refrigeration compressor

How does the refrigeration compressor work?

Refrigeration compressor as one of the most basic components of refrigeration, covers a major part of its construction cost. Optimal and correct selection, along with ensuring the authenticity of the compressor purchased, can guarantee the most optimal cost at the time of purchase, as well as reducing future maintenance costs. 

What is a refrigeration engine?

The refrigeration compressor, commonly referred to as the refrigeration engine, is the heart of a refrigeration refrigeration system. The refrigeration engine can be categorized from different perspectives. These motors may be classified according to their application and temperature range (below zero, above zero). It may be based on the refrigerant used in them (gas R22, R404A, R134a or…) or their operating mechanism (piston, scroll, screw…) or the area where the refrigerator is to be installed. Accept. The most important distinguishing feature of a refrigeration engine is its power or power consumption, refrigeration power or displacement flow. In the some cooling industry, compressors are usually classified based on horsepower. However, this statement may not be scientifically accurate. In this article, all the above angles are discussed. In addition, we get acquainted with the types of engine brands, how to choose them, the price of the refrigeration engine, installation and maintenance conditions, and much more.

Types of refrigeration compressors based on operating mechanism

In terms of operating mechanism, compressors generally fall into the following categories:

Reciprocating Compressor، Rotary Compressor، Piston Compressor، Screw Compressor، Scroll Compressor

Piston compressors come in two types, hermetic or closed (non-repairable) and toxic, hermetic or semi-closed (repairable). These compressors may be single-cylinder or multi-cylinder. These compressors have a wide range of power from one to 70 horsepower. Screw compressors used in refrigeration systems are also mainly toxic hermetic screw types that are mostly used in refrigeration rack systems. These compressors generate more pressure than other compressors in exchange for lower power consumption. Screw compressors are available in capacities up to 35 hp. Scroll compressors used in refrigeration systems usually have low noise and have a power range of 1.5 to 30 hp. All the above models are compatible with different refrigerants depending on the type of oil used in the compressor.

Types of refrigeration compressors based on the manufacturer

Reputable brands that produce refrigeration compressors around the world include Carrier, Bitzer, Danfoss, Copeland, Frascold, Bock, Dorin and Refcomp. Each of these brands have offered different models to the market according to temperature range, type of refrigerant gas, power consumption, etc. In the following, we will deal with the most important types of models of these brands in the field of cold storage.

Bitzer refrigerator compressor types based on temperature range

Refrigerator compressors are generally divided into three categories: above zero, below zero and deep freeze, depending on the type of use used and the products to be stored. Above zero refrigeration temperature range is usually designed and used for storage conditions of 0 to 4 degrees Celsius, sub-zero refrigeration for storage conditions of -18 and cold storage with deep freeze temperature range for -40 degrees Celsius.

Refrigeration compressor price

The price of a refrigeration compressor depends directly on its capacity. Also, whether it can be repaired or not has a significant effect on the price of the refrigeration compressor. At equal power, the price of the R22 gas-compatible refrigeration compressor is slightly cheaper than the 404, 134, 407 and gas refrigeration compressors. Another factor influencing the price of a refrigeration engine is the brand of the engine manufacturer. The price of refrigeration engines made in European and American countries is slightly more expensive than refrigeration engines made in China, Thailand and Taiwan.

Another parameter affecting the price of the compressor is its application. Refrigeration compressor with application below zero in the temperature range up to -45 has more special features than the refrigeration engine above zero and as a result has a higher price in equal power.

Buying a refrigeration compressor

The most important thing about buying any product is to make sure it is authentic. Buying a refrigeration compressor is no exception and requires authentication. Each refrigeration compressor is functionally tested by its manufacturer at the time of production and the results are provided by the manufacturer along with the test date. A special number (serial number) is engraved on each refrigeration compressor and the authenticity of the product is usually obtained through this code. Some compressor manufacturers, such as the German Bitzer, have special methods for identifying the compressor. For more information, refer to the identification of the Bitzer compressor.

