
The other options are incorrect because they do not accurately reflect the normal discharge pressure range for the given operating conditions and refrigerant.
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