🔍 Key Concepts

• LP (low-pressure) centrifugal chiller behavior when load changes • Purpose of a pressure maintenance system and what it protects against (air/moisture in-leakage, very low evaporator pressure) • Relationship between chiller operating / idle conditions and when an auxiliary tank-heater-pump system would need to run

💭 Think About

• Look at the illustration and trace where the tank, heater and pump connect in relation to the chiller—does this loop look like something that would run all the time, or only to keep pressure up when normal refrigerant flow is low or stopped? • Think about when an LP chiller’s evaporator pressure would be most likely to drop below design, allowing air to leak in—during high load with lots of vapor, or during very low/no load when there is little boiling taking place? • Ask yourself: would you want a pressure-maintenance system operating while you are deliberately leak‑testing the machine, or mainly during normal service to keep conditions stable?

✅ Before You Answer

• Verify which components in the figure (pressure transducer, pressure switch, pressure controller, alarm controller) are tied to the tank, heater and pump assembly • Confirm whether the label and piping suggest this system is meant to add warm refrigerant vapor back into the chiller to keep pressure from getting too low • Before choosing, decide under which option the chiller’s internal pressure would naturally fall the most, requiring an automatic system to ‘maintain’ it rather than allowing it to drift