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.
June 14th, 2010 at 6:49 pm
how often should I change the main filter ??
June 15th, 2010 at 4:43 am
Change your A/C filter at least monthly during the heating or cooling season. More often if you notice the filter is dirty. A dirty filter obstructs the airflow, lowers efficiency and raises your cooling or heating bill.
A good digital thermostat will have a “Change Filter” reminder to change the filter after the 10 running days, which equates to 240 hours of operation. I use Honeywell Digital Touchscreen thermostats with programmable schedules in my home. See the VisionPRO 8000 7-Day Programmable Thermostat.
June 17th, 2010 at 4:04 pm
Just had HVAC tech out for recent leak into ceiling. He said coil was not installed level,is now rusted, and requires replacing along with plenum. Is it possible to repair/clean coil instead? Also recommended replacing outside condenser unit to correspond with new coils on the market. Is it possible to find the older model coil? Unit is ~11 years old.
June 17th, 2010 at 5:34 pm
Which part is rusted? The coil fins and refrigerant tubes? Or only the end plates of the A frame? Is the rust cosmetic or is the structural integrity of the A frame threatened? Are the coils leaking refrigerant?
Cosmetic rust can be ignored, but will eventually become a problem. Really dirty coils usually can be cleaned, though it will take more than a casual cleaning with an aerosol spray, requiring a pump sprayer, brushes and special coil detergent by a pro.
The HVAC tech is giving you good advice: If the evaporator coil is being replaced, why not go with current products that are more efficient? The evaporator coil is matched to the condenser unit and is the reason for replacing both.
I would think you can get a direct replacement for your old coil. A few phone calls with the make, model and serial # of your air handler should answer.
June 23rd, 2010 at 2:49 pm
how often do you need to replace a coil and how expensive? Sometimes it gets frozen up?
June 23rd, 2010 at 7:25 pm
An average evaporator coil should last maybe 10 years or longer if the system is well maintained. The parts cost for a replacement coil will vary with the brand and size (tonnage) of the A/C system; usually in the range of $300 for a 2.5 ton A frame to $750 for a 5 ton unit. Labor to drain the refrigerant, remove the old coil, install the new unit and recharge the refrigerant will be extra – several hundred dollars.
> Sometimes it gets frozen up?
I’ve fortunately not had this happen to me. For advice see Troubleshooting a FROZEN Evaporator Coil at HVAC Parts Outlet.
June 29th, 2010 at 3:09 pm
The A Frame in my unit is aluminum. It is 10 years old and looks to be in great shape. It is however freezing up and the tech tells me that there is sludge clogged inside the coils and the entire A frame must be replaced. He said he tried to blow it out and pushed 200 psi through. He also said they need to install an inline dryer and filter. This is going to get real expensive but he says it is all he can do as he cannot get the unit above 31 degrees and it will just freeze up again.
June 29th, 2010 at 4:55 pm
The sludge in the coils is obstructing the warm air intake, causing the condensation on the coils to freeze due to insufficient air flow and heat exchange. Ask the HVAC tech a combination of soaking in a chemical wash, light brushing and air will get the coil clean enough to prevent freezing. It’s a trade off between cleaning labor and replacement cost.
If you open the front of the air handler, you can see how bad the sludge is by shining a flashlight inside the A-frame and looking down through the fins with a hand mirror held on the other side.
June 30th, 2010 at 11:34 am
They are telling me the sludge is inside of the tubing not on the outside. I thought it was a closed environment and do not see how sludge can get into the freon to cause a blockage.
July 13th, 2010 at 5:44 pm
Hi guys, anybody knows how to clean a sealed A frame evaporator? Mine does not have any access holes so I was thinking to cut open a panel and after cleanning screw it back together and use a metal tape to seal it. The problem is my unit does not have much flow. The top part of the A frame I could see, but does not seem to be very dirty. I can not see the bottom side. Any ideeas?
Thanks
July 13th, 2010 at 6:31 pm
It would help to see photos of the front, back and sides of your air handler unit to be sure there isn’t an access panel.
