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What Causes An Air Conditioner To Freeze Up?

When it comes to your air conditioner, you might think that colder is always better. But that is not the case when you discover that your AC has frozen solid. It looks like something that was transported from the North Pole with icicles hanging off of it. And the worst part is that when the unit freezes, it is no longer creating cold air to keep your home comfortable. But the big question is what is causing the unit to freeze itself rather than cooling your home?

How An AC Makes Cool Air

The most important part of an AC system is the coil that is full of extremely cold refrigerant. When activated, the refrigerant needs warm air to blow across the coils. This cools your air and keeps the coils warm enough that they do not freeze themselves. On a straight cool system, your indoor coil removes heat from the inside and transfers it using the refrigerant to the outdoor ring. That coil then releases the heat to the outside. This is why your outdoor unit feels like it’s blowing hot air if you stand near it when it is running. Because the system is pulling heat from the air inside your home and releasing it outside.

The process is accomplished by manipulating pressure via the refrigerant circuit. But if something stops the warm air from blowing over the coils or if the pressure is wrong inside the coils, then the coils get too cold and freeze up. 

Moisture Is A Problem

When humidity is high, it makes the freezing problem worse. As ice forms on the coils and begins to insulate them, the warm air can’t reach the coils to warm them and stop them from freezing. The more moisture in the air, the more ice builds up. It covers the inside of the AC and continues up the copper pipes.

Lack Of Airflow

The most common reason for an AC to freeze up is a lack of airflow. This can be caused by several different problems ranging from the blower motor to the air intake. If anything in the airflow system stops warm air from flowing over the coils while the compressor is running, the AC will freeze up.

Collapsed Duct

The ductwork is how air moves through the house.  If something blocks the duct, the air stops flowing correctly. And this can block airflow to the coils. Even if the rest of the system is running correctly, a collapsed or clogged air duct can cause your AC to lose airflow. The coils begin to freeze because there’s not enough warm air to keep them at the proper temperature.

Bad Blower Motor

The blower motor is critical in this system. If the blower fan stops blowing, then the air stops flowing quickly enough to warm the coils. And once that air stops blowing, the coils start freezing. You might notice a rattling sound when the blower motor starts to break down.

Low Voltage to the Fan

Sometimes, the culprit is your home’s electricity. ACs require electricity to a variety of high-power components to operate correctly. If your fan or blower motor is under-powered while the compressor keeps running, it causes airflow freezing problems.

Clogged Air Filter

Finally, your AC air filter is not something that should be neglected, though it is all too easy to forget. That filter sits between your dusty home vent and the AC itself to keep the air clean. But when it becomes clogged with dust and dirt, it slows down airflow enough that the coils begin to freeze.

Dust Blocking Coils

Running without no air filter, a cheap filter, or a clogged air filter creates another problem. Dust builds up on the AC refrigerant coils, which are often damp from moist air condensing on the cold surface. When dusty air blows past wet coils, it creates a thick coating. That dust works as an insulator, trapping the cold inside the coils and freezing them.

If you discover that your AC is frozen, the best course of action is to call (850) 831-4599. A Payne’s Heating and Air Conditioning pro will arrive quickly to determine what is causing the problem and how to fix it.