What is an Evaporator Coil?

Dantzel Cenatiempo

An evaporator coil is a vital part of any heating or cooling system. It is usually found in an air conditioner, because it is particularly good at absorbing heat when air is passed through it. These coils look like a series of pipes. A furnace, central air conditioner, or other air-modifying device passes the household air through the coil, which absorbs the air’s heat and sends it back into the house as cold air via a series of air ducts. The two main components of an air conditioner are usually the condenser and the evaporator coil.

An evaporator coil may be found in any heating or cooling system, such as an air conditioner.
An evaporator coil may be found in any heating or cooling system, such as an air conditioner.

Central furnace and air conditioning combinations often have their condenser and evaporator coil close together. These units can use the condenser to heat the air or switch over to the coil to cool the home. the coils will typically be placed on top of or next to an air-handling unit, rather than inside of it. In North America, there are three common types of evaporator coils: vertical, cased, and uncased..

Central furnace and air conditioning combinations often have their condenser and evaporator coil close together.
Central furnace and air conditioning combinations often have their condenser and evaporator coil close together.

The vertical type is best suited to handle an upward or downward air flow. It handles pre-processed air and condenses the heat from this air flow in water form. After the condensation process, the vertical coil channels the resulting water to a drain, thereby lowering the humidity of the household air as it cools it.

Cased coils have a protective outer shell and are one of the most commonly used models in North American homes. Like vertical coils, they handle an upward or downward air flow, using a coolant to attract hot air and leave only the colder air current. This cold air returns to the home after passing through the air conditioning ducts. The cased evaporator coil’s function is almost identical to that of the vertical coil, but their main difference lies in shape and size. Depending on the type and configuration of the air conditioning device or furnace being used, one model may fit better than the other for installation purposes.

The third common type of coil is the uncased coil, which is a version of the cased coil minus its protective casing. An uncased evaporator coil is much easier to customize for this reason. They are a good choice for those with a unique furnace or air conditioning unit because technicians can reconfigure the coil shape to fit the device in question.

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Discussion Comments


We lost 3 lbs of freon. I was informed that we have a leak in the coil. He recommend we replace the whole air conditioner. What choice do I have?


I have two AC condensers outside of my house. Would they each have their own evaporator coils or would they run through the same one?


What are the standard evaporator coil prices for an A-frame unit? I just bought a house and discovered that the coils had a leak and the fins were damaged. I have not called the repair technician yet, but I wanted to have a rough idea of costs before he arrived.

I also wanted to know if it matters what type of climate I live in. Are there different coils for dry climates and humid climates? I live in the desert southwest, so most of the year, humidity levels are below 15 percent. That being said, the temperatures are much higher than most regions.


@istria- If you have really dirty HVAC evaporator coils then you will have to remove the entire coil to clean it properly. Dirty and poorly maintained evaporator coils are the leading cause of HVAC failure. Ideally, you should change your filter regularly and have your coils cleaned twice a year. Taking out the coils is a pain of a job because it requires removing the coolant lines. The evaporator coils are also very fragile, and their removal requires an assortment of tools.

You should also have your condenser coils serviced regularly. They are outside and subject to the elements all year. Rodents can build nests in them, grass and dust can blow onto them, and bugs lay silk and get caught in them. I took the cover off the coils at my mother’s house last spring only to find scraps and stuffing from packrats that built their nest in the unit.


@Istria- It is a good idea to check or have your air conditioner evaporator coils checked for dirt and damage. Unmaintained HVAC units can lead to costly evaporator coil replacements. I can walk you through a simple cleaning of an A-frame Evaporator coil (the coils that look like an A-frame roof with aluminum fins).

First, you should turn off the unit at the thermostat and circuit breaker. Next you can remove the evaporator coil access panel with a flashlight, inspect the coils and fins for damage. A little white residue is okay, but bent fins or extremely heavy scale and lint may require a more advanced cleaning job. Once the cover is removed, gently brush the dust off the coils with a soft bristle brush or an air can. Next, clean the drip pan, and pour a little bleach water solution down the PVC drain line. This will kill any algae, mildew, or mold growing in the tube.

Once the previous steps have been completed, spray the evaporator coils with no-rinse air conditioner coil cleaner. The cleaner will dissolve stubborn dust and scale from the coils, liquefying them and rinsing them down the drain. Once this has been completed, pour a little water down the drain to wash all of the particles from the pan.


How should I clean my HVAC evaporator coil? I was cleaning the grates and filter on the unit the other day and I noticed that there was a lot of dust coming out of the vents on the hosing. I took the front housing cover off and noticed that the coils are covered in scale and lint. I have not touched it yet, but I read that the evaporator coils should be cleaned for the most efficient operation of my HVAC unit.

Is this something that I can do myself, or do I need special tools and solvents? Should I call my HVAC technician? I am technically inclined, and I feel like I could accomplish the job on my own if I had the proper guidance.

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