Central Air Conditioner Parts Guide

Basic Components of Air Conditioners

Air conditioners maintain comfort in spaces by controlling temperature and humidity. At the core of their functionality lie several critical components, each with a distinct role.


AC Compressor

The compressor is the heart of an air conditioner, responsible for circulating refrigerant between the evaporator and condenser coils. It compresses the refrigerant, raising its pressure and temperature, and enabling it to capture heat from within a room.

Condenser Coil

AC Condenser Clean

In the condenser coil, located in the outdoor unit, the hot refrigerant gas releases its gathered heat to the outside air. This process cools the refrigerant, transforming it into a liquid form, ready to cycle back inside.

Expansion Valve

The expansion valve controls the flow of the cooled liquid refrigerant, allowing it to expand and decrease in pressure. This step is crucial before the refrigerant enters the evaporator coil, preparing it to absorb heat effectively.

Evaporator Coil

Positioned in the indoor unit, the evaporator coil acts as a sponge. It absorbs heat from the indoor air as the low-pressure refrigerant evaporates, subsequently cooling the air before it is recirculated back into the room.


Refrigerants R22 vs R410A

Refrigerant is the fluid that flows through all the other components. Its ability to undergo phase changes easily allows it to absorb and release heat efficiently, making it the lifeblood of any air conditioning system.

Air Conditioning Cycles

Air conditioning systems rely on the principles of thermodynamics, employing various cycles to remove heat from an environment. Understanding these cycles is essential for grasping how air conditioners maintain cool temperatures indoors.

Refrigeration Cycle

The refrigeration cycle is the cornerstone of most air conditioning systems. It consists of four key components: the compressor, the condenser, the expansion valve, and the evaporator. Working fluid, often referred to as refrigerant, circulates through these components and undergoes phase changes—converting between liquid and gaseous forms. The cycle can be summarized as follows:

  • Compression: Refrigerant gas is compressed, raising its pressure and temperature.
  • Condensation: High-pressure, hot gas releases heat as it condenses into a liquid.
  • Expansion: The liquid refrigerant cools as it undergoes a pressure drop through the expansion valve.
  • Evaporation: Low-pressure liquid absorbs heat from the surroundings and evaporates into a gas.

Heat Exchange Process

Within the heat exchange process, two primary exchanges occur: the release of heat to the outdoors and the absorption of heat from the indoor environment. This process occurs in the condenser and evaporator coils, respectively. Air conditioners might leverage different types of heat exchangers, such as:

  • Air-cooled: Utilizes a fan to blow air over the coil, dissipating heat.
  • Water-cooled: Incorporates water instead of air to absorb heat from the refrigerant.

Evaporation and Condensation Cycles

The evaporation and condensation cycles enable the refrigerant to transfer heat effectively. During the evaporation cycle, the refrigerant at low pressure and temperature absorbs heat from the indoor air, resulting in cooler air. This phase change from liquid to gas captures unwanted heat. Conversely, the refrigerant releases this heat during the condensation cycle when it turns back into a liquid at a higher pressure and temperature, facilitated by the condenser unit which typically sits outside the building.

Control and Regulation Systems

The efficacy of an air conditioning system largely depends on the seamless operation of its control and regulation systems. These components work in tandem to ensure an optimal indoor climate by making real-time adjustments based on various inputs.


The Thermostat serves as the user interface for setting the desired temperature. It detects the ambient room temperature and signals the air conditioner to either start or stop cooling to maintain the set temperature. Modern thermostats can be found in various forms including digital programmable models that offer higher precision and the convenience of scheduling.

Control Board

The Control Board is the communication hub of an air conditioning system, coordinating between different parts like the compressor, fans, and motor. It processes inputs from the thermostat and sensors, and sends out commands to regulate the temperature and airflow efficiently.


Sensors in an AC system monitor various environmental and operational conditions, such as indoor and outdoor temperatures, humidity levels, and system performance. These sensors provide critical feedback, which the system uses to regulate cooling and ensure energy-efficient operation. Some advanced units feature sensors that can even detect the presence of occupants to adjust settings for maximum comfort and energy savings.

Air Distribution Parts

The air distribution system in an air conditioner is crucial for delivering cooled air throughout the space. It consists of several key components, each with a specific function to ensure efficient airflow.

