Modern refrigerators are increasingly equipped inverter compressorsthat are quieter and more economical than their predecessors. However, when such an expensive part fails, owners are faced with the high cost of the original spare part and the difficulty of finding it on sale. In such a situation, the idea arises about the possibility of installing a more affordable linear (conventional) compressor, which is time-tested and costs much less.
This procedure is technically possible, but requires deep knowledge in the field of electrical engineering and skills in working with refrigeration equipment. You will have to not only change the hardware, but also completely redo the electrical control circuit, since the operating principles of these two types of units are radically different. It is important to understand that after such an upgrade, the refrigerator will lose some of its energy-efficient properties, but will be able to continue operating for many years.
Before you begin disassembling the unit, you need to weigh all the risks and prepare the appropriate tools. Incorrect installation can lead to overheating of the wiring, failure of the thermostat, or even fire. In this material we will analyze in detail all the stages of replacement, the necessary calculations and technical nuances that will help you make an informed decision and carry out the repair safely.
Fundamental differences between inverter and linear compressors
The main difference lies in the method of motor control. Inverter compressor works constantly, but with variable rotation speed shaft, smoothly adjusting the power depending on the temperature in the chambers. For this, a complex electronic control unit is used, which converts the alternating current of the network into direct current, and then again into alternating current, but with a variable frequency. This ensures the absence of inrush currents and low noise levels.
In contrast, conventional linear compressor works on the “start-stop” principle. It turns on at full power, cools the chamber to the set value, and then turns off completely until the next temperature increase. The start of such an engine is accompanied by a high starting current, to extinguish which start-protection relays are used. It is this difference in architecture that makes direct replacement impossible without serious alteration of the electrical part.
⚠️ Attention: Direct connection of a conventional compressor to the control board of an inverter refrigerator will lead to instantaneous burnout of the electronics or the motor itself, since the voltages and control signals are incompatible.
When choosing an analogue for replacement, it is important to consider not only the overall dimensions, but also the cooling capacity. If you install a unit that is too weak, the refrigerator will not be able to reach the desired temperature, and the motor will work with overload. A compressor that is too powerful will lead to frequent starts and rapid wear of the thermostat contacts.
Selection of equipment and necessary components
The first step is to find a suitable donor or a new one linear compressor. The ideal option is to use original parts from refrigeration equipment manufacturers, such as Embraco, Secop or Danfoss. The power of the selected unit should be equal to or slightly exceed the power of the failed inverter motor. Typically, this parameter is indicated on the nameplate in watts or BTU/hour.
In addition to the compressor itself, you will need components to organize the starting system. Since standard electronics will not be used, it is necessary to purchase a universal starting protection relay corresponding to the engine power. You will also need a new filter drier, since it is absolutely impossible to open the system without replacing it - moisture from the air will instantly damage the compressor.
To seal the system, you will need copper tubes of different diameters to connect to the condenser and evaporator. If the original tubes are cut too short, they will have to be extended or replaced completely. Also stock up on solder for refrigeration systems, flux and a cylinder of freon (usually R600a or R134a) for subsequent refilling.
Dismantling the old inverter unit
Work begins with completely disconnecting the refrigerator from the power supply. You must remove the rear panel at the bottom of the chassis to gain access to the engine compartment. Before you start soldering the pipes, you need to bleed off any remaining refrigerant. It is better to do this in a well-ventilated area or outdoors, as the gas can be flammable or asphyxiating.
Using a pipe cutter, carefully cut the suction and discharge tubes of the compressor. Do not use a hacksaw for metal, as metal shavings that get inside the system are guaranteed to damage the new unit. After disconnecting the tubes, unscrew the fastening bolts and remove the faulty one inverter motor from the frame.
Together with the compressor, the condenser (heat exchanger on the rear wall) is often removed, if it is located nearby and interferes with access. Be sure to remove the old inverter control board as it will no longer be needed. In its place or next to it, a block with a starting relay for the new engine will be installed.
What to do with the inverter board?
