A refrigerant properties chart calls for 100 psia. What reading would you see on your gauges?

In a refrigeration system, the gauge pressure readings can be interpreted differently based on whether they are measured in absolute pressure (psia) or gauge pressure (psig).

When the properties chart calls for 100 psia, this measurement refers to the absolute pressure, which is the total pressure including atmospheric pressure. Standard atmospheric pressure at sea level is approximately 14.7 psi. Therefore, to find the corresponding gauge pressure, which measures the pressure relative to atmospheric pressure, the atmospheric pressure must be subtracted from the absolute pressure reading.

Calculating this gives:

100 psia - 14.7 psi = 85.3 psig

Since gauge pressure readings are typically rounded, 85 psig aligns well with the option provided. This shows a fundamental understanding of how to convert between absolute and gauge pressure, which is essential in HVAC practice for accurate system diagnostics and performance checks.