Definitive Guide About Compressors In Refrigerator

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Compressor is the heart of a refrigerator. It is the most important aspect that you need to give attention to when you buy a refrigerator. But each brand gives its own twist to the compressor that they use and we poor consumers end up confused.

So, we attempt to explain in simple terms how different types of compressors used in a refrigerator vary in terms of functioning and performance.

What is a Compressor?

A compressor essentially consists of a pump and a motor and is responsible for circulation of refrigerant throughout the refrigerator ( or any cooling appliance). 

It squeezes ( compresses)  the refrigerant and increases its pressure and temperature. The resultant hot and high pressure gaseous refrigerant then passes through the condenser coil and releases its heat outside and cools down a bit and returns back to liquid stage. Then it enters the expansion device which as the name suggests, expands the refrigerant. The sudden expansion, which means sudden drop in pressure results in refrigerant cooling down and turning into a gaseous state. This cool refrigerant gas passes through the evaporator coil inside the refrigerator panel, absorbs heat from the food and cools the food and passes back into the compressor. The cycle repeats.  This is essentially how a refrigerator works. Of course, it is simplified drastically. 

Here is a video which picturizes the process.

So, the next question that might arise is why is a compressor so important? Let us explore.

Significance of Compressor In A Refrigerator ( Or Any Cooling Appliance)

As mentioned, the compressor is responsible for circulation of refrigerant throughout the refrigerator to cool down the food inside. 

The compressor’s ability to compress the refrigerant and thus increase the pressure is what helps cool it down when it goes through the expansion device. If it is not compressed well, the pressure difference will be lesser and hence the cooling will also be lesser. So, higher the compressor’s ability to increase the refrigerant’s pressure, better the cooling. 

Every manufacturer tries to increase the power of the compressor while optimizing the energy consumption.

Difference Between Conventional and Inverter Compressor

Every compressor starts operation triggered by the rise in temperature inside the refrigerator cabin. Upon this trigger, the compressor starts running or increases its speed.

In a conventional compressor, the compressor shuts down once the temperature inside the refrigerator touches a predetermined level. After a while when the temperature inside increases, the compressor is alerted and then it starts operation again to cool down the refrigerator.

In this scenario, the compressor constantly shuts down and restarts. It is either off or working at its full capacity. This has numerous disadvantages. First of all, it is said that 85% of wear and tear occurs during the starting of the compressor. This drastically affects the durability of the compressor. The temperature variance inside the refrigerator is also greater, which could affect the lifespan of the products stored inside. Also, the power consumption is higher.

An inverter compressor resolves all the above disadvantages by never shutting itself down completely. Rather, the compressor slows itself down when the refrigerator reaches desired temperature and continues operation at the slow speed. Thus it always maintains the cool temperature.

Whenever you open the refrigerator door or keep any new food inside, the temperature inside increases. The sensor detects this and alerts the compressor to increase its speed to bring the temperature down after which it continues at the slow speed. This way, it reduces temperature variance to enhance the cooling efficiency, reduces wear and tear to thereby increase durability and also reduces power consumption. 

Now that you have understood how an inverter compressor differs from a conventional compressor, let us take a look at the various types of compressors.

Reciprocating Compressor

A reciprocating compressor consists of a cylinder and piston. The piston moves back creating a vacuum which forces the refrigerant inside from the evaporator coil. When the piston moves front, it increases the pressure, compresses the refrigerant and pushes outside to the condenser coil.

Most refrigerators use reciprocating compressor. They may be inverter compressor or non-inverter compressor.

Rotary Compressor

In terms of operation, a rotary compressor is very much like a reciprocatory compressor. Just that instead of a piston which moves back and forth, there is a rotor which moves in circular motion to take in the refrigerant and compress it and push out to the condenser coil. 

Inverter Compressor

As mentioned earlier, an inverter compressor never switches off. Rather, it adjusts the speed of operation to maintain optimal temperature inside the refrigerator. The speed of compression increases when there is an increase in food load or if the door is opened. And otherwise, it keeps running at a low speed to maintain the cooling. To achieve this, an inverter compressor uses a BLDC ( brushless direct current ) motor that allows it to run at variable speed.

Now, every manufacturer has brought about their own twist to an inverter compressor. You would have noticed that already. So, how does it vary? Or is it just another marketing gimmick? Let us explore by taking a look at the operations, advantages and disadvantages of each type.

Digital Inverter Compressor

compressors in refrigerator

Image: samsung.com

Digital Inverter Compressor is the proprietary technology used by Samsung and by a newer range of Haier refrigerators.

