A sudden breakdown of a refrigerator is always stressful, especially if there are perishable foods inside. When diagnostics show that the problem lies in the “heart” of the system - the compressor, the owner is faced with the difficult technical issue of replacement. Simply removing the old motor and installing a new one “by eye” can lead to catastrophic consequences for the entire refrigeration system.
Motor power is not just a number in watts, but a complex parameter that affects refrigerant performance, pressure in the circuit and energy consumption. An error in the calculations will lead to the fact that the refrigerator will either stop freezing or work overload, burning electricity and risking burning out in a couple of weeks. In this article, we will analyze all the intricacies of selecting a unit so that you can make the right choice.
Why you can’t ignore performance calculations
Many self-taught craftsmen make a grave mistake, believing that if the compressor is physically suitable in terms of dimensions and connecting pipes, then it will work. However compressor power must strictly correspond to the volume of the evaporator and condenser of your refrigerator. If you install a weaker motor, the freon will not have time to circulate in the required volume, and the temperature in the chambers will never drop to the specified values.
On the other hand, installing a unit that is too powerful creates excess pressure in the system, which standard tubes and filter-driers cannot cope with. This can lead to depressurization of the circuit or failure of the thermostat. Accurate calculation Necessary for a balance between the cooling capacity and energy efficiency of the device.
⚠️ Attention: Installing a compressor with the wrong cooling capacity can lead to “clogging” of the capillary tube with oil or the formation of ice plugs, which will require a complete recharge of the system and replacement of the filter.
In addition, modern inverter models require not only the correct selection of power, but also compatibility with the control unit. Replacing a conventional motor with an inverter motor without resoldering the electronics is impossible, even if their rated power is the same. Always consider the type of control and electrical characteristics.
Main parameters: power, refrigerant and motor type
When looking for a replacement, first of all you need to pay attention to the markings on the nameplate or stamped on the body. The key parameter is cooling capacity, which is often specified in watts (W) or British thermal units (BTU). It is important to distinguish between electrical power and refrigeration power: the first shows current consumption, the second shows the ability to cool.
The type of refrigerant plays a critical role. Compressors operating on R134a, R600a or R404ahave different compression characteristics and require specific oils. They cannot be confused: oil for one type of freon can curdle or lose properties upon contact with another, which will instantly disable the equipment.
It is also worth considering the type of design:
- 🔹 Piston: classic, noisy, but reliable and repairable units.
- 🔹 Rotary: quieter, often used in compact models, sensitive to the quality of installation.
- 🔹 Inverter: smoothly regulate power, save energy, but require complex diagnostics and configuration.
Pay attention to the climate class devices. If your refrigerator is designed for moderate climates and you live in a hot region, the standard motor may not be able to cope with the load in the summer. In such cases, a model with a power reserve or improved winding cooling is required.
Table of correspondence between power and volume of the fridge compartment
To simplify the initial selection, you can use averaged data. However, remember that these are reference values, and for an accurate selection it is better to start from the markings of the old motor. Below is a table to help you navigate depending on the volume of the chambers.
| Chamber volume (liters) | Required power (W) | Typical refrigerant | Note |
|---|---|---|---|
| up to 100 l | 60 - 90 W | R600a / R134a | Small refrigerators, bars |
| 100 - 250 l | 100 - 140 W | R134a | Standard single-chamber models |
| 250 - 400 l | 150 - 220 W | R134a / R404a | Two-chamber, large freezers |
| over 400 l | 230+ W | R404a / R134a | Side-by-Side, industrial |
The data in the table is relevant for proper thermal insulation and standard operating conditions. If the door seals are worn out or the refrigerator is standing close to the wall, the load on the compressor increases. In such cases critically important choose a model with a power from the upper limit of the range or eliminate the causes of heat gain.
When replacing the motor with an analogue from another manufacturer, a power deviation of no more than 10-15% upward is allowed. Installing a significantly more powerful engine will lead to frequent activation of the thermal relay and rapid wear of the starting equipment.
What are COP and EER?
These are efficiency coefficients. COP (Coefficient of Performance) shows the ratio of the cold produced to the energy expended. The higher the number, the more economical the compressor. EER (Energy Efficiency Ratio) is a similar parameter often used in American standards.
How to decipher the markings on a nameplate
Each manufacturer uses its own coding system, but the general principles remain similar. You will find the alphanumeric model code on a sticker or metal tag. For example, Secop (Danfoss) or Aspera the first letters may indicate the type of refrigerant, and the numbers may indicate cylinder volume or power.
The designation LBP (Low Back Pressure) or HBP (High Back Pressure) is often found. This indicates the pressure range for which the compressor is designed. For household refrigerators and freezers, type LBPis used. Installing an HBP motor in a household refrigerator will lead to the fact that it simply cannot create the necessary vacuum and the cold will not flow.
