Air conditioner or heat pump cooling coil / evaporator coil cleaning methods: this article discusses the how the cooling coil (evaporator coil) in the air conditioning air handler unit is cleaned. These same methods will work on the outdoor coil or condensing coil as well. Our photo at page top shows a very dirty cooling coil in the attic air handler component of a central air conditioning system.
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If your air conditioning or heat pump system has lost its cooling capacity or won't start see REPAIR GUIDE for AIR CONDITIONERS. See How to determine the cooling capacity of air conditioning equipment if the system seems to be working but is inadequate to cool your building.
Which Cooling or Heat Pump "Coil" is Which: Condensing Coil & Cooling/Evaporator Coils Defined
The COOLING COIL or EVAPORATOR COIL discussed here is the evaporator coil found inside the air handler, used to cool air blown across it and into the building occupied space. If your concern is with If your equipment is a heat pump these terms can be a bit confusing because in heating mode, your heat pump system's indoor coil is warming, not cooling the air blown across it
The CONDENSING COIL is normally on the outdoor or compressor portion of your air conditioning system. The job of the condensing coil is to cool high temperature refrigerant gas to condense it back to a liquid refrigerant form.
Why do we clean the HVAC evaporator or cooling coil, or the condenser coil?
Dirt and debris accumulating on an air conditioner or heat pump coil block airflow across the coil, increasing the cost of heating or cooling the building. In severe cases cooling or condensing coils can become so blocked that air flow is seriously reduced, possibly also leading to an evaporator or cooling coil icing problem indoors or an overheated, damaged compressor outdoors, or simply loss of cooling capacity of the system.
In addition, a blocked evaporator coil can cause the HVAC compressor to run at higher than normal temperatures - a condition that over time can break down lubricants circulating inside the system, thus shortening the life of the compressor motor itself.
BLOCKED COOLING COIL - Air Conditioner Evaporator Coil Blocked by Debris
Ice on the cooling coil is not the only (nor even the most common) cause of blocked air flow in an air conditioner. This photograph shows how easily debris can stick to and clog the inlet side of the cooling coil in an air conditioning system. This evaporator coil was nearly totally blocked with dust and debris. How does this happen?
There was no air filter installed in the system. Ordinary house dust is comprised largely of fabric fibers and skin cells.
These and other debris in building dust such as soot and organic particles like pollen and mold spores all join to form a gray mat on the fins of the cooling coil in an air handler.
Debris sticks particularly quickly to this surface because of the combination of close spacing of the cooling fins (about 1/16" apart) and the fact that condensate forming on the coil keeps the surface damp.
Details about the detection and cleaning of dirt and debris which block an air conditioner cooling coil are at DIRTY COOLING COIL.
Guide to Procedures for Cleaning Air Conditioner or Heat Pump Evaporator Coils: Using Air, Brushes, Chemicals, or Detergents to Clean A/C Coils
Thorough cooling coil or A/C evaporator coil cleaning can require cutting refrigerant lines, removal of the coil and other components for cleaning, and reinstallation, pulling a vacuum on the refrigerant lines, and recharge with refrigerant. Such service and repair may involve significant expense. For this reason there are several "in place" cleaning methods using foams and sprays that are a simpler procedure for cleaning an air conditioning or heat pump coil.
Watch out: be sure that electrical power is off to the HVAC equipment before opening access panels or working on the system. Relying only on the door safety interlock switch to turn off equipment power may be unsafe as wiring inside the unit will still be "live" in some locations.
Using Air: Compressed air for cleaning HVAC evaporator coils
Some HVAC technicians clean an evaporator coil by blowing it off with compressed air. This is a quick and probably effective method to clean the coil, which has the additional feature of blowing dust, debris, and possibly mold into the building air - not something we approve.
Air is sprayed from the cleaner side of the coil towards the dirty side - or in other words, in the opposite direction from the normal air flow across the coil. Be sure to spray from the correct side of the coil or you'll just be forcing dirt and debris more deeply into the coil fins.