A refrigerator with DIT ( digital inverter technology) has 9 sensor track variables which take into account the internal temperature, external temperature, humidity as well as usage pattern. Then, depending on these variables, the DIT operates at 7 different speeds varying from 1100 to 4300 RPM. 

Samsung claims that this technology consumes 24% less energy than conventional compressors and is up to 3 decibels quieter too. 

As with all inverter compressors, this leads to less wear and tear and therefore higher durability. Samsung, in fact, gives a 10-year warranty on its compressors.

Now, what we found interesting is that Samsung introduced DIT in the 2000s. And this same technology is being used even in the higher end fridges like the Chef Collections ( US) that they sell today. That speaks volumes about the robustness of the technology.

Smart Inverter Compressor

compressors in refrigerator

LG uses a smart inverter compressor in some of their refrigerators. It is essentially just like a regular inverter compressor. It too has smart sensors that alert when there is a change in ambient or internal temperature, humidity and load and adjusts the compression speed accordingly. There is nothing extra smart about this technology.

According to a specs sheet from LG in 2013, their reciprocatory smart inverter compressor runs in 5 varying speeds ranging from 1200 to 4500 RPM.

Linear Inverter Compressor

compressors in refrigerator

Linear inverter compressors are used in newer model refrigerators from LG and Kenmore. It is essentially an improvement over their smart inverter compressor by reducing friction points to reduce noise and energy consumption.

A smart inverter compressor uses a reciprocating drive which is connected to the piston. This drive rotates to push and pull the piston which compresses the refrigerant. But in a linear inverter compressor, the piston carrying permanent magnet is placed in the housing between two electromagnets. The alternating current changes the magnetic poles which result in the push and pull that compresses the refrigerant. As the piston is suspended between the two poles, frictional resistance is minimized. 

LG claims that a linear inverter compressor has 32% more energy savings compared to a smart inverter compressor. It emits just 22-decibel noise, which is 25% lesser than a smart inverter compressor. In fact, 22 bB is equivalent to the sound level of a quiet bedroom. 

Varioinverter Compressors

Bosch uses varioinverter compressors in its refrigerators. 

A varioinverter compressor is just like any other inverter compressor. The name seems just a marketing gimmick. It varies the compressor speed depending on the internal and ambient conditions to optimally adjust the refrigerator’s cooling for maximum performance.

Bosch claims that this technology helps save up to 40% energy compared to a conventional compressor. 

ProSmart Inverter Compressor

ProSmart Inverter Compressor is the term that Beko ( In India partnered with Voltas as Voltas Beko) uses to name its inverter compressor. Though there is a prefix, it is functionally just an inverter compressor.

The manufacturers claim ProSmart Inverter compressor reduces energy consumption by 25 per cent and brings noise level down as well. The temperature stability is also better.

IntelliSense Inverter Technology

Intellisense inverter technology is what Whirlpool calls its smart inverter compressor.  They also use the terms Adaptive Intelligence for this tech.

So, just like every other inverter compressor, there are sensors which take in to account ambient temperature, food load and usage pattern. The microprocessor analyses this information and optimizes the cooling. 

Whirlpool claims that in addition to energy savings and reduced noise, their inverter compressor is capable of cooling 40 per cent faster and can bring down the refrigerator temperature to -24 degree Celius while most inverter compressors limit it to -22 degree Celsius. 

Twin Rotary Compressor

Twin rotary compressors are not actually used in refrigerators, rather in air conditioners from LG, Toshiba etc. 

Instead of a single-piston compressing the refrigerant, there are two pistons that compress the air. As each piston is connected to a separate reciprocatory drive which moves at different frequencies, the refrigerant is compressed more efficiently. 

Toshiba claims this technology helps improve energy and cooling efficiency by 50%

Screw and Scroll Compressors

Two other types of compressors found in refrigeration systems are screw compressors and scroll compressors. 

In a screw compressor, two helical screws known as rotors are closely placed inside a cylinder. The refrigerant enters from the suction side and moves through the screw’s threads as it rotates. The meshing rotors force the refrigerant through the compressor and compacts it and forces it out at the end of the screw. They are not quite used in domestic refrigerators as they are prone to vibrate a lot.

In a scroll compressor, a spiral disk ( like a mosquito coil) is nested together. When the refrigerant passes through, it gets compressed and is pushed out through the exit valve. They are highly efficient. But being a hermetic design ( meaning completely air tight), it is very difficult to repair. However, scroll compressors are sometimes used in automobiles and commercial air conditioning appliances. 

So, with that we wrap up this guide on compressors. If you need any clarifications, please drop a comment and we shall respond to it at our earliest.

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