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 57.4 psig with an ambient temperature of 60° F, what statement is true? See illustration GS-RA-11. See illustration GS-RA-47.
• Saturation pressure vs. temperature relationship for R-134a • How to use the pressure-temperature chart to compare actual system pressure to expected pressure at ambient temperature • The purpose of the leak-test procedures decision tree (what you do when the pressure is lower, equal to, or higher than the chart value)
• At 60°F, what does the R-134a pressure-temperature chart say the saturated pressure should be, and how does that compare with the measured 57.4 psig? • If the measured pressure is slightly below, equal to, or above the chart value, what does the decision tree tell you to do about leak testing? • Which choices claim the machine "definitely" does or does not have a leak, and which leave room for uncertainty based on a small deviation from chart values?
• Verify the correct saturated pressure for R‑134a at 60°F from the chart, including whether it’s in psig (gauge) or psia (absolute). • Check how the decision tree defines the threshold for deciding "definitely has a leak" vs. "may or may not have a leak" (e.g., % below chart value). • Confirm whether the procedure ever instructs you to add nitrogen or lower refrigerant pressure before performing the initial determination about whether a leak may be present.
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