What could be the cause of indoor coil to freeze up?
To understand why an air conditioning unit may freeze up, it is important to understand how it works. Once we understand how the system works, the probable causes of the problem will make more sense and be easier to identify and prevent.
How does and air conditioning unit work?
In most HVAC systems, the air conditioning unit works by passing a refrigerant through a compressor, into a condenser and finally, the evaporation coil. The process cycles the refrigerant between liquid and gas states. The important thing to realize in terms of coils freezing is that when the refrigerant reaches the evaporation coil, it is a gas and it leaches heat from the air around the coil. This is important because it means that the coil can only operate between certain temperatures. If the air around it is too cold, ice crystals will form. So, the main cause of an indoor coil freezing up is that the air around it is too cold. There are several things that can contribute to this.
If there is not enough refrigerant in the air conditioning system, it will cool the air around the evaporator coil too quickly and ice will form from the surrounding water vapor.
One of the main elements of the refrigeration process from start to finish is pressure control. If one of the fans or pipes in the system is damaged or not working correctly, the pressure may increase or decrease, leading to too much or too little refrigerant entering the evaporation coil. This will have the same net effect as not having the right amount of refrigerant running through the system.
Another mechanical failure that can occur is poor air flow across the evaporator coil. The evaporator coil cools the air around it, which is then moved into the building. If a fan is broken, the cooled air may remain around the coil and eventually cause ice to form.
Air conditioning units are designed to work in a specific range of temperatures. If the air outside is already cold, passing it over an evaporation coil will cause ice to form.
There are several ways to identify an iced-up coil.
One of the most obvious identifiers is a warm indoor temperature. If you have set the air conditioning system to low and it still feels warm inside, there could easily be an issue with the coil.
Poor airflow in the system’s vents is a strong sign that there is an issue. This could point to a build-up of some kind, which is often ice forming on the evaporation coil. Even if the issue is not an ice build-up, it should be dealt with quickly, as poor airflow can cause an ice build-up.
If there is a lot of water in the drainage system, it could be caused by ice from the evaporator coil melting.
If you have identified a frozen evaporator coil, it is best to have a professional address the issue to avoid damage to the equipment.