While air conditioners cool the air in your home, they should not freeze up while operating normally. Frozen components indicate a problem with your air conditioner that could ruin the system and drive up your energy consumption without providing the cooling you desire. This guide will help you know if your AC has frozen, eight quick steps you should take now and how to prevent future freezes.
Signs of a Frozen AC
You may experience any number of signs or indications any time your AC freezes. The most obvious is if the outdoor unit freezes and you see ice on the lines, on the coils, or when you look inside the unit. If it freezes inside, you may notice water on the floor around the evaporator coil.
Some signs are a little less obvious and could be connected to any number of problems, including a frozen system. First, you may notice less air flowing from your supply vents, or that the air flowing from it is warmer than you expect. If you pay attention to your electric bills, you may notice a sharp increase in your energy consumption. You may find your home feels more humid than normal. Finally, you may find that your home’s temperature isn’t achieving your desired setting.
1. Turn the System Off
If you believe your system is freezing, you need to shut the system down. A frozen system can’t circulate air and will add substantial strain to your compressor. If you continue trying to run a system that’s frozen, you can burn out the compressor which is an expensive repair and often requires a full system replacement. If you’re concerned about the system trying to run, turn it off at the breaker at the panel or the one located by the condensing unit outside. With few exceptions, it’s best to leave the air conditioner off until you’ve found and resolved the cause of the freeze.
2. Find the Freeze
Once the system is off, you want to locate where the system is frozen. This is critical because it can give you an indication of the cause of the freeze. If you’ve seen ice on the outside coils, you can pretty easily stop there. However, if you don’t see that ice, look inside through the top ventilation to see if there’s ice on the compressor or accumulator. Look at the exposed refrigerant lines and junctions. If you don’t see anything frozen inside, check the floor around your inside unit to see if there’s excess moisture. Do not try to take apart the indoor unit looking for where it froze. Leave that to a professional to avoid incidental damage and voiding the manufacturer’s warranty.
3. Check Your Air Filter
If you’ve positively identified where the freeze is happening, start looking for the cause. If your issue is inside, start by inspecting your HVAC air filter. A clogged filter restricts airflow into the system. With insufficient air moving through the system the indoor coil can get too cold, freezing moisture that is condensing from the air, which becomes a compounding problem. If your filter is visibly dirty, replace it and then check the remaining easy steps because you could have several factors compounding to cause the freeze.
4. Check Your Thermostat Setting
Your thermostat setting can have a major impact on how your air conditioner operates. The lower you have the temperature setting compared to the temperature outside the more it strains your system. Setting the temperature too low can cause the coils to freeze. To prevent this and extend the life of your system, some experts recommend following the 20-degree rule. This states that you should keep your AC set no lower than 20 degrees cooler than the outside temperature. If the real temperature outside is 98 degrees, you should set your thermostat no lower than 78 degrees Fahrenheit. However, regardless of the temperature outside, setting your thermostat lower than 72 degrees increases the risk of the evaporator coil freezing.
5. Look for Blocked Vents
In addition to a dirty air filter, closed or blocked vents can inhibit necessary airflow through the system. Restricted return vents can starve the system of needed warm air, causing the evaporator coil to freeze. Closed or blocked supply vents can build unusual pressure inside the system, slowing down how much air it draws. Make sure that all of the supply vents are open and have at least 6 inches above it clear to allow cool air to circulate. The clearance required for the return vents depends on the size of the vent. Check with an experienced HVAC technician at your next maintenance visit to ensure that you know how much clearance your return vents need.
6. Check the Condensate Drain
The moisture your AC pulls from the air is called condensate, and it has to drain away through a condensate drain. When neglected, this drain can clog and cause the condensate to back up in the drip pan. In some systems, this can back up to the coil, which can then cause the condensate to freeze. This then freezes all of the moisture in the pan and drain and can cause more freezing on the coil. Cleaning the condensate drain is commonly included with routine HVAC maintenance. If you need to clean it on your own, pour distilled vinegar down the drain, wait 30 minutes, and then flush with water.
7. Thaw and Test the System
If you believe that you’ve solved the problem causing the freeze, you should test it and see if it repeats. Start by thawing the system. If the freeze was outside the system this should happen naturally and won’t take very long. If the freeze was inside, change the fan setting on your thermostat to “On” so that the circulating fan continues running. The extra airflow over the coil will help thaw the freeze more quickly. Once it’s thawed, turn the system back on and watch it closely to see if it’s freezing up again. As soon as you notice frost forming where the prior issue was, shut the system down and call for a professional inspection.
8. Schedule an AC Inspection or Repair
One of the first things a technician will do while investigating a frozen AC is to check the refrigerant charge. Insufficient refrigerant will cause the system to get too cold, allowing frost and ice to form. If the refrigerant is low, then they’ll look for the source of the leak. If not, they’ll move on to other possible causes of the freeze.
How to Prevent Future Freezes
The best way to prevent air conditioner freezes is to get regular maintenance tune-ups. During this visit, a technician will clean the evaporator and condensing coils, clean and balance the circulating fan, and test the refrigerant level among a host of other tasks. This maintenance visit can identify possible causes of mid-summer freezes and give you the chance to resolve them before damaging your system.
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