1. Water Leakage into the Refrigerant

The Malfunction: Water enters the sealed refrigerant circuit, which can lead to the formation of highly corrosive hydrochloric and hydrofluoric acids.

Why it Happens: This often occurs due to a broken tube within the water-cooled condenser or the chiller shell itself. The dehydrator cycle in a chiller is specifically designed to indicate this type of leakage by separating water from the refrigerant, which can then be observed through a sight glass.

2. Oil Management and Return Issues

The Malfunction: Oil becomes trapped in the evaporator (chiller shell) instead of returning to the compressor. This can foul heat-transfer surfaces, reducing the system’s cooling capacity.

Why it Happens:

• In Ammonia Systems: Oil is heavier than ammonia and naturally falls to the bottom. If it is not manually drained, it increases refrigerant film resistance.
• In Halocarbon Systems: Oil and refrigerant (like R-22 or R-502) can separate into layers at low temperatures. If the oil-rich layer is at the top and the drain is improperly located, the oil cannot return to the compressor.
• Foaming: Excessive oil can cause foaming, which may lead to the carryover of liquid into the suction line, risking compressor damage.

3. Inaccurate Liquid-Level Control

The Malfunction: The system may overfeed refrigerant (leading to “flood-back” to the compressor) or fail to maintain a sufficient level for cooling.

Why it Happens: This is frequently caused by oil concentration in the remote chambers of float valves or Level-Master controls. Because oil has a different density than pure refrigerant, it causes the control device to “see” an incorrect liquid level.

4. Motor Overloading and Power Failures

The Malfunction: The compressor motor may overheat or trip its internal protectors.

Why it Happens: Solid-state modules in the machine-control center are designed to prevent the compressor from exceeding full-load amperes. Overloading can be caused by high suction pressure or low-voltage operation. If the solid-state sensors embedded in the motor windings are damaged, the control module will prevent the compressor from starting to avoid a burnout.

5. Excessive Pressure or Capacity Loss

The Malfunction: The chiller fails to reach its design temperature or loses the ability to modulate its cooling output.

Why it Happens:

• Inlet-Guide Vanes: If the automatic guide vane actuator fails or the sensing device transmits incorrect signals, the vanes may not adjust to match the cooling load.
• Refrigerant Shortage: A leak (often caused by vibration-induced fatigue) will lead to a shortage, causing the system to lose its ability to absorb heat.