This is continued from Part 1.
Evaporator Coil Inspection
This is a closeup of my evaporator coils before cleaning. The coils look very clean already because I service my system regularly. Of some concern is the rust on the ends of the frame. The unit is about 9 years old and rust is common in these areas. The greenish/whitish discoloration on the copper refrigerant lines is from dissolved copper deposits that have dried. The plastic drain pan looks in good condition with no cracking or leaks. Overall, not too bad for a 9 year old evaporator coil. I should expect to replace the coil and/or air handler in a season or two as it approaches the end of its expected life.
Air Conditioning Evaporator Coils
For comparison, click here for photos of some really dirty evaporator coils. If yours looks really bad, you should consider hiring a professional HVAC technician because you may need to:
- Remove the gas furnace section to get access to the inside of the A-frame coils from underneath for a thorough cleaning inside and out.
- Remove the coils for cleaning and/or replacement.
Air Conditioning Coil Cleaner
I purchased a can of Frost King Air Conditioning foaming / no-rinse coil cleaner from Home Depot, which did a good job. You might also look at professional products such as Nu-Calgon coil cleaners and sprayers that are widely available on eBay.com.
Frost King - Foaming Air Conditioning Coil Cleaner
Cleaning the Evaporator Coils
The foaming coil cleaner is sprayed directly on the coils, coating the surfaces evenly and thoroughly. It’s best to do this on a warm day when the A/C will be running to help rinse the coils with condensate water.
Applying Foaming Coil Cleaner Spray
The spray foams nicely on the coils.
Foaming Detergent Action on the Evaporator Coils
The no-rinse foam cleaner breaks down and liquifies quickly for a good rinsing action.
Foam Cleaner Breaks Down and Liquifies Quickly
In minutes the foam is rinsing itself off and draining away. Always check the PVC drain line is free of algae and unclogged. I poured a quart of 50/50 solution of household bleach and water in the drain pan to keep the line clear. You can also buy time-release algae tablets to drop in the drain pan.
Closeup of the Plastic Drain Pan and PVC Drain Line
The access panel is reattached with the sheet metal screws. The top and bottom seams are sealed with metal foil tape.
Reattach the Evaporator Coil Access Panel and Seal with Metal Tape
Take care not to tape over the manufacturer’s label on the access panel.
Evaporate Coil Access Panel
The attic air handler is now ready for another hot summer of cooling. The last task is to turn on the thermostat.
Attic Air Handler - Ready for Summer
The Basics
By now you know the basic parts of the attic air handler and the importance of changing the air filter and performing routine system maintenance. If you need to talk to your HVAC technician, you’ll be able to better follow what he’s talking about. Annual Service Contracts are available from HVAC companies and usually cost less than the sum of ad-hoc maintenance calls.
Stay cool!
Bob Jackson
July 6th, 2009 at 4:44 pm
thanks for the great educational site and great pictures
August 4th, 2009 at 11:56 pm
Does this also clean inside coils. My outside one like the one in your picture looks clean however using a mirror and flashlight I saw that the inner part is really dusty and the AC Tech guy said it would be about $200 to get the Coil out and clean it
August 5th, 2009 at 7:20 am
It’s depends on how dirty the inside surface of the coils are. Regular cleaning will prevent buildup on both surfaces.
If you believe the inside of the coils need particular attention try an acid-based cleaner and pump sprayer with a wand to apply the cleaning chemicals with a bit more force to loosen the dirt on the inside surface.
Don’t spray too hard or the solution will shoot through the coils and rain down onto the heater and blower fan section if you have an updraft model like mine. You want the cleaning solution to wick down the coils and into the condensate pan.
Pump sprayer: http://www.nucalgon.com/products/coil_cleaners_calshieldsprayer.htm
Acid-based cleaner: http://www.nucalgon.com/products/coil_cleaners_calbrite.htm) with the pump sprayer.
A gallon of Cal-Brite will cost you about $30 and figure another $15 for the sprayer – call it $50 for supplies, plus your time and labor. You’ll need gloves and safety glasses, too. If the results are not satisfactory, you’ll be making that service call for a professional cleaning for $200, bringing the total cost to $250.
If I were in your situation, I’d call the professional to give the coils a thorough cleaning inside and out – and – have the A/C tech check my duct work for leaks may be allowing dirt to get past the filter and onto the coils.
August 20th, 2009 at 12:49 pm
Thanks for great write up. This is the only one that I searched that shows how to clean the ac evaporator coil (inside the house). Most others show how to clean the condense coil (outside of the house, I think) but since your write up is so detailed, I’d would love to see one from you if available.
Thanks
September 11th, 2009 at 5:17 pm
Thanks Bob, this is what I needed. I this article with a lot of details and pictures.
November 2nd, 2009 at 4:38 pm
I wasn’t to sure what spray to use on my indoor coils so this really helped out. Short, with important details and straight to the point.
Thanks
November 27th, 2009 at 7:57 pm
I applied Nu Calgon foam self rinse cleaner today to my evap coil in the attic. I am not running a/c as outside temps are cool (high sixites). Will I need to rinse with a sprayer?
November 28th, 2009 at 9:01 am
The Nu-Calgon Evap Foam aerosol spray can is a “no rinse” product.
Link: http://www.nucalgon.com/products/coil_cleaners_evapfoam.htm
January 10th, 2010 at 8:36 pm
great article, my question now is that it is now winter time and i want to clean my inside heatpump coils like what is described in this article and since it is heat not cooling season should i rinse the coils off carefully with a pump up garden typ sprayer just enough that it will drain into the condesate pump tank. Also, is it a good idea to lightly spray a diluted mixture of water and chlorox to kill any mildew that may be there, let it set for a few minutes then rinse it off as well.
January 11th, 2010 at 7:20 pm
The no-rinse coil cleaning products don’t need rinsing, but since it’s heating season you should shut off the heat until the foam breaks down and drains off the coils along with the dirt. The weak bleach and water rinse would hurry the rinsing action, but shouldn’t be needed with the coil cleaner as it disinfects. If in doubt, give it another shot of no-rinse coil cleaner.
Should something be sticking to the coils, it can be oh-so-gently brushed away with a very soft bristle brush. The coil fins are very fragile and bend easily – go slowly and check your work.
If you do use bleach and water, take care to spray lightly such that you don’t shoot through the coils and drip onto the gas burner and blower motor. The spray should always adhere to the coils and wick it’s way down to the condensate drain pan.
For light mildew concerns – that is so light you can’t really see it but suspect something is always living in a moist environment – give the insulated cabinet walls a good shot of Lysol spray.
January 11th, 2010 at 8:23 pm
thanks for quick reply, great site.
My heat pump is a trane unit. Going to clean mine this weekend like what you described in your article. Once i spray everything good with the lysol should i let the unit stay off for a while? I plan on cleaning the coils twice and vacumming out the insulated cabinet walls the best i can, i have duck board instead of metal.
January 12th, 2010 at 5:23 am
> Once i spray everything good with the lysol should i let the unit stay off for a while?
You don’t have to wait for the Lysol to dry. It does the job on contact.
Not sure about vacuuming the cabinet walls, use a brush attachment so it doesn’t grab and pull the insulation off the duct board.