Why Is My Air Conditioning System Freezing Up?

A: There are different reasons why your system can freeze up. The most common is a system that has a refrigerant leak. It will run so long without cycling off, that the surfaces inside the coil will get so cold they turn into an ice block. This can lead to a lot of problems including water leaks in the attic where you normally don’t have water—and sheetrock damage things like that.

Also, a restriction in airflow will cause that evaporator coil to freeze as well. If you don’t replace your filters in time you can restrict the airflow. Now, the air isn’t moving through the coil to remove heat fast enough and those temperatures will keep dropping in the coil. Moisture will get trapped in there and then it will ice up and freeze the system.

So, it depends on what’s going on with the system. If you notice that—definitely have a technician take a look at your system as soon as possible.

It doesn’t seem to make sense, does it? You figure an AC is supposed to be cold to make the air cool right? Well it’s not that simple, and there’s a reason even a Houston air conditioning system can freeze up in 90° weather.

You see, your air conditioning system works on a delicate system of checks and balances between temperature, airflow, and pressure. If any one of these is out of range, the refrigerant in the system can overwork and cause the system to freeze up. This causes the system to be unable to cool the air and your house gets hot.

A frozen AC will either blow no air at all or warm/moderately cool air—not cold enough to cool the home. Let’s take a deeper look into how this happens.

How Your Houston Air Conditioning System Works

The most important component of your AC system is the evaporator coil that is filled with very cold refrigerant. You might be surprised to know that this component responsible for cooling the air—needs warm air to work.

The warm air is cooled by the coils and then pushed out into your home. However, the warm air also keeps the coils just warm enough so they don’t freeze up. The indoor coils remove heat from inside your house and pushes it to the outside coil using refrigerant. That’s why you’ll notice your outdoor unit always blows hot air.

This process works because well, a science lesson is not going to solve your problem right now—so just know it works. However, if something keeps the process from happening and there’s no warm air over the coils, they will freeze. It can also fail due to a pressure issue within the coils due to a leak, often as small as a pinhole.

Humidity And Houston Air Conditioning Problems

When it’s humid in Houston—scratch that, it’s always humid here and Houston air conditioning problems are worse with humidity. When the humidity is high like it often is, the freezing is more likely and more intense. Ice will build up on the coils and insulates them so much that warm air is blocked from passing over. Without the warm air the coils don’t thaw and with added moisture outside—it snowballs, no pun intended. As ice freezes, it expands, so it has to go somewhere and that means through the pipes in your home. That can cause all kinds of other fun problems like sheetrock damage and pooling water. Yet, there’s other reasons you could end up needing a Houston air conditioning pro to fix your system.

Weak Airflow

AC systems are pretty reliable and consistent when cared for properly so the most common reason it fails—human error. Do you ever notice that grate on your ceiling or behind the AC closet door? Does it look dusty and dirty—if it does, you’re killing your system! Your air filter is there, that’s what keeps all the junk in the air from circulating all over the house. However, if you don’t replace the air filter regularly, you could choke your system for months. How is it possible to “choke” your system you ask?

Your air filter not only helps keep the air in your home clean, it also helps keep the coils clean. If you run the system without the filter, use a cheap filter, or don’t change it—your chancing it. What happens is that dust in the air sticks to the cold coils and builds up a thick coat—like a blanket. That blanket of dust insulates the pipes trapping the cold inside the coils instead of letting it be distributed through the ducts. That combines with moisture that mixes with the dust and then turns it into a make-shift icebox.

When this happens it makes your system work much harder, specifically the blower—eventually causing the motor to fail. When the blower fails the warm air doesn’t blow over the coils and your system freezes up and the compressor then runs nonstop.

It’s not uncommon for a minor ignored issue like a dirty filter to ultimately cause an entire system to fail beyond repair. The issues if left uncorrected will continue to wear out your system at an alarming pace. So, the moral of the story? Keep proper maintenance on your Houston air conditioning system and it will serve you for at least a decade.

Refrigerant Is Low

If you’re changing your filter regularly and your system still freezes up, it might be the refrigerant itself. Having the proper amount of refrigerant is crucial because proper operation depends on a precise level of refrigerant. Your unit outside is called a compressor because it compresses the refrigerant after it expels the heat it collected inside. See, warm air converts the refrigerant from a liquid state to a gas that gets hot and decreases pressure. The compressor turns it back into a cold liquid and pumps it back toward the blower inside the home again.

Since it relies on pressure, if there’s not enough of the refrigerant, the conversion happens prematurely due to insufficient pressure. The flashing process suffers too but does create just enough cold to condense the moisture in the coils. It then freezes instantly and the cycle repeats over and over resulting in the icebox effect. Eventually, that ice moves up into the copper pipes in your home where it can do more damage.

Is Your Houston Air Conditioning System Frozen?

If you find that your AC is putting out warm air and ice is building up within the system, don’t panic. Turn off the thermostat right away so it will stop trying to cool. The compressor will shut down and will stop cooling the refrigerant. Now that the AC is off, turn the fan to run continuously this will help melt the ice.

Now, that you’ve possibly saved yourself some other damage, call us immediately to have a tech come out. This is a serious problem that can escalate and cause permanent damage to your system. It can also cause water damage within your walls which leads to a slew of problems.

When you call us make sure you indicate that you need service because your system is freezing up. This helps us place a priority status on the ticket due to the urgency of the problem. Also, before you call, check your air filter to see if it’s dirty. That will help us diagnose the root cause much quicker if we can eliminate the air filter as a culprit.

Lastly, don’t worry a frozen AC system can be fixed when you notice the problem and take immediate action. The best way to reduce the risk of your system freezing is to keep it maintained.

Our preventative maintenance program is the most convenient and economical way to stay on top of your system’s health. Contact us today and ask about our MVP program!



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