How Long Does It Take to Thaw a Frozen Air Conditioner?


Using an Air Conditioner is the best way to counter the unbearable heat most summers bring. However, they tend to freeze at the most unexpected moments.

Defrosting the unit is the only solution at times like this, but how long would it actually take to thaw a frozen air conditioner? Generally, it takes around 2 to 24 hours to thaw out an AC unit completely. However, this is largely dependent on the size of the AC unit, the outside temperature, and the degree to which ice has already accumulated. Larger AC units, lower outside temperatures, and a lot of ice already present means that it may longer than 24 hours to thaw.

If you, however, want to further narrow down the defrosting time, you would need to know the factors that affect it. But to understand how these factors influence thawing time, you need to have a proper grasp of how an AC unit functions and why it freezes in the first place.


The Basic Operation Of An Air Conditioner

Air conditioners dispel the heat inside a room by using a refrigerant fluid that continuously runs through the system. The system is simply a loop that is  comprised of pipework that connects two coils known as the evaporator and condenser.

During the installation of an AC, the evaporator is placed indoors while the condenser is located outside. 

The refrigerant fluid running through the evaporator coils is conditioned to be colder than room temperature. The system does this using an expansion valve installed in the line that brings the refrigerant fluid from the outdoor condenser coil. Due to the difference in temperature at the evaporator coil, the fluid absorbs the indoor heat. The now heated refrigerant is then directed towards the condenser coils. 

The condenser is responsible for expelling the absorbed heat outdoors. For this to happen, the temperature of the refrigerant flowing through the condenser coils needs to be greater than the outside temperature. 

Although the heat absorbed from the inside raises the refrigerant temperature significantly, it would be efficient to increase it even more. This is because a greater temperature difference at the condenser coils will improve the rate of heat transfer. The system does this by employing a compressor that pressurizes the refrigerant flowing from the evaporator to the condenser. Pressurizing a gas naturally raises its temperature. 

Once the refrigerant passes through the compressor, it is raised to a temperature that allows heat transfer at the condenser. 

This right here is the functioning of an air conditioner at its simplest. Almost all AC’s work similarly, although modern devices might include more parts to refine the heat transfer cycle. However, they aren’t important to us. 

So recapping before moving forward:- 

Air conditioners absorb indoor heat and expel it outside. It does this using refrigerant fluid flowing in a loop. The fluid is cold at the evaporator (indoors) and hot at the condenser (outdoors). The temperature difference between the refrigerant and indoor/outdoor environment allows heat to be absorbed/expelled.


Reasons Why An Air Conditioner Freezes

Now that you know how an AC works, the reasons behind an AC freezing would be much clearer.


Blocked Airflow At The Evaporator

As we already know, the evaporator coils carry cold refrigerant fluid to absorb the indoor heat. So when the airflow across the coil is weak, the cold refrigerant freezes the surrounding moisture.

This happens because the airflow largely contributes to the heat transfer that occurs between the fluid and its surrounding. Weak airflow causes less heat exchange, causing the air around the cooling coils to freeze. 

Poor airflow can result from many factors, such as clogged registers, faulty pipes, and dirty or mismatched air filters.


Issues With The Blower Fan

A faulty blower fan can also freeze the refrigerant line. This too happens because of poor airflow. 

A blower fan boosts the airflow by driving hot air away from a room so that the dense cold air can circulate it. So the fan working at its best is crucial to avoid a frozen air conditioner. 

Further, a faulty blower fan can increase condensation around the cooling coil. This also contributes to the ice buildup within an AC.


Refrigerant Leaks

A leak in the refrigerant lines or the fluid levels falling below the recommended amount can cause an ice build-up in an AC. 

Low refrigerant levels cause the pressure within the system to decrease. This pressure shift can negatively affect the efficiency of the liquid-vapor cycle. As a result, the cooling coils can freeze. And the frozen fluid will condense the moisture, which assists the ice buildup further.


