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Michall Daimion Heating & Air Conditioning, Inc. Blog

No, You Shouldn’t See Ice on Your Air Conditioner


This a common occurrence for homeowners who have air conditioning: seeing ice forming along the length of your indoor coil and thinking, “Well, that’s not a problem. Why wouldn’t there be ice on something that sends out cold air?”

Except … that’s not how air conditioners work. We understand why people might feel confused, but not only should ice not form on the indoor evaporator coil (or anywhere on the AC), but it’s a sign something is wrong with the AC and it will soon lose cooling power—if not fail completely.

Why Ice Forms in the First Place

To start with: an air conditioner doesn’t use ice to cool air. What it does is remove heat from the air using refrigerant. When refrigerant passes through the evaporator coil, it’s extremely cold. It evaporates in the coil as warm air is drawn over it, and the evaporation draws heat out of the air to cool it. The refrigerant warms up as it absorbs the heat, and then heads to the outside unit where that heat will eventually be released.

But if something goes wrong and the evaporator coil cannot absorb enough heat to warm the refrigerant, the coil will be too cold and moisture from the air will turn to ice on it. Because ice further blocks heat absorption, it will continue to develop on the coil until the coil can no longer absorb any heat.

The Source of the Iced-Over Coil

What can cause the evaporator coil to lose heat absorption and cause ice to form? There are several possibilities:

  • The evaporator coil is covered with dirt, grime, or mildew. A dirty indoor coil will not be able to absorb heat as efficiently, and this can lead to the refrigerant not warming up enough.
  • The blower fan is not sending enough warm air across the coil. Without enough heat to draw on, the refrigerant will remain too cold. This drop in airflow over the coils is often due to a clogged air filter—and it’s one of the many reasons you must change the air filter every one to three months. The problem could also be a malfunctioning blower.
  • The air conditioner has lost refrigerant to leaks. This is often hard for people to grasp. Why would less refrigerant cause ice to appear? The reason is that the less refrigerant in the coil, the less heat is absorbed, and the remaining refrigerant will stay too cold. Refrigerant leaks will eventually lead to catastrophic damage to the AC, so please have this looked at.
  • The air conditioner is too old and is starting to fail. If the unit is more than 15 years old, it may simply be a case that it’s no longer able to effectively draw heat from the air. The best move is to install a new system.

No matter if you need a new AC installation or an air conditioning repair in West Chester, PA, you can put your trust in our team. We’re family-run and locally operated, and our technicians are experienced and NATE-certified.

Michall Daimion Heating & Air Conditioning, Inc. is the Main Line’s Premier Service Provider since 1976. Call for 24-hour air conditioning service.

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