Coil cleaning: A real maintenance value

April 19, 1999
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It can be a messy job; nobody wants to do it, and your customer wants to know if it’s really necessary.

But keeping the evaporator and condenser coils of an air conditioning or refrigeration system clean and free of foreign materials can do more to maintain operating efficiency and increase equipment life than any other preventive maintenance procedure.

Put simply, a regularly scheduled coil cleaning will help keep your customer’s equipment running better and longer.

Anyone who sells and services maintenance contracts should seriously consider a regular coil-cleaning program. It will make those maintenance agreements more valuable.

Every part of an operating system must function properly to accomplish its cooling job effectively. However, the coils are where the system provides for the actual transfer of heat.

Anything that insulates against heat transfer robs the system of its efficiency, ultimately increases operating cost, and increases the likelihood of equipment failure.

Just about everything that contacts the coil surface can have an insulating effect. Dirt, grease, dust, corrosion, cigarette smoke, and even bacteria and other microorganisms can act as an insulating barrier. All must be removed for the system to perform its function efficiently.

A cleaning schedule also must be efficient in that it must fit the type of coils and the environment in which they are placed. Obviously, a greasy, hot, dirty environment will require more frequent cleaning than, say, an office building.

Is every three months too much? Is once a year enough? Only a keen awareness of the coils’ environment and experience can help determine the optimum cleaning schedule.

Inside-Outside

Most condenser coils are exposed to the elements, including direct sunlight, extreme temperatures, dust, and dirt. Insects and small animals often take up housekeeping — and dogs seem to love them as territory marking posts.

Grass clippings, lawn mower bumps, and weed whackers all serve to damage and inhibit the operating efficiency of condenser coils.

Horror stories abound about all the critters and foreign materials found in, on, and around condensing units.

Evaporator coils are almost always indoors, so they are safe, right? Afraid not. With nearly all the air in a building passing through these coils, they are repeatedly exposed to everything in that air. Even with good filtration, there can be a substantial buildup of dust particles, grease, and smoke. In short, anything floating in the air small enough to get past the filter will build up on the evaporator coils.

But wait, there’s more! The evaporator coils are usually damp from condensate and are placed in a cool, dark place — an ideal environment for breeding bacteria and other microorganisms, some dangerous, even deadly.

Cleaning the evaporator coils not only helps the system operate properly, it can help avoid serious illness and maintain a healthy living environment for the home’s occupants.

Choosing A Cleaner

OK; you have decided to clean some coils, you have a rough idea of what the schedules should be, and you have convinced your customers of the necessity or included the cost in your maintenance agreements. Now comes the hard part: choosing a coil cleaner that fits your needs and your budget.

There are practically as many different brands and variations of coil cleaners on the market as there are commercials on TV. While this broad range of choices is good, it can be confusing. Brand formulas and concentrations vary somewhat. However, most coil cleaners fall into general groups.

Note: All types of coil cleaners are strong chemicals and should be handled with care. The manufacturer’s directions should be read carefully and followed precisely to provide the best results.

Many clothes, service vehicles, and paint jobs have been damaged by the improper use and storage of coil cleaners. I am sure many readers are aware of at least one service vehicle with a hole in the bottom, or at least one service tech who has a pair of pants with the characteristic holes eaten away.

Coil cleaners are available in two basic forms, liquid and powder.

The powder forms are relatively new to the industry and can provide several benefits. Powders are generally less expensive, easier to store, weigh less, and decrease the likelihood of spills.

Powders and liquids are used basically the same way. The coil cleaner is mixed and diluted with water to obtain the desired concentration. Most technicians mix and dilute coil cleaners in a standard pump sprayer, pressurize the sprayer, and apply the liquid to the coils.

The coil cleaner is allowed to remain on the coils for 5 to 20 min, depending on the specific directions, then rinsed with plain water or condensate.

