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The air conditioner may be responsible for cooling the whole house, but it is never normal for its mechanism to freeze over. Homeowners usually discover this situation once they notice that their AC seems to have a hard time cooling or if the air conditioner is not blowing cold air. Upon checking the unit, the homeowner finds the evaporator coils frozen. How did this happen and what does it mean?

This blog post will explain why an HVAC unit will suddenly freeze, what happens to the whole system when the coils are frozen, and what can be done about it. It will also discuss ways to prevent this from occurring.

 Always remember that the best way to keep the AC from freezing are regular air conditioning tune-ups carried out by professional HVAC technicians like us at Reliable Standard Heating and Air. Get in touch with us anytime and we will be more than happy to keep your AC unit performing at its optimal condition.

How does an air conditioning unit work?

To understand why an AC would suddenly freeze over, it will help to know first how an air conditioner works.  Contrary to common notion, air conditioners do not simply produce cold air and blow it throughout the indoor area to cool the whole place. Instead, it sucks out the warm air indoors and transfers the heat outside the house or the building.

The easiest way to comprehend how an air conditioner works is by dividing it into three working stations. These three stations include the evaporator, the compressor, and then the condenser. To make the AC work, these three stations need a substance called refrigerant. The refrigerant links these three stations, as it works through a closed loop.

First phase

The first area responsible for cooling is the evaporator. Warm air inside the house is sucked up through the vent, gets filtered, and then gets blown over the evaporator coils. Once the heat has been absorbed by the chemical called refrigerant, the heat turns from liquid and then gas. The cooled air will then get blown back to the house through the air registers.

Second phase

The second area in the cooling phase is when the refrigerant goes outdoors through the AC compressor. The compressor crams the refrigerant consequently raising its temperature all the more as it makes its way to the third phase of cooling.    

Third phase

The third and last station in the cooling process happens in the condenser. The extremely hot gas processed during the second phase gets processed in the condenser system. There, the hot vapor gets emitted outdoors. Once the heat is expelled the refrigerant immediately becomes cold and returns to its original liquid form. The liquid then goes back to the first station to repeat the whole cooling procedure.

Signs of a frozen air conditioner

So how can a homeowner know if his air conditioning heat pump unit is freezing up? AC experts assure you that at one point every homeowner will experience freezing up in their AC system especially if they have been remiss with their routine maintenance chores, and professional tuning-up or servicing. Upon discovering that the AC is freezing the homeowner should immediately call a licensed HVAC technician who can diagnose and perform the needed repairs. Postponing diagnosis and repair is costly since ACs are not meant to operate this way. Moreover, it could lead to higher utility bills and even water damage.  

Several signs point to a frozen AC system. The initial and the most obvious is ice on the refrigerant line. To check, take a look at the outdoor unit or the condenser, and then the home exterior wall where the hose runs through. Check for signs of freezing.

Another possibility is a frozen evaporator coil. Determining frozen evaporator coils though is best left to the pros as this involves opening the AC’s indoor panels and checking the evaporators. Guesswork and self-troubleshooting cause damage to the HVAC system. Call us at Reliable Standard Heating and Air if you need help in this aspect.

Apart from seeing frozen mechanical parts, other indications clue into a frozen air conditioning unit. These include:

  • The air conditioner is unable to cool the house.
  • Condensation forms in the indoor unit of the air conditioning system.
  • There is condensation forming in the condensate drain.

Why is the AC freezing up?

The simple explanation is little to absolutely no airflow within the air conditioning system. When there is not enough air circulating within the AC system, particularly through the evaporator coil, the refrigerant will freeze along the line or within the evaporator coils. This is because instead of turning into warm gas, the refrigerant just freezes over because of a lack of airflow.

But why will an AC unit suddenly lack airflow? Well, several possible factors could lead to little to complete lack of airflow. These include the following:

Clogged air filters

When air filters are clogged with dust, debris, and other contaminants, warm air from the house could not get through the air vents. When this happens, the evaporator coils or the AC line will soon freeze. To prevent this problem from occurring, homeowners should routinely replace their filters, at least every three months.

