This project is continued from Part 2.
Interior A-Frame Evaporator Coil Inspection
Homeowners are often concerned the interior (or upwind side) of the A-Frame evaporator coils that are hidden from view may be clogged with mold, algae, dirt, pet hair and other debris. The problem is the A-frame evaporator coils are sealed on both ends by the metal support plates preventing access to the interior of the A-Frame coils. Inspecting and cleaning the interior of the A-Frame coils can be a challenge, especially if you suspect the coils are very dirty.
My attic air handler an “updraft” model (air enters from the bottom right and exits the top) and consists of a natural gas furnace on the bottom with the A-Frame evaporator coils on the top:
Central Air Conditioner A-Frame Evaporator Coils
One may think it should be possible to view the interior of the A-Frame evaporator coils by opening up the gas furnace section, which looks like the following image for my unit. The heat exchangers are arrayed at the top of furnace cabinet – the air conditioner evaporator coils sits on top of the furnace, immediately above the heat exchangers.
Gas Furnace Cabinet and Heat Exchanger
An idea is to remove the inducer blower motor (orange) to look up through the heat exchanger array to the A-Frame coils. This strategy will not work because the heater exchangers are sealed by the blue and green metal baffles, blocking the view of the A-Frame coils. Due to the electrical wiring, pressure switch connection and possibility of causing a problem (i.e. carbon monoxide poisoning) with the gas exhaust or flue vent pipe, I would leave this task to the HVAC professionals if furnace maintenance or repairs were required.
Natural Gas Furnace Parts Diagram
Flashlight A-Frame Evaporator Coil Inspection
An easy way to inspect the interior of the A-Frame evaporator coils with a high intensity flashlight. No complicated disassembly required!
I’m shining my Surefire LED
A-Frame Evaporator Coil Inspection with a Flashlight
I can tell that the inside of the A-Frame evaporator coils are indeed clean because the high intensity flashlight shines brightly through to the far side, reflecting off the foil-faced cabinet insulation:
Air Conditioner Interior A-Frame Evaporator Coil Inspection
Full view of the flashlight on the right shining through the evaporator coils:
Air Conditioner A-Frame Evaporator Coils: Interior Inspection Method
In practice you should place the flashlight on the unobstructed side (i.e. left in my situation) of the coils, then wave it back and forth while watching the beam shine through to the far side of the cabinet. (It was easier to take the photo with the flashlight on the right side.) If the flashlight beam does not shine through the coils, that is strong indicator the interior of the coils are dirty. A small handheld mirror is useful to look back through coils towards the flashlight to see if the coils appear moldy or “hairy”.
Take care not to bump the coil fins with the flashlight or mirror because the fins are very delicate and bend easily.
Heavy Duty AC Evaporator Coil Cleaner
If the interior of the A-Frame coils requires a heavy duty cleaning, a hand-pump sprayer with Nu-Calgon Evap Pow’r®-C AC evaporator coil cleaner is needed to shoot through the coils to clean and remove the interior dirt and crud. The pros use Nu-Calgon and you won’t find it at the big box home improvement stores. The spray wand can reach those tight spaces and the cleaning spray will loosen the dirt and mold off the inside of the coils. I had the evaporator coils at my former home in Florida cleaned this way by an HVAC technician because the air conditioner maintenance had been neglected by the prior homeowner.
Nu-Calgon Evap Pow’r-C 4168-08: 1 gallon bottle
Evap Pow’r-C is mixed 1 part evaporator coil cleaner to 3 parts water, so a 1 gallon bottle should be sufficient for many coil cleanings.
Nu-Calgon Evap Pow’r-C 4168-08: Evaporator Coil Cleaning Instructions
Evap Pow’r-C has an ammonia like odor, but not overwhelming.
Pump Sprayer Evaporator Coil Cleaning Steps:
- Purchase a brand new hand pump sprayer in the 1 gallon to 2-1/2 gallon size.
You don’t want to risk using an old pump sprayer that may have been used for weed killer, insecticide or other poisons!
A 1 gallon pump sprayer is fine if your coils are not heavily soiled and only need a routine cleaning with 1/2 gallon of cleaning fluid & water mixture (remember to leave room in the sprayer for the air charge). A larger 2 or 2-1/2 gallon sprayer is convenient if your coils are very dirty and need a heavy cleaning with several applications of Evap Pow’r®-C.
- Turn the air conditioning system Off.
- Mix 1 part Nu-Calgon Evap Pow’r®-C evaporator coil cleaning solution with 3 parts water (hot water is better) according to the manufacturer’s instructions.
