Components of Air-Conditioner

Components of Air-Conditioner

January 6, 2019 tips 0



Have you ever wondered what are the components that actually made up the air-conditioner system? Below are all the components you need to know.


Outdoor Unit

With what are called “split systems”, as they have two units connected with refrigerant piping, the outdoor unit is called an air-cooled condenser. This unit includes the condenser coil, fan and compressor.

Indoor Unit

The indoor unit contains the indoor fan and the evaporator coil. It also has the expansion and the controls.

Packaged Unit

The packaged unit has all the components in one case.


The indoor unit or the packaged unit will be connected to ductwork, which directs the conditioned air around the house. Ductwork must be large enough to allow the air to be blown through it – if it is too small, there is a lot of resistance to the air flowing, and there may not be enough air available in the rooms.


The compressor is the heart of the cooling in your system. A compressor is selected by the manufacturer for performance and reliability, and is usually capable of many years of efficient operation. It is lubricated and cooled by the refrigerant flow, and as, long as this sealed system is not contaminated, is rarely a source of trouble. If it fails, it normally requires complete replacement, to be done by a professional aircon servicing company which includes removing and replacing the refrigerant.


Coils are the means by which heat is transferred efficiently. They are made of tubing, zigzagging back and forth, with fins mounted on the outside of the tube. These increase the surface area, which allows more heat to be transferred. To operate properly, coils must be clean, and dirty coils, which then aren’t capable of operating at design conditions, are a common problem that affects air conditioning performance.

In your air conditioning system, you have an indoor coil, which is located in the air which goes to your room, and is used for cooling. This is the evaporator coil in the above description of the refrigeration cycle. As this coil becomes cool, it can sometimes condense water from the air on its surface, so it has a metal or plastic pan underneath to catch any drips, and take the water away to a drain or to discharge outside. The outdoor coil has the opposite function. It gets hot, and has to release the heat to the outside air. This is called the condenser coil, which condenses the refrigerant inside the piping. It’s usually vertical, and the air is drawn in through it.

Indoor Fan

This is the fan that blows the air into your rooms. There are various types of fan, commonly they would be a centrifugal type, and have a rubber belt drive from an electric motor to provide power, but most common are direct drive types, where the motor is on the end of the fan shaft.

Outdoor Fan

There may be one or more outdoor fans, and their purpose is to blow heat away from the condenser coil. These are usually a propeller type fan, mounted on a motor shaft, and often blow straight upwards. The air is drawn in through the sides.


All motors in your air conditioning system operate on the main voltage coming into your house. The purpose of a motor is to convert the electricity into rotation, and in an air conditioning system this includes the fan motors and compressor motor.


You are probably familiar with the thermostat – it’s usually on the wall, and is used to adjust the temperature that the system tries to achieve. Most thermostats are low voltage (24 volts), and they may be electromechanical or electronic. They can also include timing functions, so that you can set the system to come on or go off according to a schedule, and you will need to consult the specific instructions to check how to program the unit. Not all thermostats are created equal, as some are multi-stage and have additional functions, for example to run electric heating during very cold periods on a heat pump unit. However, there is a wide selection available for most system types – you certainly aren’t limited to buying your thermostat from the equipment manufacturer. You will need to ensure that any replacements are suitable for your system, but many thermostats that are available today can be used on several types of systems. The instructions will help, and the manufacturer of the thermostat should be able to confirm in case of doubt if you give him your equipment model number. One feature that you may find useful is the ability to retain the programming during a power interruption, which is usually done by having a small battery included in the thermostat. There are other thermostats, or temperature sensors, in your system, usually to take care of safety issues. For instance, if something goes wrong causing equipment to overheat, there may well be a sensor that cuts the power to protect against damage.


An essential part of the electrical system, a transformer converts mains A.C voltage to a different voltage, as required. For instance, that’s how the thermostat gets 24 volts. This is necessary because small electronic components, the brains on your printed circuit (PC) boards, don’t function on the higher mains voltage.


These are a method of interfacing the different voltages used without mixing them. They are an electrical switch, and a common arrangement is for a low voltage to switch a higher voltage. Thus a 24 volt signal from the thermostat might switch an electric motor. Relays usually refers to a unit that switches a higher amount of electrical power, typically with multiple contacts or circuits.

PC board

The printed circuit, or PC, board is the brains and logic behind the satisfactory operation of your air conditioning system. Not only does the PC board control in sequence as required the various parts, it can usually diagnose if anything doesn’t work as needed, and provide information by flashing lights or giving codes, etc. With a manual in hand, this will often lead you directly to the problem, and save a lot of guesswork and testing.


If you have any familiarity with your household electrics, you have probably encountered breakers, or circuit breakers, to give them their full name. These are safety devices which cut off the power if the amount of electricity drawn is excessive – similar to fuses but without the inconvenience of replacement – they can just be reset, once the cause of the problem has been fixed.


The usual piping associated with air conditioning is copper or aluminium, and carries the refrigerant. As such, it is a closed system, and doesn’t need any refrigerant added to it, although loss of refrigerant when it occurs is a problem. With a split system, the refrigerant piping is connected between the two units on installation, and with a packaged system the piping is in the unit and all ready to go.


There are several types of refrigerant, each suited for slightly different design operating conditions. Some refrigerants are extremely harmful to people and to the environment, and releasing them into the air is prohibited by law. The industry has worked to replace these harmful compounds, and generally only relatively safe refrigerants are available in modern equipment. Your system still may contain a refrigerant which should not be vented to the air – as refrigerants can be expensive, it also makes sense to recover and reuse them in most cases. Strict laws govern working on such systems, and you will need to get a certified technician with proper refrigerant recovery equipment if there is a problem. You will find that you cannot obtain these refrigerants without a license.


Wiring breaks down into two groups – wiring internal to the equipment, installed by the manufacturer, and wiring outside the equipment, called field wiring, which is run and connected when the system is installed. The manufacturer’s manual will give details of both, usually illustrating the field wiring with a dashed line. This wiring diagram is extremely important for checking for faults in the system. Field wiring also falls into two groups –the line voltage wiring and the low voltage wiring, such as goes to the thermostat.


The air filter is the most common maintenance item in your system. It should be replaced or cleaned regularly as required by the manufacturer’s instructions – probably every month. If you don’t keep it serviced, your system will cost more to run and will not give satisfactory performance. The air filter may be included in the equipment, or can often be found as part of the return air grille. It may be replaced by unscrewing or unlatching the grille, which is usually hinged, and putting in a new filter.


Ducting may be made of metal, foil-covered fiberglass, or other materials. It is used to carry the airflow from the indoor unit to different parts of the house, and may also take air back to the unit with return grilles. To keep the temperature of the air consistent throughout the system the ductwork must be insulated. This saves energy, but is chiefly included to prevent condensation during cooling. For smaller systems, you may often find that the unit has a central metal box, and the duct runs to each room are made with round flexible foil covered ducting fixed to the box. This system is cheap and easy to install, although it can cause some problems in getting sufficient air to distant rooms – the round duct easily kinks and presents a high resistance to the flow of air.

Registers and Grilles

These are the familiar metal or plastic slotted plates which introduce air to your rooms or take it away. The difference between a register and a grille is that the register has a means of controlling the amount of airflow. This is the usual device for the supply air, as the several different supply outlets need “balancing” or regulation of air flow to keep each room at the right temperature. The air supply devices may also be adjustable to direct the flow, or may just have fixed directions. The returns allow the air to route back to the equipment, but really don’t have much effect on the air distribution in the house.


Information courtesy from Mike Newberry from the Aircon Repair


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