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How to Clean Air Conditioner Coils (With Pictures)

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Dan has been in the HVAC industry for 23 years, with experience ranging from installation and service to sales and distribution.

AC units need spring cleaning.

AC units need spring cleaning.

Saving Money on Air Conditioning Is Easy

As much as we all want to stay cool and comfortable during the summer months, we also want to keep from going broke in the process. As if utility and potential repair costs aren't enough, you're likely being told that a spring cleaning is the best medicine for your unit and will only cost you about $150.

While I'm sure you're grateful that the nice person you're working with has brought this to light, spending an additional $150 to kick off the summer isn't likely what you had in mind when you asked them how to save money and keep your unit running efficiently. Of course, if they're standing there, you're likely already out $75 just to be in their presence. Are you feeling the heat yet?

Do A/Cs Really Need Annual Cleaning?

That spring cleaning you're being offered is the best medicine, but while a professional HVAC technician is worth the money in most cases, this is not one of them. With the information in this article, not only will you be able to clean your own air conditioner, but you'll be able to do it for little to no cost and understand why it is important.

I believe we put off certain chores because we don't understand why they are important and, therefore, we improperly prioritize them. Perhaps understanding more about how air conditioning works will motivate us to keep up on this maintenance and help us recognize why it will pay off.

The Three Main Components of an Air Conditioning System

The three main components I will cover are:

  • Condenser
  • Evaporator
  • Line set

We will touch on other items, but the functions of these parts are the ones that most do not understand.

That said, if you ever see your "low side" frosting or icing up, you either need to change your filter or call a professional as this will not be something you can fix. Running the A/C in this state can cause major damage to your system. If it ices up, shut off the A/C and run the fan only on your furnace to defrost the coil and lines.

The Line Set, Evaporator, and Condenser Explained

The Line Set: This is the easiest part to describe. These are the two copper tubes that carry refrigerant back and forth between the condenser and the evaporator. The larger insulated tube is referred to as the "low side" or suction line. It carries refrigerant in its gaseous state through the evaporator and back to the condenser. The smaller uninsulated tube is referred to as the "high side" or liquid line as it carries refrigerant from the condenser to the evaporator in its liquid state.

The Evaporator: This is the indoor component that is located on the top of your furnace or air handler. As the liquid refrigerant enters the coil, it passes through a metering device of some type. In short, this device controls the amount of refrigerant that enters the coil where the tubing is now increased in diameter. This limitation of refrigerant and increased volume capacity causes a significant drop in pressure. Since pressure and temperature greatly affect each other, the drop in pressure causes the boiling point of the refrigerant to drop significantly as well as its temperature. Now the coil, compared to our home, is a cool 65 degrees (approximately) while the boiling point of the refrigerant is somewhere around 55 degrees. This means the liquid refrigerant has boiled off into a nice heat absorbing gas. As the warm air from our home passes over these coils, the heat is absorbed into the refrigerant and sucked back to the condenser. The humidity in this air then collects on the coil like it does on a glass of ice water on a summer day. This condensation runs down into the drain pan at the bottom of the coil and is discharged by the pipe attached to it.

The Condenser: This is the outdoor unit that really powers the whole operation. As the gaseous refrigerant that now contains the heat it has absorbed from the home returns to the condenser, it passes through all those coils you see wrapped in fins and around the compressor. As the fan in the A/C pulls air across the coils, they are cooled. As the coils cool, the gaseous refrigerant begins to return to a more liquid-like state. The compressor then finishes the job by increasing the pressure the refrigerant is under thus increasing its boiling point. This much higher boiling point now means that the refrigerant is turned back into a liquid since it is not nearly hot enough to boil over. This liquid is now pushed back into the skinny copper line and returned to the coil to start the process over again.

Why Is It Important to Clean the Air Conditioning Coils?

Now, there are a few more technical terms, parts, and science to this process we call air conditioning but I feel confident that most of you now know more about how your air conditioner works than you did when you started reading this article. Knowing what you know, how about a little quiz to explain why we need to clean our coils. It's only 4 questions, and I'm pretty sure you'll pass.

Items Used for Cleaning A/C Coils

There are a lot of tools used in HVAC; however, this project will mostly require items you likely have around the house. There are a few things you may want to purchase to do a better job, especially if you're going to continue doing this for yourself in the future.

If you cannot afford to make any purchases, the below steps will still help you to make a difference in the health of your A/C by explaining the tear down of the unit and how to do what you can with what you have.

