A frozen AC unit is a common issue that can occur in the summer. It is caused by a malfunction in one or more parts of the self-contained system, such as the coils.

Can you explain the functioning of an air conditioning system?

Contrary to popular belief, an air conditioner does not work by blowing cool air into a room, but rather by removing the warm air and expelling it outside, similar to a refrigerator. The fundamental principle behind the functioning of an air conditioner is the use of refrigerants, which are chemicals that convert quickly between gas and liquid states.

These refrigerants are contained within coils that are part of a closed loop system. The system has three main components - the evaporator coil, compressor, and condenser - that manipulate the refrigerant's state, pressure, and temperature. Despite the variety of designs and sizes, all air conditioning systems operate on this basic principle.

Station 1: The evaporator coil absorbs heat

The process begins by drawing warm air from a room into the air conditioner via a vent, where it passes over the evaporator coil. The heat is absorbed by the refrigerant, causing it to change from liquid to gas. A fan then circulates the cooled air through air ducts and into the room. The refrigerant, now in a gaseous state, continues its journey through the closed loop system to the next station, the condenser.

Station 2: The compressor increases the temperature of the refrigerant.

The cooling fluid proceeds outside the house to the compressor, where it enters as a low-pressure gas and exits as a high-pressure, hot gas before proceeding to the condenser. The compressor's function, as the name suggests, is to decrease the volume of the gas by compressing it tightly between two solid objects, thereby raising its temperature further.

Station 3: The heat is transferred to the outside.

When it reaches the condenser, the refrigerant is in the form of an extremely hot vapor. It is then exposed to the cool outside air. The metal fins present around the housing of the AC unit are for the purpose of quickly dissipating the heat. As a result, the refrigerant cools down significantly before leaving the condenser. Additionally, the high pressure causes the refrigerant to change its state from a gas to a liquid. The refrigerant, now cooled and in liquid form, is ready to return to the first station and repeat the process.

What are the reasons for the freezing of an AC Unit?

An AC unit can freeze if a malfunction affects the functioning of the evaporator coil, causing the refrigerant to cool excessively, drop below freezing point and form ice. This is a sign of a problem with the AC's health. To diagnose and fix the issue, it is important to understand the possible causes of an AC freeze-up.

There are two main causes:

Obstructed air flow

To prevent freezing, air conditioners require a steady flow of air to prevent the accumulation of humidity on the coils. Blocked or dirty air filters can impede air flow and cause the system to freeze. It is crucial to replace the system's filters every one to three months.

Technical malfunctions or leakage of refrigerant

An air conditioner is a complex machine with various moving components that can malfunction or become jammed. This can happen to the fans, filters, and refrigerant leaks. Any of these disruptions can lead to a decrease in pressure, causing the refrigerant to expand excessively and become extremely cold. Similarly, a refrigerant leak that causes low refrigerant levels can lead to freezing.

Measures to prevent freezing of your AC

An air conditioner encased in ice can be a concerning sight, but proper maintenance can prevent it from occurring. To ensure optimal performance and efficiency of your unit, it is recommended to have it serviced at least once a year, or even twice a year, depending on usage. The regular maintenance ensures all the moving parts of your AC are functioning well, reduces the burden on the AC, and minimizes the chances of unexpected repairs.

A qualified HVAC technician is trained to check for refrigerant leaks which is a common cause of frozen AC coils. Additionally, as a homeowner, you can perform simple tasks such as replacing the system air filter every month to extend the life of your AC and prevent freezing.

What actions should be taken if an AC unit becomes frozen?

If an AC unit remains frozen for an extended period of time, it may lead to more significant issues. However, the problem may be resolved with some basic troubleshooting. If not, it is recommended to contact a professional HVAC technician for assistance.

The following steps can be taken to address this issue.

Step 1: Thaw

The first step to take when the AC unit is frozen is to turn off the system and allow the ice to melt. It is important not to operate the system until it is completely defrosted and dried. Using the system while it is frozen can put unnecessary stress on the compressor, which is the most expensive component of the AC unit. To avoid costly repairs or replacements, it is best to avoid breaking up the ice to speed up the thawing process. Instead, allow the system time to thaw and dry.

In some cases, turning the system back on after it has thawed and dried is enough to get it running normally again. Power can be restored to the system, and the blower can be turned on.

Step 2: Locate Cause and Fix It

There are various reasons that could lead to an AC unit freezing up.

Check air filters and change them

Air filters play an important role in maintaining clean air circulation in the home. For optimal functioning, they should be cleaned or changed on a regular basis. During high-use seasons, it is recommended to clean the AC filter every two weeks and replace them every three months.

Check your thermostat & fan settings

If the temperature setting is too low, the AC may struggle to effectively transfer heat from inside to outside. Similarly, a low fan speed can put excessive stress on the unit, making it difficult to maintain the desired temperature. To fix this, it is recommended to increase the fan speed on particularly hot days to ensure proper airflow is maintained.

Running AC on cold nights

During cool summer nights, AC units can freeze as they are designed to work within a specific temperature range. When the temperature drops below this range, the refrigerant becomes too cold and causes any moisture in the air to freeze before it can circulate properly.

Bad compressor

A damaged compressor can lead to frozen AC coils, and it is the worst-case scenario. The compressor is unable to compress the refrigerant efficiently. Unfortunately, a damaged compressor cannot be repaired and requires the assistance of a professional HVAC technician. In such cases, it is best to contact an HVAC provider for emergency support.

Some issues with air conditioning units can be resolved with simple troubleshooting methods, but more complex issues require the expertise of a qualified HVAC professional.

Trust Maryland HVAC Repair

Thank you for offering emergency HVAC repair services. It is important for homeowners to have access to reliable and professional HVAC technicians who can quickly address any issues and ensure the comfort of their home. If someone is in need of HVAC repair, they should contact your company to schedule an appointment with a technician.