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what does an ac expansion valve do

What Does an AC Expansion Valve Do: A Brief Guide

If your air conditioner isn’t working, the problem could be a faulty air conditioning expansion valve. Call Green Energy Mechanical Inc. at (781) 236-3421 at the first sign of trouble to prevent a total system failure. 

One common question we get as Canton’s AC maintenance experts is, “What does an AC expansion valve do?” When a home or business’s air conditioner stops working, there’s a chance that this small yet integral component is the source of the problem. When it malfunctions, it can affect the refrigerant flow and prevent the air conditioner from producing cold air or cause a total breakdown of other parts like the compressor or evaporator coils. 

To give you a better sense of what this critical part does and how to prevent problems, check out our guide below.

How Air Conditioners Work

In explaining the role and the importance of an expansion valve, it’s first essential to understand how air conditioners work, particularly in terms of refrigerant. 

Refrigerant, also known as R410-A, switches between liquid and gas forms and removes heat from the air. The refrigerant in the evaporator coils inside your home is in cold gas form; when air flows over the coils, they absorb the heat. The gas then flows to the compressor, which increases pressure on the gas, transforming it back into liquid refrigerant so it can more easily release the heat in the condenser coils.

Once the refrigerant passes through the condenser coils, it’s in a high-pressure state and not ready to remove heat from the air, and that’s where the AC expansion valve comes in. The valve reduces the pressure on the refrigerant, so it cools down rapidly and returns to its gaseous state, enabling it to remove heat from the air. Without the thermostatic expansion valve, the refrigerant would remain in liquid form and never become cold enough to absorb heat from the air.

How the Expansion Valve Works 

Now that you have a basic understanding of “What does an AC expansion valve do?” we can get into more detail about how it works. 

The foundation of expansion valves rests on the relationship between temperature and pressure. High pressure increases the temperature and packs molecules together—this is why refrigerant turns into liquid as it passes through the compressor. Reducing the pressure allows molecules to spread out, reducing their temperature, and in the case of refrigerant, turns it back into a gas.  

The expansion valve controls the pressure of the refrigerant as it moves from the compressor to the evaporator coils. The valve restricts the amount of refrigerant that enters the evaporator coils, only allowing a small amount to pass through at a time. This helps maintain the correct evaporator pressure and a low enough refrigerant temperature to ensure cooling.  

Common Issues with Air Conditioner Expansion Valves 

Air conditioner expansion valves are typically reliable and not as prone to issues as other mechanical components. They have to withstand a great deal of pressure from the liquid refrigerant coming from the compressor, so they have to be durable.

Still, issues can occur. Ongoing pressure can cause the valve to fail and allow excess liquid refrigerant into the evaporator coils. When this happens, the air conditioner won’t cool as effectively or produce any cold air at all.

Dirt and debris buildup inside the expansion valve can also cause problems. The valve has a tiny opening that can easily clog, preventing refrigerant from entering the evaporator coils. This keeps the air conditioner from cooling the air and can cause the compressor to fail. 

Regular air conditioning maintenance is the best way to prevent problems with the air conditioner expansion valve. Professional technicians clean components to prevent debris from clogging the valve, check the compressor and evaporator pressure, and ensure every part of the unit is in top condition.

Call Canton’s Leading Air Conditioning Maintenance and Repair Team Today

Now that you know the answer to “What does an AC expansion valve do?” you have a better understanding of how your air conditioner cools your home. Because a faulty expansion valve can cause other problems, call the experienced and certified technicians of Green Energy Mechanical Inc. for fast, efficient repairs right away. Our Canton, MA-based team of experts can quickly diagnose and solve residential and commercial HVAC problems so you feel cool and comfortable as soon as possible.

To make an appointment with our local company with an A+ Better Business Bureau rating, call (781) 236-3421.

Author Bio:

Jonathan Neves

Worked in the HVAC industry since he was 17. He started as an HVAC service technician for commercial buildings and eventually came into the residential market because of his love of working with people. He believes that what really sets Green Energy Mechanical apart is how long they stand behind their work and how compassionate his employees are for their clients.


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