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Evaporator Coil: Service it or Replace it?

In this article, we discuss the function of the evaporator coil of your AC unit. We can what an evaporator coil is and the different types available, as well as the common technical issues that can occur with it. Our article will also help you detect the signs that this part may require servicing, and inform you of what happens when a faulty evap coil is not replaced in time. Lastly, we discuss the reasons why maintaining and replacing this coil is not a DIY job.

1- What is an evaporator coil?

An evaporator coil is a crucial component in the refrigeration or air conditioning system. Its primary function is to absorb heat from the air within a space, effectively cooling the area.

The evaporator coil contains refrigerant, a substance that changes from a liquid to a gas as it absorbs heat.

This transformation process is at the base of the cooling cycle, because it allows the refrigerant to carry the absorbed heat outside, where it is expelled.

The refrigerant is converted back into a liquid to repeat the cycle.

The evaporator coil works in tandem with other components of the HVAC system, such as the compressor and the condenser coil. The compressor pumps the refrigerant to the evaporator coil, where it absorbs heat and turns into a gas.

The gaseous refrigerant then travels to the condenser coil, where it releases the heat and returns to a liquid state, ready to be pumped back to the evaporator coil.

2- Types of evaporator coils and differences

Here are various types of evaporator coils, each designed to suit different AC configurations and requirements. The two main types are the “cased coil” and the “uncased coil”.

Cased Coil: Cased coils are enclosed in a metal case, providing protection and easy installation. They are typically used in forced air systems where the coil is placed in the air duct system.

An example of a cased coil is the A-coil (named for its shape resembling the letter "A") commonly used in residential HVAC systems.

It is efficient at absorbing heat from the air passing through the coils.

Uncased Coil: Uncased coils, on the other hand, are not housed within a metal case, which makes them more flexible for custom AC installations.

They work well in tight spaces where a standard cased coil won’t fit. For instance, in a historical home renovation project in Berlin, NJ, we used an uncased coil to adapt to the existing HVAC setup without extensive modification.

Differences: The primary difference between the 2 types of evap coils lies in their installation and application. Cased coils are more straightforward to install; uncased coils offer more flexibility for custom installations. The choice between the two depends on the specific requirements of the HVAC system and the space constraints on site.

3- Common technical issues

Evaporator coils are workhorses, but like any mechanical component, they will have technical issues. Here are some of the most common:

Refrigerant Leaks: A leak can cause the refrigerant level to drop, leading to insufficient cooling and overworking the system. A very common example is the homeowner calling Filan & Conner because their air does not seem to cool down their house normally and they see a large bump in their energy bills.

Freezing: Insufficient airflow or low refrigerant levels will often cause the coil to freeze. When this happens, the heat absorption process stops and the system malfunctions.

A homeowner might find their air conditioner blowing warm air due to a frozen evaporator coil.

Corrosion: Corrosion affects the longevity and performance of the evap coil. Corrosion occurs due to exposure to moisture and air. The problem is exacerbated in coastal areas such as New Jersey due to the salt content in the air. We have seen many cases of coastal resorts and restaurants needing to replace their evap coil just because of this factor.

Dirt Accumulation: Dirt and debris accumulation reduce the coil efficiency. The outcomes: inadequate cooling and increased energy consumption.

4- Signs an Evaporator Coil Needs Service

Warm Air from Vents: When the evap coil is malfunctioning, the air emitted from the vents is noticeably warmer. Despite the air conditioner running continuously, the expected cool air is absent, signaling a need for coil service.

Increased Humidity: A functioning evaporator coil removes moisture from the air, contributing to a comfortable indoor environment. If you notice an unexpected increase in indoor humidity levels, it's a sign the evaporator coil requires attention.

Unpleasant Odors: A malfunctioning evaporator coil often emits unpleasant odors. If a musty or burnt smell permeates the air when the air conditioner operates, it indicates the coil needs servicing.

Reduced Airflow: A noticeable reduction in airflow from the HVAC system is a clear sign of an issue with the evaporator coil. Reduced airflow indicates blockages or damage to the coil. At this point, call Filan & Conner: the evap coil needs immediate service.

AC Unit Constantly Running: If the air conditioning unit is continuously running without adequately cooling the home, the evaporator coil is probably not functioning correctly.

Water Leaks: Visible water leaks around the air conditioning unit are a telltale sign of a malfunction. The coil is unable to absorb heat and moisture effectively, which leads to condensation buildup and subsequent leaking.

Frequent AC Cycles: Frequent and erratic cycling of the air conditioning unit (on-off, on-off, etc.), regardless of the weather, signals a problem with the evaporator coil. You need an HVAC technician look immediately at the evap coil to prevent further damage to the system.

Thermostat Issues: If adjusting the thermostat doesn’t result in the desired temperature changes, the evaporator coil is not effectively communicating with the thermostat and needs service.

Ice Buildup: Ice buildup on the exterior of the air conditioning unit is a clear sign of evaporator coil issues. The ice indicates the coil is not properly absorbing heat: the condensation freezes. Call Filan & Conner for immediate service.