Let's look at an example of marking: NL6CLB. Here NL can mean the series, 6 the cylinder volume in cubic centimeters, and CLB the type of refrigerant and voltage. It is important to check the supply voltage: 220-240V for our networks. A 110V motor will burn out instantly, but a 380V motor will simply not start.
⚠️ Attention: On some Chinese compressors, the markings may be applied incorrectly or may be missing. In such cases, it is necessary to measure the cylinder volume and piston diameter, comparing them with manufacturers' catalogs.
Also pay attention to the production date. Compressors that have been in storage for more than 5 years without preservation may have dried out seals or oxidized contacts. It is better to choose units with a recent release date.
Compatibility of oils and refrigerants
One of the most common reasons for repeated breakdowns after replacing a compressor is mixing of oils. Mineral oils (used with R12 freon) and synthetic oils (polyester POE for R134a or R600a) are not compatible. When they are mixed, a thick emulsion is formed that clogs the capillary tube.
If you are replacing an old R12 compressor with a new R134a one, you must thoroughly flush the entire system or replace the condenser and evaporator, since it is almost impossible to wash out the old mineral oil from the tubes. Ignoring this rule will lead to failure of the new motor within a month.
List of main compatibility:
- 🛢️ R12: Mineral oil (MO) or Alkylbenzene (AB).
- 🛢️ R134a: Polyester oil (POE) - hygroscopic, requires fast rations.
- 🛢️ R600a: Mineral or Alkylbenzene (but compatible with butylane).
When working with polyester oils, remember their hygroscopicity. They actively absorb moisture from the air, so the compressor cannot be kept open for more than 15 minutes. Moisture in the system will turn into acid, which will corrode the motor windings from the inside.
Instructions for selection and preparation for installation
The process of selection and replacement requires accuracy and adherence to technology. First you need to completely remove the old refrigerant and cut out the faulty compressor. Then you should evaluate the condition of the pipelines: if black deposits (varnish) are visible inside, the system must be flushed with nitrogen or a special solvent.
Next, an analogue is selected. If the original model is no longer in production, look for the cross-code in the manufacturers' correspondence tables (for example, Secop, Embraco, LG). Make sure that the geometric dimensions of the new motor will allow it to be installed on standard shock absorbers without altering the frame.
☑️ Check before installation
Before soldering the pipes of the new compressor, be sure to remove the shipping plugs only at the last moment. Immediately after installing the motor in place and before soldering, purge the system with nitrogen to remove any possible dust. Solder using solder with a silver content of at least 5-15%, using nitrogen purge to prevent the formation of oxides inside the tubes.
After assembling the circuit, a vacuum procedure is required. The pump should run for at least 30-40 minutes until the pressure reaches a reading close to absolute vacuum. This will remove moisture and air. Only after this can the system be filled with freon strictly according to the weight indicated on the refrigerator nameplate.
⚠️ Attention: Technical characteristics and requirements for oils may vary depending on specific modifications of the equipment. Always check the official documentation of the compressor manufacturer before starting work.
Common mistakes when replacing yourself
The most common mistake is trying to start a new compressor on an old start relay. The relay contacts burn out over time, and the calibration of the thermocouple gets lost. Installing a new motor with an old relay is guaranteed to lead to burnout of the starting winding in the first minutes of operation.
The second mistake is ignoring the valve check. Before installation, a new compressor must be “ringed”: it must actively suck in air at the inlet and blow out air at the outlet. If the compressor hums but does not pump, it means that its valves are broken, and it is useless to install it.
The third mistake is incorrect filling with oil. New compressors are already filled with oil. It only needs to be topped up if a part was lost during transportation, and only strictly according to the level specified in the instructions. Excess oil will cause water hammer and destruction of the valve group.
Is it possible to install a compressor of greater power than originally installed?
It is possible, but with restrictions. An increase in power is permissible by 10-15%. This will allow the refrigerator to reach temperature faster. However, if you install a motor that is too powerful, the thermostat will often click, and the evaporator tubes may not have time to release the cold, which will lead to freezing and improper operation of the defrost system.
Why does the new compressor get hotter than the old one?
Modern motors often have lower efficiency in terms of heat transfer from the housing, but greater energy efficiency. Also, heating depends on the correct freon filling. A lack of refrigerant causes the compressor to idle and overheat, and an excess overloads the system.
Does it need to be replaced when replacing a compressor?
Ideally, yes, especially if the old refrigerator has been in operation for more than 10 years. Oxidation products and old oil accumulate in the condenser. If it is not possible to replace the radiator, it must be thoroughly washed with a special solvent and purged with nitrogen under high pressure.
How to determine that the compressor is not suitable for power without starting?
An accurate calculation is only possible using the refrigeration capacity tables at certain boiling and condensation temperatures. Visually you can only assess the dimensions and type. If the motor is visually much smaller than the standard one, most likely, its power will not be enough for a large volume of chambers.