Aircon Compressors: The Different Types and How They Work

outdoor aircon unit

Air-conditioning is already an essential component of everyone’s life these days, whether it is in offices, homes, or schools.

The hot and humid weather of Singapore calls for the use of air conditioners almost throughout the year to ensure a pleasant and cool atmosphere indoors. When we talk about air conditioners, their main component is the compressor.

The compressor is responsible for transferring the hot air from the inside of a room to the outside, absorbing heat, allowing for the refrigerant to flow, reducing humidity, and generally keeping the room cold. If the compressor becomes faulty, it can decrease the aircon efficiency and consequently, can even lead to the aircon being shut down.

In this article, we will describe the different types of aircon compressors and how each one works. If you have an understanding of how a compressor works, you will be in a better position to assess any compressor-related problem in your aircon and fix it accordingly.

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Main Functions Of An Aircon Compressor

A compressor is the most important part of an aircon that determines how well the device will work. The compressor is responsible for several tasks which ensure the smooth working of the unit. The main functions of a compressor are listed below.

  • A compressor is responsible for heat transfer from inside the house to the outside. This transfer takes place when the compressor pushes the hot air towards the condenser coil. The condenser will then make the air cold and blow it back. In the case of an inverter, the cold air from the room will be pushed to the condenser coils by the compressor where it will be heated and blown back.
  • The compressor is also responsible for turning the warm air into liquid by compressing it. This liquid is then passed through an expansion valve where it is turned into a cold liquid and absorbs more hot air from the room. As a result, cold air is blown back indoors.
  • The compressor helps in absorbing heat from the room, and the refrigerant is evaporated because of the low pressure. Thus this transfer of heat from the room to the evaporating refrigerant helps in making the room cold.
  • The compressor also helps in lowering the humidity. It absorbs humidity from the hot air as well as the cold air when it is blown back into the room.
  • The compressor also raises the pressure of the refrigerant to allow the refrigerant to flow freely in the evaporator coils and consequently aid in the process of cooling.

Helpful read: How to calculate aircon BTU

How do I check my aircon compressor?

To ensure the durability of your aircon, you can perform maintenance checks, regular cleaning and pay attention to the tell-tale signs of a faulty aircon compressor.

You can also check your aircon compressor by inspecting the interior with the following steps.

  1. Turn off the power for your aircon unit.
  2. Unscrew the faceplate of your aircon to inspect the interior.
  3. If your aircon has an electrical access panel, remove it to take a look at the aircon’s wiring.
  4. To inspect the state of your aircon compressor, check for damaged wires and for signs of damage on the aircon compressor. In the case that there is visible damage to your aircon unit, it is advisable to contact professional services.
  5. You should also take note of signs of damage or burns on the terminals on the compressor. Terminals are usually located on the sides of the compressor and are connected via wires. If you have a multimeter, you may want to perform a test on the terminals to check if they are able to hold a current. If the ohm readings from your multimeter are extremely high (usually above the range of 30), you may need to consider replacing your aircon compressor or engaging a professional aircon service to help in repairing your faulty aircon compressor.

How do I know if my aircon compressor is broken?

  1. It doesn’t turn on

Sometimes, when you turn on the aircon, you’ll realise that the indoor unit is working perfectly fine, but the condensing unit is not. In this case, you may be able to hear the fan working, yet the compressor does not seem to be running. In such a scenario, your compressor may be failing due to several underlying factors.

  1. It blows warm air

If your aircon is on and the condenser is working fine – but the air being blown out is warm instead of cold, something is wrong. If an aircon compressor is broken, it will not be able to pump refrigerant throughout the system, which leads to the lack of cool air.

However, do note that if your aircon is not cold, this may also be caused by other factors, such as refrigerant leaks.

  1. It generates a lot of noise

If your aircon is making a lot more noise than usual when it’s working, this may be a sign that the aircon compressor is broken. The noise can be generated due to various reasons, from a dislodged component of the aircon to faulty electrical components.

Whatever the case is, if your aircon is being unusually loud, it is best to turn it off and contact professional aircon services.

  1. It vibrates when it’s turned on

If your condensing unit shakes violently every single time it is turned on, this may be a sign that your aircon compressor is struggling to start or turn on. This often precedes a full breakdown of the aircon compressor, so it would be best to turn off your aircon and call in a professional for help.

What happens when an aircon compressor goes bad?

As mentioned earlier, if the aircon compressor goes bad, your aircon will fail to produce cool air. This is due to the fact that a faulty compressor cannot process the warm air that has been absorbed by the aircon into cooler air.

With a bad aircon compressor, the room will also start to feel humid, as the aircon is unable to reduce the humidity in the room.

Types of Aircon Compressors

As there are various models and variations of air conditioners, there are different types of compressors as well. Each works in its different way to achieve the goal of making a room cold. If your aircon is not cooling enough, you can find some answers here.