Watch out: if you are using high pressure air to try to clean a coil, be sure you blow air at right-angles or straight through the coil fins. Blowing high pressure air (or water or steam) at the HVAC coil fins on an angle is likely to bend over the fins, clogging the coil and possibly ruining it. If just a few fins have been bent on a coil they can often be straightened by working gently with an HVAC coil comb designed for that purpose.
Watch out: if you are not careful, just using compressed air to blow off a coil may leave a large amount of dust and debris inside the air handler where it collects anew on coil surfaces, or in your eyes (dangerous). Using a shop vac in concert with the compressed air sprayer and moving carefully (to avoid damaging coil fins) can reduce dust and debris spillover and make cleaning up easier.
Condenser coil cleaning: We don't have a complaint about using compressed air to clean an outdoor evaporator coil since we don't have the same concern about blowing debris into the building or its duct work.
Brush-cleaning of A/C or heat pump cooling or heating coils
When the coil is soiled by a fairly light coating of dust and debris, it can often be successfully cleaned using a soft brush. If you clean you A/C or heat pump coil every three or four months using this method you may reduce cooling (or heating) costs and you may be able to avoid more costly or troublesome coil cleaning procedures.
If your HVAC equipment is operating in a dusty area or if no one has been maintaining proper filters in the system it is likely that you'll need to clean the coil more frequently, perhaps even monthly to keep the A/C or heat pump system at peak operating efficiency and effectiveness.
We have tried using a shop vac with a soft brush attachment to clean the A/C coils, but if your coil is mounted in the air handler so as to not leave much room to access all of its surface this approach doesn't work well.
Watch out to avoid damaging coil fins when using any tools, brushes, or vacuum cleaners around the equipment.
Using Chemicals to Clean A/C Coils
There are plenty of coil cleaning chemicals sold for cleaning A/C or heat pump systems, both acid and alkaline-based.
Watch out: We do not recommend using strong chemicals on an A/C or heat pump coil because of the risk of corrosion damage to the coil or the production of noxious odors & fumes. To be safe, check with your HVAC equipment manufacturer to be sure that your cleaning approach is one they approve.
Indeed there are foaming cooling coil cleaners on the market that can gently lift and help remove coil-clogging debris with minimum damage to the cooling coil.
Field Report: corrosion visible after a cooling coil was cleaned
[Click to enlarge any image]
I called the technicians who came back to look and then explained that what I was seeing was corroded aluminum that was more visible since the cooing fins are now clean. Although this sounds plausible I have two concerns.
1. if if is corroded aluminum do I need to be concerned about using the ducts.
2. it is not corroded aluminum and they did a really bad job at cleaning
The cleaners are part of the national duct cleaners association (NADCA), seemed quite knowledgeable and experienced (no complaints, A+ at BBB), but I am surprised that the fins look so bad. I would like to know whether what I am seeing is to be expected.
l. I did snap a picture on the one side of the "V" that was easily accessible, here it is. This is the AFTER cleaning picture, I dont have a before. The schmutz has a slightly greenish hue.
The AC handler and ductwork is old, and based on the amount of crud throughout the system appeared as if it may have never been cleaned before.(the condenser unit itself is 25+ years old, but still working). That conclusion also comes from the fact that the prior owners seemed to take pride in performing NO basic maintenance on the house for many years. I just hope that firing up the AC system in a couple weeks won't endanger my family. - Kevin 4/28/2014
thanks. K.C. 4/28/2014
In my initial reply I said "I am not sure I buy the explanation that "you only see the crud because now we've cleaned the coils". That would be the case if we saw thick green crud that was actually blocking or covering-over the coil assembly.
But now that I can benefit from seeing your photo (above left) I think that we are looking at corroded aluminum fins on the coil and that the cleaning company is being dead honest in saying you couldn't see this before - this condition would have been covered if there were a layer of thick dust and debris.
