Common Signs and Symptoms of Compressor Malfunction or Inefficiency in Refrigeration Systems

Equipment failures, although unavoidable, should not catch us off guard. Understanding the signs and symptoms of compressor malfunctions in a refrigeration system can help us take corrective actions promptly. This article discusses the most common issues that may arise in commercial refrigeration units and provides solutions to address them.

1. Undercharging of the Refrigeration System

When the refrigeration system is undercharged, the compressor may exhibit several signs:

The compressor is running hot, and performance is lower than usual. Suction and discharge pressures drop. Vapor bubbles are present in the liquid sight glass. The condenser has low readings. The compressor shows low ammeter readings. Cold room temperatures are warmer than usual. The compressor runs for longer periods than normal.

Causes: This may happen due to refrigerant leakage which can occur at the shaft seal, flanges, couplings, or valve gaskets.

Solution:

Check and address refrigerant leakages at the shaft seal, flanges, and couplings. Clean the filters and driers. Replace the lost refrigerant with fresh alternatives. Follow the manufacturer's instructions.

2. Overcharge of the Refrigeration System

An overcharged refrigeration system runs on more refrigerant than it can handle, leading to the following indicators:

High condenser gauge readings. Abnormal start and stop sequences of the compressor. High suction and discharge pressures.

Causes: Overcharge may result from excessively high refrigerant levels or air being included in the system.

Solution:

Drain the excess refrigerant from the system using a cylinder connected to the charging valve liquid line. Start the compressor and operate the charging valve. If air is the cause, purging the air will rectify the overcharge.

3. Moisture in the System

Potential moisture in the system can create issues like the expansion valve freezing, leading to mistaken signs of undercharging. Additionally, moisture can cause corrosion within the system.

Solution:

Replace silica gel if there is a minor moisture problem. Drain the refrigerant and pump out all the air from the system.

4. Air in the System

The indicators of air in the system include overheating the compressor with high discharge pressures, air bubbles in the liquid sight glass, and the compressor running for an extended period.

Solution:

Remove air from the system using the condenser, cooling water left on, and venting from the top of the condenser. Connect a collecting cylinder to the purging line and open the line to drain out the air. Seal the purge valve tightly after purging the air. Check refrigerant levels and charge accordingly with fresh refrigerant.

5. Oil in the Refrigeration System

Signs of oil in the system include a drop in temperature in the cold room, excessive frost on the suction line, and a drop in lubrication levels.

Causes: A malfunctioning oil separator may contribute to oil leakage, along with worn-out compressor linings and defective pistons.

Solution:

Check and replace the oil separator if it is defective. Clean the drier if necessary. Drain the evaporator coil to remove any oil traces. Increase the differential temperature between the evaporator and condenser to defrost the suction pipe. Warm the pipes using a blow torch.

6. Refrigerant Flooding

When liquid seeps back to the suction of the refrigerant compressor, the result is flooding. This issue may be due to incorrectly adjusted or faulty expansion valves, leakage at the solenoid valve, or overcharging.

Solution: Drain the excessive refrigerant from the system by connecting a cylinder to the charging valve liquid line and starting the compressor to operate the charging valve.

Conclusion: Understanding and addressing these signs and symptoms can help maintain the efficiency and longevity of your refrigeration system. Regular checks and appropriate maintenance practices are essential to avoid costly and time-consuming issues.