5- Signs the evap coil needs replacement

Extensive corrosion or damage: When we observe extensive corrosion or damage to the evaporator coil, it is beyond repair. This level of deterioration reduces the HVAC system performance and requires a complete coil replacement.

Chronic leaks: Persistent refrigerant leaks despite repeated repairs are a bad sign. Our technicians will identify a recurring issue of the sort as a sign that patching or repairing the coil is no longer a viable solution.

Inefficient cooling: When the evaporator coil fails to provide adequate cooling even after comprehensive servicing and repairs, it’s a clear indicator for our technicians that replacement is necessary to restore efficiency.

Age of the AC system: The first time you call us for AC service because your unit has frequent issues, we will look at its age. Replacing the evaporator coil is not the first option to consider, but in some aged systems it often becomes necessary to return to a better performance level and regain energy efficiency.

Recurrent freezing: Consistent issues with coil freezing, despite regular maintenance and repairs, indicate the coil is no longer functioning optimally.

Increased energy consumption: A significant increase in your power bills without a corresponding increase in usage is a red flag.

Incompatibility with new refrigerant: With advancements in refrigerant types, older evaporator coils are generally not be compatible with newer, more environmentally friendly refrigerants.

There are only 3 possible outcomes to this case: (a) Conversion of the old system (and evap coil) to the new refrigerant specifications; (b) Complete replacement of the air conditioner; (c) you keep buy the old refrigerant and pay a fortune for it (this is the case with R22 refrigerant today).

Note that converting the system may not even be an option.

Frequent breakdowns: Frequent breakdowns and the need for constant repairs signal to HVAC technicians that the evaporator coil is no longer reliable.

Visible cracks and holes: Visible cracks and holes are undeniable signs that the coil is beyond repair and needs immediate replacement to prevent further damage to the HVAC system.

6- What happens if an evaporator coil is not replaced in time?

System breakdown: Delay replacing a faulty evaporator coil… and you will wind up with a complete system breakdown. Your HVAC unit struggles to function with a malfunctioning coil, and this causes further damage to other components. It will eventually lead to a total system failure.

Increased energy bills: A defective evap coil consumes more energy as the AC unit works harder to compensate for the inefficiency. This results in significantly higher energy bills.

Inadequate cooling: The primary function of the evaporator coil (absorbing heat from the air) is compromised. The result is inadequate cooling, and uncomfortable indoor spaces.

Further damage to the air conditioner: A faulty evaporator coil puts additional strain on other components of the HVAC system. This strain exacerbates wear and tear. Over time, other important parts like the compressor and the condenser will fail. These parts are very expensive.

Environmental harm: Old or damaged evaporator coils often leak refrigerant. These leaks contribute to environmental damage by releasing harmful substances into the atmosphere.

Health risks: A malfunctioning evaporator coil affects indoor air quality as it fails to remove moisture effectively. This will lead to increased humidity levels and potential mold growth, and therefore health hazards for occupants.

Increased repair costs: Continued operation with a faulty evaporator coil entails frequent breakdowns and repairs. These, coupled with the potential damage to other components, lead to escalating maintenance costs.

Reduced system lifespan: The additional strain that a malfunctioning evap coil imposes on an HVAC unit significantly reduces the overall lifespan of the unit. Earlier-than-expected replacement is a costly move.

7- Can homeowners maintain their evap coil themselves?

Never, and for many reasons. The maintenance of the evaporator coil can only be done qualified HVAC technicians who will ensure proper handling, effective repairs, and optimal system operation, safeguarding your investment in your HVAC system.

Here are some good reasons not to DIY it.

Lack of expertise: You can watch YouTube videos, but that does not give you the necessary expertise to do the service or repair of your evap coil. Handle the coil incorrectly and you will cause further damage to it and to the entire HVAC system.

Risk of injury: Generally speaking, handling the components of an AC unit, including the evaporator coil, poses a risk of injury.

Ineffective diagnosis: What if you fail to diagnose accurately the issues with the evaporator coil? A misdiagnosis leads to the wrong repairs, and exacerbates the original problem.

Reduced system efficiency: Ineffective maintenance will reduce the efficiency of the evaporator coil and the HVAC system, and more energy consumption.

Voiding your manufacturer’s warranty: Most manufacturers require their units to be professional serviced. Attempting to DIY the evaporator coil maintenance will usually void your warranty. You will bear the cost of future repairs or part replacements.

Improper tools: Professional HVAC technicians use specific tools. Homeowners typically don’t possess to these tools, which means that they will gerrymander their AC and potentially damage it.

Time: Maintaining or replacing an evaporator coil requires significant time and effort. Are you ready for it?

Environmental concerns: Handling refrigerants requires a special certification, and knowledge of environmental regulations. Handling an evap coil incorrectly can result in refrigerant leaks, contributing to environmental harm.

Cost implications: DIY is great to save on professional service costs. But incorrect DIY will result in unfortunate expenses. An improper repair will most often further damage your HVAC, and cost you much more money.

The best advice we can give you is to trust our technicians to do their job well. Be alert to any sign of malfunction, however. You know your home better than anyone else. If you see an unusual worsening of the performance of your AC, call Final & Conner. We will diagnose the exact issue, and do our best to keep the cost of any repair necessary to the minimum.

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