Have you ever checked on the indoor portion of your air conditioner after suspecting a problem and discovered that it’s all covered in ice? Air conditioners operate when temperatures are warm, so what on earth could cause your system to freeze up? This is a much more common problem than you might expect, and it can happen for several different reasons. Today we’re going to help you understand this perplexing issue by answering the question, “Why is my air conditioner freezing up?”

Freezing typically occurs on the evaporator coils
When air conditioners freeze up, the ice is almost always located on and around the system’s evaporator coils. An air conditioner’s evaporator coils contain cold refrigerant inside of them. When warm air from your home is blown over those coils, the heat from your home’s air transfers to the evaporator coils, and the coils warm up when that heat is absorbed. As a side effect of this process, moisture from the air is removed and drips off of the coils in the form of condensation.
If something is wrong with your air conditioner that is preventing your evaporator coils from absorbing enough heat, the condensation that builds up on them can freeze over because the refrigerant inside of the coils stays cold. This results in evaporator coils that look like they are covered in snow.

Why is my air conditioner freezing up?

  • Low refrigerant.
  • The refrigerant inside of the evaporator coils is what actually absorbs heat from your home’s air and transfers it outside. If your air conditioner has a refrigerant leak, there won’t be enough refrigerant available to adequately remove heat from the air. As a result, the evaporator coils will stay cold and freeze over.

  • Poor airflow. Even if your system has enough refrigerant, it can freeze over when there isn’t enough return air blowing over the coils. This makes sense when you think about it. The heat that your evaporator coils absorb comes from the air inside your home. If something is blocking airflow (such as a dirty air filter, closed air registers, or issues with the blower motor) then there won’t be enough heat available to warm up the coils.
  • Dirty coils. When dirt builds up on your evaporator coils, it creates an extra layer between the warm air that’s blown over them and the refrigerant inside the coils. This makes it much harder for heat to transfer between the air and the coils, which causes the coils to get too cold and freeze up.
  • Cold weather outside. This can be a problem during the springtime when temperature levels can rise and fall unpredictably. If your air conditioner is operating when the temperature outside is below 60 degrees, your coils have a chance of freezing over.

How can you prevent your air conditioner from freezing up?

The best way to prevent your air conditioner from freezing up is to schedule a tune-up every year. During your tune-up, we’ll check your system’s refrigerant levels, inspect the blower motor and clean your coils so that the heat transfer process can execute with ease. In addition, make sure to change your air filter regularly and keep all of your air registers open and clear of obstructions so that your system doesn’t operate with any airflow issues.
If you have any questions about why your air conditioner is freezing up, or if you’d like a cooling system serviced or installed in your home, contact Jerry Kelly Heating & Air Conditioning, your St. Louis area air conditioning contractor. We provide service all over the St. Louis area, including towns like Clayton, Cottleville, and Creve Coeur, MO.

photo credit: mirsasha via photopin (license)

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