After measuring pressure at the liquid line, what is the next step in measuring subcooling?

To determine the subcooling in a refrigeration system, the first step after measuring the pressure in the liquid line is to convert that pressure reading to temperature using a pressure-temperature chart. Subcooling is defined as the difference between the temperature of the refrigerant and its saturation temperature at the measured pressure. By referencing a pressure-temperature chart, one can accurately find the saturation temperature corresponding to the liquid line pressure. This temperature will then be used to calculate the subcooling by comparing it to the actual temperature of the refrigerant in the liquid line.

Other actions, such as closing service valves, measuring superheat, or adding refrigerant, do not directly contribute to calculating subcooling and would be considered steps that either precede or follow the determination of subcooling, thus making them unsuitable as the next immediate step after taking a pressure measurement.