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Like any piece of machinery or machine component, air-conditioning coils work better, and last longer, when properly cared for.

That means regularly cleaning indoor and outdoor a/c coils, plugging tiny leaks when possible, and sometimes using proper coatings that inhibit corrosion, especially when coils are to be used in environments that subject them to harsh conditions, such as in coastal regions or near swimming pools, food-processing plants, and even airports.

“We all know that the dirtier something gets, the less efficient it is. Condenser and evaporator coils are no different,” said Mark Roth, national sales director at Goodway Technologies Corp. “Dirty condenser and evaporator coils can reduce energy efficiencies by about 60%, making the system work harder for less optimal results.”

Goodway, in Stamford, Connecticut, makes tools for cleaning a/c coils, such as pressure-washer kits and vacuums, and also provides cleaning products and advice to HVACR manufacturers and contractors and technicians in the field.

Weatherproofing – and Fume-Proofing – A/C Coils

If the end use calls for it, applying the right coating is the first step that should be taken to extend a coil system’s lifespan. Often, that is done at the manufacturing stage, before the equipment is put into service, said Kayla Oehldrich, the sales and marketing manager at Heresite Protective Coatings LLC.

TAKING A DIP: Heresite Protective Coatings LLC makes coatings for the HVACR industry and has a full-immersion application and curing facility in Manitowoc, Wisconsin. (Courtesy of Heresite)

Based in Manitowoc, Wisconsin, Heresite makes both spray-on and full-immersion coatings, and 95% of its business involves coatings for the HVACR industry, Oehldrich said. The company has a dipping and curing shop in Manitowoc, and manufacturers can send coils there, or to other authorized facilities, for treatment before the coils are shipped to installation sites.

Heresite’s P-413 is an all-purpose phenolic epoxy coating, best applied via full immersion, that protects outdoor coils from salt air and fumes from harsh chemicals, jet fuel, and other corrosive products, Oehldrich said. The coating is thin, flexible, and has little effect on the coils’ heat-transfer process.

“It’s going to run efficiently for longer,” she said.

P-413 can be applied directly to any type of metal after only a basic cleaning — no special cleaners or prep work needed, she said. Same with HereShield, a spray-on, air-dried coating specially formulated to protect coils in coastal areas that are subjected to salt air, Oehldrich said.

HereShield can be carried by techs to their job sites.

“They’re the ones who come to your home when you’re getting new air conditioning and you want that extra layer” of protection to make the equipment last longer, Oehldrich said.

Oehldrich said that, for optimal effectiveness, Heresite coatings should be applied when HVACR products are new.

“They’re not designed to come in at year five and year six and make it look pretty,” she said.

Cleanup Time

The importance of keeping coils clean can be explained by simple physics: A buildup of any type of debris, from aerosolized cooking fumes and dust to leaves and seeds, will impede the ability of coils to transfer heat.

“You’re trying to remove anything that’s a thermal insulating blanket on the surface,” said Eric Martini, a product line manager at DiversiTech Corp. in Duluth, Georgia, which makes a variety of products for the HVACR industry, including cleaners, cleaning tools, and sealants that can seal coil leaks of 300 microns (300 thousandths of a millimeter) or less.

Dirty evaporator coils can also lead to an increase in static pressure, which can hurt the performance of the coils, said Jason Makowski, vice president of product management at Aspen Manufacturing, a Humble, Texas, company that builds evaporator coils both for HVACR equipment manufacturers and aftermarket, or coil replacement, use.

Both evaporator coils and condenser coils should be on a regular inspection and cleaning schedule, experts say.

REMOTE USE: Goodway Technologies Corp.’s CC 100 Coil Pro is a backpack unit allowing techs to combine a pressure washer with cleaning solution and water and clean condenser coils in hard-to-reach places that may not have a water source. (Courtesy of Goodway)

“This will ensure they are working at maximum efficiencies, which will reduce overall operating costs as well as improve indoor air quality for building occupants,” said Goodway’s Roth.

But different coils should be cleaned differently, depending on their location and specific use.

Evaporator coils, which are indoors, are typically not subject to the same degree of contamination as outdoor coils, and gentler cleaners, even some that don’t require rinsing, can be used. Cleaning some coils requires extra precautions; the coils in an indoor mini-split unit, for example, are in proximity to walls, floors, and furniture, so care must be taken to not overspray cleaning product or rinsing water.

Outdoor condenser coils get dirtier faster, as they’re subject to contaminants such as leaves, seeds, grass clippings, and bird droppings. More aggressive cleaning products can be used, Martini said, and rinsing is required.

Both Goodway and DiversiTech offer products that take a proactive approach to coil maintenance. DiversiTech coil cleaners, for example, have corrosion inhibitors that protect metals. Goodway’s CoilShine-T BIO tablets, for use with its CC-200 coil-cleaning system, fight bacteria growth that can occur on coils.

Maintenance Tips

Experts warn against using corrosive cleaning agents, such as acids, on coils. They’re good at controlling oxidization but also eat at metals, which could lead to leaks and other problems.

In addition, “Whenever you do any cleaning, the system is definitely off,” said Martini.

Makowski, at Aspen Manufacturing, offered these further tips for maintaining coils:

• Cleaning should be done only by a trained technician using the proper equipment.
• Cleaning products that are hazardous if inhaled should not be used on evaporator coils. “The evaporator coil is located in the plenum, creating a hazard to occupants if cleaning agents that are harmful to breathe are used,” Makowski said.
• The manufacturer’s recommendations should be followed when it comes to both coil cleaners and coatings. Cleaners that leave a residue should not be used on evaporator coils.

The use of a coating on an evaporator coil may necessitate a larger coil or an alternative coil configuration; Aspen has coating options for its coils, when there is a need for a coating, and can provide guidance on their use, Makowski said.