Most people don’t really understand or does not even have the slightest clue on what air conditioner compressors are and how they work. Others may not even know that their air cons have these.

It is not as if people really look in to the operating systems of their air conditioners when they buy them, all we really give notice to is how much horse power they have or how comfortable it would make us feel once we have installed them in our homes.

In this article, we will discuss about this vital piece of air conditioner anatomy, the types of compressors and its pros and cons of each compressor systems. After finished reading, you will have very good knowledge on how compressors work.

Are you ready?

Let us start now…

What is a compressor?

Aircon Compressor

An aircon compressor is the heart of your cooling system. It is the most commonly misdiagnosed component in the system. It helps to take out the hot vapor refrigerant from the aircon unit’s evaporator system.

In layman’s terms, the compressor condenses the vapor into a reduced volume at a high temperature. There are some compressors that operate with a pulley and belt system and there are also some that use electric motors.

The compressor encompasses reed valves which helps it to regulate the circulation of refrigerants in the pumping process. If they are not tightly held, gas might ooze back into the low side during the compression stroke.

Most of the compressor units consists of a relief valve which helps to control the pressure of the unit. If the system discharge pressure exceeds norms, the valve will open automatically and stay open until the pressure drops. The noise that you hear from your aircons can also be pointed to the compressor mount.

Aircon conditioner compressors can be broadly classified into five types: Reciprocating, Scroll, Screw, Rotary, and Centrifugal. I will discuss each to you later on.

How do they work?

Aircon system Cycle

Aircon units help to reduce the temperature of a single room, a complete house, or even a building. By using chemicals, aircon units convert from a gas to liquid and repeat the same process over and again. These chemicals help to transfer heat energy from the air inside a space and expels it to the air outside, thus bringing down the temperature.

The compressor and the condenser are usually located on the outside portion of the air conditioner. The working fluid reaches at the compressor as a chilled, low-pressure gas. The compressor then condenses the fluid which renders the molecules of the fluid to stay together.

As they stay more closer, energy and temperature associated with it would be more. The working fluid then leaves the compressor as a hot and high pressure gas which then flows into the condenser. After it leaves the condenser, its temperature is much cooler now and has changed from a gas to liquid under high pressure.

The liquid then goes into the metering device which is a flow restricting device that provides pressure drop point. After that, the fluid will goes to evaporator. Now the fluid comes out of the evaporator as a chilled, low pressure gas. It then moves back to the compressor unit to start its movement through it all over again.

It is a continuous cycle until the room reaches the temperature you want the room cooled to.

What are the different types of compressors?

As we have mentioned earlier in the article, there are 5 types of air conditioner compressors that are commonly used in the HVAC (Heating, Ventilation, and Air Conditioning) industry. They are

  1. Reciprocating Compressor
  2. Rotary Compressor
  3. Centrifugal Compressor
  4. Screw Compressor
  5. Scroll Compressor

All five of them work the same way, but their methods of compressing refrigerant vapor are different from one another. we will talk about specific details on each compressor and how they work to give you a closer look on how they help your air conditioner systems work perfectly.

1. Reciprocating Compressor

Reciprocating Compressor

Reciprocating compressor is also known as piston compressor. The reciprocating compressor makes use of a piston, which moves within a cylinder, to compress the refrigerant propelled by a crankshaft.

Vapor emanating from the suction line is carried to the intake valve as the piston is pushed down. When it goes up, it compresses the vapor refrigerant. It is then moved through the exhaust valve which later finds path to the condenser. This rotary motion is achieved by the use of a motor and the construction is quite similar to that of a car engine.

Absorption of air and expelling is performed by two valve sets. One-way valves ensure that the air which is absorbed cannot seep through. It also makes sure that the compressed air would not move back as the piston goes down again.

This type of compressor may have multiple cylinders that is called as the multi-cylinder compressor. There are different types like two-cylinder, four-cylinder, eight-cylinder compressors and the like. This type of compressors can deliver power in range of small (a few HP) to medium sized. It is based on the air needed.

Reciprocating compressors are divided into different types like Single-acting reciprocating compressor, Double-acting reciprocating compressor and Diaphragm reciprocating compressor.

2. Rotary Compressor


Rotary compressors are sealed tightly, which brings about an enhanced drive method. compressor and motor are positioned inside a single enclosed space. Hence, there is continuous interaction between motor and refrigerant element.

As the gas is compressed, a pressure variance is created in the rotary compressor which assists in easy movement of the refrigerant easily through the system. Gas compression is achieved by means of rotor movement with respect to pump chamber.

Working of stationary rotary compressor

An electric motor drives the cam. The cam causes the ring to rotate along with the cam. Ring now moves to external rim across the cylinder’s wall. Evaporator produces vapour which then finds its way to condenser across the holes made inside the frame of compressor.

Compression of gas is achieved by the help of an offset-rotating ring. There is a barrier which splits up both ports (intake and exhaust). As the compressor absorbs the vapour, barrier is grasped against ring with the help of spring. Ring now moves around cylinder and performs the gas compression. It is then moved into the condenser.

Working of rotating- blade compressorRotary Compressor

There would be 2 roller blades which are aligned 180 degrees apart. Blades move across cylinder’s side. Roller is erected in such a way that it could get in contact with the cylinder in between both ports (discharge and intake).

Now when the roller moves, vapour flows to intake port which finds its way to the cylinder.Vapour is sealed inside. When the subsequent blade moves past the point of contact, vapour would be compressed. Once the pressure reaches a certain value, vapour finds its way through exhaust port and then moves to condenser.

3. Centrifugal Compressor

Centrifugal Compressor

Centrifugal compressors are also know as radial compressors. It is used in refrigerating system with bigger capacity. In centrifugal compressor, the vapor is rotated in a circular motion which is termed as centrifugal force.

An impeller (disk) which consists of radial blades rotate quickly within this housing which drives the gas to attain higher speed. Now, a diffuser transforms this energy into pressure energy which is then oozed into the condenser. As the speed increase, pumping efficiency. Therefore, centrifugal compressors are conceived to work at more velocity.


Traditional centrifugal compressors works with hydrodynamic bearings that demand a mixture of pumps, filters and monitoring units. Latest units make use of a mixture of refrigerant and oil, or solely the refrigerant alone, to lubricate the rolling bearings.

Removing oil as a lubricant decreases the intricacy and expense associated with the unit while increasing compressor efficiency and dependability.

Working of Centrifugal compressors are comparable to that of axial compressors. They also consists of rotating airfoil based compressors. One of the main difference of centrifugal compressors from axial compressor is that they make use of a higher change in radius from inlet to exit of the rotor or impeller.

Centrifugal compressors are well-known for their straightforward design, lower number of moving parts, and improved energy efficiency when they need to operate in multiple stages.

4. Screw Compressor

Screw Compressor

A lot of buildings especially engineering plants require compressed air that can be obtained with this type of compressor. Screw compressor is driven by either an electric motor or a diesel engine.

As the name indicates, Screw compressors make use of a couple of helical rotors or screws which interlace together to comp