Occurrence Frost or blocks of ice on one of the refrigeration circuit pipes is an alarm that cannot be ignored. In normal operation icing it should be uniform or absent altogether, depending on the type of defrosting system. If you notice that the tube leading from the compressor or to the evaporator is covered with a “fur coat,” it means that the pressure balance or circulation of the refrigerant in the system is disturbed.
Often equipment owners notice this defect by accident, looking behind the back wall of the unit. However, ignoring the problem can lead to more serious consequences, such as compressor failure or complete loss of circuit tightness. Understanding the physics of the process will help you quickly identify the root of the evil and make a decision: call a technician or try to fix the problem yourself.
In this article we will analyze in detail the mechanics of the refrigeration cycle and explain why sudden cooling occurs at certain points in the circuit, leading to condensation of moisture and its subsequent freezing. You will learn how to distinguish normal operation of the system from an emergency situation that requires immediate intervention.
The principle of operation of the refrigeration circuit
To understand the nature of icing, you need to briefly recall how the cooling system works. The refrigerant (freon) circulates in a closed circle, changing its state of aggregation. The compressor compresses the freon gas, turning it into a hot liquid under high pressure, which then enters the condenser (grid at the back).
After the condenser, the refrigerant passes through a filter drier and enters capillary tube. This is where the critical point occurs: the diameter of the tube decreases sharply, creating high resistance. The pressure drops and the liquid expands sharply, turning into a cold gas. This process is accompanied by a sharp temperature decrease at the throttling point.
Ideally, this area is located inside the housing, in the evaporator area. But if the cycle is broken, the boiling point moves outward. The temperature of the metal tube can drop below -10...-15°C, which causes moisture from the air to instantly crystallize on the surface.
- ❄️ The compressor builds up pressure, creating hot gas.
- 💧 In the condenser, the gas cools and becomes liquid.
- 📉 In the capillary tube, the pressure drops, causing the freon to boil.
- 🌡️ The evaporator absorbs heat from the chamber, cooling the products.
Localization of the problem: where exactly the ice freezes
The location of the ice plug formation is a key diagnostic sign. If a section of the tube freezes immediately after leaving the refrigerator body (near the compressor), this often indicates clogging of the capillary tube. Freon cannot pass freely through a narrow hole, the pressure in front of the plug increases, and the temperature drops.
Another common situation is icing of the return tube (suction) going from the evaporator to the compressor. In this case, liquid freon does not have time to completely evaporate in the evaporator and enters the compressor. This phenomenon is called “wet running” and is extremely dangerous for the mechanics of the motor.
Why is wet running dangerous?
Liquid freon is not compressed, but hydraulically hits the compressor valves. This can lead to damage to the valve group or jamming of the pistons, which will require an expensive replacement of the compressor.
Sometimes frost covers the entire length of the tube unevenly, forming characteristic “bumps”. This is a sure sign that the amount of refrigerant in the system has changed. Accurate diagnosis requires a visual inspection and, often, connecting a pressure manifold.
Freon leakage as the main cause
The most common cause of a shift in the boiling point and subsequent icing is refrigerant leak. When the amount of freon in the system decreases, the pressure drops throughout the entire circuit. As a result, freon begins to boil earlier than expected, even before it enters the evaporator.
The process looks like this: due to a lack of substance, the speed of gas movement drops. Cooling is ineffective and the compressor runs longer trying to reach the temperature. At some point, the section of the tube in front of the evaporator becomes so cold that the moisture in the air turns into ice.
⚠️ Attention: If you find an oily stain under the refrigerator or at the junction of the tubes, this is almost guaranteed to indicate a leak. The freon evaporates, but the oil remains.
Fixing a leak is a complex process that requires finding the fistula, sealing the hole, evacuating the system and refilling with new freon. It is impossible to perform these operations independently without special tools.
| Symptom | Probable cause | Required actions |
|---|---|---|
| Ice at the evaporator inlet | Leakage freon | Search for leaks, evacuation, refilling |
| Ice at the outlet of the capillary | Clogged system | Purge with nitrogen, replace the filter |
| Icing of the suction pipes | Faulty heating element/thermostat | Defective electronics, replacement of sensors |
Clogged capillary tube and filter drier
The second most popular reason is clogging of the narrow part of the circuit. The capillary tube has a microscopic diameter, so even the smallest particles of oxides that have entered the system during poor-quality repairs, or oil breakdown products can block the freon current.
