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? Illustration 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&deg;F, what statement is true? Illustration 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.. At 60°F ambient, R-134a saturation pressure is approximately 57 psig. An equalized pressure of 10 psig indicates air and moisture in-leakage. Standard procedures require pressurizing with dry nitrogen or refrigerant vapor to raise pressure before effective leak testing.