Your photo is not quite clear on the point, but if there is good air flow between the fins on the coil and presuming it's not leaking, it should be functional. This is about as good as you're going to get in cleaning this coil. It would not be likely that the coil cleaning procedure using approved methods and materials would endanger your family. (You might however want to inspect the HVAC system ductwork for cleanliness, including the air handler and blower fan assembly.)
There is some heat transfer loss where aluminum coil fins are deteriorated by corrosion, but most likely a significant gain in coil performance overall by cleaning if it was previously debris-clogged.
To understand this coil's performance better, an in-focus photograph looking directly into the coil fins - at right angles to the plane of the coil - would let us see whether or not there is open air space between the fins. Take care not to damage the fins nor cut yourself on sharp edges. It may help to try shining a light from the other side of the coil if it's accessible. If not the photograph will rely on lighting or a flash from the camera's side.
If we see open air space between the fins then the coli has been successfully as opened as we're going to get it.
Unfortunately I cannot recommend any more aggressive cleaning like brushing. The aluminum fin material is thin to begin with and is more fragile now as it has been corroded. More aggressive cleaning that bends (which means blocks) or removes (which means still more capacity loss) fin material just makes matters worse.
Replace the coil, or the whole unit, if/when the coil leaks refrigerant.
Field Report: Using Hydrogen Peroxide to Clean an HVAC Coil?
While we have read reports that the oxide on the surface of aluminum HVAC coil parts reduces the severity of chemical reaction between an acid or base cleaner and the metal, we have also had reports of problems with corrosion and odors when this approach was tried.
So while the "bubbling" action of hydrogen peroxide is appealing as a cleaner, we are warned that chemical reactions between some coil cleaning products and the aluminum or copper A/C or heat pump coil parts can corrode the fins or tubing, damaging the system, ultimately leading to leaks and the need for a costly coil replacement.
Chemical reactions between some coil cleaning products and the aluminum or copper A/C or heat pump coil parts can also produce obnoxious odors or fumes, possibly toxic or irritating fumes, and in some cases may leave an odor in the system that itself becomes an issue.
See our discussion of detergents and foam sprays for coil cleaning, below - those are safer approaches to coil cleaning, especially if you're not an expert.
Using Detergents or Water for cleaning A/C coils
Using a simple hand sprayer or garden sprayer (these produce a gentle spray) it may be possible to clean your A/C or heat pump coil effectively using tap water or a mild detergent. The advantage of using these gentle solutions is that there is little risk of damaging the coil fins or tubing compared with the use of more harsh chemicals.
Wet the A/C or heat pump coil surfaces with your spray-on detergent, let it soak in for 15 minutes or so (but not long enough to dry out), then rinse the coil and coil fins clean. Remove spillover and debris from the condensate pan where your spray and debris land, using a shop vac or hand wiping.
Watch out: don't bang around inside the air handler with your shop vac or you may damage the evaporator/cooling coil or coil fins; and be careful when wiping by hand that you don't get cut on sharp fin edges.
If using water or a non-sudsing mild detergent doesn't work to clean off your coil, you may need to use a more aggressive coil cleaning method such as those described below.
Using Foam or spray HVAC coil and fin cleaners
Using a garden sprayer (or a sprayer that may be included in some pre-packaged A/C coil cleaning systems and products), the coils are sprayed with a foaming cleaner specifically designed for HVAC systems. An advantage of this approach is that it is mechanically gentle, reducing the risk of damage to the coil or its fins. And if you select a benign cleaner it is also chemically gentle, avoiding corrosion damage to the coil.
Where to Buy HVAC and Refrigeration Equipment Coil Cleaning Products
List of HVAC coil cleaning chemicals and sprays:
The HVAC coil spray approach has the appeal that the total cleaning cost is low, no rinsing is necessary with some products, and the coil looks nice.
Where does the debris and run-off cleaner go? It should drip into the condensate pan for disposal through the condensate drain system. The manufacturer says the coil and fin cleaner also removes odors from the system, but if your HVAC system is quite dirty additional steps will be needed to clean the blower assembly and the ductwork.
