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

Illustration GS-RA-52: the U.S. Coast Guard has not released this illustration.

Question

An air-cooled refrigerated container unit using R-134a as a refrigerant has a box temperature set point of -15&deg;F, but it is currently operating with a stable return air temperature of 0&deg;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&deg;F? Illustration GS-RA-52

Illustration GS-RA-52: the U.S. Coast Guard has not released this illustration.

Accepted Answer

Option A: 150-190 psig. Under standard R-134a container refrigeration performance curves with a 90°F ambient, operating at full capacity yields a normal head pressure range of 150 to 190 psig, reflecting efficient heat rejection across an air-cooled condenser coil.