A Quick Guide on Keeping Your Air Conditioner from Freezing Over

Imagine needing your air conditioner on the hottest day of the year, only to find it encased in a block of ice. It's not unusual for air conditioners to form a light coating of frost during operation. However, that light coating can easily turn into thick sheets of ice under the right circumstances. The following examines how this phenomenon happens and what you can do to prevent it from happening.

Why Frost Happens

Your air conditioner creates cool air by removing the latent heat found in warmer air passing through the evaporator coil. This also causes small amounts of moisture to condense out of the air from vapor to liquid form. Small amounts of condensation that make contact with the evaporator coil can turn into a light coating of frost.

A steady supply of warm air is essential for the air conditioner's frost-free operation. Otherwise, the lack of airflow can cause the evaporator coil's own temperature to drop below freezing. When this happens, the surrounding condensation collects on the coil and forms an ice layer.

Common Causes of Ice Buildup

There are several issues that could be in play when your air conditioner suffers an ice buildup:

  • Restricted airflow—Airflow issues can be caused by a dirty air filter, closed supply registers or a faulty blower fan.
  • Dirty evaporator coil—Accumulated dirt and grime can prevent the evaporator coil from effectively absorbing latent heat, eventually leading to ice buildup.
  • Insufficient refrigerant charge—Low refrigerant levels can cause evaporator coil temperatures to drop below freezing, forming ice on the coil.
  • Drainage issues—Poor drainage can prevent water from exiting the evaporator coil area, increasing your air conditioner's chances of freezing up.
  • Thermostat malfunction—A faulty thermostat can cause your air conditioner to run longer than necessary, increasing its chances of icing over during operation.

How to Prevent Ice Buildup

Under most circumstances, being proactive about your air conditioner's maintenance can help prevent ice buildup from occurring. Here are a few things you can do to keep ice at bay this summer:

  • Always change your air filter on a regular basis: Most experts recommend monthly replacements to prevent airflow obstructions while improving indoor air quality.
  • Have an experienced HVAC technician check your refrigerant levels: Only your technician will have the proper tools and training to safely and accurately check your air conditioner's refrigerant.
  • Inspect and clear the condensate drain and clean the drain pan: Both can be covered in mold, algae and assorted debris, preventing condensate from draining properly.
  • Make sure the evaporator coil is free of any dirt or debris buildup: In some cases, it may be necessary to carefully clean the evaporator coil.
  • Have a professional check the blower fan to ensure it's running at its rated speeds.
  • Make sure that most of your supply registers remain open throughout your home: Too many closed registers can lead to eventual ice buildup.
  • Make sure there aren't any obstructions blocking the return air intake grille.
  • Have a professional check your thermostat to ensure is working properly: In some cases, you may have to replace your thermostat with a newer and more capable model.

What to Do if Ice Buildup Happens

If ice buildup has already happened, then it's important to remove the buildup as soon as possible to restore normal air conditioning operation. After checking your air filter, return air intake and supply registers for blockages, switch your air conditioner to "fan only" mode and wait for the ice to melt. For unusually thick ice buildup, you can use a hair dryer set on medium heat to help speed up the process.

What you shouldn't do, however, is attempt to remove the ice buildup with an ice pick or any other sharp object. Doing so could damage your evaporator coil and place you at risk of severe injury. To learn more about fixing the issue, contact local AC installation and repair services. 


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