After the coil cleaning foam has worked on the coil surfaces and dripped to the condensate pan below, use a wet-dry shop vac to clean up the mess from the pan, followed by careful wiping as we cited above.
Using Pressure Washers to Clean A/C or Heat Pump Coil Fins & Tubing
Professional HVAC service companies often use a portable A/C coil pressure washer designed for that purpose. Unlike cleaning detergents or foams, a pressure washer is physically more aggressive coil cleaning method and is perhaps the most thorough or effective method for cleaning a badly soiled or blocked HVAC evaporator or condenser coil.
A portable pressure washer unit such as Goodway's CC-140 contains both a coil cleaning solution (typically a detergent mix) and a battery-operated pressure sprayer that can deliver as much as 140 psi. Heavier-duty coil cleaning pressure sprayers are available for commercial units and larger, or heavier, wider coils.
Watch out: as we warned earlier, if you are using high pressure air, water, or steam to try to clean a coil, be sure you blow air at right-angles or straight through the coil fins. Blowing high pressure air (or water or steam) at the HVAC coil fins on an angle is likely to bend over the coil fins. And don't over-do it and don't spray more cleaner than needed - you'll just have more liquid cleanup to do after the coil has been treated.
Using Steam-Cleaning of A/C or Heat Pump Coils
Steam is used by some technicians to clean HVAC coils, in a process similar to that we described above for compressed air.
Watch out: as we warned earlier, if you are using high pressure air, water, or steam to try to clean a coil, be sure you blow air at right-angles or straight through the coil fins. Blowing high pressure air (or water or steam) at the HVAC coil fins on an angle is likely to bend over the coil fins.
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Frequently Asked Questions (FAQs) About Dirty HVACR Cooling Coils & Evaporator Coil Cleaning Methods
Question: When cleaning a cooling coil do you blow air or water from inside or outside the unit?
Do you blow the pressure air or pressure water from the inside out or from the outside in on the unit? I sprayed it from the outside in I think It may have been the wrong direction. - Sherry 6/7/11
If you are trying to clean a dirt-clogged A/C coil, the best result is achieved if you can blow from the clean side so that you are pushing the dirt and debris back off instead of forcing it in between the coil fins. However sometimes it is so difficult to access the clean or outlet side of the cooling coil that technicians use cleaning foams and water instead. In that case they may spray from the most accessible side.
Question: Don't confuse a dirt-blocked coil from ice or frost formation on cooling coils
I cleaned the outside unit by removing the panel and the fan which was attached to some wires. I didn't disconnect or damage anything. I collected 1/4 a garbage bag with the dirt and debris found to the bottom. In attempting to clean the inside unit and fan, I noticed lots of ice on a grid like thingy and some tubes or lines.
The inside however looks to be pretty clean but I will wipe it down anyways. I purchased this house in 2006 and so far had to change the compositor battery looking thingy professionally. 2 years ago but still have freezing when it is about 100 degrees outside or more. What else could I do? How do I know if I need freon or refrigerant and where does it goes? Please help ...thank you! - Pamela 6/10/11
Pamela it sounds as if you are describing frost and ice formation on the cooling coil (evaporator coil) inside the indoor air handler unit.
Icing coils are caused by low air flow (dirty cooling coil, dirty air filter or duct defects) or by a low refrigerant charge. Adding freon is something that needs a service call from a trained HVAC technician - it's not something a homeowner can or should try to do.
While ice or frost on on the coil could be caused by a dirty coil, the technician needs to defrost the system and inspect the coil as part of diagnosing and fixing the trouble. If on defrost (just leave the system turned off for an hour or so) shows that the evaporator coil is actually clean, then the problem is elsewhere in the system and you'll want to see the diagnostic advice at FROST BUILD-UP on AIR CONDITIONER COILS.
Question: Can chemicals or cleaning products damage a cooling coil in an air conditioner or heat pump?
