Numerous factors can contribute to decreases in a refrigeration system’s energy efficiency, not the least of which is its cleanliness. Much of the time, when facility operators see a facility’s efficiency drop, they believe that indicates they must replace the systems with larger units, when in fact, they often simply need to clean the systems they’re currently using – particularly the evaporators.

The evaporator is the component of a closed-circuit refrigeration system that absorbs heat by vaporizing liquid refrigerant. The evaporator coil is the part of the system not enclosed in a pressure vessel.

There are two types of evaporators: forced draft, in which air is pushed through the coils, and induced draft, with air pulled through the coils by fans.

Without proper maintenance, either type of systems can be negatively affected in significant ways by various types of contamination, including dust, process or product particles, pollen, mold and bacteria, according to IIAR materials.

Evaporator coils and fan surfaces attract debris, and dirty fans and coils decrease their efficiencies and the system’s refrigeration effect while increasing compressor discharge head pressures and delivered supply air temperatures. The adverse effects of these contaminants all lead to increased energy usage.

“A unit may typically be oversized by 10 to 30 percent. Engineers must then select compressors in to meet that overage in their design,” said Brian Hindt, president of Ecoclear Coil Cleaning. “A clean coil should shut down and quit asking for ammonia periodically during the day – ideally every hour.” However, if the coils are dirty, the system can begin running so inefficiently that to maintain the temperature of a particular space, it never stops running.

In fact, according to manufacturer’s maintenance materials, a coil with a layer of contamination just the thickness of a dime will lose up to 21 percent of its efficiency. Therefore, it’s imperative that any facility looking to lower its energy usage and associated costs should schedule regular cleaning and maintenance.

“Clean evaporator coils deliver improved airflow to provide lower chilled air temperatures and absorb heat at greater efficiencies,” said Tony Lundell, director of standards and safety at IIAR. “[Cleaning] reduces an operation’s energy usage, optimizes compressor capacities and enhances the system’s refrigeration effect.”

The frequency of this required maintenance depends on the type and size of the facility, but Hindt said roughly speaking, a system should be cleaned about once a year or year-and-a-half. It depends on the load that you’re putting through the coil and what type of materials are in the environment you’re trying to cool, he added.

However, it’s not enough to wheel in a pressure washer and hose everything off. In fact, Hindt said that can often cause more harm than good. By pushing the contaminants to the middle of the coil apparatus, debris can become compacted, degrading airflow through the system and potentially damaging components.

There are three levels of cleaning, according to coil manufacturers, and IIAR materials: cleaning, sanitizing and protecting.

The objective of cleaning is to remove visible contaminants from fans, coil tubes, fin surfaces, drain pans and lines. There are four basic types of cleaners to accomplish this: acids, alkalines, solvents and detergents. It’s imperative that the right chemicals be selected for the right application, coil manufacturers warn. If not, components could be damaged.

A step beyond cleaning is sanitization. This removes visible and non-visible growing contaminates from all components, including bacteria, mold and other pathogens. This type of cleaning is particularly important in facilities that handle food products, because avoiding contamination is always a major consideration. To sanitize a system, proper water temperatures, pressures and techniques must be applied to prevent pushing contaminates deeper into the system, and chemical cleaners must be thoroughly rinsed from every surface of the system.

“Removing contamination from evaporator coil surfaces not only reduces energy usage and improves the refrigeration effect, but also reduces or eliminates product safety risks, such as in food and other open-product manufacturing facilities,” Lundell said.

Hindt agreed. “These units are huge harborage points for bacteria – the Listeria, the Salmonella, the E. coli that may be found in these food processing plants, most of it is harbored in a dark, wet, cold place,” he said.

The final level is protection, in which a protective coating is applied to the coils to prevent the accumulation of contaminants, increase overall energy efficiency and extend equipment life. According to coil manufacturer’s recommendations, there are two basic types of coatings – water attractive and water repellant. Each coating type has its benefits, and which to employ depends on the type of system in consideration.

One of the best ways to measure the increased efficiencies of a particular cleaning regimen is to examine the cost savings over time. Hindt says these savings can be tremendous. “We typically see the cost for cleaning the coils in a facility returned to the customer very quickly through the improved operating efficiencies,” he said. By comparison, he noted that replacing standard lighting with LEDs usually takes three to five years to see a return on investment, while proper cleaning can return the cost in five to six months.

Unfortunately, proper cleaning is rarely thought about in terms of increasing energy efficiencies and decreasing costs. Most operators fail to consider the operating efficiencies, Hindt said. they just want to keep their facility at the right temperature, and they’ll pay whatever it costs to do so. Many don’t realize that by simply cleaning their systems, they could realize tremendous cost savings as well as decreased energy consumption.