What is an AC Compressor? Everything You Need to Know

Figure 1: Outdoor unit of air conditioner.

The air conditioner is one of the most used home appliances in hot summer. We all know that the air conditioner includes two parts: the outdoor unit and the indoor unit. The two work together to bring us cool air, and the air conditioner compressor (AC compressor) plays a big role in the cooling process. Then what is an air conditioner compressor?

1. What is an AC Compressor?

Air conditioning systems have several components that assist in the cooling of the air. These components are compressors, throttling devices (such as capillary tubes, expansion valves), condensers and evaporators.

The air conditioning compressor is an important part of the air-conditioning refrigeration system. It provides power for the flowing of refrigerant in the pipeline, and sends the refrigerant from the low-pressure area to the high-pressure area for cooling and condensation. During this process, the heat is dissipated through the heat sink into the air, and the refrigerant also changes from a gaseous state to a liquid state.

The air conditioning compressor keeps working, and it continuously absorbs the heat at one end of the low-pressure area into the refrigerant, and then sends the absorbed heat to the high-pressure area to radiate into the air, playing a role in regulating the temperature.

Figure 2: The high pressure area and low pressure area of the air conditioning system.

1.1 Types of Air Conditioning Compressors

According to the principle of increasing gas pressure,
·Positive displacement compressor (volumetric compressor), including piston compressor (reciprocating compressor), screw compressor, scroll compressor, rolling piston compressor, etc.
·Dynamic compressor, including centrifugal compressor, axial flow compressor, etc.

Classified by sealing method,
·Open compressor
·Semi-hermetic compressor
·Fully hermetic compressor

Home air conditioners mainly use rotary compressors and scroll compressors, 1 to 3 horsepower air conditioners use rotary compressors, and 3 horsepower and above air conditioners use scroll compressors.

1.2 Structure of the Air Conditioner Compressor

1. Rotary compressor structure

Figure 3: Rotary compressor cutaway view.

2. Scroll compressor structure

Figure 4: Scroll compressor cutaway view.

1.3 AC Compressor Wiring Method

1. Single-phase compressor wiring diagram

Figure 5: Single-phase compressor wiring diagram.

2. Three-phase compressor wiring diagram

Figure 6: Three-phase compressor wiring diagram.

2. Where is the AC Compressor Located?

2.1 Home AC Compressor

The vast majority of air conditioners that people see are divided into outdoor units and indoor units. The main function of the indoor unit is to blow air and filter, and most of the important components are generally installed in the outdoor unit.

The air conditioner compressor is generally installed in the outdoor unit of the air conditioner, next to the fan of the external unit. The air conditioner compressor is a cylindrical black (different brands of air conditioners have slightly different compressors), and its main function is to provide power for the refrigeration cycle to adjust the temperature in the air-conditioned room.

Why is the compressor installed inside the outdoor air conditioner unit?
1. The air conditioner compressor makes noise when working.
The air conditioner compressor will produce a lot of noise when it is working. If people hear these noises when resting, they will not be able to calm down and have a good rest, which will have a negative impact on people's lives.

Therefore, deliberately install the compressor inside the outdoor unit. Moreover, people will close the doors and windows when using the air conditioner, so as to reduce the impact of compressor noise on people.

2. For the overall beauty.
Compared with other components of the air conditioner, the individual compressor is relatively large, so there is a requirement for the space for installing the compressor. In contrast, the compressor is more suitable to be installed in the outdoor air conditioner unit. If the compressor is installed in the indoor unit of the air conditioner, it will affect the appearance and position of the indoor unit of the air conditioner.

Figure 7: AC compressor installed in the outdoor unit.

2.2 Car AC Compressor

Car air conditioner refers to the air-conditioning device installed on the automobile, it can cool, heat, ventilate and purify the air in the compartment, provides a comfortable riding environment for the passengers, reduces the fatigue severity of the driver, and improves driving safety.

The car air conditioning compressor is installed on the engine, and different engines have different installation positions. The car AC compressor is driven by the belt to work together with the engine. You can find the specific location of the car air conditioning compressor by looking for the belt.

Figure 8: Car air conditioning system structure.

3. How an AC Compressor Works?

When the air conditioner is working and cooling,
·The low-temperature and low-pressure refrigerant gas is sucked in by the compressor and then pressurized to become high-temperature and high-pressure refrigerant gas;
·The high-temperature and high-pressure refrigerant gas releases heat in the outdoor heat exchanger and becomes a medium-temperature and high-pressure refrigerant liquid;
·The medium-temperature and high-pressure refrigerant liquid becomes a low-temperature and low-pressure liquid after being throttled and depressurized by the throttling device;
·The low-temperature and low-pressure refrigerant liquid absorbs heat and evaporates in the indoor heat exchanger, and then becomes a low-temperature and low-pressure gas；
·Then the low-temperature and low-pressure gas enters the compressor again to perform the refrigeration cycle.

4. What Does an AC Compressor Do?

The AC compressor is the heart of the air-conditioning and refrigeration system, and it plays the role of suction, compression, and circulation.

The refrigerant is driven to flow in the pipe by the compressor. The liquid refrigerant is turned into vapor in the evaporator, and then the refrigerant in the vapor state is transformed into a liquid state in the condenser, achieving the purpose of cooling through heat conversion. This process can continuously absorb heat, so the air conditioner will blow out cold air in summer.

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