I recently had some problems with the AC unit. At one point the tech cleaned the coils and etc. and I remember him saying that he used some kind of coil cleaner. After this was done, I started having a major problem of toxic or exhaust like fumes coming through the ducts. I had to turn the unit off because it started burning my eyes, skin and throat. The techs have checked several times and can find nothing wrong.
I read above where it says "Chemical reactions between some coil cleaning products and the aluminum or copper A/C or heat pump coil parts can also produce obnoxious odors or fumes, possibly toxic or irritating fumes, and in some cases may leave an odor in the system that itself becomes an issue". My question is, If this is the problem, what needs to be done to get rid of the fumes and clear out my system? Any help is appreciated. Thanks. - M.B. 6/20/11
MB: there are more benign foaming cleaning agents that should not corrode or otherwise damage a cooling coil when used according to directions. If your technician has already used a caustic agent (which is what your question indicates) it may be necessary to further clean the coil and air handler with a non-caustic cleaner to neutralize any ongoing corrosion and to stop generating the odors and fumes you described.
If the service technicians are sure that the odors and irritants you describe are not due to the cooling coil cleaning procedure then it's appropriate to perform some further diagnosis, perhaps by technicians with more experience. That procedure should address the question "Why did the fumes begin only after the coil was cleaned?"
I used vinegar. It has an low acid base, yet it produces some results to smell. I also come back with baking soda to off set any acid. I heard where it was good for drains so I tried it. I like the garden sprayer idea, may use it next time. I used a spray bottle this time and it worked fair. I vacuumed with a shop vac and it still was as clean as I wanted but over time, maybe.
Indeed further coil cleaning with a more gentle cleaner to remove left-over chemicals from the coil cleaning job may help; take a further look at the coil fins for damage.
Question: using WEB coil cleaner containing 2-butoxyethanol and diethylene glycol to clean frozen A/C coils
Is it safe to use WEB Coil Cleaner on the Heat Coil (inside)? It contains 2-butoxyethanol and diethylene glycol. The heat pump cooling coils are frozen. I already cleaned the condensate drain pipes.
Anon, if your coil(s) are frosting or frozen, the cleaner is not designed to remove ice; you'll need to turn off the system, let the ice melt, inspect the coils for dirt and debris or other damage, and clean them if that's the case. It's odd to have simultaneous icing on both condensing and cooling coils; has anyone checked the refrigerant charge level?
Question: using Simple Green to clean a cooling coil or evaporator A-coil in an air conditioner
Question: I want to clean my evaporator coil,(A-Coil) inside the air handler, with Simple Green and tap water. I'm concerned about the water washing down into unit and damaging the blower motor and electronics. I know there is a narrow drip pan around the base of the coil but i'm afraid of the overflow. Are my fears unfounded or.? - Paul - 10/19/11
Cleaning with simple Green or even plain water will risk damage to the blower motor and electronics if you get them wet - they are not intended to be immersed nor soaked in liquid. You should be able to keep water and cleaner on the coil and fins and in the condensate pan. If you do so and there is trivial overspray onto the motor just wipe it off. If you can't clean in the air handler without spraying more water about then you'll want to use taped up plastic to protect electrical components from the spraying procedure.
Question: air conditioner coils still freeze up after cleaning with water
My air conditioner coils and fins are still freezing or icing up after cleaning them with water ...could there be something else wrong that it still freeze or ice up? I have to turn on and off the A/C 's thermostat every 15 minutes or so just to melt the ice and for it to cool up again. anything else i can do to fix this problem? - Jack 10/20/11
Question: Is using an evaporator coil cleaner regulated by environmental discharge regulations?
