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Aircon Unit Expansion Valve: The What’s And How’s

We all know that an aircon unit is a powerful machine capable of providing maximum cooling for every office and household. And since everyone swears by an aircon unit to keep them cool and comfortable all day, then they must always be kept in great condition, both internally and externally and that is also with the help of a professional aircon servicing company.

An entire aircon unit relies on different parts in order to continue providing families and businesses with maximum cooling and ventilation especially during the hot summer days when humidity would feel like at its extremes in Singapore. From compressors to filters to coils, each part counts in making sure that the aircon unit is able to perform at the best of its capacity. However, apart from these essential aircon unit parts, few are familiar with the function and in most cases, the aircon expansion valve.

What is an Aircon Unit Expansion Valve?

As one of the most important and crucial parts of an entire aircon unit, expansion valves are devices used to control the refrigerant flow in a refrigeration system. They assist by facilitating the changes that occur from the liquid higher-pressure refrigerant in a condensing unit into a gas lower-pressure refrigerant inside the evaporator.

How does an Aircon Unit Expansion Valve work?

To understand how the expansion valve works, you must realize that temperature and pressure have a direct relationship. Increasing the pressure of refrigerant also increases its temperature, literally packing its molecules more tightly together. This dual increase is exactly what happens as the refrigerant passes through the compressor.

The pressure-temperature relationship works in the opposite direction as well. In other words, by reducing the refrigerant’s pressure, you can effectively cool the refrigerant off. The expansion valve accomplishes this task by restricting the flow of refrigerant into the evaporator coil.

Without the expansion valve, the refrigerant would rush into the evaporator coil without losing any of its pressure. The expansion valve permits only a small part of the refrigerant to enter the coil. As this refrigerant enters, it suddenly finds itself able to spread out in the relatively empty evaporator coil. This expansion causes its pressure to rapidly drop. The temperature drops right along with it.

What happens when an Aircon Unit Expansion Valve goes bad?

You will notice when the aircon unit expansion valve goes bad because your aircon unit will ultimately stop functioning properly. It will either produce less cool air or it won’t produce any cool air at all. At this point, you will need to call for a professional aircon servicing company to replace your aircon unit expansion valve to fix the aircon issue.

What are the most common Aircon Unit Expansion Valve problems?

As far as aircon unit components go, expansion valves tend to be tough. As a result, they experience fewer aircon issues than more delicate parts such as the compressor. Yet expansion valves have to withstand large amounts of pressure from the liquid line side.

Over time, this pressure can cause the expansion valve to break down. A failed expansion valve will no longer be capable of limiting the flow of refrigerant. Instead, excessive amounts of refrigerant may flow into the evaporator coil. The refrigerant won’t experience the necessary temperature decrease, meaning your aircon unit won’t be able to cool as efficiently.

On the other hand, the tiny diameter of an expansion valve means that it may also experience unwanted restrictions. Debris can become lodged inside of the valve, keeping refrigerant from passing through it at all. Such a restriction will prevent your entire aircon unit from cooling. It will also lead to refrigerant starvation on the suction side of the aircon unit. Compressor burnouts and other aircon issues may soon arise.

The expansion valve plays a key role in the proper functioning of an entire aircon unit. For more information about how to keep your expansion valve in good working order, reach out to your trusted professional aircon servicing company.

Pro 338 Reminder: When it comes to replacement or repairs of any part of your aircon unit, always call for a professional aircon servicing company to do it. Not only do they have the right and complete tools but they are as well skilled and well-trained.

What are the different types of an Aircon Unit Expansion Valve?

1) Automatic Expansion Valve

This type of aircon unit expansion valve type works by using a pressure-actuated diaphragm that regulates the refrigerant flow from the liquid line down to the evaporator. Its usual disadvantage lies in the fact that it’s counterproductive if the load fluctuates. This type is strongly recommended to not be used in aircon units as the load is likely to fluctuate a lot.

2) Thermostatic Expansion Valve

The thermostatic expansion valve or TEV is known to use a valve mechanism that controls the liquid refrigerant’s flow into the evaporator coil. Afterward, the flow is controlled by the evaporator by way of its pressure. This type of expansion valve operates well even during different cases of fluctuations, making it suitable for an aircon unit. Once the evaporator warms, the valve is able to provide a higher flow rate. Once it cools, this flow rate is then reduced. Additionally, there is a sensor bulb located at a higher temperature in the evaporator that detects the coil’s temperature.

3) Capillary Tube

The capillary tube is a tube with a small internal diameter. This tube can be coiled for its length and is usually installed on the suction line. To remove dirt and moisture from the refrigerant, a filter-drier is commonly fitted before the tube. To ensure that the device performs exceptionally well, the refrigerant found in the aircon unit must be properly calibrated at its factory level. Compared to the thermal expansion valve or TXV/TEV, the capillary tube is generally cheaper and used in-room or window-type aircon units.

4) Float Valve

The float valve is a valve that is operated by a float immersed in the liquid refrigerant. To control the flow of this liquid refrigerant, both low-side and high-side floats are used. The low-side float functions by helping the liquid refrigerant be maintained at a constant level inside the evaporator. When there is no liquid inside the evaporator, it opens and closes when there is some.

On the other hand, the high-side float, located at the system’s high-pressure side, maintains the refrigerant at a constant level in the condenser. Once the compressor works, the float chamber receives a flow or condensed refrigerant inside and the valve is opened. This reaction allows the refrigerant to make its way into the evaporator. Once the liquid level found in the float chamber goes down, the valve opening will close. It is during this process that the liquid is further prevented from flowing into the evaporator.

Pro 338 Reminder: When you are not sure about the type of expansion valve to use for your aircon unit, taking the time to read and do some research can be a great help. However, you can also call on your reliable professional aircon servicing company since they are knowledgeable and can recommend you on what’s good and right for your any aircon unit needs.


It’s always a good time to talk about the common issues that aircon units have. This way, you’ll be able to spot if there are problems with your unit or not and prepare for its replacement accordingly. If you require our aircon servicing services, Whatsapp us at +65 9222 4141 for a fast and transparent quote.

338 Aircon Servicing Singapore provides an extensive range of Aircon Services including Aircon Servicing, Aircon Repairs, Aircon Installation of the best aircon brands, Chemical Overhaul, Gas Top-up, Aircon Leaking Water, and Aircon Not Cold Fix, and more. We have a team of professional technicians who are equipped with vast knowledge and experience in the Aircon industry.

We have over 15 years of experience in dealing with aircon works and have completed thousands of aircon works for both residential (Landed, Condo, and HDB) and commercial. We are a highly recommended Aircon Company in Singapore, with many delighted customers and reviews over the years on Google and Facebook.

WhatsApp us at +65 9222 4141 for a transparent quotation and honest pricing for all your aircon needs or Call us at +65 9222 4141. We offer a fast and efficient service to serve any of your aircon needs!


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