The filter drier is also often clogged. Its task is to retain moisture that accidentally gets into the circuit. Over time, the silica gel inside the filter becomes saturated and turns into dust, which clogs the outlet. The pressure in front of the filter increases, and immediately behind it drops to a vacuum, causing severe icing.
☑️ Diagnosis of blockage
To fix the problem, the technician performs purging the system with nitrogen under high pressure. If the blockage is serious, the capillary tube must be replaced and a new filter drier must be installed. Simple defrosting will not help here.
Malfunctions of the No Frost system
In refrigerators with the system No Frost the reasons may lie in a violation of the evaporator defrosting algorithm. If the heating element is turned off and the fan continues to blow air, or vice versa - the sensor is “buggy”, ice can build up on the pipes leaving the freezer.
Often the problem lies in malfunction of the defrost sensor or the timer. The system “thinks” that there is no ice and does not turn on the heating. The ice coat grows, blocks the channels and begins to “crawl” onto the visible parts of the pipes. In such cases, complete defrosting of the unit for 24 hours is often required.
Electronics diagnostics are carried out using a multimeter. The resistance of the heating element, the integrity of the thermal defrost fuse and the readings of temperature sensors are checked. Replacing these elements usually solves the problem.
Errors during refueling and repair
If the refrigerator was recently serviced, and after that a problem appeared, the refueling technology was most likely broken. Insufficient amount of freon leads to the leakage symptoms described above, even if there are no holes in the system.
Excess refrigerant is also dangerous. The excess volume has nowhere to evaporate, and the liquid phase reaches the compressor, causing icing of the suction pipe. In addition, it is important to use freon of the brand indicated on the nameplate (for example, R600a or R134a). Replacing one type with another without recalculating the weight and changing the oil is unacceptable.
⚠️ Attention: Never try to refuel the refrigerator yourself “by eye”. The wrong dose of refrigerant can kill the compressor within a few hours of operation.
The quality of the oil also plays a role. If highly hygroscopic oil was used during the repair and the system was poorly evacuated, the moisture in the oil will freeze in the capillary during the first cooling cycle.
Methods of diagnosis and elimination
The first thing to do when ice is detected is to completely defrost the refrigerator. Unplug it for at least a day, leaving the doors open. If after turning on the problem does not return within 2-3 days, there may have been a single electronics failure or temporary blockage with ice.
If ice appears again, professional diagnostics will be required. The technician uses a thermal imager or simply tactilely checks the temperature of the circuit. If there is a leak, the tube will be cold to the point of damage, and then at room temperature. If clogged, a sharp temperature drop will be observed in the area of the capillary.
Is it possible to use heat to defrost ice on the tube?
It is strictly forbidden to heat the tubes with an open fire or a powerful hairdryer under pressure. This will lead to depressurization of solder joints and a freon fire.
Repair usually includes the following steps: finding and eliminating leaks (if any), replacing the filter drier, evacuation of the system for 30-40 minutes and charging with an exact dose of refrigerant according to the scale. Only adherence to technology guarantees a long service life of the unit.
Why does the tube freeze only at night?
This may be due to a drop in voltage in the network at night, which causes the compressor to operate abnormally, or to a change in humidity in the room. It is also possible that at night the refrigerator is opened less often, and the thermal conditions inside change.
Is it dangerous to touch a frozen pipe?
You can touch it, but there is a risk of your skin freezing to the metal if the temperature is very low. It's better to use gloves. The danger is posed by the ice itself - if you chip it, you can damage the thin walls of the tube and cause a leak.
How much does it cost to repair if the system is clogged?
The cost consists of the work of the technician, the cost of nitrogen, a new filter and freon. The price may vary depending on the region and model of the refrigerator, but usually this is an average-cost repair.
Does it need to be replaced when there is ice?
In most cases, no. The compressor is replaced only if it has already failed (burnt out, jammed) or if a lot of moisture/acid has entered the system, which requires flushing the circuit, which is easier to replace with a new motor.