Introduction
Have you ever heard of an evaporator coil? Maybe you have but have no idea what it does or that it is even part of an HVAC system in the first place. Are you now wondering what an evaporator coil is and what it does? Don’t worry, we can help. In this blog post, we will be talking about what an evaporator coil is and what it does, common problems with it, how to maintain it, and more. We hope this blog post helps you and answers all your questions about evaporator coils. If it doesn’t, let us know!
What Is an Evaporator Coil?
An evaporator coil is an HVAC part located in the air handler—a part inside the air conditioner—or the very outside of the furnace. It is not only used in HVAC systems but also in refrigeration systems. The name “evaporator coil” was coined for the coil because the refrigerant inside of it reaches a high enough temperature that it boils and then evaporates. Contrary to popular belief, refrigerant boils at low temperatures, and that is why both the coil and refrigerant are able to stay cool.
What Are Evaporator Coils Made Of?
Evaporator coils are made of metals such as aluminum, copper, and steel. Copper evaporator coils are considered the best due to their high conductivity when compared to aluminum and steel evaporator coils. An evaporator coil also has fins that add more surface area so the refrigerant has more time to absorb heat.
Conditions Needed For an Evaporator Coil to Work
In order for an evaporator coil to work properly, the coil must be colder than what it is in. For an HVAC system, this can be around 40 degrees Fahrenheit or lower. In a refrigeration system, the temperature is wildly different: an evaporator coil in a refrigeration system can reach -20 degrees Fahrenheit.
There are different rules for evaporator coils in HVAC systems. For example, unlike refrigeration systems, evaporator coils can not reach below freezing, or frost may build up.
All in all, the temperature of an evaporator coil can range dramatically depending on the system’s needs. While the evaporator coil is only a small part of an HVAC system, it can be complex in its usage.
What Does an Evaporator Coil Do?
Located inside of the air handler as mentioned above, the evaporator coil’s main purpose is to absorb heat from the air to change the temperature of refrigerant. In doing this, the evaporator coil and refrigerant work together to remove heat from the air, making it cold.
The Evaporator Coil’s Process
The evaporator coil goes through a complex process to do its job. Before it is able to though, a pressure drop has to occur before liquid refrigerant enters the coil. This is so the coil can work at a lower temperature, and pressure can be used to manipulate the temperature of the refrigerant.
Once all of that is done, the evaporator coil finally comes into play. First, heat is attracted to the coil as air flows over it. The coil then pulls in the heat to control the temperature of the refrigerant located inside the coil. During this process, the evaporator coil must be able to control temperature and the flow of refrigerant. After heat is pulled in, two stages take place to change the refrigerant to the right temperature: the boiling phase and superheating phase.
The Boiling Phase
In the boiling phase, the liquid refrigerant is boiled and changes to refrigerant vapor. The goal is to fully vaporize it.
When the refrigerant is fully vaporized, preparation for the second stage, superheating, can occur. For reference, the superheating stage uses temperature and pressure to tell how far the liquid vapor is boiling. An example of telling how far the liquid vapor is to its boiling point would be if it was 55% liquid refrigerant and 45% vapor. The goal would be to reach 0% liquid refrigerant and 100% vapor.
The Superheating Phase
Once 0% of liquid refrigerant is found, the actual superheating can begin. Superheating takes place when heat is added to the refrigerant above its boiling point. This allows the refrigerant to reach a higher temperature due to the evaporator coil. The heat added to the refrigerant is called sensible heat because of the nature of superheating. The superheated refrigerant, now boiling, goes to the compressor.
You can read more about what the evaporator coil does in the refrigeration cycle here.
Common Problems with Evaporator Coils
When you have an HVAC system, there are several common problems you may encounter with an evaporator coil. These problems can exist from lack of maintenance, negligence, or extreme weather.