- (Optional) For a heavy cleaning pre-soak:
- Adjust the spray wand to a wide fine spray pattern.
- Spray down the evaporator coils. Let the cleaning solution soak for 5 minutes.
- Adjust the spray wand to a narrow 1/2 inch heavy spray pattern.
- Methodically spray the down the coils; you should see the dirty cleaning solution running
down to the condensate drain pan. Lots of dirt in the condensate drain pan means it’s working. - Check that the spray jet is not so forceful that it’s bending the coil fins.
Most 1 and 2 gallon pump sprayers won’t generate enough force to be a concern, but larger sprayers may. - Wait a few minutes for the cleaning solution to run off the coils.
- Check the condition of the coils with a flashlight as described above.
- Turn On the air conditioner system.
The evaporator coil cabinet cover is removed to expose the A-frame coils. I’ve mixed 1/2 gallon of cleaning fluid [3 pints water + 1 pint Nu-Calgon Evap Pow'r®-C] in a pump sprayer. I don’t need a lot of cleaning fluid since my evaporator coils need only a routine maintenance cleaning.
Cleaning AC Evaporator Coils with Nu-Calgon Evap Pow’r-C
Both sides of the A-frame evaporator coils are methodically sprayed with the coil cleaner. The spray wand is great for reaching way back in the cabinet. The cleaning fluid quickly wicked down the coils and into the condensate drain pan, which is good because it disinfects the drain pan and condensate drain line. There was almost no overshoot past the interior side of the coils because I didn’t hear any dripping noises inside the cabinet and the healthy volume of fluid running out the condensate drain line.
Spraying the AC Evaporator Coils with Nu-Calgon Evap Pow’r-C
If you believe the coils need a second cleaning, wait an hour while the system is running for everything to dry in case some of the cleaning fluid dribbled onto the furnace heat exchangers, this way you won’t have the cleaning solution forming a puddle on the blower motor in the bottom of the unit.
Dirty Evaporator Coil Prevention
The #1 air conditioner maintenance item is to regularly change your air filter. A clogged air filter makes the air conditioner work extra hard, running up your electric bill. Check that the air ducts, plenums (rigid ductwork) and air filter housing are sealed to prevent unfiltered air bypassing the air filter. Unfiltered air which will turn your evaporator coils into dirt catchers. I seal the end of my air filter slot with a strip of metal foil HVAC tape to prevent unfiltered air being being drawn in.
Regular coil cleaning in the Spring and Fall will keep the coils from becoming really dirty.
Hope this helps,
Bob Jackson
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Very helpful in making me informed enough to do he job with confidence. Thank you!
You are a blessing Bob. Thank you for all the valuable information. I now have cold air again…and I am sure my utility bill will decrease.
I searched the web for hours before finding your posting. You are an awesome teacher, and your pictures and your instructions were excellent. Thank you for providing such a great overview and directions on how to clean our air conditioner. I cannot thank you enough.
Thank You!
Thank you so much for these how-to instructions. I feel like I can now clean my evaporator coils with confidence. I live in Texas and have a similarly set up system to the one you have. The pictures helped a great deal and were very well explained. I am going to share your website with my friends!
Thank you for the compliments!
Thanks for the information. I’m doing my pre-planning before I tackle this today. I’m concerned about being able to get clearance inside the cabinet where the coils are, enough to spray the aerosol can of cleaner.
I’ve replaced other items on my furnace previously like the draft motor, and iginitor but this is the first time I’ve been inside the Coil Cabinet also a Heil, similar to your unit.
Thanks again for the illustrations. If I can get some decent photos maybe I will try to send you some.
Follow-up … finished the chore after starting on it about 10:30 and taking 1 1/2 hr trip to Lowes to get a pair of metal snips to cut the housing in order to remove it from the input and output lines. The lines were not as dirty as I thought although 1 side seemed to be worse than the other. The one dirty side had more of a lime like scale which surprised me. The fin comb was great although cleaning the fins was very tedious. With it I was able to straighten some of the fins. I don’t think the unit had ever been accessed before. I will probably try the cleaner again in about 30 days. The one can of aerosol probably wasn’t enough.
Thanks for the walk through. It gave me a lot of confidence to get it done.
Odd that tin snips were required to cut the cabinet panel away from the refrigerant lines. Please send photos to bob (at) handymanhowto.com [replace the (at) with the @ symbol]. I’m happy you were successful. Now’s the time to clean the evaporator coils before warm weather sets in. Thanks for writing.
Thank you so much for this Bob, easy to follow and step by step. Saved me an expensive service call!!!!