In an R410A system, if the compound gauge reads 124 psig and the suction line temperature is 54 degrees F, what is the operating system superheat?

To determine the operating system superheat in an R410A system, you first need to calculate the saturation temperature corresponding to the pressure indicated by the compound gauge. With a gauge reading of 124 psig, you can refer to refrigerant pressure-temperature charts for R410A. At 124 psig, the saturation temperature is approximately 54 degrees F.

Operating system superheat is defined as the difference between the actual vapor temperature in the suction line and the saturation temperature of the refrigerant at the measured pressure. Since the suction line temperature is also 54 degrees F, the calculation for superheat would be:

Superheat = Actual suction line temperature - Saturation temperature

In this case, it would be:

Superheat = 54 degrees F - 54 degrees F = 0 degrees F.

However, this calculation indicates an error, as superheat typically should not be zero under normal operating conditions. It suggests that the system may be flooded with liquid refrigerant, or there may be an issue with the gauge or the measurement process.

When analyzing the choices given, choice C, which states 12 degrees F, would arise from a different interpretation, possibly involving a different pressure or temperature reading, or given the possibility that the temperature gauge operates