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Air Conditioning 101: What Does the Expansion Valve Do?

Aircon Parts

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Most people know air conditioners work to cool the air in the room, but in the process of lowering the room temperature, an air conditioner must move refrigerant around the unit. The expansion valve is one of those components that work with refrigerant flow. In this article, we'll take a look at expansion valves, and what they do in air conditioning units.

What is an Air Conditioner Expansion Valve?

The expansion valve is what regulates the pressure drop in your air conditioning system as the unit transforms liquid refrigerant to its vapor state in the evaporator coil. By managing the evaporator pressure, the unit allows refrigerant to expand into a gaseous form, and the expansion valve is what ensures the refrigerant flow is consistent.

The way an expansion valve works in an air conditioning unit is by facilitating how liquid refrigerant flows into the evaporator coil. The expansion valve allows only a minute amount of liquid refrigerant to flow into the coils at a time, allowing the liquid to expand in a vapor form, causing a significant drop in temperature.

There are various types of expansion valves, including: Automatic Expansion Valve, Thermal Expansion Valve, Thermostatic Expansion Valve, and Capillary Tube among others. Each type may operate slightly differently, but all facilitate refrigerant flow from high-pressure points (compressor) to low-pressure points (evaporator) for efficient cooling effect.

The Importance of Expansion Valves in an Air Conditioning System

1. Maintaining Evaporator Pressure

Maintaining low pressures in the evaporator coils is vital in the efficiency of a cooling system as the refrigerant needs low pressure to turn back into a gas form. The valve allows only a small amount of refrigerant to flow into the evaporator coil at a time, regulating evaporator pressure. Refrigerant has ample space to expand.

2. Keeps the Air Cool

Expansion valves do not directly affect the temperature in the room, but they do function to move refrigerant into the evaporator, which provides the cooling effect. In an air conditioning system, refrigerant moves from a gaseous state, to a liquid state, and back to a gaseous refrigerant form as it flows along the unit.

It is this movement that cools the air, and pulls the heat from the room. For the refrigerant to return to its gaseous state, it must have enough space and low pressure to turn into vapor. This is where the expansion valve enters. As the refrigerant has enough space in the empty coils to expand, they turn into gas. This process pulls heat from the unit.

Diagnosing a Faulty Expansion Valve

#1 Air Conditioner is Not Cooling Properly

The main symptom of a faulty expansion valve is an air conditioner that can not blow cold air into the room. Because expansion valves are responsible for moving refrigerant from high-pressure points to low-pressure points at a facilitated rate, faulty components may cause fluctuations in the liquid line that prevents refrigerant from turning into a gas.

As a result, the refrigerant cannot properly pull the heat from the air, and cool the air. You may notice your air conditioning system blowing warm air instead. While there are many causes for an air conditioner to blow warm air, a faulty expansion valve is one of the causes.

#2 Air Conditioner is Making Whistling Noise

High pressure liquid refrigerant can flow out of a faulty expansion valve with force, causing a whistling or high-pitched noise as the refrigerant passes through the valve body. Other components, such as a faulty fan motor or leaking refrigerant lines, can also cause a high-pitched whistling or squealing noise.

If you suspect the expansion valve is the problem, have a licensed HVAC professional at Luce Aircon assess and inspect your unit for an accurate diagnosis. Our technicians can also repair any problems with expansion valves, and replace the valve as needed.

Cost of Replacing an Expansion Valve

Repairing and replacing an expansion valve can cost between $200 to $700, depending on the scope of work that needs to be done. It is an essential part of aircon maintenance, as the AC unit cannot function properly without refrigerant flowing through the valve. Expect to pay an average of $400 to replace the valve body, however.

Scouting for Air Conditioner Repair Services in SG

Luce Aircon is the leading air conditioner service company in Singapore, and our experienced technicians will be able to give you an accurate diagnosis of any aircon problem you may have. Remove the guesswork, and trace the problem back to its source!

Not looking for repairs? We offer purchasing, cleaning and maintenance services to ensure your AC unit is running smoothly for longer! We're just a call away, so contacting us is as convenient as dialing our number.

Make that call, and contact us today for any air conditioner concerns! 

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Staff Writer

This article is written by our passionate staff writers who seek to share our knowledge from our business

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