Houston Heating, Cooling, and Electrical

What Does It Mean When Your AC Unit Freezes Up?

When an air conditioner freezes up, it’s a clear sign that there’s something wrong with the unit. The problem may be minor, or it may be something that requires a professional. It’s difficult to know until the air conditioner is inspected, and especially the evaporator.

When an air conditioner freezes up, it’s the evaporator coils that do the freezing. These coils are designed to drop down in temperature and remove heat from the air. This is what makes the building comfortable for its occupants. However, this part of the system is sensitive to any disruption. Even a simple, easily correctible issue can be enough to make the evaporator coils cool too much, resulting in freezing. It’s important that this problem be resolved immediately, as a frozen evaporator will not cool the building properly, and repeated freezing can damage the system.

Five Common Causes of a Frozen Evaporator

If your AC is freezing up, the problem may not be with the evaporator. Frozen coils are usually a symptom that something is wrong somewhere, so the entire system will need to be inspected during troubleshooting. The five most common reasons for an AC to freeze up include:

1. Poor air flow – Restricted air flow is the root of many AC problems, and the problem is usually the result of a heavily soiled air filter. As an air filter is matted with dust and other contaminants, air has a tougher time getting through. The evaporator, though, is designed to handle a specified volume of air, and may freeze if it’s not getting enough. That’s because there isn’t enough heat being removed from the air and absorbed by the refrigerant running in the coils. Less heat means colder coils, and that means freezing.

Replacing the air filter may solve the problem, but if it doesn’t, the air flow restriction may be impossible for someone to find without the necessary training.

2. Dirty coils – Dirt is the enemy of air conditioners, and it can cause issues wherever it ends up. If it ends up on the evaporator coils, it will reduce their ability to absorb heat from the air. The cause is different but the result is the same – less heat getting to the coils, and colder coils that end up freezing.

Evaporator coils can be rinsed and cleaned off, but some people aren’t comfortable tinkering with their unit, and a professional can handle it for them.

3. Damaged or dirty ductwork – Air flow restrictions can also originate from inside ductwork, especially if the ductwork is old and hasn’t been cleaned in some time. It’s surprising how dirty ducts can get, especially if the home’s air filters aren’t being changed out regularly. Over time, this will clog up the ducts a bit and make it tougher for air to push through, resulting in reduced air flow.

Damaged or collapsed ductwork can have a dramatic effect on system performance and result in repeated freezing. It can be difficult to spot damage to the ducts, and it can also be hazardous, so this is an area that professionals are well-equipped to handle.

4. Damaged or dirty compressor – Sometimes the problem is inside the compressor. Compressors are subjected to the elements and all kinds of debris. Although air conditioners are designed with protection, eventually that dirt and debris will make its way inside. This can damage the compressor’s fan and dirty up the unit to the point where air flow is restricted. Even overgrown weeds can be enough to affect the compressor, so keep the area around the unit well-maintained.

If damage is suspected, it’s tough to know what components have sustained the damage. This is another scenario where a professional is recommended.

5. Low refrigerant – If there are no apparent issues with the system – no damage and no air flow restrictions, then the most likely culprit is insufficient refrigerant. If there isn’t enough refrigerant running through the coils, there isn’t enough heat being taken out of the air, and the coils freeze as a result.

In most cases, if low refrigerant is the problem, there’s a leak somewhere in the refrigerant line. This leak could appear anywhere along the line, which means the entire thing will need to be inspected. A telltale sign that the leak is nearby is a constant hissing noise. That’s the sound of refrigerant evaporating as it escapes into the open air.

If low refrigerant is suspected, a professional will be needed to find and fix any leaks, as well as replace the lost refrigerant.

When an air conditioner freezes, the underlying problem could come from anywhere in the system. It could be the evaporator itself, the air filter, the compressor, the ducts, the refrigerant line or a number of other components. Narrowing down the exact cause is tough, especially if the system is older, as there could be multiple problems leading to a frozen evaporator.

Experienced AC technicians know what to look for and where to look for it. Whether it’s a compressor fan, a damaged duct or just a bad filter, professional technicians can correct the problem and get the system functioning once again.


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25654 Kimbro Rd Hockley, TX 77447.
Phone: 281-355-9100
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