If there isn’t an access panel, you could cut a 5 inch square access panel on the left and right sides in the plenum (rigid ductwork) above the coils to inspect with a flashlight and spray the foaming coil cleaner. The method is the same as cutting a hole for the take-off starting collar in this project: http://www.handymanhowto.com/2010/07/05/speedi-boot-part-3/ – see about midway down the page for the work with a utility knife. When you’re done, apply metal foil HVAC tape the panel cutouts first with the 1/2 width of the tape exposed along the sides – it’ll look like a big bandaid – then reinsert the panel and seal tape against the plenum ductwork. Smooth down the foil tape to ensure there are no air leaks.
July 13th, 2010 at 7:06 pm
Hi Bob, thanks for the info. I have a hole in the back of the unit where the 6 in duct from the humidifier unit goes in and I think I can squize my hand in there but I was afraid all the goo and stuff from the A frame will go into the blower at the bottom and short everything. The whole unit looks like it was built like a Rolls Royce: “No problems for life”. I wished. What if I cut a 12in x 12in hole to access the A frame?
July 14th, 2010 at 7:25 am
> I have a hole in the back of the unit where the 6 in duct from the humidifier unit goes in…
That could work, but if there’s a starting collar you wouldn’t be able to see what you’re doing or inspect the condition of the coils.
> I was afraid all the goo and stuff from the A frame will go into the blower at the bottom and short everything.
The foaming aerosol coil cleaner is designed to adhere to the coils, break down over several minutes and run down the coils into the condensate drain pan, washing away the dirt. There shouldn’t any drips on to the blower fan or motor when applied per the manufacturer’s instructions.
> What if I cut a 12in x 12in hole to access the A frame?
I don’t recommend such a large cutout in the plenum if held only with metal foil tape. There’s a fair amount of air pressure in the plenum when the system is running and I wouldn’t trust metal foil tape to withstand the pressure over time, risking a break in the seal and/or panel blowout. Hence the reason for two small field expedient 5″x5″ access panels – large enough to see what you’re doing, but small enough the total surface area and air pressure should be OK for metal foil tape. Be sure to dust off the plenum so the tape seals well.
If you’re set on installing a large duct access panel in the plenum, or want a professional looking job, Lau Industries and Kees make duct access panels. These are insulated duct access doors with a gasket to seal against the plenum and metal tabs (similar to a starting collar) that grip the inside of the plenum to prevent blowouts.
July 20th, 2010 at 12:36 pm
My evaporator in the crawl space is leaking. I opened it up and it has a lot of rust on the bottom tray. Everything else is in good shape. The leaking condensate collects under the unit. Should I just install a second pan and drain to the exterior?
July 20th, 2010 at 6:24 pm
If you can replace the rusted condensate pan with a new plastic pan, that’d be the way to go. It’s worth a service call from an HVAC tech to get an estimate.
> Should I just install a second pan and drain to the exterior?
Not exactly sure where you intend to place the second pan. If you mean immediately underneath the rusty evaporator coil condensate pan, I doubt it would work because water will wick along the sides of the rusty pan, dribble off to the side and miss the new pan wetting the insulated walls causing mold/mildew.
Post back with what you decide to do.
Thanks
July 30th, 2010 at 8:58 pm
Hello Bob:
Thank you for all the information. You are very kind to respond to so many people.
August 5th, 2010 at 1:58 pm
I took the cover off my evaporator, its not an A-frame but slanted. The previous home owners obviously didn’t change filters as dust was completely covering fins on intake side of evap. Took a vacuum and soft brush and got the top layer off, I am assuming there is a lot still trapped between the fins as air flow still seems very restricted. Would the Frost king sprayed into the outtake side push the dust out? I have to try something as in this 105 degree weather, we can only get to 90 degrees and the air is just barely blowing out of the vents. Thanks for this informative site.
August 5th, 2010 at 4:54 pm
Shine a flashlight through the fins onto a hand mirror to inspect how badly the fins are clogged.
Buy a new garden pump sprayer with a spray wand, fill it with warm water, adjust the spray nozzle to a slightly open pattern. Turn off the A/C system. Place a plastic pan under the coils to keep the blower motor dry and catch the water. Spray the coils to knock out the dirt that’s between the fins. Spray gently (this isn’t a pressure washing) so as not to bend the fins, which would further block the airflow. Spray on the coil cleaner and let it do its work. Rinse with the pump sprayer and reinspect with the flashlight and mirror. Repeat if necessary.
I say “buy a new pump sprayer” because you definitely don’t want to reuse a garden sprayer that’s had chemicals in it.