Converting a household refrigerator into a full-fledged freezer is a task that requires not only technical skills, but also a deep understanding of the principles operation of the refrigeration circuit. Many owners of old equipment are thinking about such an upgrade in order to get additional space for storing frozen food without buying an expensive specialized unit. However, it is worth immediately noting that a standard single-compressor refrigerator is not structurally designed to maintain temperatures below -18°C for a long time without modernization.
The main difficulty lies in the difference in operating ranges temperatures. A regular refrigerator is designed to maintain +2...+5°C in the main chamber, while a freezer must provide intensive cooling to extreme values. Simply turning the regulator to the maximum often leads to freezing of the evaporator, overload compressor and failure of the system. In this article, we will analyze the technical nuances of such a modification so that you can weigh the pros and cons.
Before you begin dismantling the panels and soldering the tubes, you need to evaluate the economic feasibility of the idea. The cost of new components, refrigerant and electricity can exceed the cost of a used freezer. However, if you have experience working with refrigeration equipment and a desire to experiment, this project can be an excellent way to get a unique unit with specified parameters.
Fundamental differences between a refrigerator and a freezer
Fundamental difference lies in the design of the evaporator and the settings of the thermostat. In a conventional refrigerator, the evaporator, as a rule, is located behind the back wall or in the upper part of the chamber, and its task is to remove heat until a given positive temperature is reached. Freezer evaporator has a large heat exchange area and is often equipped with a system No Frost or a powerful defrosting element to cope with large volumes of ice.
In addition, the compression ratio of the refrigerant is a critical parameter. Compressors installed in refrigerators often have lower capacity compared to freezer units. When trying to reach a temperature of -24°C, a standard motor-compressor will work almost non-stop, which sharply reduces its life. The key point is that the oil in the refrigerator compressor may not have the necessary fluidity at ultra-low temperatures, which will lead to jamming.
It is also worth considering thermal insulation. Freezer walls are usually thicker and door seals are stronger to minimize heat gain from outside. In a conventional refrigerator, when deep frozen, the outer surface may begin to become intensively covered with condensation (“cry”), as the dew point will shift to the outer wall of the case.
Necessary tools and materials for modernization
To successfully implement the project, you will need not only a basic kit for a home craftsman, but also specific equipment for working with the refrigeration circuit. Without the tightness of the system and proper evacuation, any alteration is doomed to failure. You will have to deal with soldering copper tubes and filling the system with gas, which requires caution and compliance with safety precautions.
The list of necessary equipment includes:
- 🛠️ Soldering kit (torch, solder, flux) for connecting copper tubes.
- 🧊 Vacuum pump and a pressure gauge station for removing moisture and air from the circuit.
- ⚙️ Thermoregulator (thermostat) with an operating range for freezers (for example, from -10 to -25°C).
- ❄️ Cylinder with refrigerant (freon) of a suitable brand (R134a, R600a or R12 depending on the year of manufacture).
Special attention should be paid to thermal insulation materials. If you plan to reinforce the walls, you will need polyurethane foam or extruded polystyrene foam. Don't forget about polyurethane foam for sealing cracks and sealant for sealing doors. All materials must be resistant to low temperatures and not emit harmful substances.
☑️ Preparation for rework
Replacing the thermostat and adjusting the temperature mode
The simplest, but not very effective way to turn a refrigerator into a freezer is to replace the thermostat. The standard regulator opens the circuit at a temperature of about +3...+5°C, which is absolutely not suitable for freezing. You need to install a model that will keep the cycle on until it reaches -18°C and below.
The replacement process is as follows:
- 🔌 Disconnect plug the refrigerator into the mains and remove the plastic cover from the thermostat.
- ❄️ Dismantle the old sensor, carefully removing it from its seat in the evaporator.
- 🔧 Install a new thermostat, making sure that the sensitive bulb fits tightly to the surface of the evaporator.
- ⚡ Check the operation of the contacts with a multimeter before assembly.
⚠️ Attention: Simply replacing the thermostat without modifying the insulation and checking the compressor will lead to the unit operating continuously. This will cause overheating of the motor windings and rapid destruction of the oil.
