A sudden stop in the operation of a refrigeration unit often takes you by surprise, and the first thing that comes to mind is calling a technician. However, for those who are accustomed to understanding technology on their own, the question refilling the refrigerator becomes a completely solvable task if you have the necessary equipment. The process of restoring the functionality of the cooling system requires not only technical skills, but also a deep understanding of the physical processes occurring inside the circuit.
Before taking active steps, you must clearly understand that refrigerant is under pressure, and the system itself is sealed. Improper handling of freon or violation of vacuum technology can lead to compressor failure or even an explosive situation, especially if a flammable gas is used. In this article, we will analyze in detail each stage of the procedure, from diagnosing the leak to the final start-up of the unit.
It is worth noting right away that self-refilling is justified only if you have accurately diagnosed the leak and fixed it, or are changing the compressor. You cannot simply add gas to a system where it has “gone somewhere” - you first need to find and seal the leak, otherwise all efforts will be in vain. If you are ready for painstaking work with metal and pressure, then we move on to preparing the equipment.
Necessary tools and preparation of the workplace
High-quality repairs are impossible without specialized tools. A basic set for working with refrigeration systems includes not only wrenches, but also devices for monitoring pressure and vacuum. You will definitely need a pressure gauge station (manifold), which allows you to monitor the pressure in the discharge and suction system, as well as control the vacuum process.
The second critical element is vacuum pump. Its task is to remove air and moisture vapor from the circuit, which, when mixed with compressor oil, form acid that destroys the system from the inside. It is absolutely impossible to start the unit without a deep vacuum. You will also need a cylinder with a refrigerant of the appropriate brand, a scale for accurate dosing of gas and a kit for soldering copper pipes.
⚠️ Attention: When working with copper pipes, use only hard solder (phosphorus-containing) for copper and soft solder with flux for brass. Using unsuitable materials will result in repeated leakage within a short time.
Different types of refrigerants may require different hoses. For example, R600a (isobutane) requires hoses with threads that prevent entanglement, since this gas is flammable. Don't forget to prepare a leak detector or soap solution to check the tightness of the joints after soldering. The workplace should be well ventilated, especially if you work with flammable gases.
Diagnostics of the system and search for freon leaks
Before opening the system, you need to make sure that the problem is the lack of refrigerant, and not a malfunction of the thermostat or start relay. If the compressor runs continuously, but there is no cold, and the condenser (grid at the back) remains only partially cold or warm, this is a sure sign of a leak. The first step is always a visual inspection of the pipelines for oil stains, since freon carries oil with it.
To accurately determine the location of depressurization, the system must be pressurized (create excess pressure) with nitrogen. The use of oxygen or ordinary air from a compressor is unacceptable: oxygen mixed with oil creates an explosive mixture, and the air contains moisture that will freeze in the capillary. The nitrogen pressure is usually raised to 10-15 atmospheres, but do not exceed the limit values indicated on the compressor.
Searching for leaks can be done using several methods. The simplest is to use a soap solution, which generously lubricates all suspicious joints, elbows and sealed areas. The appearance of bubbles will indicate a defect. A more professional approach involves the use of an electronic one, which reacts to the concentration of halogens in the air. In difficult cases, when the leak is microscopic, the circuit is immersed in water and waiting for bubbles to appear. leak detector, which responds to the concentration of halogens in the air. In difficult cases, when the leak is microscopic, the circuit is immersed in water and bubbles are waited for to appear.
After identifying the leak location, the defective area is cut out and replaced with a new one, or sealed. If the leak occurs in the foamed part of the housing (the evaporator inside the chamber), repair becomes difficult: either the thermal insulation is opened, or an external evaporator (“crying” or hinged) is cut in, cutting off the damaged internal circuit.
Why can’t you use air for pressure testing?
Air contains moisture and oxygen. Moisture at low temperatures will turn into an ice plug in the capillary tube, blocking the circulation of freon. Oxygen oxidizes the oil, turning it into an aggressive acid that corrodes the tubes from the inside, leading to new leaks after a few months.
Technology for soldering and replacing the filter drier
Soldering copper tubes is a skill that requires practice. Copper melts at about 1083°C, but solder flows at much lower temperatures (about 600-700°C for hard solder). It is important not to overheat the tube, otherwise it may burn out. Before soldering, the joints are cleaned to a shine, and flux is applied (if soft solder is used) or soldering is carried out in a torch flame using phosphorus-containing solder (self-fluxing).
One of the mandatory procedures when opening a circuit is replacement filter drier. This element is responsible for removing moisture from the system. As soon as you unsolder the tube and let air inside, the zeolite (the substance inside the filter) instantly absorbs moisture from the atmosphere and loses its properties. An old filter cannot be reused, even if it looks new.
The filter is installed on the high pressure side, immediately after the condenser, before the capillary tube. When soldering the filter, you must act quickly so as not to overheat the filter housing, since high temperature can also activate the zeolite prematurely. Some craftsmen recommend heating the new filter with a hair dryer before installation to remove moisture from the surface.
| System element | Function | Replacement when opened | Material |
|---|---|---|---|
| Filter drier | Removal of moisture and acids | Required | Copper/Steel |
| Capillary tube | Throttling freon | When clogged | Copper |
| Compressor | Gas compression | With wedge/winding | Steel |
| Condenser | Gas cooling | If there is a leak | Steel/Aluminium |
After installing all the elements, the system is again checked for leaks with nitrogen. Only after making sure that the pressure remains stable for several hours (ideally, a day) can you move on to the next stage. Saving time on checking the tightness often leads to the fact that after a month the refrigerator stops cooling again.
