An understanding of how to clean AC coils and why you should do so goes a long way toward maintaining the health of your home's central air conditioning system. The first step in AC cleaning is knowing what parts perform which functions and where to find the ones that require attention.
Your central air conditioner system has two different coils: the condenser coil and the evaporator coil. The condenser coil is part of the big outdoor unit and actually forms the walls of the unit. The evaporator coil is smaller and sits inside your furnace housing or in a separate air handler unit, if you have one. The outdoor coil gets dirtier and needs more frequent cleaning because it's exposed to the elements, but it's a good idea to check the evaporator coil and clean it as needed along with your regular AC maintenance.
Keeping both coils clean is crucial, not just to optimize the performance of your AC but to ensure your system operates with as little maintenance and repair trouble as possible.
How Often to Clean AC Coils?
Most homeowners with a central air conditioning system find that thoroughly cleaning the condenser and evaporator coils or having them professionally cleaned once a year in spring is adequate for solid AC performance. However, depending on the conditions in your location, two cleanings per year may be necessary for the best system performance and efficiency.
Because the evaporator coil is enclosed and indoors, it is much less prone to collecting debris than the exterior condenser coil. In all but extreme cases, an annual deep cleaning followed by regular furnace air filter changes throughout the cooling season is enough maintenance to keep things running smoothly at the evaporator coil.
The outdoor condenser coil is constantly exposed to dust, leaves, pollen, and other plant debris, all of which can land on the unit and restrict airflow through the coil. While an annual deep cleaning is crucial, the conditions in your area will determine how often you'll need to at least brush off the coil fins from outside the unit during the summer. In locations that experience a large amount of wind-blown dust and debris, or if your AC is in constant use throughout the season, two thorough cleanings may be necessary each year.
How Does AC Work?
Contrary to common belief, a central AC system doesn't directly cool a home's interior. Instead, it removes heat from the indoor air and transfers it outdoors. This is the same process used by a refrigerator but on a much larger scale.
The process of absorbing and releasing heat is pretty straightforward. The system's refrigerant (commonly called Freon, after the well-known refrigerant brand) readily transforms from a liquid to a gas depending on temperature and pressure. The conversion of gas to liquid and back allows the refrigerant to absorb and release heat at various stages within the system.
Regardless of the AC system's size or brand, the component that starts the process is the air conditioner's compressor. Besides the blower fan that distributes the conditioned air through the home, the compressor is the system's workhorse. It works so that the other two crucial components, the condenser and evaporator coils, can allow the refrigerant to do the rest of the work.
AC Evaporator Coil
An evaporator coil is inside the air handler section of your home's furnace system. The coil is often shaped like an upside-down letter V and consists of zigzagging copper tubing (containing the refrigerant) running through a collection of thin metal plates called fins.
Inside the evaporator coil, the refrigerant is in its gaseous state while passing through the copper tubing. A blower fan in the system (often the same fan the furnace uses) pulls warm air from inside the house and passes it through the evaporator's fins. The refrigerant gas absorbs heat from the moving air and leaves the evaporator, heading for the compressor and condenser for the next steps.
AC Condenser Coil
In the compressor, the refrigerant gas with the collected heat becomes compressed and is forced outside through copper tubes leading to the condenser coil. The condenser coil is the often sizable exterior AC component with copper tubing and fins similar to the evaporator coil. However, the condenser's coil usually creates the unit's walls, which house a large fan and motor.
Inside the condenser, the compressed gas expands and gives off heat while the refrigerant turns back into a liquid as it cools and heads back indoors to repeat the cycle. The condenser coil's large fan turns on intermittently to dissipate the collected heat into the surrounding outdoor air.
Why Clean AC Coils?
Cleaning AC coils improves efficiency, minimizes wear on the equipment, and saves you money on electricity and repair bills. Checking the coils is also one of the first things do when you have an AC not cooling.
- The coils rely on airflow through the fins to absorb and release heat efficiently. Dust and debris on the coils insulate them from the air that passes over them and reduces the entire system's efficiency.
- The reduction in efficiency due to dirty AC coils also reduces the system's ability to remove humidity from the indoor air. Higher indoor humidity coupled with warmer air is a recipe for discomfort.
- Because the system must work harder under dirty coil conditions, it requires more energy to operate, which increases your monthly electric bill.
- Dirty AC coils also insulate against heat dissipation, which means the system runs at a higher temperature than it should, potentially resulting in a shorter life span or higher and more frequent repair bills.
Things You'll Need
How to Clean AC Coils — Outdoor Unit
Cleaning the outdoor condenser coil requires about an hour of your time, and you likely have most of the necessary tools.
Use caution when working around any electrical device. When working around the fan of a condenser coil, stay well away from any capacitors near the fan motor or mounted to the fan support. These devices store energy even after the power is turned off to the unit and can cause electrical injury anytime they hold a charge. Capacitors may look like cylinders, rectangles, or battery-pack-shaped devices.
1. Turn Off the Power to the AC Unit
Locate the main disconnect switch near the unit or the system circuit breaker inside your home's electrical service panel (breaker box). You may see a metal box mounted to the house near the condenser unit. Inside is a switch of some sort that disconnects power to the unit. The switch may be one you simply flip from ON to OFF, or it may have a handle you pull out to disconnect power.
Flip the switch to the OFF position, or remove the handle and reinsert it upside down so the word "OFF" is visible. If there's no metal box near the unit, switch the AC breaker in the home's service panel to the OFF position.
