Technical Corner: Tips for Cleaning Dirty Air Conditioner Coils

Properly cleaning coils as part of a preventative HVAC maintenance program can save a building owner thousands of dollars.

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It is difficult to clean HVAC coils effectively due in part to coil design.  For multiple row coils, the copper tubing is staggered, and this prevents a stream of water from entering into the coils too deeply.  Usually the water velocity penetrates only the first few inches of a coil to loosen deposits.

Fouled coils lead to increased pressure drop across the coils. When pressure drop increases, more fan horsepower is required. This in turn draws more power, resulting in greater current consumption.

Pressure drop measurements across the coil when it is new are a valuable base line for performance.  Differential pressure that increases by more than one and a half to two times for sure indicates problems with coil cleanliness.

Cleaning coils also plays an important part in air quality.

Here are some rules to follow in cleaning coils:

1)Hot water always works better than cold water when it comes to cleaning.

2)Foaming cleaners, such as our product Instant Powder Keg, are generally better than non-foaming cleaners to remove biofilm and other deposits.

3)Certain areas of the coil may have more deposition than other areas.  A gentle flush of water through the coil may identify areas that are particularly fouled.

4)Cleaning from the bottom of the coil to the top is recommended. Multiple cleanings of the coil may be necessary due to heavy deposition.

5)After completion of cleaning, again run the hose through the coil to see if water now flows freely through areas previously found to be restricted.

6)Coil cleaners may be either acid, neutral, or alkaline in nature.  Many manufacturers call neutral pH or alkaline pH cleaners “non-acid” cleaners. Both acid and alkaline cleaners will attack coil fins, causing pitting and other corrosion. To reduce this problem, coils must be copiously rinsed with water to neutralize any chemical residual left on them.

7)Sanitize the coils using an iodine-based anti-microbial.

8)Apply a molecular coating to the coils, such as our product First Strike Micro Coat, to reduce future build up.

Properly cleaning coils as part of a preventative HVAC maintenance program can save a building owner thousands of dollars.

Lynn Burkhart is the founder and president of Controlled Release Technologies, Inc. located in Shelby, North Carolina. More information about the company, and its products, can be found at and by calling (800) 766-9057.

1 comments on “Technical Corner: Tips for Cleaning Dirty Air Conditioner Coils”

  1. Coil cleaning has to be one of the nastiest jobs. Done wrong it is destructive to the metal, reducing efficiency instead of enhancing it. Everyone should pay close attention to #6: and keep in mind that alkaline is just as corrosive as acid, so ALL coil cleaners should be rinsed away.


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