You can try to hand over the inverter board to electronics collection points, since it contains non-ferrous metals. However, for the operation of a refrigerator with a conventional compressor, it is useless and should be completely excluded from the circuit.
Connection diagram and electrical part
The most difficult stage is organizing a new control. You will need to build a circuit where the thermostat will directly control the compressor start relay. The standard circuit includes a thermostat, a start relay and the compressor itself. All connections must be made in compliance with the color coding of the wires.
Usually the wires from the thermostat are connected to the contacts of the starting relay, which, in turn, supplies voltage to the motor windings. It is important to correctly identify the “Start” and “Run” contacts on the compressor block, since mixing them up will lead to a humming sound from the motor and tripping of the protection. Data for a specific model is always on the diagram pasted on the relay body or in the technical documentation.
| Component | Function | Installation location |
|---|---|---|
| Thermostat | Open the circuit when it reaches temperature | Inside the chamber or on the housing |
| Start relay | Starts the engine and protects against overloads | On the compressor block |
| Compressor | Creates pressure and circulation of freon | In the engine compartment |
| Filter drier | Retains moisture and dirt | At the outlet of the condenser |
If in your refrigerator had an electronic control module with sensors, they will have to be excluded from the circuit or short-circuited, simulating normal operation, otherwise the circuit will not close. In the simplest upgrade, a mechanical thermostat becomes the only control element.
Soldering tubes and preparing the system
After installing the new compressor on the frame (use original rubber shock absorbers to reduce vibration), it is necessary to connect it to the refrigerant circulation system. The condenser and evaporator tubes are connected end-to-end to the compressor nozzles using a copper sleeve or the pipe-to-pipe method.
The soldering process requires the use of a gas torch with a flame temperature of at least 1000 degrees. The joint is heated evenly, after which a solder bar is brought in. It is critical not to overheat the tubes, otherwise the copper may burn out or change its structure, becoming brittle. Soldering should be done quickly and carefully, avoiding solder getting into the tubes, which could cause blockage of the capillary.
Be sure to install a new filter drier in front of the capillary tube. It removes moisture that entered the system during soldering and replacing parts. Without this step, the moisture will freeze in the capillary, forming an ice plug, and the refrigerator will stop cooling after a few hours of operation.
⚠️ Attention: When soldering next to the plastic elements of the refrigerator, use a wet cloth or metal screen so as not to melt the case or wire insulation.
Evacuation and charging with refrigerant
After assembling the entire system and checking the tightness (you can blow nitrogen under pressure) it is necessary to remove air and moisture from the circuit. To do this, a vacuum pump is connected to the process pipe of the compressor. The pumping process should last at least 30-40 minutes until a deep vacuum is achieved.
Refrigerant is charged strictly by weight. The number of grams is indicated on the nameplate of the refrigerator or on the label of the new compressor. The use of electronic scales when filling is mandatory, since filling “by eye” or by pressure (for gas mixtures) often leads to incorrect operation.
☑️ Checklist before starting
After filling, the process pipe is sealed. Turn on the refrigerator and let it run idle for about an hour. Check the temperature in the chambers and make sure that the condenser (grid at the back) heats up evenly, and the evaporator inside is covered with frost.
Frequently asked questions (FAQ)
Will electricity consumption increase significantly after replacement?
Yes, consumption will increase by about 20-30%, so how smooth power control disappears. However, given the low cost of a conventional compressor, the payback will come quickly.
Is it possible to leave electronic temperature control?
You can keep the original electronics only if you find a universal control module that supports working with linear compressors, but this will complicate the circuit. It is easier to use a mechanical thermostat.
What is the service life of an installed conventional compressor?
If installed correctly and following the freon filling scales, a high-quality freon linear compressor can last 10 years or more, which is comparable to the service life of inverter models.
Is it necessary to change the capacitor (radiator at the rear)?
It is not necessary to change it if it is intact and has no leaks. However, if the old capacitor was designed to work with an inverter (where the temperature is lower), it may heat up more with a conventional motor, but usually there is enough safety margin.