Electrical Components of Air Conditioning System and their function

Air conditioning systems have standard electrical parts that are essential for temperature control, equipment protection and minimizing equipment operation costs.  These electric parts vary from wiring to sophisticated control system circuitry.

Electrical Components of Air Conditioning System


The capacitor absorbs and stores electricity from the main supply. Capacitors maintain a constant supply of charge that produces efficient and continuous power sources, necessary for starting up and running fan motors.  A capacitor unit is equipped with both the start capacitor and a run capacitor. A start capacitor will usually power up the motor whenever a cooling cycle begins, whereas the run capacitor keeps the motor running steadily through the cycle.


Contactor controls the flow of electricity within the air conditioning system, by providing and cutting off the supply whenever necessary. When the cooling cycle has not been initiated, the contactor will maintain an ‘up’ position, blocking flow of electricity to any of the components. As the cooling cycle begins, a signal from the thermostat will initiate a voltage flow that takes the contactor to a ‘down’ position, paving way for the flow of electricity.


Relays are responsible for dictating the amount of time between the closing and opening of electric circuits, to allow the flow of current in the air conditioning system. Time delays allow the blower motor to continue running, even after the compressor has been turned off by the thermostat. As the motor continues running, it utilizes the cooling effect of the evaporator, producing additional chilled air and improving overall air conditioning efficiency.

Fan Motor

The motor is solely responsible for the flow of air in and out of a conditioned space. Running of the motor enables circulation of air within the room, keeping internal room parameters such as temperature, humidity and air quality.  Fan motors are equipped with overload protection within its windings, preventing serious damages due to overheating.

Indoor air conditioning units are fitted with bi-directional motors, which turn the fans through several angles, providing sufficient spread of air within the room. Rheem air conditioners are known for their long warranties on fan motors.

Crankcase Heater

It is an electric resistance heater connected to the mains supply of the air conditioner. Most crankcase heaters are operational, even when the system is off. The electric heaters are required to keep the refrigerant, which handles the heating and cooling, at a temperature that is slightly higher than the coldest part of the system. A heated crankcase prevents migration of the refrigerant, which tends to flow back to the condenser, especially over long-off cycles.


It is responsible for monitoring room temperature conditions. An increase in room temperatures will prompt the thermostat contacts to close, sending a signal to the contactors, thereby starting the compressor. On achieving required room conditions, the thermostat contacts open, stopping the compressor.

Pressure Switches

These are safety equipment, mounted on both the low pressure and high-pressure sides of the air conditioner. The switches monitor variations in refrigerant pressure, protecting the compressor from extremely low or extremely high pressures. The high pressure causes overheating, while low pressure causes mechanical damage to the compressor. In case of a sharp rise or drop in refrigerant pressure within the system, the switches will send electric signals to the contactors, thereby turning off the compressor.

Electrical Wiring and Cabling

Air conditioners have two sets of electrical cabling. There is a dedicated voltage line that supplies the electric power from the main supply to the air conditioner. Usually, the voltage ratings for most air conditioners is 240V. The other set of wiring is the communication cables, which relays electric signals between the outdoor and indoor air conditioning units. The communication wiring starts at the thermostat and is usually rated 24V.

Automatic Voltage Switcher (AVS)

This acts as a surge protector, ensuring that the air conditioning units receive correct voltages for their operations, preventing under voltage or over voltage which may cause damage to equipment. The AVS turns off the equipment automatically whenever the power exceeds the preset acceptable limits and automatically reconnects when main supply reverts to normal.

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