evaporator coil repairOne of the most common HVAC issues is a frozen AC evaporator coil, which will affect your AC’s ability to function properly. Fortunately, however, it is a relatively easy fix. The following is a brief explanation of the evaporator coil’s function, the reasons evaporator coils freeze, and what to do to get your cooling system working again.

What Does an Evaporator Do?

Your air conditioner works by circulating refrigerant through two sets of coils or copper pipes. The refrigerant starts out as a liquid and is converted into a gaseous form in the evaporator and evaporator coils. As it changes state, it absorbs heat. The gaseous refrigerant travels to the condenser coils where it changes back to a liquid again and releases the heat it contains. This process is how cool air is produced in both central air conditioning units and heat pumps.

In standard central air conditioning systems, the evaporator coil will be part of the inside components. In a heat pump, the evaporator can be in either the outside or inside unit, depending on whether or not the equipment is providing heating or cooling for your home. Outdoor coils serve as the evaporator coils when the heat pump is generating heat.

Why Evaporator Coils Freeze

Evaporator coils can freeze for several reasons including:

  • Cold coils: If the temperature of the evaporator coils falls below 32 degrees, water vapor in the air surrounding the coils will begin to freeze when it comes into contact with the coils. At first, there may be only a thin film of ice or frost but over time, a large coating of ice can build up.
  • Low refrigerant: The refrigerant in your AC system absorbs heat. Low levels of refrigerant, as a result of a leak for example, reduces the system’s ability to absorb heat, resulting in colder air passing over the coils.
  • Malfunctioning defrost cycle: Cooling systems have a defrost cycle that helps keep frost and ice from accumulating on the evaporator coils. This cycle most commonly works by temporarily reversing the flow of refrigerant and allowing hot refrigerant to flow through the coils, melting any ice on their exterior. If the defrost cycle is malfunctioning, it may not be able to remove ice and frost on the coils.

Fixing a Frozen Evaporator Coil

A coating of ice on the evaporator coils will prevent the coils from working properly. Since they are no longer in contact with the surrounding air they will not be able to absorb that heat, and air coming out of the supply vents will be warm. This will interfere with the creation of cool air for indoor comfort. For such a project, it is best to contact your local HVAC professional. Your technician will generally:

  • Turn off power to the air conditioner to ensure it has stopped operating – for safety reasons.
  • He will need to open the access door to the evaporator coils and check to see if there is ice on the coils.
  • If the coils are in fact frozen, there are a number of simple remedies your technician can use to get rid of accumulated ice. It is important to note that chipping or hammering at the ice should never be an option, as this could damage the coils.
  • The technician should ensure defrosted coils are clean and in good condition. Coils can be gently scrubbed with a soft-bristled brush. Manufacturer’s directions generally specify how coils should be cleaned in order to prevent damage, especially to the fins. The fins provide extra surface area for heat transfer.
  • If the heat transfer fins are bent, they can be straightened with a specialized tool called a fin comb. Such tasks are definitely best left to your HVAC professional.

After the technician has completed these steps and the ice has melted, turn the air conditioner on, and the system should be functioning properly once again. Your HVAC pro will be able to provide advice regarding ways you can help to prevent your evaporator coils from freezing again.

The technicians at Bodine-Scott Air Conditioning Co. are fully qualified to handle frozen evaporator coils and other HVAC concerns. Give us a call today, at (361) 883-9900 for solutions to your HVAC needs.

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