Bad Drainage System

Apart from cooling the air, the AC also dehumidifies it. The dehumidifying action happens on the evaporator coils because of the cooling effect it has. Therefore, the AC requires a drainage system to remove the condensed moisture. 

However, if an air conditioner has a faulty draining system, there’s a risk of water pooling inside which can cause the AC to freeze. This is a common issue seen in many households. At moments like this, just thawing an AC will be a temporary fix unless the drainage system is mended.


Factors That Influence The Thawing Time Of An AC

The time taken to thaw a frozen air conditioner depends on many factors. However, we can narrow them down to three very important ones. These factors are namely the AC size, ambient temperature, and degree of ice accumulation.


The Size Of The AC Unit

As mentioned before, there are several reasons behind a frozen AC. And the contribution from each of these reasons to the ice buildup multiplies as the size of an AC unit increases. 

For example, large air conditioner units have relatively bigger evaporator coils. Therefore, with such machines freezing, the time taken to defrost them will be comparatively high. 

Usually, the time taken to thaw a smaller unit is about 2 hours, while a larger unit might require over 8 hours to defrost completely.


Ambient Temperature

It’s quite clear that ambient temperature plays an important role in an AC’s operation. So it’s no surprise that the temperature directly influences the time taken to thaw an air conditioner. 

The unit will defrost much faster when it’s hot outdoors. Similarly, it will take more time to thaw when it’s colder. During hot days, you might even be able to thaw a compact unit using a blow dryer. Although it might not be as effective as the defrosting method we will tackle later.


The Degree Of Ice Accumulation

If an air conditioner has been freezing for quite some time, the amount of ice accumulated within it can be massive. Therefore, it would require more time to thaw completely. 

However, we suggest you check if the device is frozen frequently before it gets out of hand. This is because a large build-up of ice can put stress on the compressor, which can lead to expensive repairs. Further, it will affect the AC’s life span as well.


How to Speed Up Thawing A Frozen Air Conditioner

If you ever come across an air conditioner that’s been iced over, the first thing you need to do when defrosting it is to switch off the thermostat. 

The primary reason for an ice build-up is the refrigerant being too cold. Therefore, if the machine continues to work with refrigerant colder than the recommended value, there’s a risk of it being damaged. 

Once the thermostat is switched off, you can leave it to thaw itself out, especially if it’s a hot day. And depending on the factors that influence defrosting time, it might take around 2 to 24 hours to completely de-ice.

However, if you want to speed up the thawing process, you can switch the fan on so that warm air blows over the coils. 

Further, you can use an air dryer in its lowest setting. But it should be done with care, as too much heat can damage the components of the system. Usually, just turning off the thermostat and switching on the fan is the course of action many experts recommend. 

While you wait for the AC to thaw out, make sure to investigate the reasons that might have caused the ice buildup. If it’s a technical issue like dirty air filters or clogged drains, you would need to solve it in order to stop it from happening again. 

Once the unit has been defrosted, make sure that the coils are completely dry before powering up the machine. A partially dry air conditioner is bound to freeze up again. 

If your AC freezes regularly, it would be wise to contact an expert on the matter ASAP. The longer you wait, the more harm the freezing will cause your air conditioner. Eventually, the AC might get damaged beyond repair.


Related Questions

What are the usual signs of a frozen AC?

Unless there’s visible ice forming on your AC, there aren’t many clear-cut signs of a frozen unit. However, the following might give you a sign of an ice buildup within the system.

  • Lack of cool air
  • Increased electric bill because of the stress a frozen AC puts on the compressor.
  • Water leaks because of condensation 
  • A continuous hissing sound during operation


Can you pour hot water on a frozen AC?

This is probably the worst way to thaw a frozen air conditioner. It would not just damage the components, but would also fry the circuitry of the control unit. There’s also the risk of water shorting the electrical connections leading to electrical fires.

The best way of defrosting an AC is by letting the ice buildup melt naturally.