Diagnostics and repair

To minimize issues related to excessive repair costs or significant financial losses due to spoiled cargo, timely maintenance of your equipment is essential. One of the first rules is to keep the condenser clean. No special equipment or skills are required to visually assess the degree of coil contamination. The condenser fan motor, cooling the condenser coil with outside air, contributes to its contamination, which leads to negative consequences such as loss of performance, especially in hot weather. This significantly increases condensation pressure and places unnecessary load on the compressor.

You should also ensure that the system’s drainage pipeline is clean and that water can freely exit through the drain. At first glance, such a minor issue as a clogged drainage system may lead to very serious consequences. If the water has nowhere to go, it will simply return into the container and turn into ice. After some time, the amount of ice will reach a critical level and will prevent the system from functioning. The ice will block airflow supply and circulation inside the container, resulting in reduced performance.

As a rule, pipelines do not fail often, but nevertheless, leaks are not uncommon. If it is simply a poorly tightened nut on the filter-drier, the issue is not too serious—but what if the condenser is leaking? It should not be forgotten that containers enter the secondary market after having operated for decades in some cases. Such an aggressive environment as saltwater and sunlight leaves its mark. Typically, leaks appear in the weakest spots—joints and soldered areas.

The first and simplest way to detect a condenser leak is by spotting oil stains. Refrigerant mixed with oil, escaping from the high-pressure line, leaves an oily trace. Often, the leak can be located and repaired. Motors are another important component. They are designed for a long service life (10–15 years). It is practically impossible to influence their operation or prevent a breakdown. The main motor issues are winding burnout, bearing wear, or capacitor failure. The heart of the entire system is the compressor. The most common type today is the reciprocating compressor. These compressors have proven themselves as reliable and durable “workhorses.” However, even they are not immune to problems and failures.

Mechanical failure. In this type of malfunction, the compressor seizes. There are several reasons for this. One of them is the accumulation of excessive refrigerant in the compressor crankcase, and during startup, refrigerant enters the moving parts of the compressor instead of oil. This naturally leads to wear and failure of components. On some models, upon special request, a crankcase heater is installed.

Another cause of compressor seizure may be a simple lack of oil. A small amount of oil is carried into the discharge line during compressor operation and circulates through the system mixed with the refrigerant. A normal amount of oil circulation is considered to be approximately 1% of the mass of the circulating refrigerant.

A common problem is the entry of liquid refrigerant into the compressor cylinders, which results in valve destruction. The cause may be an overcharged refrigerant system or improper operation of the TXV. Another significant issue is the entry of air. This typically happens due to improper installation of refrigeration system components or leaks in the suction line. Air in the system, particularly in the compressor, can lead to very serious consequences. As we know, air contains moisture, which reacts with oil and causes hydrolysis. The oil breaks down, the motor and valves overheat, and acids form during this process, which destroy the compressor motor windings. Once air enters the system, it causes a sharp increase in discharge pressure, valve overheating, and gasket destruction.

You must pay attention to unusual noises during compressor startup and operation. Compressors are usually equipped with internal protection that disconnects the circuit when the windings overheat, cutting off power to the compressor. There are also high- and low-pressure switches that shut down the compressor under certain conditions to prevent damage. However, they cannot always prevent failures, which is why you should listen to the compressor during operation and startup. Abnormal noise may be caused by incorrect power supply—for example, low line voltage, a faulty contactor, or a phase loss. Therefore, remember that proper, timely, and professional maintenance can save your nerves, money, and cargo.