Why Do I Have Frozen AC Coils?

Why Do I Have a Frozen AC Coil?

The AC coil is one of the most important components in your HVAC system because it’s tasked with removing heat from the air that’s passing through your system. The coils are designed to operate at a cool temperature so they can cool the air, but problems in your AC unit may cause the coils to get too cold and start to freeze.

Frozen coils will prevent your AC from effectively cooling your home, so it’s important to resolve this problem as soon as possible.

How do you know whether you have a frozen AC coil, and what can you do to unfreeze it?

Wondering Why Your AC Coils are Frozen?

AC coils can freeze in any temperature, any time of year—even here in hot Southwest Florida. It might be strange to think that your AC components can freeze even when you’re living in the tropics. What causes this to happen?

It helps to understand how your AC coils work.

AC coils remove heat from a home by drawing in indoor ambient heat using the refrigerant that’s flowing through these coils. These coils rely on evaporative processes that result in extremely cold coils when heat is removed, but typically not cold enough to freeze. Most AC units circulate refrigerant vapor that’s 40 degrees, which is the ideal temperature to cool air passing through the unit but not cool enough to produce ice.

A frozen AC line is usually a sign there’s a problem involving your AC’s refrigerant or airflow. This is a problem that should be treated immediately because frozen coils will impact your AC’s ability to blow cool air into your home. Furthermore, you could damage your HVAC system by continuing to run it when the coils are frozen.

What Causes an AC Coil to Freeze?

There are several issues that may cause your AC coils to freeze:

  • Dirty Air Filters: Dirty air filters block air from circulating through your AC unit. Warm air can’t reach your coils in sufficient quantities, and without the warm air your coils get too cold and become frozen.
  • Broken Fan: The same problem can happen if you have a broken fan or fan blower motor. If the fan is broken, there will be no airflow through your air handler and the coils can freeze because they have no exposure to regular air flow.
  • Leaking / Low Refrigerant: Your AC uses refrigerant to keep the coils at the right temperature to ensure that it continues absorbing heat. If your AC doesn’t have enough refrigerant, the coils will be exposed to too much heat. Condensation will form on the coils, which can turn into ice. This problem might be caused by a refrigerant leak, or because your AC unit is simply running low on refrigerant due to lack of maintenance.
  • Blocked Condensate Lines: Condensate lines allow excess water to be drained out of your air conditioning system. When the condensate lines become blocked, the water overflow or spillage can get frozen around your AC coils.
  • Dirty Evaporator Coils: When your coils become dirty, they won’t be able to transfer heat very well and become frozen. It’s a good idea to have your coils cleaned during an annual AC tune-up.
  • Broken Thermostat: A broken thermostat can also cause frozen AC coils, although this is the least likely culprit. A broken thermostat might fail to accurately gauge the temperature in your home and make the AC work longer than it needs to. This can lead to ice buildup on the coils.

Signs of a Frozen AC Coil

How do you know if you have a frozen AC coil? You’ll notice the following symptoms, no matter what caused the AC coil to freeze.

  • Your AC isn’t pumping cool air
  • There’s little air flowing in or out of your AC
  • There’s ice or moisture visible on the AC unit

Ultimately, a frozen AC coil will cause your HVAC system to stop working, which could leave you with a hot and uncomfortable house in the middle of the summer.

Troubleshooting Frozen AC Coils

What can you do to unfreeze a frozen air conditioner line? Here are some troubleshooting tips that can help:

  • Replace the Air Filter: Change the air filter so your AC can get enough airflow. If your air filter isn’t very dirty or you’ve changed it recently, then you know there might be a different reason your coils are freezing.
  • Let the System Thaw: Turn off the thermostat and let your HVAC system thaw for several hours. Running your AC while the coils are frozen can cause significant damage to your HVAC system.
  • Use Defrost Mode: Use the “Defrost” or “Thaw” mode if your AC has one. Follow all the instructions on the manufacturer’s manual.
  • Check Vents: Double check to ensure that you don’t have any closed supply vents or return vents
  • Don’t Scrape the Ice: Don’t try to scrape or chip away ice on the coils or you could risk damaging them.
  • Call an HVAC Technician: Even after you’ve thawed your AC unit, your coils could freeze again if there’s a problem such as leaking refrigerant or dirty coils. Have an HVAC specialist inspect your AC and fix any problems that may be causing frozen coils.

How Do You Fix a Frozen AC Coil?

Call an HVAC technician if the troubleshooting steps didn’t work. Most of the time, changing the air filter and letting your AC thaw will get your AC back into working order. If that doesn’t work, there could be another problem with your AC that requires a professional fix.

HVAC technicians can:

  • Clean the Coils: Coils will naturally gather dirt and debris over time. Only HVAC technicians should attempt to clean the coils because they’re fragile and very difficult to access.
  • Refill Refrigerant: Refrigerant can be a toxic chemical, so it’s best to let HVAC technicians add more refrigerant to your system.
  • Fix Refrigerant Leaks: HVAC technicians can also inspect your AC for leaks and fix them.
  • Clear Clogged Lines: Condensate lines can also be difficult to access, but HVAC technicians have the proper tools to reach them and clear debris. They can also safely remove extra water that’s been trapped in your AC unit and make sure it hasn’t damaged other components.
  • Repair Fans and Ductwork: HVAC technicians can make repairs to broken fans and motors, and they can also inspect your ductwork for air leaks or damage.

Preventative Maintenance to Keep AC Coils Working Great

The best way to prevent a frozen AC line is to schedule an AC tune-up once or twice per year. During a tune up, HVAC technicians will change the air filters, add refrigerant, and inspect your AC for any other problems that could cause it to fail. In many cases, all that’s needed to keep the AC coils from freezing is to give it a quick and professional cleaning. Plus, tune-ups are much less expensive than paying for an emergency AC repair and will improve the lifespan and efficiency of your system.

Contact Hurricane Air if Your AC Coils Keep Freezing

Do your AC coils keep freezing, even after you’ve changed the air filter? Call Hurricane AC technicians to have your AC system inspected and repaired. Hurricane Air can fix any problems that are causing your AC coils to freeze, and we can work with any type of home or AC system in Southwest Florida. We also offer annual maintenance plans to reduce the risk of your AC breaking down in the hottest months of the year.

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    Frozen AC Coil FAQs FAQs

    What do I do if my AC coil is frozen?
    If your AC coil is frozen, immediately turn off your thermostat so you don’t cause further damage to your AC system. Change the air filter and give your AC several hours to thaw. Check to see if your AC has a “Defrost” or “Thaw” mode and follow the instructions on how to use it. If your AC coil freezes again after you’ve changed the air filter, it’s best to enlist the help of a certified HVAC technician.
    Why is my AC line frozen?
    A frozen evaporator coil may be caused by dirty air filters, broken fans or motors, leaking or low refrigerant levels, blocked condensate lines, dirty evaporator coils, or a broken thermostat.
    How do you unfreeze an air conditioner?
    You can unfreeze your air conditioner by turning off the thermostat and giving it a few hours to thaw. Replace the air filter while the system is thawing. You can also use your AC’s “Thaw” or “Defrost” mode, if it has one. Call an HVAC technician if your AC coils keep freezing, even after you’ve changed the air filter.
    How do you thaw out frozen AC Coils?
    You can thaw out frozen AC coils by turning off the AC and letting it sit for a few hours. Wait for the ice and moisture that’s gathered around the AC to melt and dry out. Do not try to scrape ice off of the coils or else you could risk damaging them.

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