Climate Works Blog

What is An Evaporator Coil?

If you have an air conditioner, or something that uses a heat pump, then you have an evaporator coil. This coil works to cool and condition indoor air that flows over it by drawing out heat and moisture from the air as it passes by. Also known as the indoor coil, it is essential to any home that has a heating or cooling system, which is suffice to say that it is found in nearly every home in the country. The job of the evaporator coil is one of the most important factors in keeping our homes in a climate controlled setting throughout the year.

How does an evaporator coil work?

The evaporator coil will be found in your furnace, or your air conditioning unit, and is located indoors. Within the coil, the refrigerant will evaporate as it absorbs the heat from the air that is passing over it. The coil is then serving as a heat exchanger, working to help your heating system in the winter, and working to provide cooling air in the summer.

Once again, it is an essential part of your heating and cooling system, and most people don’t even know what it is. To say it is the unsung hero of our home would be an understatement.

Fan Speeds

Essential to the whole process is the fan speed. The heat exchange depends on the temperature differential between the refrigerant in the coil, and the air going over it. The greater the differential, the greater the heat exchanged. A high heat load usually happens when the system is turned on and a blower fan turned on its highest level will provide the most air across the coils and fins, allowing for rapid evaporation. The blower fan on its lowest speed will provide the lowest air temperature, because the air moves more slowly over the coil, allowing more heat to be removed.


Obviously, it is very important that you practice proper maintenance with your evaporator coil. A dirty indoor coil will not only lower the efficiency of your system, but it will greatly impact the performance of it as well. You need to keep your system in peak operating order, and that involves having your coils cleaned on a regular basis.

There are a number of reasons that coils can become dirty, and one of the biggest is that they are not cleaned regularly since they are difficult to access. Some coils now come on a rail system for easy cleaning, but either way you should have someone come in in the fall every year to clean your furnace and to deal with the evaporator coil.

There are two coil problems that can occur, and can be dealt with by a technician. The first is a flooded coil, which is when too much refrigerant is passed through the coils, which causes unexpanded liquid to pass into the suction line and compressor. The second is a starved coil, which is when not enough refrigerant is being supplied through the entire coil length.

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