There are a few different issues that can cause an air conditioning system to start freezing up. The first thing you’ll usually notice if your AC is frozen is that the air coming out of your vents is hot. Once the ice starts building up on the evaporator coil, the AC system won’t work, and you’ll quickly have hot air coming out of your vents. If you ever notice this problem, it is important to shut the AC off since serious damage can occur to the AC compressor if the system runs for too long when frozen. Leaving the system on is also a waste of energy since all it will do is circulate hot air throughout your house. If you’re having problems with your air conditioning freezing, here are the potential reasons why it is happening, what can be done to fix them and if you’re going to need an AC repair service.
Clogged Air Filter
By far the most common reason that an air conditioning system will freeze up is because the air filter is dirty and clogged. Replacing or washing your air filter every month or two is an essential maintenance task and can help to prevent your AC from freezing and many other HVAC issues. If the filter isn’t replaced or cleaned regularly, it will eventually become covered in a thick layer of dust, hair, and debris. All of the pores in the filter will also become clogged, and these issues will make it extremely difficult for the AC blower to pull air in through the filter.
A clogged filter can make the blower can’t draw enough warm air into the system. Whenever the AC is running, there needs to be a sufficient volume of warm air coming in and blowing over the evaporator coil. The less warm air there is, the less heat the refrigerant that flows through the evaporator coil will absorb. The refrigerant is extremely cold when it flows into the evaporator coil, and its temperature quickly rises as it absorbs heat from the air. If the refrigerant doesn’t absorb sufficient heat, it will remain so cold that the condensation that naturally collects on the evaporator coil starts to freeze. Once the coil begins to freeze, ice will quickly build up until the coil is completely frozen and coated in a thick layer.
The fact that a dirty air filter can drastically reduce how much warm air comes into the system means that this is always the first thing to check for if your AC ever freezes up. After shutting the system off and replacing the air filter, you will need to wait for the coil to completely thaw and all the ice to melt. Once thawed, you can then turn the AC back on. If it doesn’t freeze up again, you can be fairly certain that the air filter was the culprit.
In addition to replacing the air filter, it is also a good idea to check all of your supply and return air vents while waiting for your AC to thaw out. Specifically, you’ll want to make sure that the vents are fully open and not clogged by hair and debris or obstructed by furniture.
The return air vents are where the blower pulls air into the system, whereas the supply vents are where the cold air from the AC comes out. Clogged or obstructed return vents can make it so the blower can’t draw in enough hot air, and the evaporator coil starts to freeze.
The system can also freeze if too many supply vents are clogged, closed, or obstructed, but for a different reason. The more supply vents that are closed or otherwise blocked, the higher the air resistance in the ductwork will be. This increased air resistance makes it more difficult for the blower to circulate. If the air resistance and pressure in the ducts are too high, it can also make it difficult for the blower to bring in enough warm air to prevent the evaporator coil from freezing. While these problems are less common, they are still worth checking for.
Low Refrigerant Level
All AC systems require a specific amount of refrigerant to function properly. If the system has a leak and the refrigerant level is low, it can also lead to the evaporator coil freezing. If there isn’t the proper amount of refrigerant, the system will have less pressure. The lower the refrigerant pressure is, the colder the refrigerant will be. This can lead to the refrigerant temperature dropping low enough that the evaporator coil will start to freeze even when there is lots of warm air blowing over it.
This is not a problem you can identify on your own as you will need to have an AC technician measure the refrigerant level. If the level is low, it almost always indicates that the evaporator coil, the condenser coil, or one of the refrigerant lines has a leak. In this case, it will be first necessary to find and repair the leak and then recharge the system with more refrigerant. A leaking refrigerant line is usually fairly easy to fix, but a leaky coil will need to be replaced.
Dirty Evaporator Coil
Along with a dirty air filter, a dirty evaporator coil is the other most common reason an AC will freeze. Dust and debris coating the evaporator coil will act like insulation and make it so that the warm air doesn’t directly contact the coil. As a result, the refrigerant won’t be able to absorb much heat, and the coil could start to freeze up. The best way to prevent this problem is to have your AC system cleaned and maintained every spring.
How to Clean AC Coils
Your AC system has two different coils, and both need to be cleaned yearly, or else the system may start to freeze up or have other issues. A dirty condenser coil in the outdoor AC unit won’t cause the system to freeze, but it can reduce the system’s effectiveness and lead to other issues. While the evaporator coil works to absorb and remove heat from the home, the condenser coil works oppositely and releases all of the heat back into the air outside.
If the condenser coil is dirty, it can prevent the heat from being released. This can cause the refrigerant to be at a higher temperature when it flows to the evaporator coil, which means that the refrigerant won’t be able to absorb as much heat, and the system will cool more slowly. A dirty condenser coil can also lead to the unit overheating. If your AC compressor isn’t turning on, it could be that the outdoor unit overheated due to a dirty condenser coil or some other issue.
Cleaning the evaporator coil and the condenser coil is an essential maintenance task, but it is not something you should attempt on your own. The coils and the fins on them are quite fragile, and you could easily damage them and cause a leak or other issues if you don’t know what you’re doing. For this reason, we always recommend scheduling a yearly AC tune-up, as the technician will clean the coils properly to prevent the system from freezing or experiencing other issues.
At Protek Roofing, Heating, Air & Solar, our technicians can help if your AC is freezing or has any other problems. We service and repair all types and models of central AC units as well as ductless mini-splits, heat pumps, and furnaces, and we also specialize in HVAC installation, indoor air quality, roofing, and solar services. For more information or to schedule an AC inspection in the Tampa area, contact us today.