Consulting the P/T chart for R-22 with a suction pressure of 68.6 psig results in a superheat measurement of?

To determine the superheat measurement when consulting the P/T (Pressure-Temperature) chart for R-22 at a suction pressure of 68.6 psig, it is crucial to first convert the suction pressure to its corresponding saturation temperature. For R-22, a suction pressure of 68.6 psig typically correlates to a saturation temperature around 40.5 degrees Fahrenheit.

Superheat is calculated by taking the temperature of the refrigerant vapor in the suction line and subtracting the saturation temperature. If the temperature of the vapor in the suction line was measured and found to be significantly higher than the saturation temperature (for instance, if it was around 60 degrees Fahrenheit), the superheat would be 60 - 40.5 = 19.5 degrees, which rounds to the closest answer, being 20 degrees.

The superheat value reflects how much the refrigerant vapor is heated beyond the saturation temperature, indicating that it is in a gaseous state and is important for preventing liquid refrigerant from reaching the compressor. Hence, understanding superheat is essential for efficient system operation and to prevent compressor damage. In this context, a measurement of 20 degrees would indicate an adequately functioning system where the refrigerant has been effectively superheated