A high-pressure centrifugal chiller currently charged with R-134a is being evaluated for the need for leak testing. Using the leak-test procedures decision tree illustrated and the R-134a pressure-temperature chart illustrated, with the machine idle and the pressures equalized at 10 psig with an ambient temperature of 60 ° F, what statement is true? GS-RA-47

Illustration GS-RA-47: the U.S. Coast Guard has not released this illustration.

Question

A high-pressure centrifugal chiller currently charged with R-134a is being evaluated for the need for leak testing. Using the leak-test procedures decision tree illustrated and the R-134a pressure-temperature chart illustrated, with the machine idle and the pressures equalized at 10 psig with an ambient temperature of 60 ° F, what statement is true? GS-RA-47

Illustration GS-RA-47: the U.S. Coast Guard has not released this illustration.

Accepted Answer

Option B: The machine has a suspected leak, therefore the refrigerant pressure should be raised to 35 psig by adding refrigerant prior to checking for leaks.. An idle R-134a centrifugal chiller at 60 °F equalizing at 10 psig indicates air and moisture contamination because saturated R-134a at 60 °F exerts approximately 57 psig. The lower pressure confirms a vacuum leak; pressure must be raised with refrigerant before leak testing.