Why Do Air Conditioner Freeze Up?

May 17, 2021

You may have noticed your air conditioner freezing up. In most cases, this occurs outdoors in the condensing unit, usually on the refrigerant lines or possibly on the condenser. This is certainly a sign your system is not running properly, but what causes this, and should you be concerned?

Understanding Your Air Conditioner

Before learning what causes your air conditioner to freeze up, it is important to understand the basics of your system. Your air conditioner works by circulating air and circulating refrigerant.

The air comes in through your system inside your house and comes out cooler than it went in. The air conditioner is actually absorbing warmth from the circulating air, making it cooler.

The refrigerant absorbs the heat in the evaporator coil. When the refrigerant comes into the coil, its temperature drops significantly, allowing it to absorb the heat more effectively.

If there is a problem preventing either the air or refrigerant from circulating properly, it can freeze your system. A frozen system damages the coils, which can lead to a refrigerant leak. It can also damage the compressor, which is responsible for helping the refrigerant transfer the heat outside.

Signs That Your System May Be Frozen

The most obvious sign that your air conditioner has frozen is ice on the visible refrigerant lines or compressor. However, by the time ice has formed here, the issue may have already been present for quite a while.

The first sign that something may be amiss, including a frozen block in the system, is reduced airflow coming from your vents. You may notice this when you walk by a vent while the system is running.

You may also check your airflow if it seems that your system is struggling to achieve your desired temperature. Just a little attention to subtle changes will often uncover smaller problems before they become substantial repairs.

If you notice less air coming from your vents, check to see if there is any visible ice. Also, notice any sounds coming from your system. Sometimes, a freeze in the system will cause the air conditioner to stutter, or turn on and off rapidly. It may also prevent the condensing unit from initializing when the system turns on.

Low Refrigerant Levels

Refrigerant works by changing the pressure in the system at the correct times. When the refrigerant comes into the evaporator coil, the pressure drops significantly, lowering the temperature. Then, when it goes to the compressor, the pressure increases, which brings the temperature up, allowing it to transfer heat more effectively.

When the pressure drops unexpectedly and at a rate greater than intended, it causes parts to freeze. So, if the pressure drops too much at the evaporator coil, it will cause those coils to freeze. If the pressure drops suddenly at the compressor, it can cause the lines and the compressor to freeze.

Clogged Air Filters

Your air filters are a very simple and inexpensive part of your system, but they play such an important role. On a basic level, they filter contaminants out of the air before it flows through your system. This keeps those contaminants from building up anywhere in your system.

However, when the filter gets clogged, it can cause a litany of problems within your system, including causing your system to freeze. This happens when there is not enough warm air flowing over your evaporator coils.

As the air flows over your coils, it condenses water vapor from the air, which normally drips down and drains away. However, if there is not enough heat for the refrigerant to absorb, it causes the water vapor to freeze on the coils.

As the evaporator coils freeze, they can form a block, preventing the refrigerant from flowing properly. However, it also creates an airflow restriction at the coil, creating even more problems getting warm air through.

Dirty Evaporator Coils

No matter how good your filters are, some contaminants eventually make their way into your system. These will settle on various components like the evaporator coil. When your evaporator coil is dirty, it prevents the air from flowing through it properly.

This will result in reduced airflow from your vents, warmer air coming out, and even a frozen evaporator coil. The dirt will collect on the evaporator coil, which then absorbs the condensing moisture from circulating air.

This becomes a cycle of dirt collecting, getting wet, and collecting more dirt. Over time, it insulates the coils, preventing the refrigerant from absorbing the heat from the circulating air. Eventually, it creates an airflow restriction, preventing the air from flowing through the coils altogether.

Ineffective Circulating Fan

Along with your air filters, air circulation plays an incredibly important role in the function of your system. The circulating fan draws the air in through the filters, through the evaporator coil, and then pushes it back out into your house.

Like the evaporator coil, the fan tends to collect the few airborne contaminants that enter your system as it runs. As these build up, the fan cannot continue circulating the same volume of air. This reduces the vacuum effect at the filter, which further reduces the air flowing through the system.

Not only do collected contaminants affect the circulating fan, but so does normal wear and tear. The bearings in the fan motor will eventually wear out if not regularly lubricated. This can cause the fan to seize and not spin as rapidly, also reducing airflow. Your fan needs regular attention to keep it from becoming a problem leading to a frozen system.

Preventing System Freezing

The best way of dealing with a frozen air conditioner is to prevent this from happening in the first place. Start by checking and changing your air filter regularly.

Most air filters should be replaced about every three months, depending on your air quality and the filter type. To help extend the filter’s life and effectiveness, plan to check it monthly and gently vacuum the intake side.

Next, plan to have your system maintained every spring by a professional. Your technician will check the refrigerant level, ensuring that it is at the optimal level and inspecting for signs of leaks. This alone is often enough to help prevent many common freezes, especially in older systems still using R22 refrigerants.

The technician will also carefully clean your evaporator coil and circulating fan. This ensures that the air can flow effectively through your system and that your refrigerant is uninhibited from absorbing heat.

A professional technician from 4 Seasons Heating & Air will also balance and lubricate your circulating fan motor. This extends the life of your circulating fan motor in addition to preventing system freezes.

Finally, they will also inspect and clean your condensing coil. This helps ensure that it can effectively vent the heat outside, but it is also an important step in looking for refrigerant leaks.

4 Seasons Heating & Air has been offering air conditioning installation, maintenance, and repair to businesses and homeowners around Alpharetta for over 45 years. Our experts also provide heating installation, maintenance, and repair along with indoor air quality improvement. Call today to schedule your air conditioning consultation with our experts.

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