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The Expansion Valve: A Small Component That Plays a Big Role in AC Systems

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Troubleshooting cooling problems requires an understanding of air conditioning system components. Central air conditioning systems contain dozens of components. Some of these components are large, whereas others are small.  Coils, for example, are large. The expansion valve, on the other hand, is small. While small size, the expansion valve still plays a big role in your air conditioning system’s performance.

What Is the Expansion Valve?

The expansion valve is an air conditioning system component that’s designed to depressurize refrigerant while in a liquid state. It’s located near the evaporator coil. Before entering the evaporator coil, refrigerant must travel through the expansion valve. The expansion valve will release some of the pressure within the refrigerant so that it changes from a liquid state to a gas state.

How the Expansion Valve Works

You might be wondering how the expansion valve works. There are two types of expansion valves: internally equalized and externally equalized. Most air conditioning systems use the former type.

With an internally equalized expansion valve, refrigerant will be depressurized internally. They feature a small passage that connects to a larger and open passage. This small passage restricts the flow of refrigerant. As refrigerant travels through the expansion valve’s small passage, it becomes depressurized. And with less pressure, the refrigerant changes from a liquid state to a gas state.


The Impact of a Bad Expansion Valve

Your air conditioning system’s performance is dependent upon a functional expansion valve. If the expansion valve is bad, you may experience one or more problems with running your air conditioning system.

A bad expansion valve, for example, can cause ice to form on the coils. Iced-over coils are often the result of excessively cold refrigerant. If the expansion valve is bad, refrigerant may fail to absorb a sufficient amount of heat at the evaporator coil, resulting in cold refrigerant that can cause ice to form on the coils.

Along with iced-over coils, a bad expansion valve can cause issues with your air conditioning system’s compressor. The compressor may run continuously if the expansion valve is bad. With a bad expansion valve, refrigerant will continue to travel to the compressor, so the compressor will run nonstop.

Over time, the compressor may fail because it’s forced to run nonstop. Compressors aren’t cheap to replace. Depending on the type, you can expect to pay over $1,000 for a replacement. And if the compressor failed because of a bad expansion valve, you’ll have to replace the expansion valve as well.