Blower Fans

Blower fans are responsible for moving air through the air conditioner and into the room. They work by drawing warm air in, allowing it to be cooled, and then pushing it out through the duct system. Efficient operation of blower fans is vital for maintaining consistent cooling and air circulation.

Air Filters

Air filters capture and remove particles from the air, such as dust, pollen, and other contaminants. They are essential for maintaining indoor air quality and preventing the buildup of debris in HVAC components. Filters should be checked regularly and replaced or cleaned as needed to uphold air flow and system efficiency.


Ducts form the network of pathways that facilitate the movement of conditioned air from the air conditioner throughout the building. Properly installed and maintained ductwork ensures that air is distributed evenly and energy loss is minimized. Leaks or blockages in the ducts can lead to inefficiencies and uneven cooling.

Additional Features

In the realm of air conditioning, various supplementary features enhance comfort, air quality, and energy efficiency. These include dehumidifiers to manage moisture levels, air purifiers to improve indoor air quality, and programmable thermostats for better temperature control.


A dehumidifier function within an air conditioning system is crucial for reducing indoor humidity levels. Excess humidity can cause discomfort and lead to the growth of mold and mildew. Some air conditioners have integrated dehumidifying features that allow them to maintain a comfortable humidity level without overcooling the space.

Air Purifiers

Many modern air conditioning units incorporate air purifiers that utilize HEPA filters, UV lamps, or ionizers to remove pollutants, allergens, and pathogens from the air. This is especially beneficial for individuals with allergies or respiratory issues. By having an air purifier as part of the system, air conditioners can play a vital role in maintaining a healthy indoor environment.

Programmable Thermostats

Programmable thermostats provide the user with the ability to set customized heating and cooling schedules. These devices are designed for convenience and energy savings, allowing air conditioners to run more efficiently by adjusting the temperature based on the time of day or the occupants’ presence. Energy-saving and convenience aside, smart multi-function air conditioners may include features that go beyond simple temperature adjustments, offering extensive control over the system’s operation.

Maintenance Components

Proper maintenance of an air conditioner is crucial to its performance and longevity. Specific components require regular attention to ensure efficient operation of the system.

Air Filter Replacements

The air filter is a critical part of an air conditioner, trapping dust, pollen, and other airborne particles to improve indoor air quality. Filters should be checked monthly and replaced every 30 to 90 days, depending on usage and environmental conditions. Failing to replace air filters can lead to reduced airflow and compromised system efficiency.

Refrigerant Refill Ports

Refrigerant refill ports serve as the access points for HVAC professionals to replenish the refrigerant in an air conditioning system, ensuring it continues to cool the air effectively. These ports must be sealed properly to prevent leaks, which can decrease system performance and cause environmental harm.

Drainage Systems

The drainage system, comprising the condensate drain pan and drain lines, allows for the removal of condensation produced during the cooling process. Regular cleaning of these components is necessary to prevent water buildup and potential microbial growth, which can result from clogged drainage lines.

Types and Variants of Air Conditioners

Air conditioners are diverse in their designs to cater to different needs and spaces. They range from large centralized systems to individual units serving single rooms.

Central Air Conditioning

Central air conditioning systems provide cooling for entire buildings by circulating cool air through a network of ducts and vents. These systems are designed for efficiency and are commonly used in larger residential homes, offices, and other substantial structures. The setup usually includes a large outdoor unit housing the compressor, condenser coils, and an indoor unit containing the evaporator coils and air handler.

Window Units

Window units are compact air conditioners designed to fit into a window frame. They are a common choice for single-room applications due to their simplicity and ease of installation. These units combine all air conditioning components in a single box with a control panel for operability, making them a convenient standalone solution.

Portable Air Conditioners

Portable air conditioners are self-contained mobile units that can be moved easily from room to room. They are equipped with wheels and typically require venting through a window or a wall using an exhaust hose. These units are versatile and suitable for places where traditional air conditioning installation is not feasible.

Ductless Mini-Splits

Ductless mini-splits consist of an outdoor compressor connected to one or more indoor air handling units by electrical lines and refrigerant tubing, avoiding the use of ductwork. They provide targeted cooling to specific zones in a building, offering a flexible and energy-efficient approach for both residential and commercial environments.

Written by

Rene has worked 10 years in the HVAC field and now is the Senior Comfort Specialist for PICKHVAC. He holds an HVAC associate degree and EPA & R-410A Certifications.

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