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2 Types Of Aircon Unit Coils And Their Mechanisms

aircon coil

What are the 2 types of coils in an aircon unit?

Your aircon unit actually has two different types of coils: condenser coils and evaporator coils. Each has its own extremely important function, and any problems with either one could cause your entire aircon unit to break down and stop working.

What is the difference between a Condenser Coil and Evaporator Coil?

The difference between an aircon unit evaporator and condenser coils goes beyond simply their locations in the system. When an aircon unit fails to deliver the expected comfort level, many homeowners assume the internal coolness generator must have malfunctioned and immediately think they need an aircon repair.

That problem can be quickly ruled out because there isn’t any such component, since aircon units are all about moving heat, not making coolness. The cool comfort you enjoy in your home provided by an aircon unit is merely a by-product of effective heat transfer. The functional difference between an aircon unit evaporator and condenser coils is one of the principal forces that moves heat from here to there.

Pro 338 Trivia: Did you know when Willis Carrier (Carrier) patented the first aircon unit in 1906, he called it an air conditioner, not an air cooler, and for good reason. Carrier wasn’t primarily concerned with cooling the interior of the printing factory where he installed that first system.

He mainly wanted to reduce indoor humidity to improve printing quality control. As it happened, his process that condenses humidity from the air also extracted heat energy, producing a cooler building as a side effect.

Today, as then, a mechanical process that effectively extracts indoor heat and moves it outdoors leaves behind cool comfort. The evaporator and condenser coils in an aircon unit are the system components that perform the heavy lifting of heat transfer, yet they function in exactly opposite ways.

The Mechanism of Evaporator Coil:

Extracting indoor heat from the air and adding it to refrigerants is the function of the evaporator coil. Installed inside the indoor air handler, the evaporator is continuously exposed to the flow of warm air drawn by the system blower from individual rooms in the house through return ducts.

Refrigerant circulating through copper tubes in the coil is a cold vapor around 40 degrees. In this state, the heat-absorbent properties of the refrigerant are maximized.

Heat energy from the warm house airflow transfers through the chilled copper coil tubing and is readily absorbed by the refrigerant flow. With its heat energy extracted by the coil, the cooling airflow is pushed by the blower into the supply ducts and dispersed throughout the house.

At the same time heat is being extracted, the warm air contacting frigid evaporator coil surfaces triggers condensation, which lowers the humidity level in the airflow, or the so-called “conditioning”.

After leaving the evaporator coil, the refrigerant flows through an insulated conduit to the outdoor aircon unit component that’s usually directly behind the house. This cabinet contains both the compressor and the condenser coil.

The refrigerant entering the compressor is pressurized, concentrating the molecules of heat energy and raising the temperature of the refrigerant vapor to over 100 degrees. This superheated state ensures efficient transfer of the heat energy into the outdoor air, even when the outdoor temperature is high, such as on a hot summer day.

Evaporator Coil Issues:

Because the evaporator coil is continuously exposed to airflow circulated by the blower, it’s susceptible to the buildup of dust or dirt. When airborne particles form a layer on coil surfaces, the efficiency of the all-important heat transfer from the air to the refrigerant is diminished.

This can result in poor cooling performance and higher operating costs as the aircon unit runs longer “on” cycles to meet thermostat settings.

Another factor specific to the evaporator coil is mold contamination. Dormant airborne mold spores are among the microscopic particles circulating through the entire aircon unit and its airflow. Once these spores contact the surfaces of the coil that are wet from the condensation factor, the presence of moisture activates the dormant spores and active mold growth results.

Like dirt and dust except more stubborn, mold growth on evaporator coil surfaces impacts proper heat transfer. Left to thrive, mold growth inside the coil air passages may eventually obstruct airflow entirely and cause the entire aircon unit to shut down.

Evaporator Coil Maintenance:

In most aircon units, the evaporator coil is sealed within the air handler and may not be readily accessible to the average do-it-yourselfer. Annual maintenance by a professional aircon servicing company, however, includes coil inspection and cleaning to remove dust and dirt.

If evidence of mold growth is noted, the professional ac servicing company will utilize EPA-approved biocides to disinfect the evaporator coil as well as the condensation drip pan under the coil.

The mechanism of Condenser Coil:

The condenser coil is of a similar design to the indoor evaporator coil. However, the difference between an aircon unit evaporator and the condenser coil is exactly reversed. While the evaporator coil picks up heat from indoor air, the condenser coil releases heat into the outdoor air. 

