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Frozen AC Evaporator Coil | Lakeside Heating & Air Conditioning

  • Jul 07, 2019
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Focused handyman fixing air conditioning in a new house

Why Your Air Conditioner’s Evaporator Coil Is Freezing

Your home’s central air conditioner is designed to produce cold air to help make your home feel more comfortable during the hot summer months. Unfortunately, you may think that having a frozen evaporator coil is not a big deal or that it actually makes the air colder. This is not true. If the coil is frozen, the air conditioning unit can’t do its job and your house will be warmer than usual.

Here is what you need to know about how an evaporator coil works, why it can freeze up, and how to fix it.

How an Evaporator Coil Works

The job of the evaporator coil is to absorb heat. It works the opposite of how you may think an air conditioner works because it does not actually create cold air. Instead, it removes heat from the air to make it colder. Think of the evaporator coil as a heat absorber that attracts heat from the air that flows over the coil.

The air needs to make contact with the metal coils in order for the coils to absorb heat. Anything that blocks that direct contact with the coils will interfere with how the evaporator coil works, making the air produced by your air conditioner feel warmer than desired. Frozen coils, which develop a layer of ice, block the direct contact needed to cool the air.

Why an Evaporator Coil Freezes

Your evaporator coil can freeze for a few reasons. Restricted airflow in your home can often cause a problem where air gets trapped within the air handler, which causes the temperatures to become too cold and ice to form on the coil. This often happens when people close vents to too many unoccupied rooms within their home. Closed vents restrict how much air can flow through the ductwork.

Temperatures will drop inside the air handler if the air cannot easily force its way through the filter. When the air no longer flows through the evaporator coil and stays within it for too long, the temperature of the air drops further than what is intended and causes the coils to freeze up. This can happen if a filter has not been changed in a very long time and has become covered with debris.

Dirt that has covered the evaporator coils will prevent the air from making direct contact, which leads to frozen coils as a result. If dirt or other debris blocks contact with the coil, you’ll need to take steps to clean the evaporator coils and related filters so that air can pass through the evaporator unobstructed.

A thermostat that is set to too-cool temperatures can sometimes cause a frozen evaporator coil. This mistake often happens when homeowners want to cool down their home quickly by turning the thermostat to a really cold temperature. Unfortunately, the air conditioner does not produce colder air when this happens; it only produces cold air for a longer period of time. Long periods of too cold temperatures can cause the evaporator to freeze up.

Low refrigerant can also lead to frozen evaporator coils. Without refrigerant passing through the coils, there will be no way for that absorbed heat to be transferred out of the air handler. The lack of pressure within the coil continues to drop, the moisture freezes onto the coils, and ice forms as a result. Low refrigerant could be caused by a leak, which should be fixed by a professional.

How to Fix Evaporator Coil Freezing

While there are some things you can easily do to prevent your evaporator coil from freezing, such as changing the air filter and keeping the thermostat at a consistent temperature, others require professional help. Reach out to Lakeside Heating & Air Conditioning for help finding refrigerant leaks or cleaning a dirty evaporator coil.