All You Need to Know About the Aircon Expansion Valve


  June 30th 2020            👤   Aircon Heroes Team

How an Expansion Valve Works

Your entire air conditioning system contains components that are essential to the cooling cycle and the expansion valve is a lesser known but essential component of this cycle. Understanding how this key part of your air conditioner works is important as it contributes to how your air conditioning unit operates and functions. This article discusses your air conditioner’s cooling system and the role of the expansion valve in it. 

Your air conditioner system works to absorb the heat from the inside air and disperse that heat out of your indoor environment, lowering the temperature of the inside air in the process. This cycle starts when the air from the room reaches the evaporator coils inside the indoor unit.

Here the heat from this incoming air is absorbed by the refrigerant inside the evaporator coil and it flows towards the outdoor unit via pipes. The outdoor unit has condenser coils, compressor and an expansion valve installed within it. When the hot refrigerant coming from indoor unit passes undergoes compression, its pressure increases and it becomes hotter.

But when it is subjected to pass through the expansion valve, the sudden expansion removes the pressure of the compressor from the refrigerant and its temperature drops to a minimum. This is the point where the hot air from the room interacts with this cold refrigerant and gets cold. The expansion valve thus inhibits refrigerant flow, effectively reducing the refrigerant temperature to the desired level before it passes into the evaporator coil.

Categories of Expansion Valves

There are different categories of expansion valves which are being used on the market. Some of these are designed for some particular models of air conditioners and some of them are universal valves which can be utilized in any air conditioning unit. 

Automatic Expansion Valve

The automatic expansion valve utilizes a pressure-actuated diaphragm which helps to process the flow of the refrigerant throughout the process. Its disadvantage is its inability to deal with any voltage fluctuations. Since it is an automatic expansion valve, its efficiency gets undermined due to this disadvantage.

Capillary Tube Expansion Valve

This is a relatively cheaper and easy to install category of the expansion valve. It can be adjusted to any desired shape and helps process the flow of the refrigerant quite conveniently throughout the pipes. 

Thermostatic Expansion Valve

The thermostatic expansion valve operates in a unique way. It regulates the amount of refrigerant flow in the evaporator coils and when the temperature inside the coil reduces, the flow increases and vice versa. This is one of the most suitable expansion valves that can be installed inside an air conditioning unit.

Float Type Expansion Valve

In the float type expansion valve, two different floats are used. They are termed as high side and low side floats. The low side float directs the flow of the refrigerant. When the amount of refrigerant reduces inside the evaporator coil, the low side float operates to process the flow of the refrigerant from the valve and the cycle goes on.

Why is the Expansion Valve Important?

Without an expansion valve, the air conditioner cannot operate. This is one of the most important components of the air conditioning unit. It helps to lower the temperature of the refrigerant which then absorbs the heat from the room. 

It not only lowers the temperature of the refrigerant but also holds the pressurized hot refrigerant behind itself. Any sort of leakage or blocking in this expansion valve is potentially dangerous.

Why is Maintenance of the Expansion Valve Important?

It is important to get the expansion valve cleaned regularly in order to improve the performance of the entire air conditioner. When there is a leakage in the valve, it is no longer capable of limiting the flow of refrigerant. Instead, excessive amounts of refrigerant may flow into the evaporator coil. As a result, the refrigerant won’t experience a significant enough temperature drop to absorb heat from the inside air. 

Sometimes, blockage in the expansion valve can occur due to clogged dust particles or debris inside the pipe. When this happens, it blocks the passage of the refrigerant through the expansion valve. Since this refrigerant is hot and pressurized liquid prior to passage through the expansion valve, it can become catastrophically damaging. The entire air conditioning system can get damaged and may also result in an accident.


The aircon valve isn’t immune to damage and malfunction just like any other component of your air conditioner. It is best to let a professional aircon technician check for any defects in your aircon valve. Regular maintenance checks can assess all the components of your air conditioner including the expansion valve, ensuring maximum cooling efficiency and saving you from potentially bigger maintenance and repair costs in the long run.


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