There are several reasons why your air conditioning system and refrigerant lines are freezing up. Failure to fix the problems that make your AC freeze might easily result in more significant problems, including your Air Conditioner not working altogether.
When you notice that your air conditioner is freezing, you should take steps to ensure it is appropriately fixed and prevent them from happening in the future.
Keep reading to learn more about what could cause your Air Conditioner to freeze and what you can do to prevent it.
NOTE: The same can be applied to a heat pump since its operation is the same as an AC in summer.
AC Unit Frozen Up?
The primary reason why air conditioners freeze is a lack of proper maintenance. This includes failure to clean the system regularly.
When air conditioners go for long periods without being cleaned, dirt and dust accumulate, especially on your evaporator coil or evap coil, as we like to call it. This reduces its ability to work correctly. The coils inside the air conditioner can get dirty, consequently reducing the entire system's ability to regulate temperatures.
A refrigerant (or freon as it's sometimes called) leak can also make your AC freeze. You would think that low refrigerant levels would make your AC warmer, but it's actually the opposite. We will talk about this further in the article.
How moisture contributes to the problem
Moisture plays a significant role in causing air conditioning systems to freeze even when the outdoor temperature is high. When the ice starts to form on the evap coil, it insulates it so that any warm air flowing through your system cannot reach the coil. This starts a cascade effect.
The more moisture in the air, the more the ice will continue to build up until your evap coil is a solid block of ice. High humidity, such as what we get during summer here in Northwest Florida, will make a bad problem worse.
Now you have to let the ice thaw in your air conditioner, which takes time. This means no AC and no cold air while this happens, so it's best to avoid it in the first place...
The 3 top reasons why your air conditioner freezes up
Lack of Proper Airflow
The top reason your AC can freeze up is poor airflow. When your AC is operating correctly, warm air from inside your home is circulated over the cold evap coils to produce cool air. If anything is blocking this warm air flow, the coils will freeze up.
So what can cause a lack of airflow?
Dirty Air Filter
Air filters are the first line of defense between the dirty air in your dusty home and the clean evap coils. Its other job, of course, is to ensure clean air for yourself and your family. If your air filter becomes clogged for any reason, it's now a blockage instead of just being a filter.
That blockage now slows the airflow to your air conditioner's evaporator coil in sufficient quantities to keep the AC from operating optimally. This is turn, will cause your AC to freeze.
Collapsed Ductwork.
Your AC moves air around your home via ducts. Again, if anything blocks this airflow, such as a collapsed or blocked air duct, it will reduce the hot air moving across the evap coil.
Even if your AC is running smoothly, a collapsed duct anywhere in your home can reduce the airflow, causing the system to freeze up.
Malfunctioning Blower Motor
The blower fan motor is what keeps the airflow moving within the system. Any malfunction with the blower fan motor will cause a reduction in the hot air moving over the coils, or if the motor stops working completely, it will stop the airflow altogether. All of which will cause your AC unit to freeze up.
Fan Low Voltage
Low voltage to your fan can sometimes be the offender. Your AC's high power components need electricity to run correctly. Hence why your AC is a more significant portion of your energy bill in summer.
If any of these components are underpowered, such as the AC fan or the blower motor while the compressor is running, this will reduce the system's airflow, causing it to freeze.
Dirty Evaporator Coil
Your air conditioner coil works best when it's clean, hence the filter…. If dirt or dust accumulates on your evap coils, expect ice to find its way onto your coil.
Evap coils are usually damp from the excess moisture from your home condensing on its cold surface. When dust or dirt flows over your damp coils, it will stick to the condensation and build up a thick layer.
This thick layer of dust acts as an insulator, trapping the cold temperatures normally released into the warm air flow. This causes a buildup of cold temperature within the coil, causing that moisture to freeze. Once that freezing starts, it will attract more moisture and build up a thicker layer of ice.
Some coils can also be affected by rust, especially if made with cheaper metals that can corrode easily. If corrosion starts, your dirty coil will suffer the same problem as your coil as it will not absorb warmth from the hot air, causing the same freezing problem.
