1. Overcharge of Refrigerant

An overcharged system contains excess refrigerant, which adversely affects condenser performance and system pressures. The following indications are observed:

• The liquid level in the condenser becomes excessively high, resulting in a reduction of the effective condensing surface area. This leads to an increase in saturation temperature and pressure.
• The condenser pressure gauge shows high readings, indicating elevated system pressure.
• The high-pressure cut-out switch may activate, automatically stopping the compressor to prevent damage.
• Both suction pressure and discharge pressure are higher than normal, reflecting the overall overload condition of the system.

2. Undercharge of Refrigerant

An undercharged system has insufficient refrigerant, leading to poor cooling performance and abnormal compressor operation. The typical indications include:

• The compressor runs at a higher temperature due to high superheat at the suction side, which reduces its efficiency.
• Both suction and discharge pressures are lower than normal.
• Large vapour bubbles appear in the liquid sight glass, indicating insufficient liquid refrigerant flow.
• The condenser gauge shows low pressure readings.
• The compressor motor current (ammeter reading) is lower than normal, due to reduced load.
• There is a rise in the temperature of the refrigerated space, indicating inadequate cooling.
• The compressor runs continuously or for extended periods in an attempt to maintain the desired temperature.

3. Air Ingress into the System

The presence of air (non-condensable gases) in the refrigeration system affects heat transfer and pressure conditions. The following symptoms are observed:

• The compressor may overheat, accompanied by high discharge pressure, even though the condensing temperature may remain normal.
• Small air bubbles may be visible in the liquid sight glass.
• The condenser pressure tends to be higher than normal, due to the presence of non-condensable gases.
• Cooling efficiency is reduced, causing the compressor to run for longer durations.
• The condenser pressure gauge pointer may fluctuate or jump irregularly, indicating unstable system conditions.

1. Rectification of Overcharge

Causes:

• Excess refrigerant charged into the system.
• Air in the system may sometimes give a false indication of overcharge.

Corrective Actions:

• Remove excess refrigerant by connecting a recovery cylinder to the liquid line charging valve. Run the compressor and carefully discharge refrigerant into the cylinder.
• Purge any air present in the system to ensure correct pressure conditions.
• If icing is observed in control components (such as regulators), carry out defrosting using appropriate methods.

2. Rectification of Undercharge

Causes:

• Leakage of refrigerant from components such as shaft seals, flanges, valve glands, or joints.
• Blockage in the expansion valve strainer.
• Partial restrictions in filters, driers, or evaporator passages.

Corrective Actions:

• Identify and repair all refrigerant leaks in the system.
• Clean or replace blocked filters and driers to restore proper flow.
• After rectification, charge the system with the required amount of fresh refrigerant to restore normal operation.

3. Rectification of Air Ingress

Causes:

• Entry of air during improper charging procedures.
• In low-pressure systems (such as those using certain refrigerants), air may leak into the suction side when system pressure falls below atmospheric pressure.

Corrective Actions:

• Purge air from the system via the condenser, as air (being non-condensable) accumulates at the top of the condenser above the հեղ liquid refrigerant.
• Keep the condenser cooling active, and vent out the air carefully through the purging line.
• If required, connect a collecting cylinder to safely remove the air.
• After purging, close all valves properly and check the refrigerant level.
• Recharge the system if necessary, and restart the compressor while observing all safety precautions.