Refrigeration Plant Operator B Practice Test

Can a pressure-actuated control be used in conjunction with an automatic expansion valve?

1. Yes, always

2. No, never

3. Only in specific systems

4. Only with a direct thermostat

The correct answer is: No, never

Pressure-actuated controls regulate systems based on pressure readings and are typically designed for refrigeration systems that require constant adjustments based on changes in load and pressure. Automatic expansion valves, on the other hand, function by controlling refrigerant flow based on the pressure at the evaporator outlet, aiming for a constant superheat. When a pressure-actuated control is used, it can conflict with the automatic adjustment of the expansion valve. Since the pressure-actuated control continually responds to changes in system pressure, it may disrupt the specific feedback mechanism that the automatic expansion valve relies on to maintain optimal performance. This can lead to inefficiencies or erratic operation, which is why these two systems are generally not recommended to be used together in commercial refrigeration applications. Understanding the interaction between these controls is crucial in refrigeration plant operations, as inappropriate pairings can compromise system efficiency and reliability.