Air Conditioning Freeze-Ups – Causes and Solutions

Let us set a scene for you:

So, you’re sitting in your living room enjoying a TV show during a hot summer day and your air conditioner is running smoothly. After a while, you end up noticing that your AC system is having a hard time keeping the space cool, so you decide to go and give it a quick look-see only to discover that the entire evaporator coil is covered with a layer of ice!

This is known as an air conditioning freeze-up and it is a pretty common AC system problem during heavy use seasons like Spring and Summer. Let’s talk about just what causes a freeze-up and some ways that you can prevent them from occurring in the first place.

What Causes an Air Conditioning Freeze-Up?

Air conditioners work by pulling the heat out of the air by utilizing the properties of a principal in physics known as the Joule-Thompson Effect. Basically, what the Joule-Thompson Effect states is that as pressure drops, so does temperature (and vice versa).

Air conditioning systems utilize this effect to cool your air by running super-cooled, low-pressure refrigerant through an evaporator coil. Then they pull air from the area to be cooled over the coil, sucking the heat right out of it. After that, they send the cooled air into the space to be cooled and the process starts all over again.

Freeze-ups are what happens when this effect is taken beyond the operating thresholds of your HVAC system. Basically, what happens is that the Joule-Thompson Effect causes the evaporator coil to get so cold that it begins to freeze the moisture in the air that is being cooled. That frozen moisture begins to build up on the coil until the system can no longer pull air through it. This causes the HVAC system to work so hard that it will eventually shut itself off to preserve its future functionality.

Why is Your AC Freezing Up?

Since you now have a more thorough understanding of what physical principals allow for AC freeze-ups, let’s discuss the potential reasons that your air conditioner may have issues with freeze-ups. They are often a result of the following AC problems:

  • Low Air Flow
    The most common cause of air conditioner freeze-ups is low air flow. If too little air is being moved through the system (specifically over the evaporator coil), then the necessary heat exchange (transfer of heat from the air to the liquid refrigerant in the evaporator coil) cannot occur. This causes the temperature of the coil to continue to drop until it reaches equilibrium with the refrigerant inside it. That drop in temperature causes the moisture in the air to freeze and accumulate on the coil. Low air flow can be caused by a number of things including dirty air filters and obstructions in your ductwork.
  • Low on Refrigerant
    Another common cause for air conditioner freeze-ups is a low level of refrigerant in the system. If your air conditioning system doesn’t have enough refrigerant to run, then the pressure inside the evaporator coil is going to be lower by default. And if the coil temp drops far enough, moisture in the air will freeze and accumulate on the coil as it tries to continue to function.
  • It’s Too Hot or Too Cold
    Modern air conditioning systems are designed to operate in a very specific range of environmental temperatures. If the environmental temperature is too far outside of this range, then temperatures and pressures within the system will vary to the point of causing a failure and/or freeze-up.

Ways to Prevent Air Conditioning Freeze-Ups

Preventing a freeze-up is as easy as making sure that you keep up with all your HVAC maintenance procedures. Changing your filters, having us here at Albuquerque Plumbing, Heating & Cooling provide you with reliable maintenance service, and keeping yourself from running the system when it is too hot or too cold outside, are all valid ways to keep your HVAC system from experiencing a freeze-up.

Contact Us Today

Is keeping up with your HVAC maintenance too complex or time-consuming for you? Don’t worry! Here at Albuquerque Plumbing, Heating & Cooling, we offer reliable, affordable, and professional air conditioning maintenance services that will help keep your HVAC system functioning to the best of its ability. Contact us for reliable HVAC maintenance services today!

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