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 specified full-capacity operating conditions with an ambient air temperature of 90°F, R-134a head pressure falls within the normal operational range of 150 to 190 psig as outlined in marine refrigeration troubleshooting and performance curves.