After installing a new regulator, it is necessary to carry out a test run. Connect an external thermometer inside the chamber and monitor the cooling dynamics. If the temperature drops only to -5...-8°C and does not go further, it means that the system’s performance is not enough to create deep cold, and a more serious upgrade of the circuit is required.
How to check the thermostat with a multimeter?
Put the multimeter into dial mode. Connect the probes to the thermostat contacts. At room temperature the circuit should be closed (beeping). If you put the sensor in the freezer, after some time the circuit should open.
Modernization of thermal insulation and sealing
The efficiency of any refrigeration unit directly depends on the quality of thermal insulation. Standard walls of a household refrigerator have an insulation thickness of about 3-4 cm, which is not enough to maintain a deep minus. When trying to cool the chamber to -20°C, the outer walls may begin to freeze through, forming “cold bridges.”
To improve the situation, you can use the method of additional insulation. The internal volume of the chamber decreases, but the efficiency increases. You can stick sheets of penofol penofol or polyethylene foam with a foil layer on the inner walls (under decorative plastic). The foil should look inside the chamber, reflecting the cold.
Pay special attention to the door seal (cuff). Over time, rubber becomes tanned and no longer fits tightly. This is critical for a freezer. Replace the seal with a new, more elastic one, or treat the existing one with silicone grease. In some cases, it is necessary to install a second internal door or create a vestibule.
Material Thermal conductivity (W/m K) Temperature conditions Application Polyurethane foam 0.022 - 0.027 -60°C ... +90°C Filling into voids Penofol (foil) 0.037 - 0.051 -60°C ... +100°C Reflective insulation Foam plastic (PSB) 0.035 - 0.043 -180°C ... +80°C External insulation Mineral wool 0.045 - 0.070 -60°C ... +400°C Not recommended (hygroscopic) Modification of the compressor and defrost system
If you decide on a deep modernization, you may need to replace the compressor with a more powerful one designed for low-temperature conditions (class LBP - Low Back Pressure). However, you can often get away with installing an additional fan to improve airflow to the evaporator and more efficient heat transfer.
The defrost system is another unit that requires attention. In deep freezing mode, moisture from the food will actively condense on the evaporator, turning into an ice coat. This will drastically reduce cooling efficiency. It is necessary to introduce or modify the existing defrost timer so that it starts the heating element (heating element) at certain intervals.
Procedure for modification:
- 🔌 Install a defrosting heating element under the evaporator, if it is not structurally available.
- ⏱️ Introduce into the control circuit a timer or an electronic relay that will turn on defrosting every 6-12 hours.
- 💧 Organize the drainage of melt water into a drainage tray located above compressor.
⚠️ Attention: Never leave the defrost system uncontrolled. A faulty heating element or a stuck relay can lead to defrosting of food and damage to the compressor due to water hammer with liquid refrigerant.
It is also important to check the condition of the oil in the compressor. When used for long periods of time at low temperatures, standard mineral oil may thicken. In professional practice, oil is sometimes replaced with synthetic oil (POE), but at home this is a complex procedure that requires complete disassembly of the engine.
FAQ: Often asked questions about remodeling
Is it possible to make a freezer by simply unscrewing the screw on the thermostat?
No, that's a myth. The adjusting screw inside the thermostat only shifts the response range within small limits. A standard thermostat will physically not be able to maintain a temperature of -18°C, since its contacts open at positive values. A complete replacement of the unit is required.
Will power consumption increase significantly?
Yes, consumption will increase 2-3 times. The compressor will work almost continuously, trying to reach temperatures unattainable for this design. Heat gain through thin walls will also cause the system to work harder.
Is it safe to use an old refrigerator for deep freezing?
It's risky. Old seals and insulation may not withstand temperature changes. In addition, an old compressor, working in extreme mode 24/7, can fail at any time, creating the risk of a short circuit.
Which refrigerant is best to use when refilling?
You need to use only the gas for which the system is designed (indicated on the compressor nameplate). Replacing R12 with R134a requires changing the oil and filter drier. Experiments with gas are dangerous and require a license.