Conversion of the standard converting a refrigerator into a full-fledged freezer is a technically difficult task, but quite feasible for a master with basic skills in working with tools. The main difficulty lies in the fact that evaporator design in a regular refrigerator it is designed to maintain a temperature of about +4°C, while deep freezing requires a stable mode below -18°C. Simply changing the controller settings will not be enough here; intervention in the refrigeration circuit will be required.
Many owners of old equipment think about this when the compressor is still working properly, but the shelves or internal lining have become unusable. Instead of recycling unit, you can give it a second life in the garage or in the country. However, it is worth immediately assessing the risks: a violation of the tightness of the system or errors in the selection of refrigerant can lead to breakdown of the compressor.
In this article we will analyze the physical principles of the system, the necessary tools and a step-by-step algorithm of actions. It is critically important to understand that without evacuation of the system and accurate dosage of refrigerant, rework is impossible. This is not just replacing a wire, this is work with pressure and chemicals, requiring strict adherence to technology.
Physical principles and feasibility assessment
Before proceeding with disassembly, it is necessary to clearly realize the difference in the thermodynamics of processes. A conventional refrigerator operates in a cycle where freon evaporates at a boiling point of about -20...-25°C, but the thermostat turns off the compressor as soon as +4°C is reached in the chamber. For a freezer, the cycle must continue until the temperature inside drops to -18°C or lower.
The main obstacle is the heat transfer area. A standard evaporator (often foamed in the walls or made in the form of a sheet on the back wall) does not have enough power to quickly freeze food. If you try to force the system to operate in deep-freeze mode without upgrading, the compressor will work without stopping, which will lead to overheating of the oil and jamming of the piston group.
In addition, thermostat (thermostat) as standard has a shutdown range that is not suitable for low temperatures. You will need to replace it with an analogue with markings intended for freezers, for example, series TAM-133 or their modern analogues. Without this step, the system will not know when to stop.
⚠️ Attention: If your refrigerator is equipped with a No Frost system, the modification becomes much more complicated. You will have to either completely redo the defrost system, or dismantle the fan and air ducts, switching to static cooling, which requires the installation of a new, more powerful plate evaporator.
Necessary tools and materials
For high-quality implementation of the project, you will need a specific set of tools that goes beyond frames of a standard home craftsman's kit. Particular attention should be paid to equipment handling copper pipes and refrigerant. Without vacuum pump i pressure gauge station (collector) it is strictly not recommended to start work, since the presence of moisture or air in the system is guaranteed to disable the equipment.
You the following components will be needed to modernize the circuit:
- 🛠️ Burner (gas or oxygen-acetylene) and solder for copper with flux.
- ❄️ New evaporator (plate or tubular) with a heat exchange area corresponding chamber volume.
- 🌡️ Thermoregulator with an operating range up to -24°C (for example, Danfoss or analogue).
- 💧 Cylinder with refrigerant (R134a or R600a, depending on the type of oil in the compressor).
- 🔧 Pipe cutter, rolling, pipe cleaner and a set of keys.
You will also need filter-drier, which is a disposable element and must be replaced at any time opening the circuit. Its task is to absorb moisture that entered the system during installation. Ignoring the replacement of the filter will lead to the formation of ice plugs in the capillary tube and system failure.
Dismantling the old equipment and preparing the chamber
The first stage is the complete preparation of the internal volume. If you are remodeling an old refrigerator, you will need to remove all plastic parts, shelves and, most importantly, the old evaporator, if it is not foamed into the body. In models with a foamed evaporator (“crying wall”) the situation is more complicated: you often have to cut off the back panel or carefully dismantle the old heat exchanger, trying not to damage the insulation.
After dismantling, the inside of the chamber must be thoroughly cleaned and degreased. The walls may require additional thermal insulation if the standard polyurethane foam is damaged or its thickness is insufficient for temperatures below -20°C. Insulation must be moisture resistant to avoid ice freezing inside the walls of the housing.
It is important to provide space for installing a new evaporator. It should not touch the products directly, otherwise they will freeze and it will be impossible to remove them without damaging the heat exchanger. The optimal location is on the back wall or ceiling of the chamber, ensuring free air circulation.
☑️ Preparation for installation
Installation of a new evaporator and replacement of the thermostat
Installation of a new heat exchanger element is the key point of remodeling. The selected one evaporator must be securely fastened to the back wall. To improve heat transfer between the evaporator tubes and the wall of the refrigerator, aluminum foil or special heat-conducting pastes are often used, although gluing or rolling is used on an industrial scale.
The capillary tube of the new evaporator requires careful handling. It cannot be bent, cut or compressed, since the internal diameter is a fraction of a millimeter. Any deformation will disrupt the circulation of freon. The connection to the suction tube of the compressor is made through a copper fitting, which is soldered into the existing line.