Vacuuming the system: removing moisture and air
Vacuuming is perhaps the most important stage, which is most often ignored by beginners, which leads to breakdown. The purpose of the process is to reduce the pressure in the circuit to a minimum in order to boil and remove all moisture remaining in the oil and on the walls of the pipes. Water boils at low pressure even at room temperature, turning into steam, which is pumped out by a pump.
A pressure gauge station is used to connect the vacuum pump. The blue hose (low pressure) is connected to the service fitting or capillary, the yellow hose is connected to the pump. The red valve (high pressure) should be closed if you are vacuuming only through the suction line, but it is better to open both valves on the manifold to create a vacuum in the entire circuit at once. The operating time of the pump depends on the power of the unit, usually from 30 minutes to 1 hour.
⚠️ Attention: Never turn on the refrigerator compressor to create a vacuum (“self-vacuum”). This leads to engine operation without cooling, overheating of the windings and eventual combustion of the motor. Use only an external vacuum pump!
During the vacuum process, the pressure gauge needle should go into the “green zone” (below zero). After pumping is completed, first close the valves on the manifold, and only then turn off the pump so that oil from the pump does not flow back into the system. If the arrow begins to creep up after turning off the pump, it means that there is moisture left in the system (it evaporates) or there is a leak.
Filling the refrigerator with refrigerant by weight
There are two main methods of charging: by pressure and by weight. Refilling by pressure (“by eye” or according to temperature and pressure correspondence tables) is only permissible for experienced craftsmen and requires a running compressor for control. For self-repair, the only correct and safe method is filling by scale.
On the refrigerator nameplate (usually inside the chamber or on the back) the exact mass of refrigerant required for this model is indicated. For example, "Refrigerant R600a 52g". You will need an electronic kitchen scale that is accurate to 1 gram. The cylinder with freon is placed on the scales upside down (if filling with the liquid phase, which is faster) or in the normal position (gas phase, which is safer for R600a, but longer).
The process looks like this: the cylinder is weighed on the scales, the mass of the required gas is subtracted from its current mass, and filling begins, monitoring the readings of the scales. As soon as the weight has decreased by the desired value (for example, by 52 grams), the valve is closed. It is important to refuel the system in the off state so that the gas fills the circuit evenly, and only then start the compressor to check.
☑️ Refilling algorithm using scales
If you use R134a, filling with the liquid phase (cylinder upside down) is acceptable, but requires caution so that there is no water hammer in the compressor at start. For R600a (isobutane), refueling in the gas state (cylinder standing upright) is highly recommended due to its flammability, although it takes longer. In this case, gas is supplied to the suction tube of the operating compressor in small portions.
Monitoring and adjusting the system
After refueling, you need to start the refrigerator and let it run for at least 30-40 minutes. At this time, the main parameters are monitored. Check the temperature of the condenser with your hand (or a thermometer): it should be hot at the beginning (2/3 of the length) and warm at the end. The evaporator inside the chamber should be evenly covered with frost or be cold over the entire area.
The most important indicator of correct refueling is the temperature of the suction tube (the one that goes from the evaporator to the compressor). It should be slightly cool, perhaps with droplets of condensation, but under no circumstances should it become overgrown with a “coat” of ice. Icing of the tube to the compressor indicates refilling or clogged capillary, which is dangerous for the motor. If the tube is warm or at room temperature, and there is not enough cold, freon is not enough.
You should also control the current consumption of the compressor using current clamps. The current should not exceed the rated current indicated on the relay or in the documentation. Exceeding the current at normal condenser temperature may indicate problems with the compressor itself or poor-quality oil.
⚠️ Attention: If after refueling you hear gurgling or hissing in the area of the filter-drier, this is a sign of an “air lock” or under-charging. The system will have to be evacuated again and recharged again, since air prevents normal circulation of the refrigerant.
Frequently asked questions (FAQ)
Is it possible to fill a refrigerator with regular car freon?
No, this is strictly prohibited. Car air conditioners run on R134a freon (often), but refrigerators can use R600a (isobutane) or R12. Mixing different types of refrigerants or oils (mineral, synthetic POE, alkylbenzene) will lead to the formation of dense sediment, capillary blockage and compressor failure. Use only the type of gas that is indicated on the nameplate.
How long does the refrigerator work after proper filling?
If the automation is working properly and there are no leaks, a properly charged refrigerator should work cyclically: it works for 10-20 minutes, rests for 20-40 minutes (depending on the load and the temperature in the room). If it works non-stop, but does not freeze, the problem is not in the amount of gas, but in a leak, a clogged capillary or loss of compressor performance.
Is R600a freon dangerous for humans?
Isobutane (R600a) itself is not toxic in small quantities, but it is extremely flammable and explosive at concentrations in air from 1.3% to 8.4%. That is why, when refilling R600a, do not smoke, use an open flame or use a sparking tool near the refrigerator. In household refrigerators, the amount of gas is small (up to 150 grams), so there is no risk of a large-scale explosion, but a flash of flame is possible.
Is it necessary to change the oil in the compressor when refueling?
During normal refueling, there is no need to change the oil due to a leak if the compressor is working properly and has not overheated. The oil is changed only when the compressor itself is replaced or if the system is heavily contaminated (for example, after the windings burn out, when the oil turns black and becomes acidic). In normal mode, the oil lasts the entire service life of the unit.