It is also possible that the air vents are closed or blocked. When the vents are blocked by furniture or upholstery like curtains, they could not suck in the warm air in the house. When this happens, the system is unable to complete the whole cooling process.

Some homeowners on the other hand purposely close the vents to curb cooling bills. This however is not an effective way to lower utility costs. It is counterproductive because it strains the AC to produce cooler air, and when the system gets strained it tries to compensate by using up more energy. This then increases utility bills, plus it shortens the lifespan of the system.

Damaged blower fan

Sometimes, the blower fan malfunctions. When this occurs, warm air will not get pushed through the coils, consequently freezing them. When the whole evaporator coil freezes over, the AC will refrain from working.

Clogged condensate lines

The water coming from the moisture in the warm air absorbed by the air conditioner is expelled through the condensate drain lines. There however are instances that these drainage lines get clogged, either by slime or mildew. When the condensate lines are clogged, water can no longer get out of the system, and gets frozen.

Filthy evaporator coil

Over time, evaporator coils gather dust and grime. Sometimes, even molds and mildew grow on it due to ill maintenance. A dirty evaptor coil can also be a frozen evaporator coil, when this occurs, air conditioners tend to cease cooling the house since airflow gets impeded. Homeowners should not forget to have routine professional cleaning to avoid dirt build-up in the coils. Find out how to clean your air conditioner condenser coils and diy if you feel comfortable.

Collapsed air ducts

Sometimes, cooling issues occur not because of the AC mechanism, but because of damage in the air ducts. Sometimes, damage occurs when it is accidentally damaged or ripped during repairs. It is also likely that pests could go through the ductwork, and cause damage. If the air duct collapses, the AC will not get enough airflow that it needs to cool the whole house. Eventually, it will lead to freezing and non-cooling.

Low refrigerant levels

Refrigerant is the substance that transforms warm indoor air, to cool, air-conditioned air. While it is not supposed to run low ever because it works on a closed loop, damage and incorrect installation can lead to low refrigerant levels. When the AC is low on refrigerant, it tends to freeze the AC line and fails to make the whole house comfortably cool.

Try these frozen AC fixes before calling in an HVAC technician

Try the following steps before calling for professional air conditioner repair. By doing these, the homeowner can save time and money in case the simple fix works.

Turn off the air conditioner from the thermostat. Check to see if the thermostat is getting up to temp. Make sure to stop the cooling process. After that, make sure that it is in fan mode. This step is meant to thaw out the ice that formed in the AC system.

Replace the existing filter, especially if it was installed more than three months ago. Dirt build-up can seriously affect airflow. By replacing the AC filter, air will flow freely through the AC system.    

Check the vents throughout the home. Closed vents can lead to AC problems, so make sure that all the supply vents are open in all the areas at home.

Turn on the AC once again, and observe if it freezes again.

If the AC line still freezes, then it is time to call in an HVAC technician for repair.

Prevention is better than having repairs!

The best way to prevent a frozen AC is to keep it from occurring. And the key to avoiding it is by ensuring that there is a smooth airflow within the HVAC system. If blockages or clogs happen anywhere such as in the evaporator, filter, or any of the lines, then it will surely give way to freezing.

Homeowners should make sure to replace their filters regularly. By doing this, it allows the AC to breathe, and not get needlessly strained to operate. Homes with family members who have sensitivity to indoor air contaminants, as well as families with indoor pets should change their filters more often than normal as contaminants including dander tend to accumulate fast.

Scheduling a bi-annual professional HVAC tune-up will also help in keeping the AC well-maintained. By having professional air conditioning care, cooling issues will get solved even before they get complicated. Professional AC care does not only inspects, but also cleans, and tunes up AC mechanisms. It also checks airflow through the various ductwork throughout the house. Lastly, regular AC maintenance will also help prolong the life of an air conditioner and keep cooling bills from increasing unnecessarily.

If you need help with a frozen AC

If you need help with a frozen AC within the San Diego area, get in touch with us at Reliable Standard Heating and Air. We can help you with a preventive maintenance plan that ensures that your AC works in top condition when you need it the most. Call us today!

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