Should Facility Managers Consider Coil Coating On Their HVAC Units?

Should Facility Managers Consider Coil Coating On Their HVAC Units?

by | Commercial HVAC, Facility Management | 0 comments

HVAC Tech Charging Condenser - CMI MechanicalHVAC contractors working near the coast or in proximity to industrial plants face a never-ending battle between equipment maintaining condenser coils and the corrosiveness of the air.

Without a properly functioning coil, the HVAC system will not work properly. Most condenser coils are constructed by welding thin aluminum fins to a copper tube.

As the refrigerant passes through the condenser coil, the fins increase the heat transfer surface area allowing more heat extraction from the refrigerant.

This extra surface area is necessary for the function of the unit, but aluminum fins are very susceptible to salt-air and pollution corrosion.

This Is Why Many Building Managers Choose Coil Coating

Condenser Coils - CMI MechanicalWhen operating in these environments, coil damage may be visible in less than one year after installation. Damaged fins become brittle and flake off restricting airflow through the coil and reducing heat transfer leading to high head pressure shutdowns of the equipment.

Commercial mechanical contractors do have options to protect the coil and, if not eliminate, at least alleviate the damage caused by salty or polluted air.

Covering the coil with an epoxy phenolic coating so neither the fins nor the tubing comes into direct contact with the corrosive air prevents the reaction between the coil metal and the salt or pollution.

2 Common Ways To Cover & Protect Condenser Coils

The two most common methods of coating are to either dip the coil into the liquid coating to cover it completely or use an “e-coating” method where the coil and the epoxy coating have opposite electrical charges to bond the two together.

The most well-known anti-corrosion coating is Heresite which is a brand name for a specific phenolic dip, but has become the generic term for coil coatings.

Adding a coating between the coil and the air does reduce the coil’s heat transfer capability between 1% and 3%, but this efficiency loss is minor compared to the cost of replacing a coil or the entire HVAC unit early because of severe corrosion.

Protective coatings are best applied during coil construction and before the coil is installed in the HVAC equipment.

For the dipping method, the entire coil assembly is dipped into the liquid coating to get total coverage even deep within the coil’s fins.

Any part of the coil not coated can be the starting point of corrosion and lead to the deterioration of the entire coil.

But What If Your Commercial HVAC Unit Is In Service?

Coils already in service can be coated by cutting out the coil and sending it to a company to perform a coil-dip, but this is often prohibitively expensive.

More common for coils already in operation are spray-on coatings which, although this method can be effective and preventing corrosion, it is very difficult to evenly spray the product over the coil to ensure complete coverage and not spray the coating too thick.

Regardless of the method, the product, or when the coil coating is applied, HVAC coils exposed to coastal air or pollution should be coated to prevent deterioration, costly repairs, and early replacements.

Work with your commercial HVAC contractor and equipment vendor to find out what coatings are best for your equipment.

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The experiences I have had with the CMI team out of Denver has been nothing but positive.

Maile K.

Facilities Manager, REI Co-Op