What you'll need to clean your air conditioner's coils.

HoseDrill or Hex DriverSoft Paint or Toothbrush

Spray Bottle

Coil Cleaner

Zip or Wire Tie

Side Cuts

Coil Comb

Non-Absorbant Gloves

Most things in this list you should be able to find around the house. A coil comb (needed in step 5) and coil cleaner (needed in step 7) are the only exceptions to this. Take a look at each step below for my recommendation on what you should get.

How to Clean Air Conditioning Coils

Step 1: Turn Off the A/C at the Thermostat and Shut Off the Power to the Condensing Unit

First, you need to turn off the A/C at the thermostat and shut off the power going o the condensing unit. You can do this by opening the disconnect mounted to the house near the unit and removing the stab connection or fuses. Just pull the handle that you see and the terminal should come out. If you do not have a disconnect for some reason, shut down the power at the breaker panel. There should be a dedicated breaker for your A/C.

  • IMPORTANT NOTE: Pulling the disconnect cuts the power to the unit, NOT to the disconnect. Electricity is still being supplied to the disconnect itself. Only the breaker at the panel can cut the power to the disconnect itself.

DO NOT SKIP THIS STEP! Our safety is most important when working on any electrically powered appliance.

Step 2: Remove the Top of the Condenser

With the power off, remove the top of the condenser. Remove the bolts that are attaching the lid to the rest of the condenser but not the bolts that hold the fan to the lid. Leave the fan attached as shown in the pictures. You can use your hex driver or drill to remove these bolts which are usually 1/4", 3/8" or 1/2".

Set the lid with the fan attached aside. Hopefully you have enough slack in the wiring to do so but if not, it is likely because the slack is tied up inside the access panel. If you remove the access cover, you can cut the tie on the wires and should be able to obtain the slack you need. Again, the power is off so there is no worry about shock, just be sure not to cut or nick the wires as you cut the tie. Also be sure the metal on the unit doesn't cut or nick the wires as you maneuver the lid around to a stable resting place. This is a good time to use a paper towel or paint brush to clean out the webs and dirt inside the access panel.

  • IMPORTANT NOTE: Pay attention to how the wires are wrapped inside the access panel so that you can tie them back in a similar manner when you're done. Do not disconnect any wires. If you find that you cannot do this without disconnecting wires, contact a professional. Misplacement of wires can cause immediate damage to your unit and present potential safety hazards.

Step 3: Remove the Caging

Now with the top off, we should be able to remove our caging. If you have a metal casing or cabinet around your condenser, the theory here will still be quite the same. Remove the bolts at the base of the unit that are attached to the cage and it will come off rather easily. Again, use care as we don't want to smash down any more of those fins than are already.

Step 4: Clean Out the Debris in the Base of the Unit

Clean out the debris in the base of the unit where the compressor is located. Leaves and other of natures falling gifts get into the top of the unit when it's not running. When they get wet and decay in the unit, they promote corrosion and in the summer form a blanket of insulation under the compressor that decreases the airflow that we need to help cool the compressor.

Step 5: Comb Out the Smashed Fins

We want to open the fins up first so we will be able to clean the space between them. Here's where we need this little air conditioning coil comb. Make sure you're using the side of the comb with the properly spaced teeth or you will cause more damage than good.

Also, do not force the comb through any areas that are resistant. You will tear these very thin pieces of metal. Give the comb a little wiggle as you work through a dented area. Lastly, if you don't have this comb, you could use a butter knife or something similar. The only down side here is that it takes a bit longer.

Step 6: Presoak the Unit

Go ahead, hose that thing down. Spray from the inside out to push back what was trying to be sucked in. You want to avoid spraying directly at the disconnect or the electrical components inside the access panel but a splash here and there isn't going to hurt anything. Other than that, let her have it. It's built to be outside so water isn't going to harm it at all. Pay attention to the outer base of the unit where heavier grass deposits are likely to build up.

Step 7: Spray the Coils Down With Your Cleaner Mix

Cover the coils front and back, bottom to top with a healthy dose of your coil cleaner. Let the cleaner sit for a bit and then hose it down again. Follow the directions provided by the manufacturer of your coil cleaner for mixing ratios and stand time. These may very a bit based on the product you choose.

I suggest a self cleaning, non-corrosive type of cleaner that is environmentally sound, such as this Nu-Calgon brand coil cleaner. It works well, gets things very clean, and is reasonably priced.