It can definitely be alarming to discover a huge block of ice in your AC! Luckily, it’s not as scary as it looks.
AC freezing is actually an incredibly common problem. Sometimes a frozen AC requires professional help, but you may even be able to repair it yourself depending on the source of the freeze!
Why Does My AC Freeze?
One of your air conditioner’s jobs is to dehumidify your home. That means it sucks water out of the air, to make the air inside your home drier. Inside of your AC unit are some metal frames (usually visible when you take the filter out). These are your AC’s evaporator coils. Your air conditioner works by pumping freon from your condenser outside, through these metal coils. The water in the air is sucked onto these cold metal coils as condensation when the air passes over them. Usually, while your air conditioner is running more and more water is collecting on these metal coils. The water drips off the coils, and they dry when the system is not cycling. Sometimes problems can cause the water to hang around too long on these coils, and they turn to ice. We’re going to talk about how to fix a frozen AC, and look at some of the problems that may cause freezing.
How to Fix a Frozen AC
Dry Your AC
The only way to get the ice out of your air conditioner is to shut it off and allow the ice time to melt.
When your unit cycles on, that means freon is pumping through the evaporator coils – which means they’re pretty cold, and the ice won’t melt. You can either turn your system off, or you can set it to the “fan only” option. If your system does have the fan only option, definitely use that – it will help the evaporator coils dry off faster. It should take about 24 hours for the ice to melt, but it could be longer if you have a solid block on there!
A solid block of ice can look really scary, but getting rid of that is going to be about the same as someone with a little bit of frost. The only difference is that while your ice is melting, you’ll want to keep an eye on your condensate drip pan. If your thermostat does not have a “fan only” option, note that you should take a towel or paper towels and dry off the evaporator coils and fins. If you have the fan, leaving that blowing for 24 to 48 hours.
Locate the Cause of the Freezing
Increase Air Flow
The #1 most common cause of a frozen AC is a dirty filter.
Sounds crazy right?
It doesn’t make sense that such a small piece of paper could cause such a huge malfunction in your high-tech air conditioner. The reason why dirty filters cause freezes is that they lower the amount of air going through your system. Your AC is built to work only one way, at a specific balance of airflow and pressure. Just the right amount of water has to collect on the fins, for the perfect amount of air to pass over it so the drops drip just right into the condensation drip pan.
One slight change to this equation, like say less air passing over the fins because less air can get through your clogged filter, can completely throw your AC’s balance out of whack. When there isn’t enough air passing over the fins, the water droplets hang out on the metal for a little bit too long and turn into frost.
How Are the Evaporator Coils?
Your air conditioner filters all kind of gross stuff out of the air in your home like hair, pet dander, dust, dirt, and mold. Because it’s doing this, the evaporator coils inside your system can sometimes become caked in layers of grime. You can call a friendly Blair’s Air licensed HVAC professional to do a deep cleaning for you, which you might need to do depending on how bad the dirt is. Otherwise, you can try to remove some of the gunk yourself!
First, be sure to turn the air conditioner OFF. (Some people recommend switching the breaker to the system off as well.) You can use a soft brush like a toilet brush or a toothbrush to scrub buildup off of your evaporator coils. You could also use a paper towel, and gently try to loosen the grime on the fins with your hand. Be careful not to use too much pressure, you don’t want to bend any of the metal fins or coils.
Professionals like Blair’s Air have special chemicals they use to loosen more intense buildup, but if you have minor grime you can try to use some water to loosen it, then scrub it off with a soft brush or a paper towel.
When Do I Need Professional Help?
If you have tried these remedies and your AC is still freezing, you may need the help of a professional. Luckily these are not major, or expensive repairs – but they are generally a little too complicated for the DIYer to handle. Another common cause of freezing is if the refrigerant level is too low. The reason this causes freezes is all because of the pesky chemical freon. Freon is the refrigerant used to cool the evaporator coils in your AC. As a chemical, it is very sensitive and can change states of matter very quickly. For example, freon could be a liquid that is boiling or not boiling at the same temperature – but with different pressure. The pressure inside of your AC depends on your system having the perfect amount of air flow. We talked about how a clogged filter can mess up the air flow, and change the pressure a little bit earlier.
If any part from your compressor, to your inside unit is obstructing air flow, or changing the temperature of the system then this delicate balance can be thrown off. In a normally operator AC system, your condenser holds the freon as gas – that’s what HVAC professionals come “charge” in your system. Your compressor makes this freon super hot, and the 100F chemical turns from a gas into a liquid. When anything is extremely hot, it also has a high pressure – so your AC system shoots this high pressure, liquid hot freon towards your house. Before the hot liquid freon reaches the inside part of your AC system, it’s pushed through a special device that makes it incredibly cold (20F) very quickly.
When you take a liquid from hot to cold, you’re also taking it from high pressure to low pressure. Freon can be a liquid when it’s very hot OR very cold, that’s why it’s super important for your AC to have the perfect balance of temperature, airflow, and pressure at all times. That super cold freon is pumped through the evaporator coils, then it works how you learned earlier: the water from the air in your home is attracted to that very cold metal.
When the refrigerant is too low, that means that the pressure inside of the little tubes the freon travels through will also be too low. When the pressure is low, the freon is colder than usual when it gets to the “super cooling” stage just before being run through your evaporator coils. This makes the evaporator coils extra cold, and causes the water to freeze! Measuring the pressure, and the level of refrigerant in your system takes some special tools – so you’re best to leave that to the professionals.
Another common reason for AC freezes can be an issue with your fan. That might sound concerning, but don’t worry! Fans just get dinged, and worn as they’re used. Sometimes a larger object travels through your system and it can knock the AC fan out of balance.
An HVAC professional will be able to tell you if your fan is running properly, and get it back to spinning level.
Call Blair’s Air, the Best Air Conditioning Team in Tampa Bay
Woke up to a glacier in your AC? Don’t sweat. You can get immediate support from one of our friendly, licensed HVAC technicians in Tampa, St. Petersburg, Pinellas, or Hillsborough. Just give us a call (tel:(727) 800-4148), or easily schedule a service online.