Low Refrigerant Levels
Since your AC is a well-oiled machine, it needs just the right amount of refrigerant in the system. If there's a coolant leak, then naturally, there's less freon which causes AC freeze-ups.
What happens now is a lesser amount of freon still has to expand the same amount as if you had more. More expansion leads to colder temperatures. As the temperature in your evap coil drops below freezing, moisture in the air flowing over the coil will freeze on the coil's surface, causing ice to build up.
The way your air conditioner cools the evaporator coil is known as the Joule-Thomson effect. If you want to learn more about how it works, check out this article on Wikipedia.
If you suspect that you have refrigerant leaks, call your local HVAC professional to inspect your system. In both the US and Canada, it is illegal to knowingly vent refrigerants containing ozone-depleting refrigerants as well as their substitutes.
Don't break the law or destroy the environment. Call your local reputable HVAC company
How to prevent an AC system from getting frozen
A frozen AC doesn't have to be a major problem if you know what to do to prevent it. Some of these are definitely DIY, and some require the support of a licensed HVAC professional. Knowing what to do or who to call can prevent your Air Conditioning from freezing up.
So what are the best ways to prevent an AC from freezing?
Change the air filter
Air filters are meant to ensure that dust and other impurities do not get into your AC unit. They work by trapping the dust and ensuring your airflow doesn't become blocked.
Dirty air filters that are clogged won't allow air to pass through them efficiently, and as a result, you will need to replace them. They do a pretty good job of keeping you healthy as well .
The primary reason it is advisable to replace an air filter instead of cleaning them is that cleaning filters can be sophisticated. Some types of dirt cannot be removed with cleaning, no matter how well you clean the air filter.
While changing the filters on your Air Conditioner, you should ensure that the replacement filters you get are compatible with your unit. The importance of this is that there are filters of different sizes and designed in different ways.
Take your old air filter with you when you go to buy a new one. Call us at Air and Energy for free advice on choosing the right air filters for your AC, and we can even order you a replacement and change it as well.
Clean your evaporator coil
You can also prevent your AC from freezing by cleaning the evaporator coil. The importance of this is that when impurities such as dust accumulate around the coil, they reduce their effectiveness. To remove the dust and other foreign things that might be on the coil, you should clean it regularly.
Since evap coils are delicate creatures that require special tooling, we recommend you call an HVAC professional. The best prevention is to schedule preventative maintenance with your local friendly HVAC company such as Air and Energy.
We can check and clean your Evap coils during a seasonal tune-up to ensure your evap coils work perfectly the next time you fire up your AC.
Get an airflow inspection
Collapsed ducts or obstructions in registers or vent returns can cause freezing even when the rest of the system works perfectly. Getting an airflow inspection should be part of your preventative maintenance schedule.
You may even have a problem with the ductwork's original design, or it was poorly fitted when your home was first built. A proper inspection by qualified ductwork professionals will ascertain if it's a problem.
A trained professional can help clear a blockage if you have one. If it's a design problem, offer a redesign solution for your home. If you live in the Pensacola area, you're in luck because we are also experts at duct inspection and cleaning.
Schedule regular maintenance
You might not see the need to maintain your AC including your outdoor unit, especially if it is working correctly. But it is advisable to maintain it regularly since this is the only way to identify underlying problems that might reduce your AC's functionality later.
Maintenance also enhances the unit's durability since it eliminates the problem of your AC breaking down without notice. The same goes for all of your HVAC equipment.
Frozen AC units are a common problem, especially in areas of high humidity like Pensacola. Knowing the primary reasons why your HVAC system is freezing up can help you deal with it if it ever happens to you. Knowing what to do when your ac unit freezes up is half the battle.
Changing filters, checking ducts, and cleaning evaporator coils are straightforward tasks and can be done by a homeowner. If it's a leak, mechanical failure, or a blocked duct, it's best to call your local HVAC company to check it out.
If you live in the Northwest Florida area, then give us a call. We will happily check out your HVAC equipment and get it working again or give you a free quote on a new system installation. And if you need Emergency Service, we are only a phone call away.
This article was written by:
Co-founder and Home Comfort Specialist