Clean and Save: Proper HVAC equipment cleaning means big energy savings
The role of the facility engineer is more important than ever, expected to do more with less finances and staff. At the same time, managers are asked to improve productivity, reduce energy and improve equipment sustainability, so HVAC energy expenditures are important. In fact, HVAC expenses can add up to 50 percent or more of a building’s energy costs.
Recent Studies and New Technology
Cooling and heating coils are much less efficient when dirt, biological films and other contaminants cover their surfaces. Dirt and contaminants have an insulating effect and cannot adjust the building air as well as they would if they were clean. The American Society of Heating Refrigeration and Air Conditioning Engineers performed an engineering study in 2006, demonstrating that dirty coils increased energy costs by 10 percent or more. This study was done on air handlers that were cleaned only one year prior to the study, and unfortunately, many engineers overlook their impact and may clean them as infrequent as once every five years.
New information shows that a film of bacteria and other microbials can also accumulate on coil surfaces. Similar to what occurs in chiller condenser tubes, biofilms are five or more times more insulative than scale. In addition, the limit of human visibility is 30 microns (and a micron is very small, equal to one-thousandth of a millimeter), so in a majority of cases, the coil looks clean even if it isn’t. Because of this, biofilms on coil surfaces are often not seen until they get to 50 or even 150 microns thick. And since they are somewhat sticky, they attract dirt and other small particulates that further impinge on the coils during its operation.
One way to look at this is to say coil heat transfer is gradually impeded immediately after cleaning, and trouble builds up as time goes on. Previously, the only way to handle this and to keep efficiency high was to spend staff hours to clean frequently. Since staff is not always readily available, this solution was often not contemplated.
Some have used ultraviolet light to help with the biofilm problem. This helps, but it’s of limited use since light travels in straight lines and cannot get into the interiors of the coil bank.
Newer technology is available to keep coils clean for longer periods without maintenance attention and capital costs. There are now a variety of user-applied coatings specifically engineered for HVAC coils; these shield the coils from dirt, biological film, greases encountered in fast food restaurants, bakery dust, mineral scale and other contamination that can accumulate. Benefits to the engineer include a decrease in the number of cleanings needed, saving valuable staff hours.
Metal corrosion is one of the leading causes of air-handler replacement. After 15 years, many air handlers show signs of internal corrosion of the metal. Areas most commonly affected include HVAC condensate collection pans, coil support structures, and sidewalls. Fan enclosures and filter support racks also may be affected.
Understandably, removal and replacement of air handlers is a significant expense. Since facility’s air handlers are typically all installed at the same time, if one is in need of replacement, there is a good chance many others will queue behind it for replacement as well.
Over the past 10 years, new technology used in commercial buildings, nuclear plants, industrial facilities and hospitals has allowed for like-new refurbishment of corroded air handlers. This effectively stops HVAC removal, downtime and replacement. Monetary savings with this permanent fix are significant for rooftop units as well as larger-sized equipment. The solution can be done in-house, at a fraction of the replacement cost.
Time tested methods to maintain efficiency — such as condenser water treatment to prevent scale and biofilms, regular filtration changes and elimination of filter bypass in air handlers — are all good ways to maintain efficiency. However, newer technology enhances these methods to provide even more significant cuts in expenses.
Lynn Burkhart Jr. is the president and founder of Controlled Release Technologies Inc. For more information visit www.cleanac.com.