In parallel, replacement is carried out thermostat. The sensor of the new thermostat (bellows tube) is attached to the outlet tube of the evaporator or inserted into a special sleeve. The on/off differential is adjusted experimentally or according to the device’s passport data. An error in setting will lead to either insufficient cooling or freezing of food and freezing of the door.
⚠️ Attention: When soldering copper connections, be sure to use nitrogen purge or keep the burner flame strictly localized. Overheating of the tubes inside the refrigerator body can lead to ignition of the insulation or deformation of the plastic, which will create a fire hazard.
Evacuation and charging with refrigerant
After installing all elements and checking the tightness of the connections (pressure testing with nitrogen 10-15 bar), the most important stage begins - evacuation. Vacuum pump connects to the service fitting, and the system is pumped out until a deep vacuum is achieved. This is necessary to remove air and, more importantly, evaporate moisture from hard-to-reach places in the system.
The vacuuming process should last at least 30-40 minutes. After stopping the pump, you need to close the valve and wait 15-20 minutes, monitoring the pressure gauge readings. If the arrow begins to creep up, it means that there is a leak in the system that needs to be eliminated.
Refilling refrigerant is made strictly according to the weight indicated on the compressor nameplate (or calculated based on the characteristics of the new evaporator). For accuracy, it is better to use electronic scales. Refilling “by eye” or by pressure in static conditions is unacceptable, since the amount of refrigerant is critical for the proper operation of the throttling device (capillary tube). the fact that liquid freon enters the compressor, causing water hammer. This can instantly destroy the valves or piston group. In addition, excess pressure increases the condensation temperature, and the refrigerator will stop freezing, and the compressor will overheat.
What happens if you overdo it with freon?
Overcharging with refrigerant causes liquid freon to enter the compressor, causing water hammer. This can instantly destroy the valves or piston group. In addition, excess pressure increases the condensation temperature, and the refrigerator will stop freezing and the compressor will overheat.
Technical characteristics and comparison of modes
Understanding the difference in operating parameters will help to correctly configure the converted device. The table below shows a comparison of the standard refrigerator mode and the required parameters for the freezer.
| Parameter | Standard refrigerator | Freezer (after modification) |
|---|---|---|
| Freon boiling point | -20...-25°C | -30...-35°C and below |
| Temperature in the chamber | +2...+6°C | -18...-24°C |
| Working time coefficient | 30-40% (on for 10 minutes, stopped for 20 minutes) | 70-90% (works almost constantly) |
| Required compressor power | Standard (for example, 1/5 hp) | Higher power is desirable (1/4 hp and above) |
As can be seen from the table, the load on the unit increases many times over. The standard compressor of a small refrigerator may not be able to cope with the task of maintaining low temperatures in a large volume, especially in a hot room. In such cases performance the system drops, and the desired temperature may not be achieved.
To compensate for the increased load, an additional fan is sometimes installed inside the chamber for forced air circulation. This helps to even out the temperature field and avoid local areas with insufficient cooling. However, this increases power consumption and noise.
Testing and first launch
The first launch after refueling should be under constant monitoring. Turn on the unit and leave it running empty for 2-3 hours. At this time, it is necessary to monitor the compressor current consumption (using current clamps) and the housing temperature. The current should not exceed the rated current indicated on the tag.
Pay attention to freezing of the evaporator. In a working system with proper charging, the entire heat exchanger should be covered with a uniform layer of frost. If only a part freezes over (for example, the first 20 cm of the tube), this is a sign of underfilling of freon or a blockage. If the frost reaches the compressor itself, this is a sign of overflow, which is deadly for the engine.
After a successful test at idle, you can load the chamber with products. It is important not to overload the freezer with warm food at once, as this will cause a long cycle and a temperature jump. It is better to load in small portions, giving the system time to stabilize.
⚠️ Attention: On the first day of operation, regularly check the connections for leaks with a soap solution. Vibration during compressor operation could weaken poorly soldered joints. Detection of a leak requires an immediate stop and repeated evacuation.
Is it possible to use an ordinary refrigerator as a freezer without replacing freon and the evaporator?
No, this is technically impossible. The standard system will not be able to reach and maintain a temperature of -18°C. The compressor will run continuously, the oil will thicken, and the motor will burn out in a short time. A complete modernization of the circuit is required.
Which refrigerant is better to use for the conversion: R134a or R600a?
The choice depends on the type of oil in the compressor. For mineral oil, only R12 (prohibited) or transition mixtures (not recommended) are suitable. For synthetic oil (POE) R134a is intended. R600a (isobutane) requires special equipment due to its explosion hazard and is used in modern compact models. It is better to use the gas for which the compressor is designed.
Why does the compressor work without stopping after modification?
This can be caused by three reasons: 1) Insufficient compressor power for the new volume/temperature. 2) Incorrect setting or malfunction of the thermostat. 3) A refrigerant leak or a blockage in the system, due to which the temperature in the chamber does not drop to the thermostat cut-off value.