Most homeowners think about their air conditioner in simpler terms: it either cools your home or it doesn’t. But there is a lot happening inside that system that quietly determines how well it performs and how much it costs you to run it every month. One of the most overlooked culprits behind an underperforming AC is something you don’t see without opening the unit: dirty coils.
Whether it is the evaporator coil inside the air handler or the condenser coil in the outdoor unit, both are important in the heat exchange process that makes cooling possible. When either gets covered in dirt, dust, grime, or algae, your entire system will pay the price.
Know what that means for your home, your comfort, and your wallet. Contact Aire Serv of Louisville for reliable HVAC Services.
The Two Coils Every Homeowner Should Know About
Before you can fully understand what can go wrong, you need to understand what these coils actually do.
The Evaporator Coil (Indoor Unit)
The evaporator coil is located inside the air handler or furnace cabinet. Warm hair from your home passes over this coil, which contains cold refrigerant. The refrigerant absorbs the heat from the air, and the now-cooled air gets pushed back into your home. Any moisture in the air condenses on the coil and drains away, which is also how your AC dehumidifies your home.
Since the coil is always wet from condensation and is constantly exposed to airflow, it is a prime environment for dust, mold, and mildew to accumulate, especially when the air filter is not changed regularly.
The Condenser Coil (Outdoor Unit)
The condenser coil is the big metal box that sits outside your home. After the refrigerant absorbs heat from inside, it moves to the outdoor side and releases that heat into the outdoor air through the condenser coil. A large fan pulls air across the coil to help dissipate the heat.
Since this coil is exposed to outdoor elements year-round, it collects whatever is in the air around it: grass clippings, cottonwood fluff, dirt, pollen, and debris. In the spring and summer, the weather is hard on outdoor coils due to humidity, and buildup can occur faster than most people realize.
What Happens When Coils Get Dirty
Both coils work for the same principle: they need unrestricted airflow and clean surfaces to transfer heat efficiently. When that surface gets covered in grime, the heat transfer is compromised.
Your AC Loses Cooling Capacity
A dirty evaporator coil cannot absorb heat from the air as effectively as a clean one. The layer of insulation that dirt creates impedes heat transfer. The result is that the air coming out of your vents is not as cold as it should be, even when the system is running full blast. Your home stays warmer than the thermostat setting, and you keep turning it down without getting any relief.
The System Runs Longer to Compensate
When the coils cannot do their job, the system must run longer cycles to achieve the same level of cooling. What used to take 15 minutes to cool down may now take 25 to 30. That extra runtime adds up fast on your monthly electric bill.
The Compressor Gets Overworked
The compressor is the heart of your cooling system and is the most expensive component. When dirty coils force the system to work longer and harder, the compressor bears the strain. Overheating becomes a risk, and an overworked compressor wears out faster than one that is operating under normal conditions. Replacement can be very expensive, a cost that proper coil maintenance could have prevented.
Indoor Humidity Control Suffers
The evaporator coil does more than just cool the air; it also pulls moisture out of it. When the coil is dirty, the dehumidification process is impaired. If your home feels muggy and sticky even with the AC running, dirty coils can be the reason. High indoor humidity is uncomfortable, but it also creates conditions where mold and mildew can form in your ductwork and throughout your home.
You May Experience Frozen Coils
When an evaporator coil is dirty, airflow is restricted. Without enough warm air moving over the coil, the refrigerant inside gets too cold and begins to ice over. A frozen coil blocks airflow almost entirely and can cause water to overflow from the drain pan when it melts. If you have noticed ice on the copper lines near your indoor unit, a dirty coil is often the cause.
Air Quality Inside Your Home Declines
A dirty evaporator coil is a breeding ground for mildew, mold, and bacteria. Every time your system runs, air passes over that coil, carrying those contaminants into your home. If anyone in your home has allergies or respiratory sensitivities, a dirty coil can affect how they feel day to day. It is one of those HVAC issues that goes well beyond comfort and into the realm of health.