Four Categories

Whether liquid or powder, most coil cleaners will fall into one of four categories:

  • 1. Acid;
  • 2. Alkaline;
  • 3. Solvent; or
  • 4. Detergent.

Acid-based coil cleaners are very effective and will remove any material from coils — including the metal on the coils if you are not careful. While proving effective as a coil cleaner, the acid-based products come with a few hazards.

Acids produce vapors that carry a strong acid smell which, in the right concentrations, can cause teary eyes and choking. The very properties that make acid a good cleaning agent for coils are also what make it dangerous — it will dissolve just about anything it touches.

Thorough rinsing is absolutely necessary and when acid is used on evaporator coils, the building should be vacant, and extreme care should be taken to protect surrounding equipment and materials from damage. Acid-based cleaners are most often used on condenser coils, where a very strong cleaner is required.

Alkaline-based coil cleaners are also very effective, fairly safe, and offer excellent cleaning results in most all conditions, on both condenser and evaporator coils. These cleaners usually produce a mild odor, if any, while effectively removing foreign materials from the surface of the coils.

However, alkaline-based cleaners are caustic, so care is necessary when they are used. While alkaline-based cleaners do not damage property and equipment as readily as acids, overspray and residue should be rinsed thoroughly to avoid potential problems.

Due to mild odors and general cleaning ability, alkaline-based cleaners can be used as a general-purpose coil cleaner.

Solvents used as coil cleaners are most effective at removing grease and smoke residue, but fall short of removing heavy particulates and corrosion. Benefits include a short dry time and limited rinsing.

Many solvents are flammable and most give off strong smells and vapors. Solvent-based coil cleaners tend to work best in areas where a lot of water cannot be used for rinsing, and close quarters present an overspray problem.

Detergent coil cleaners are just that, a strong detergent, usually slightly alkaline, with surfactant agents and/or foaming agents to speed the cleaning process. Most new detergent coil cleaners are relatively safe, since they are at least environmentally friendly, if not biodegradable.

This type of cleaner also tends to work very well in areas where there is buildup of grease and tar, but still falls short in removing particulates and corrosion. Depending on the foaming agents, detergent compounds usually require thorough rinsing as a final step.

Most technicians use an acid- or alkaline-based coil cleaner because they provide very good cleaning capability in a broad range of situations. However, in conditions where heavy grease or tar is present, a solvent- or detergent-based coil cleaner may be needed.

To Foam Or Not To Foam

Many technicians feel that if a coil cleaner is not foaming, it’s not working. Consequently, most manufacturers make sure their formulas foam, at least a little.

In reality, the amount of foam is not directly related to a product’s cleaning ability. As in most situations, optimal foaming action is somewhere between no foam and heavy foam.

Too much foam can actually keep the cleaning materials from contacting all surfaces and push debris toward the center of the coils. The thicker the coil, the more prevalent this particular problem.

If there’s absolutely no foam, on the other hand, the cleaner does not take full advantage of its cleaning ability by leaving debris on the surface and not exposing the next layer. Mild foaming action is preferable and provides for optimum cleaning.

Bright = Clean?

A clean coil is not necessarily bright.

In all probability, the brighter the coil’s surfaces, the more metal you have just removed. Consistent use of products that result in bright coils can diminish the life of the coil, because they dissolve the outer surface of the metal.

Liquid or powder, acid or alkaline, foam or no foam — different situations call for different measures and only experience, knowledge, and personal preference can dictate the choice of products.

Careful consideration should always be used when choosing a coil cleaner. Where are the coils located? What equipment is close by? What material is being removed from the coils’ surface?

Regardless of choice, remember that coil cleaners are serious chemicals designed to do a tough job.

Follow directions, protect yourself and any surrounding equipment or property, and above all, be careful.

William Dyle is director, Highside Chemicals, Inc., Gulfport, Miss.; 228-896-9220; 228-896-9544 (fax); admin@high sidechem.com (e-mail); www. highsidechem.com (website).

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