Climate Control

HVACR Tech Tip: How to Properly Clean a Condenser Coil

How to Clean a Condenser Coil - AC unit being sprayed - Parker SporlanCondenser coil cleaning is one of those subjects in which there is much misdirection and misinformation being propagated by some manufacturers/distributors that has caused unfortunate confusion in the industry. Addressed below are answers to common questions to set the record straight on the use of these products.

Why do condenser coil cleaners foam and evaporator coils usually don’t?

Condenser coils depend on a chemical reaction between the aluminum fins and either a strong acid or alkaline solution to clean the coils. This chemical reaction produces heat and several fumes and gasses (primarily hydrogen) which causes the coil cleaner to foam and push out the dirt loosened by the wetting and heating process. If a foaming condenser coil cleaner is used and does not foam, it means that aluminum is not in the coil (possibly a steel or copper coil), or grease, oil, paint or some other substance is keeping the cleaner from contacting the aluminum and creating the reaction. Due to the fumes are given off in this process, these types of cleaners are not suitable for use inside. Evaporator coil cleaners are specifically formulated for indoor use and, although probably not as effective as the foaming condenser coil cleaners, they are effective cleaners on the types of dirt commonly found on evaporator coils.


What is the difference between the acid and non-acid condenser coil cleaners?

In the past, acid-based condenser coil cleaners were the standard. There really was no other option. The primary acid of choice was hydrofluoric acid (HF) because it reacted well with aluminum to create the desired foam. It was common knowledge that HF was a serious chemical and needed to be used with a certain amount of caution. One of the peculiar things about HF is that if it comes in contact with skin, it typically does not create a burning sensation immediately. Instead, it can soak into the skin and later cause the user pain. By this time, skin and tissue damage is advanced and may require a trip to the doctor for a neutralizing injection.

Due to this danger, coil cleaner manufacturers developed alternative acidic cleaner formulas that did not contain HF directly, as well as non-acid (alkaline) coil cleaners whose primary ingredient was either sodium hydroxide or potassium hydroxide, both of which are very similar chemically. These chemicals do cause a burning sensation when in contact with skin and the discomfort will encourage the user to rinse the cleaner off before serious skin and tissue damage occurs. It should be noted, however, that neither type of cleaner should be called safe. Both the acid and alkaline condenser coil cleaners can cause serious skin and eye damage, and the vapors, especially those during the cleaning process, can cause serious lung and throat problems and should be used with caution. Due to the change of ground pH, both types of cleaners can kill grass and other foliage immediately around the condenser coil. Both types of coil cleaners are technically biodegradable. Both types are for outdoor use only. Both types should be rinsed thoroughly from the coil and surrounding area when the coil cleaning process is complete. These are serious chemicals and demand serious respect.

Both acidic and alkaline cleaners continue to have roles in your arsenal of coil cleaning products. The acid based Acti-Brite remains the cleaner of choice for removing corrosion by-products and scale build-up. Alkaline-based Alki-Foam is recommended to remove excess dirt, grease, and grime.

How much foam do I need to clean the coil?

One of the interesting things that have come about in recent years is the push for cleaners with more and more foam generation. This begs the question “how much foam is really enough?” The idea to keep in mind is that you need enough foam to push out the quantity of dirt down in the coil. More foam does not necessarily mean that the unit is getting any cleaner. Clean is clean - anything more is too much. Before cleaning the condenser coil, the coil should be inspected to determine how dirty it really is. In the vast majority of cases, the coil just has a light coat of dirt and dust covering the surfaces and really just needs a light cleaning. Using super-high foaming cleaners straight out of the bottle is overkill. In most applications, a good coil cleaner such as Acti-Brite or Alki-Foam mixed to a dilution ratio of between 1:2 and 1:4 is usually adequate for most cleaning jobs. The reality is that most technicians love to see thick foam and tend to use the cleaners straight. We discourage this practice because it usually is not needed, can result in damage to the fin stock and results in unnecessary amounts of chemicals that are transferred into the ground. If the inspection determines that a condenser coil is very dirty with grease or other difficult dirt, then a dilution ratio of 1:1 will usually result in very thick foam and enough chemical to clean virtually any application. If the coil remains dirty after one application, then rinse it off and reapply at a 1:1 ratio.


Before cleaning a condenser coil, make sure to break power to the unit. Perform an inspection of the coil to determine how dirty it is. This should entail disassembly of the unit to the extent that if there are multiple rows of coils, you can inspect between the rows to determine the depth of dirt. On multiple row coils, it is not uncommon to have a quantity of dirt make it through the outside row of coils and block the inside row of coils. The unit may look clean from the outside, but airflow is blocked.


HVACR Tech Tip: How to Properly Clean a Condenser Coil - Condenser Coil Cleaning before and after - Parker Sporlan

If accumulations of dirt, dust, cottonwood or other contaminants are matted on the face of the coil, it is a good idea to use a coil brush similar to the one discussed in the evaporator coil section to quickly brush the condenser coil face. This will aid in the penetration of the coil cleaner and speed up the job considerably. After inspection, mix your coil cleaner in a low-pressure sprayer to a ratio appropriate for the amount of dirt on the coil (1:1 to 1:2 for heavily soiled coils, 1:3 to 1:4 for light to medium soiled coils). It is recommended that due to the nature of these chemicals, chemical impervious gloves, goggles, and apron are worn. Always make sure to put the water in the sprayer first, then add the appropriate amount of cleaner. Wet the coil with water first as this will aid penetration of the cleaner into the coils. Apply the cleaner to both the inlet and outlet side of the coil, saturating the coil with cleaner. Caution should be taken on windy days as condenser coil cleaners can etch glass and remove paint from vehicles, as well as cause harm to anyone standing downwind. Do not allow the cleaner to rest on other system components. Sprayers with foaming tips are not recommended as pre foaming the cleaner will hinder penetration into the coils. The foam generated is a chemical reaction with the aluminum, not from a spray tip.

Allow the cleaner to work for a maximum of five minutes. During this time, the foam should form and dirt should be visibly carried out on the foam. Smoke or other vapors may be visible during this time which is a side effect of the chemical reaction and is not something to be concerned about. Begin rinsing the coil from the top down, taking care not to splash the cleaner on yourself or other surfaces as damage may occur. Continue to rinse the coil until no more foam is visible coming out the bottom of the condenser coil. Be sure to rinse all of the cleaner out of the coil as the cleaners may cause coil damage if left to dry on the coil. Rinse the surrounding area thoroughly with water, reassemble the unit and restore power to the condenser. Always be sure to rinse out the sprayer when finished as the chemicals may cause damage to all but the best sprayers over time.

For more information see Catalog G-1.


HVACR Tech Tip: Coil Cleaning Basics for the HVACR Service Technician - Chris Reeves, Product Manager Contamination Control Products, Parker Hannifin Sporlan Division Article contributed by Chris Reeves, product manager, Contaminant Control Products, Sporlan Division of Parker Hannifin






For more articles on climate control:

HVACR Tech Tip: Coil Cleaning Basics for the HVACR Service Technician

HVACR Tech Tip: How to Clean Evaporator Coils for Preventive Maintenance 

HVACR Tech Tip: When Should a Catch-All Filter-Drier be Changed?



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Comments for HVACR Tech Tip: How to Properly Clean a Condenser Coil

Trish Blassingame
I can say with all honesty, I've never read a better explanation on why and how to clean condenser coils! Thanks!
Muhammad Imran
Superb and thanks for such a informative note. Thanks

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