Warning Signs Your Coils May Be Dirty
You do not have to open your system to get a sense of coil buildup. These are the signs worth paying attention to:
- Rooms that used to cool quickly now take longer to reach the set temperature
- Your AC runs almost continuously on days when it used to cycle on and off normally
- Energy bills are higher than last year during the same time period, with no obvious explanation
- The air coming from your vents feels less cold than it should
- You notice musty or stale odors when your AC runs
- You can see visible debris, cottonwood, or grass clippings packed against your outdoor unit
- There is ice on the refrigerant lines or the indoor unit
- The area around your indoor air handler feels more humid than usual
Any one of these on its own might have another explanation. But if two or three are showing at the same time, dirty coils are often the reason.
How Often Should Coils Be Cleaned?
For most Louisville homes, once a year is recommended, typically in the spring before cooling season. That said, here are a few factors that may require you to clean your coils twice a year:
- Pets in the home (dander and hair can accelerate buildup on the evaporator coil)
- A home near construction, farmland, or heavily wooded areas with cottonwood
- Anyone in the home with allergies or respiratory conditions
- An older system with less efficient air filters
- A system that runs nearly year-round because of long warm seasons
The condenser coil in your outdoor unit needs a quick inspection once a month or every other month during the cooling season. If you can see debris packed against the fins, a gentle rise can help. But a proper professional cleaning goes much deeper than that. Contact Aire Serv of Louisville today to schedule your coil cleanings.
What a Professional Coil Cleaning Involves
Rising off the outdoor unit is a start, but a thorough coil cleaning by a certified HVAC technician is a different level of service. Here is what that process looks like:
- System Shutdown and Safety Checks: Our technicians power down the system safely before any cleaning begins.
- Access and Inspection: Both the evaporator and condenser coils are accessed and evaluated for the extent of buildup, corrosion, or damage.
- Brushing and Bacuuming: Loose debris is removed from the fins and coil surfaces before any liquid cleaner is applied.
- Application of Coil Cleaner: A professional-grade, low-foaming coil cleaner is applied and allowed to penetrate the buildup. The type of cleaner varies based on the coil and the degree of contamination.
- Rinsing and Flushing: The coil is then rinsed thoroughly, including the condensate drain pan and drain line to prevent clogs.
- Fin Straightening: Bent or crushed fins on the condenser coil are straightened with a fin comb to restore proper airflow.
- System Restart and Performance Check: Our technician will then turn the system back on, verify pressures, temperatures, and airflow, and confirm the system is operating within normal parameters.
Can You Clean Coils Yourself?
There are coil-cleaning sprays sold at hardware stores, and some homeowners use them with reasonable results. For the outdoor unit, removing obvious debris and rinsing the coil are tasks homeowners can safely handle. A few things to keep in mind if you do go that route:
- Always turn the power to the unit off at the disconnect box before touching anything
- Never spray water directly into the electrical components or the fan motor
- Spray water from the inside out if possible, pushing debris out rather than in
- Avoid pressure washers, which can easily bend the delicate aluminum fins
- Do not use harsh degreasers not designed for HVAC coils
The evaporator coil is a different story. This involves removing access panels from your air handler, and the coil is in a much more confined and delicate space. Applying the wrong cleaner or using too much pressure can damage the fins or, worse, introduce moisture into areas where it does not belong. For the evaporator coil, professional cleanings from Aire Serv of Louisville are a safer option.
Best Ways to Protect Your Coils: Regular Maintenance
The most effective way to keep your coils clean is to change your air filter on schedule. A clogged filter is the primary reason evaporator coils get dirty. When the filter is overloaded, it stops effectively capturing particles, allowing them to drift onto the coil surface. Most Louisville homes should be changing their standard 1-inch filters every 30 to 60 days during the cooling season.
Beyond filter changes, a yearly maintenance visit from Aire Serv of Louisville is your best protection. Our tune-up service includes coil inspection and cleaning as part of a comprehensive system check, so you can go into each summer knowing your equipment is clean, efficient, and ready for the heat.
Why Louisville Homeowners Trust Aire Serv
At Aire Serv of Louisville, we know how hard your AC works during the summer. We have seen firsthand how much of a difference a clean, properly maintained system makes in comfort, energy costs, and equipment longevity. We show up on time, we explain exactly what we find, and we back every job with the Neighborly Done Right Promise®.
Whether you are due for a seasonal tune-up, dealing with a system that isn't performing as it should, or just want to make sure your coils are in good shape before the heat arrives, we are ready to help.