Evaporator Coil Leak or Low Refrigerant
An evaporator coil may start to leak because of corrosion of the metal or damaged seams. When a coil becomes damaged, it leaks refrigerant. Low refrigerant can cause several issues, not just for the coil, but for the entire HVAC system.
If you suspect a refrigerant leak, the best thing you can do is call a licensed HVAC technician. The HVAC technician can check the refrigerant levels and determine if the evaporator coil is leaking. If it is leaking, they may recommend replacing the coil. If it isn’t leaking, then it can be ruled out as the source of the problem. This can help save time and money when trying to troubleshoot.
Frozen Evaporator Coil
Usually, when an evaporator coil freezes, the freezing is a symptom and not the direct cause of why it is not working.
Evaporator coils can freeze over due to plenty of reasons:
- Low outdoor temperatures
- Low refrigerant
- Dirty AC filters
- Clogged evaporator coils
When the coils freeze over, the best thing to do is call a professional HVAC technician.
Dirty Coils
Dirty evaporator coils can occur from a buildup of debris or dust and become clogged. Not only can evaporator coils in an HVAC system become clogged, but other coils, such as condenser coils, can as well.
When a coil becomes clogged, the debris restricts airflow, and it can’t work at full capacity. Just like when an HVAC filter has an excessive buildup of debris and stops working correctly, dirty coils do too. The best way to prevent a buildup of debris in the coils is to have the HVAC system maintained at least once a year.
You should not attempt to clean your evaporator coil unless you are a licensed HVAC technician. According to Trane, doing so could damage your coil or void your warranty.
How to Maintain an Evaporator Coil
There are some easy ways to maintain an evaporator coil. Some basic maintenance can go a long way in keeping an evaporator coil running for a very long time. It may seem overly simple, but it can be the difference between saving money and paying a large, unexpected HVAC bill.
Keep the Outdoor Unit Clean
An evaporator coil relies heavily on the outdoor AC unit to be working in proper order. The best way to keep an outdoor unit from experiencing unexpected issues is to keep debris away from the unit. Keeping debris away from the unit can mean clearing away branches, making sure the grass isn’t too high around the unit, or just keeping outside decorations away from it. A good rule of thumb is to keep anything at least three feet away from an AC unit that is not HVAC-related. With the outdoor unit clean, the outside AC unit has access to proper airflow, which helps the AC evaporator coil run better in the long run.
Change Air Filters
One of the best ways to keep an HVAC system running smoothly is by changing the air filters regularly. For an evaporator coil, this is especially crucial. Over time, dirt and debris collect on an air filter, and eventually, when it is not changed, it becomes clogged. A dirty air filter reduces airflow, causing the whole system to slow down. This lowers the pressure of the evaporator coil and prevents it from functioning properly. An evaporator coil requires good airflow in order to continue working.
Changing the air filters not only helps to maintain the coil, but the entire HVAC system. Replace the HVAC filters every three months or sooner based on your household’s needs.
Schedule Yearly Maintenance
While keeping an outdoor AC unit clear of debris and changing the HVAC filters as needed is crucial for the function of an HVAC system, scheduling regular maintenance is also a must. Most homeowners are unable to check the level of refrigerant in their HVAC systems by themselves. The level of refrigerant must be at a stable level for the evaporator coil to continue working optimally.
Scheduling yearly maintenance with a trusted HVAC company can help you not only ensure your evaporator coil is working, but that the rest of your HVAC system is too. Scheduling yearly maintenance is an investment that will help you save money in the long run.
Conclusion
An evaporator coil may only be a small part of an HVAC system, but it plays a large role. Without it, refrigerant wouldn’t be able to change states.
In this blog post, we covered what an evaporator coil is, what it does, common problems with it, how to maintain it, and more. If you have any more questions about evaporator coils, leave a comment below.
Do you need your evaporator coil looked at, and live in Jefferson County or the surrounding areas? Give us a call! Our phone number is 636-475-9384. We look forward to helping you out with all your HVAC needs.