During a recent audit finding, and regarding our regular and routine coil cleaning, we were told it is a code violation if you discharge any pollutant or cause, permit, or allow a discharge of any pollutant from a point source without a permit. I don't think this is true or even applicable to coil cleaning...your input is greatly appreciated. 10/18/11
Frank, that's a new one on me. Who defined HVAC coil cleaning as a polluting process? If you used soap and water would that be a pollutant? Typically coil cleaners are a foaming agent that is used to help lift dirt off of coil fins. The material is water soluble. If you give us the name of the coil cleaning product you or your HVAC tech intends to use we can further research this question by taking a look at the MSDS for that cleaner. That ought to put an end to what sounds like a bit of an odd question. Finally, I suspect that someone might have been worried that you were going to dump refrigerant into the environment. If that's the case then s/he does not understand that HVAC coil cleaning is an external cleaning procedure that does not address the interior of the HVAC refrigerant piping system.
Question: how often should you acid-wash the air conditioenr coils
Usually, how often should you acid wash the inside air conditioning coils? Please don't tell me when they're dirty.... THANK YOU - Terry 5/6/12
Terry: well "when the coils are dirty" is nevertheless the right answer, sort-of.
Really you want your service technician to inspect visually for the presence of enough dust and crud that air passage through (between) the fins has become partly blocked.
Light dusting on the cooling coils is not worth a wash.
Watch out: And we want to "acid wash" coils as seldom as possible because you are using a corrosive material. I'd look into less corrosive cleaning methods.
Question: cooling coils on HVACR equipment in a cement company environment
What should be the recommended fin material and fpi for condenser coils in cement company enviroment?
Question: Can a dirty cooling coil cause HVAC system vibration? Also the service policy & warranty I purchased is not being honored by the service company.
I have a question concerning the A/C unit. When the A/C Unit turned on (inside furnace located in hallway) had a noise (vibration on the A/C Unit) I have a warranty plan and they send a technician.
Technician checked the blower by sliding the blower from its position and stated blower was OK. Technician went on and check Other parts of the furnace and was unable to determined what was causing the vibration. He had a device (camera) to check inside air handler and notice that the coils were dirty. He stated that it is possible that dirty coils (A/C Unit still operating OK) could cause the vibration on the unit. Technician stated that A/C unit must be pulled/removed from its location in order to clean the Coils, which would cost over $1000.00 to include cleaning coils plus the labor.
Unfortunately the Warranty plan does not cover cleaning the Coils (maintenance), the Warranty Company interpretation of dirty coils is "Clogged coils", which technician stated coils were not clogged just dirty.
My question is: Could dirty coils (unit still cooling & running OK) can cause the vibration? R.V. 5/11/12
The assertion that a dirty coil caused the unit to vibrate leaves me baffled. How did the tech explain that?
Indeed if the coil is really dirty and blocked it may frost over or fail to pass enough air and your cooling air will be reduced, but that's not vibration.
Look for loose parts that move when motors or fans run, including a bad blower fan bearing, mounts, loose duct work, etc. Try pressing gently on components to see if the vibration stops - DO NOT GET YOUR FINGERS CUT OFF IN MOVING PARTS - so you may want to have a more qualified tech take a look.
Thank so much for your response. As I mention on my email below that the Warranty plan does not cover cleaning the Coils (maintenance), and their interpretation of the technician report that vibration is because of dirty
I did contacted the technician, and explained to him that Customer Service denied the claim because of his report stating that the coils were 100% dirty. The technician contacted Customer Service but the claim was still denied based on this report.
As I stated to customer Service and the technician that the Vibration was not FIXED, I still have to PAY $75 Deductable (service Fee) and the vibration problem was not fixed.
My conclusion is that the technician stop searching to determined what was causing the vibration after he saw that the coils needed to be clean and stated that could cause the vibration and he stated that it should be cover under the warranty (technician estimate cost for cleaning the coils $850.00 submitted on his report).
Again, I mention to the technician that he did not fix the vibration problem. I did read the Warranty Plan and it states that cleaning of the coils is not cover under the plan, but my point was to customer service and technician that the vibration problem was not fix. Again, thank you for your response. 5/31/12
You can inform the customer service people that a dirty coil blocks airflow but does not cause vibration in the system. I would ask that a more qualified, experienced tech be sent to the job. It sounds from your description as if the tech you had knew that he could blame an excluded item and thus escape honoring the warranty.