Select a refrigeration compressor

Several basic parameters are required to select the optimal refrigeration compressor. The most important of these parameters are the temperature of the evaporator and condenser and the required refrigeration capacity (usually expressed in kilowatts). With these parameters in hand, you can refer to the catalog of the compressor manufacturer. Usually, the refrigeration compressor is selected by the software of the compressor manufacturer. For example, Bitzer Company has considered two routes of the company’s website at, as well as its Bitzer compressor selection software for compressor selection. Danfoss Company, through its software called Cole Selector selection software, has put the compressor selection path in front of its customers. Also, other manufacturers such as Book, Fraskeld, Refcomp and Dorin have each developed their own compressor selection software. 

Calculate the power of the refrigeration compressor

Refrigeration compressor power is usually expressed in horsepower. This number indicates the power consumption of the compressor. This method is not scientifically accurate. The best way to calculate compressor power is to identify the refrigeration capacity from the manufacturer’s catalog based on the evaporator and condenser temperatures.


The operation of each refrigeration compressor consists of two parts, mechanical and electrical. The mechanical part of the refrigeration compressor includes connecting the suction and discharge parts to the refrigeration piping system and ensuring that the appropriate control components are considered to prevent damage to the compressor. The electrical part of starting the refrigeration compressor also includes the correct way of wiring the compressor for three-phase compressors (star or triangle) or using the appropriate starter kit (capacitor) to start the compressor. 

Refrigeration engine equivalence

Comparing refrigeration engines between different models and brands is one of the issues that can always occur. Lack of spare parts, dissatisfaction with engine performance, price and… are the most important reasons for moving to change the model and brand of refrigeration engine. To do this, all the technical considerations required for this work must be taken into account. One of the most important parameters for the correct equation of the refrigeration engine is to pay attention to the amount of displacement (Displacement) and the refrigeration capacity produced by the engine at equal temperature conditions.

Refrigeration compressor repair

As mentioned above, refrigeration compressors made by different brands are designed and marketed in repairable or non-repairable types. Refrigeration compressor repair should be done by a reputable repair shop so that the cost of repairing the compressor leads to the desired performance of the compressor for a suitable period of time. The most important parts used in the refrigeration compressor that may need to be replaced during repair are the compressor crankshaft, compressor connecting rod, compressor thermistor, compressor valve, compressor bearing and compressor washer.

Refrigeration compressor oil

The refrigeration compressor, like other compressors in the ventilation and refrigeration industry, is charged with different oils by its manufacturer. The type of refrigeration compressor oil used in refrigeration compressors is mainly a function of the type of use and temperature range of using the refrigeration engine. Generally, refrigeration compressor oil is divided into two popular categories: mineral and POE or polyolester. In addition, there are Alkylbenzene and PVE or Polyvinylester compressors, which are used in more specific compressors. Each of these categories includes different models according to parameters such as Viscosity of compressor oil, Density of compressor oil, Flash point of compressor oil, Pour point of Pour compressor oil.

R22 gas is mainly compatible with mineral oils and other refrigerants such as R134a, R404A, R407C and R410A with non-mineral oils such as polyolester oil (POE). Using high quality original oil has a great effect on increasing the life of a refrigeration compressor and one of the most important reasons for the failure of the refrigeration engine is the presence of contamination and moisture in the refrigeration compressor oil.

The most common causes of refrigeration compressor failure

The most common causes of refrigeration compressor failure that can have costly consequences are:

Compressor operation at high pressure Refrigerant gas shortage in refrigeration cycle Unconventional power consumption No moisture in refrigeration cycle Unsuitable refrigerant oil and gas charge

Due to the high price of refrigeration compressors and the need to repair it in the years used, one of the most important characteristics of evaluating a compressor is the presence of spare parts and compressor parts in the market. The more these parts are in repair shops, the more the tendency to use that brand increases. Ensuring the authenticity of compressor parts and spare parts is one of the most important issues considered by customers in this industry. For this purpose, many companies importing refrigeration compressors also supply refrigeration compressor parts to ease the minds of their customers about the authenticity of these parts. 

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