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Coil Failure (Formicary Corrosion)

Written by BooAdmin on . Posted in Uncategorized


Most coil failures are actually the result of a specific coil failure known in the industry as Formicary Corrosion. This is a very specific type of corrosion that has become more and more common. It’s not to be confused with the “Chinese Drywall” syndrome the industry suffered from a few years back.

Formicary Corrosion occurs when a chemical compound is introduced to the blend of moisture, oxygen and metal. When the off gassing of unknown chemicals (building materials, paint, cleaning supplies, furnishings, etc.) which pass through the Indoor Coil and generate an organic acid (Formic Acid). While we’ve not found anything to indicate it’s dangerous to the occupants of the home, it can definitely have catastrophic effects on the A/C System. To date, there’s no proven corrective measure for this type of corrosion.

Manufacturers have tried using different types of copper, some converted from copper to aluminum Coils, as well as tried implementing coil coatings or even and corrosion inhibitors (sometimes called corrosion bombs), much like the anode on the back of a boat; yet the failures continue.

The problem in identifying the cause of Formicary Corrosion is that each home is as unique as its end user; from building materials, to cleaning products, to finishes and furnishing used, the possible combinations are practically limitless.

We know that manufacturers are (and have been) investing heavily in research in the goal of identifying specific components, and viable remedies; however, that’s little relief to the homeowner suffering these costly, repeat failures. As you likely know by now, the Manufacturer Parts Warranty (regardless of brand), provides only the replacement part; so replacing a warranty part, outside of the installers labor warranty, can still be quite costly. We encourage the purchase of an extended warranty.


While we agree that much has changed in the manufacturing of equipment, insofar as meeting more stringent energy efficiency codes, the largest change has been in the building envelope itself. The old norm’ was open soffits, which allowed the home to “breath”. While this wasn’t very efficient, it did allow newly constructed homes to off gas in a fraction of the time that a sealed home takes.

In meeting more stringent wind and energy codes, the sealed envelope has become the standard; and the practice it’s still relatively new to mainstream building.

Although Fresh Air Intake was added to the requirements for a sealed home, bringing in fresh air from outside, in timed increments, it doesn’t exchange air from within the home (fresh air is introduced, however, ‘stale’ air is not vented in exchange). It’s our opinion that fresh air exchange, combined with improved filtration, offers a healthier approach to regulating cleaner, healthier indoor air quality in a sealed home.

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CNR Air Conditioning, Inc.

(239) 455-5972 | 3888 Mannix Drive, #312 Naples, FL 34114

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