Before choosing one, you need to talk to different aircon installation experts before going ahead with the installation. That being said, let’s go through the five types of aircon compressors:

Reciprocating Compressor

The most common type of aircon compressor is the reciprocating compressor. It comprises pistons, cylinders, and valves. An air-conditioner unit can have up to 8 cylinders within the compressor.

Each cylinder has a piston that moves up and down in a reciprocating manner. The working process of a reciprocating compressor is as follow:

  • During the step of re-expansion, the piston moves down, creating a vacuum in the cylinder. As a result, the refrigerant is sucked into space. The pressure decreases, which causes the refrigerant to expand.
  • In the next step of suction, the low pressure of the refrigerant causes the suction valve to open. As a result, suction gas is drawn into the compression chamber till the time the piston keeps moving downwards.
  • The next step is that of compression in which the piston in the cylinder starts to move back upwards. The suction valve is closed, and the refrigerant is compressed in the tight space in the cylinder. Space keeps getting tighter, further compressing the refrigerant. This also increases the refrigerant pressure.
  • As the refrigerant pressure increase, the process of discharge starts. The discharge valve is opened, the refrigerant is pushed out of the cylinder until the piston reaches its top point in the cylinder. At this point, the discharge valve closes, and the piston starts moving to do once again. This cycle then continues.

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Scroll Compressor

Scroll compressors are a newer type of compressors that are being used in aircon units. Because of its lesser components, it is considered more reliable than a reciprocating compressor. It comprises two sets of coils. The working process of a scroll compressor is as follow:

  • One of the two coils is fixed and stationary whereas the other coil vibrates or revolves at an axis. The fixed coil is called the scroll, and the other coil rotates over it.
  • The moving scroll pushes the refrigerant towards the centre of the compressor where it is compressed.
  • The compressed refrigerant is then discharged from the compressor, and the cycle continues.
  • Scroll compressors do not have any discharge or suction valves and are, therefore, more reliable.

Helpful read: Aircon Leaking Water Problem And How To Fix It?

Rotary Compressor

Rotary compressors are becoming a popular choice in air conditioners because of their small size and the very less noise they make. A rotary compressor comprises a cylindrical shaft with a roller attached to it. The working process of a rotary compressor is described below:

  • In this compressor, there are suction and discharge lines at the top of the cylinder.
  • As the roller rotates in the cylinder, it is blocking the discharge line at first. The refrigerant is thus able to enter the cylinder through the suction line.
  • As the roller rotates, the suction line is blocked, and no more refrigerant can enter the chamber.
  • The refrigerant pressure increases, and it starts to get compressed as the roller rotates.
  • The increased refrigerant pressure opens up the discharge line during the rotation of the roller. The refrigerant, thus, leaves the compressor chamber through the discharge line as a high-pressure refrigerant vapour.
  • The discharge line then closes, and the suction line opens, drawing more refrigerant into the compressor chamber, and this cycle continues.

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Centrifugal Compressor

A centrifugal compressor is also called a radial compressor. It comprises a rotating impeller with radial blades, a diffuser, and a volute. This a type of dynamic compressors which work at constant pressures. The exact working of a centrifugal compressor is described below:

  • The impeller starts rotating at full speed and draws in refrigerant air towards its centre.
  • In the next step, the drawn-in air is pushed towards the centre of the compressor with a centrifugal force.
  • The refrigerant gas is spun rapidly through the impeller, causing it to compress.
  • The compressed gas is pushed out of the compressor through the same centrifugal force.
  • More refrigerant gas is then drawn in once again, and the cycle continues.
  • Centrifugal compressors are usually used in high-performance and large air conditioning systems.

Helpful read: Aircon maintenance and repair cost in Singapore

Screw Compressor

Screw compressors are mainly used in air-conditioners which are used to cool large halls and rooms. They comprise two sets of rotors that rotate in opposite directions. The working process of a screw compressor is described below:

  • The two rotors rotate in opposite directions. This opposing rotation causes the refrigerant gas to be drawn in between them.
  • As the gas moves between them, space keeps on restricting, which causes the gas to compress.
  • The compressed air is then dispersed through the unit.
  • When the air is dispersed, the space increases, causing more air to be drawn inside and hence, the cycle continues.
  • The screw compressor does not have any suction or discharge valve, so it is also considered more reliable than a reciprocating or a rotary compressor.

These are some of the common types of compressors which are used in air conditioners these days. Although the function of a compressor is the same in each type, the process of how they work varies.

If you know the working of your aircon compressor, you would better be able to take care of it and make sure that the aircon continues to work smoothly and efficiently. Compressors are important to keep your aircon cool and if that is not happening, you can find out more here

Homees provides a list of the best-reviewed aircon servicing companies in Singapore. You can look for more services such as aircon installationchemical wash and troubleshoot on Homees today.

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