2. Open the Condenser Unit
Your AC condenser may include louvered metal covers or a metal cage-like framework on each side. Remove the screws or nuts that secure the covering to remove these covers, including the top piece.
If possible, remove the screws, nuts, or bolts securing the fan in place, disconnect the fan wiring harness, and set the fan aside. If the wiring harness doesn't have an easy disconnect, set the fan aside on a support near the unit or leave the fan in place.
3. Clear Debris From the Fins
Use the bristle brush and wet/dry vacuum with a brush attachment to remove dust and debris from the outside and inside of the fin surfaces.
4. Repair Fin Damage
Use the fin repair comb to brush out any dents or bends in the fins surrounding the copper wiring. The fin comb won't restore damage to perfect condition. However, it will open up the fins to restore proper airflow.
5. Clean the Coil
Spray the evaporator coil cleaner onto the inside and outside of the condenser coil and fins. Following the manufacturer's instructions, wait 10 to 15 minutes and rinse with a garden hose using a gentle spray pattern from the sprayer nozzle. Start inside the unit and finish by rinsing off the outside.
AC Coil Cleaner
Air conditioner coil cleaner is available at hardware and home center stores. Often sold in aerosol cans, it's a foaming, heavy-duty dirt remover and degreaser that you can spray directly onto indoor and outdoor AC coils. However, use caution when using it indoors by protecting nearby items and working in a ventilated area. The product is also available in nonaerosol forms that contain similar ingredients.
While most coil cleaner products are available in no-rinse formulas, you can still rinse off the coils with water after using them if you wish.
You can also make a homemade coil cleaner by mixing 1 teaspoon of dishwashing soap with 1 cup of water in a spray bottle. This solution should be rinsed after cleaning.
6. Put the Condenser Back Together
Reinstall the fan and protective metal covers. Allow the unit to dry thoroughly before turning on the power to the air conditioner unit.
Things You'll Need
Can of compressed air or compressor with blower attachment
Soft- to medium-bristle brush
Fin repair comb
AC coil cleaner
Spray bottle with water
Stiff wire or pipe cleaner
How to Clean AC Evaporator Coils Inside House
Cleaning the indoor evaporator coils will take up another hour of your time and is a little trickier than cleaning the outdoor unit. Refer to the owner's manual for your furnace or AC system if you have trouble locating or accessing the evaporator coil.
Replace your furnace filter regularly to keep both the furnace unit and the evaporator coil (not to mention your indoor air) as clean as possible. Filters should be replaced every 1 to 3 months, depending on how dirty they get.
1. Turn Off the Power
Turn off the power to both the indoor and outdoor units. For the outdoor unit, use the disconnect switch located in the box near the unit (see Step 1 above) or the AC system's circuit breaker in your home's electrical service panel (breaker box). For the indoor unit (furnace or air handler), turn off the appropriate breaker in the service panel.
2. Access the Evaporator Coil
Your evaporator coil is typically inside your furnace's blower compartment. Locate the access panel for the coil by identifying a metal panel with one or more screws holding it in place. Remove the screws and lift out the access panel.
3. Remove Dust and Debris
Use a can of compressed air or an air compressor with a blower nozzle to dislodge any dust and debris from the coils. Use a soft- to medium-bristle brush to help remove the dust from areas you can reach. Wipe up fallen dust and debris from the drain pan below with a soft, damp cloth. Wipe down any other surfaces within the air handler that you can reach.
4. Repair the Fins
Use a fin repair comb to fix any dented or bent fins. If you're unable to reach damaged areas or if the damage is severe, consider contacting a professional for assistance.
5. Clean the Coil
Spray the surface of the fins with coil cleaner. Allow the compound to work for 10 to 15 minutes, then spray the areas with tap water from a spray bottle to rinse off excess coil cleaner. Work slowly to allow the water time to make its way down the drain hole.
6. Clean the Pan and Drain
Directly below the evaporator coil is a drain pan with a hole in it, typically connected to a drain line that leads away from the furnace or into a condensate pump. Insert a stiff wire or pipe cleaner into the drain hole to clear any debris. Follow up by pouring 1/8 cup of bleach into the hole to kill any organic material in the drain.
7. Replace the Evaporator Cover
Allow the coils to dry for 30 to 60 minutes before reinstalling the access panel cover and turning on the power to the AC units.
Air Conditioner Cleaning FAQs
Does cleaning AC coils really help?
Dust and debris are excellent insulators against airflow and heat transfer. For these reasons, cleaning your AC coils really helps to maximize performance and to give your system its best chance for a long life while saving money on your electricity bill.
How long to wait before turning on AC after cleaning coils?
Typically, your air conditioner will be dry enough after about an hour to turn the system back on and resume air conditioning. In humid conditions, drying will take longer.
Can you clean the inside of a window unit AC?
You can clean the inside of your window AC unit in much the same way as you would clean central air conditioner coils. However, the process happens on a much smaller scale, and accessing the coils can be challenging on smaller units.
When to Call an HVAC Pro
While AC cleaning is an excellent DIY project for homeowners who are willing to get a little dirty and who have some patience, sometimes, calling in an HVAC professional is necessary. In fact, at the very least, have a service technician inspect or inspect and clean your system once a year before the cooling season. Call a pro if an electrical system component fails to work after cleaning the coils or if you encounter fin damage that's not repairable with a fin comb.