A load of heat energy extracted from your home and compressed in the hot refrigerant vapor is rapidly released when refrigerant circulates into the coil and condenses to liquid. As the refrigerant releases its heat load, a fan incorporated in the unit blows air through the condenser coil passages, and heat is dispersed into the outdoor air.

High-pressure liquid refrigerant leaving the condenser coil makes a u-turn and flows back to the evaporator coil. An expansion valve before the evaporator restricts the flow of refrigerant, forcing it through a narrow orifice and converting it back to a vaporized state, ready to absorb more heat energy from your home.

Condenser Coil Issues:

A major difference between an aircon unit evaporator and condenser coils when it comes to maintenance is the fact that the condenser is located outdoors and exposed to the elements.

Coil surfaces may accumulate windblown dust and dirt, as well as debris such as fallen leaves and grass clippings. On the other hand, because condenser coils don’t generate condensation moisture like the evaporator coil, mold is not usually an issue.

Condenser Coil Maintenance:

Turning off the electrical power to the outdoor aircon unit once a year and hosing down the coil with a garden hose is a good way to maintain condenser coil efficiency. In addition, the upper fan grille should be inspected for damage from fallen limbs or other objects.

The outdoor condenser unit also requires open space on all sides to facilitate the free flow of air into the coil intake vents. Cut back any encroaching vegetation to create at least two feet of clearance around the aircon unit.

There’s no difference between an aircon unit evaporator and condenser coils when it comes to the need to schedule an annual tune-up by a professional aircon servicing company. It’s a critical part of maintaining your aircon unit to the manufacturer’s specs for performance and efficiency. The individual maintenance requirements for each coil are affected by their different functions as well as location.

In most cases, you can get away with cleaning your coils once a year with a seasonal aircon unit tune-up. However, you should consider where your unit is located. If you’re in a big city with heavy air pollution like Singapore, you may want to have the coils cleaned two times a year. Also, if the equipment is older or it’s running most of the day, frequent tune-ups will keep your aircon unit running better.

Checking both your evaporator and condenser coils every couple of months by a professional aircon servicing company to thoroughly clean off debris can be an easy way to keep your system up and running in between tune-ups. Aircon units repair can be costly, so keeping your system clean year-round can save you a nice amount of money in the long run.

Pro 338 Reminder: Refrigerant Problems

Low refrigerant can affect the performance of both the evaporator and condenser coils. When a new central aircon unit is installed, the indoor and outdoor units come pre-charged with refrigerant. In a professional ac installation, they will measure the refrigerant level before installing and after the unit has been test-run.

When this doesn’t happen and refrigerant is insufficient, the unit may chronically underperform in terms of both energy efficiency and effective cooling. Ironically, low refrigerant levels may also cause evaporator coil surfaces to become excessively cold, freezing condensation and triggering a sequence of events that eventually culminates in coil icing which may shut down the system.

During annual maintenance done by a professional aircon servicing company, measuring the refrigerant level is also standard procedure. Aircon units don’t use refrigerant the way an automobile may consume motor oil and require occasional topping up. If a low refrigerant level is detected, a leak is almost always the cause. Leak detection will focus on the evaporator coil, the condenser coil, and connections in the refrigerant conduit.

It’s always a good time to talk about the common issues that aircon units have. This way, you’ll be able to spot if there are problems with your unit or not and prepare for its replacement accordingly. If you require our aircon servicing services, Whatsapp us at +65 9222 4141 for a fast and transparent quote.

338 Aircon Servicing Singapore provides an extensive range of Aircon Services including Aircon Servicing, Aircon Repairs, Aircon Installation of the best aircon brands, Chemical Overhaul, Gas Top-up, Aircon Leaking Water, and Aircon Not Cold Fix, and more. We have a team of professional technicians who are equipped with vast knowledge and experience in the Aircon industry. 


We have over 15 years of experience in dealing with aircon works and have completed thousands of aircon works for both residential (Landed, Condo, and HDB) and commercial. We are a highly recommended Aircon Company in Singapore, with many delighted customers and reviews over the years on Google and Facebook.

WhatsApp us at +65 9222 4141 for a transparent quotation and honest pricing for all your aircon needs or Call us at +65 9222 4141. We offer a fast and efficient service to serve any of your aircon needs!  


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